the crystal photoeffect in

THE CRYSTAL PHOTOEFFECT IN

D-TARTARIC ACID SINGLE CRYSTALS

by

CHUNG KWAI LUI

A THESIS

submitted to the

OREGON STATE COLLEGE

in partial fulfillment of the requirements for the

degree of

DOCTOR OF PHILOSOPHY

June 1941

- - - -

fin^Jo frofesson)

Redacted for Privacy

AN ABSTNACT OF TIE TIIE8IS OF

-9Fgq 5rtl-l-gt - - ror trre -EljD-- - - 1r - -[ssfa-sshy( ttarae ) ( Degree ) ( ua5 or )

Date Ehe s ls pne senteaJhf l-- -1-q4-1- - - shy11s1--lllrs--cgurtgl-ampo-tqette-gt--19-Qtegttt1q-tc-l-rgtsl9--shy

-c-rurltlrl

Abstnact Approved

By neana of a eensltlve eunrent lneasurng devloe oonshyueotod la senles rlth a d-tertarlc aeld cnystall a flor of ounnont can bo detected rhen tbc c4yetal ls lllunlnatedl rltblleht fron an ordlnary tungsten ftlaent larap lfre cunrent rosponse ls greatly deBendont ou the onlentatlon of tho orTsshytal rlth neapeot to the dlneetlon of the lnoldent bcan ofItght Uogt of the cnystal faces glve a ourront rccponse upon lllumlnatton rlrlsb rlses napldly to a naxtnuu Just aftor tJee 1lgbt 1g trrrned oar then decrcageg and flael3y neaobes a ooastant ya1ue |l|hls type of reeponso ls callcQnlhe nortaleffect

lllhere are oentain neglons of the cr1rstaI horeven Chtohglve e cuJplrent flor rlrlcb gtantg out ln ono dfupectloa Justaftcn the llgpt ls turtred oa deeneasss naplclly rlth the ttne of lllrutnatloa and tben florE ln the opposlte dlneetlonEhls ls ealled the abnomal effeot It ts found that thls abnoraal effect alrays ocours rhen a polnt (srall neglon) ls tlhmlnated tbet LLog betseen tro regtons rhose nomel ounnent flors eno opBosltely dllrected Iho Buporposltlm of ths tro nomel orurncnt-ttne rosBonso onrYes glvoe a nesu1taut rhloh agneor rlth the obsenved abnomal rosponso rlthll the expenlshyuental error

A study ras uade of the verlatioa of pbotoounent dth taperature betveen 23oC end 15100 llhe crnrent ras found to hecrease rapidIy as tbe tcn1renature ras raleed fp 25oC to SOoC et rbloh point tbe orrrnent becaoe too mall to mealurolt 151oC a maII rovorro onpreat ras noted

Palntlag tbe onystal faoes drlch mede oonteot lth the eleetrodes r][th iaguidagi resuted la aa lncroase tn Bbotoshyourent

- 2 shy

The current response was studied when the crystal was examined with a light probe When the light fell on the crystal near the electrodes the response was found to be slightly less than when the light probe was used mid-waybetween the two electrodes

The fatigue effect of the crystals was examined bymeasuring the current response after comparatively longperiods ot illumination It was found that the decrease in current caused by the illumination was much greater for freshly grown crystals than for those grown several months before the test

Several theories relating to the crystal photoeffect are discussed With a alight extension the assumption of a bullconductivity axisbull or direction of max~ conductivitythe diffusion theory explains all results obtained includingthe new bullabnormal effect

IDPROVEDT


Xa Gbarge of ltral or




Ghslruea of State Collcgo

ACKNOWLEDGMENT

The author wishes to express her gratitude to

Dr James J Brady Associate Professor ot Physics

who suggested the problem and whose untiling interest

and helpful suggestions have proved invaluable for

the completion ot the work

The author also wishes to thank Dr w Weniger

Head of the Physics Department who has made the

necessary apparatus available

~LE OF CONTENTS

Part Page

I Introduction bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull 1

The Barrier Layer Theory bull bull bull bull bull bull bull bull bull 3

The Light Pressure Theory bull bull bull bull bull bull bull bull bull 4

The Electrochemical Theory bull bull bull bull bull bull bull bull 5

Difpoundusion Theory bull bull bull bull bull bull bull bull bull bull bull bull bull 5

II Apparatus and Material bull bull bull bull bull bull bull bull bull bull bull bull 14

III Experbnent s bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull 24

A The Effect of Crystal Thicknessbullbull bull bull bull 26

B The -Effect of a Coat of Aquadag on the Crystal Surfaces in Contact with Elecshytrodes bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull 28

c The Effect of Crystal Orientationbullbull bull 30bull

D The Temperature Effect bull bull bull bull bull bull bull bull bull 32

E The Effect of a Light Probe Near the Electrode and at the Center of the Crystal bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull 35

F The Fatigue Effect bull bull bull bull bull bull bull bull bull bull bull 35

IV Discussion bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull 39

v Conclusions bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull 48

Bibliography bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull 49

bull bull

bull bull bull

LIST OF FIGURES

Figure Page

1 Circuit for Crystal Photoeffect (Longitudinal Ulumination) bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull 13

2 Circuit for Crystal Photoeffect (Transverse illumination) middot bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull 13

3 Energy Level Diagram for Crystals bull bull bull bull bull bull 13

4 A Complete Circuit for Crystal Photoeffect with FP-54 Amplifier bull bull bull bull bull bull bull bull bull bull bull bull 16

5 General View of the Apparatus bullbullbull bull bull bull bull bull 17

6 Diagram Showing the Cross-aection of the Crystal Holder bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull 19

Temperature-current Curve of the CrystalHolder bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull 21

a A Tartaric Acid Single Crystal bull bull bull bull bull bull bull 23

9 Diagram of a Tartaric Acid Single Crystal Showing Crystal Faces bull bull bull bull bull bull bull bull bull bull bull bull 23

10 Variation of Photocurrent with Time of Illumination bull bull bull bull bull bull bull bull bull bull bull bull bull 25

11 Variation of Photocurrent with Thickness of the Crystal bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull 27

12 Effect on Photocurrent Due to Aquadag LayerBetween Crystal and Electrodes bull bull bull bull bull bull bull 29

13 Change of Photocurrent ])le to IlluminatingDifferent Crystal Faces bull bull bull bull bull bull bull bull bull bull bull 31

14 Curves Showing the Relationship of Normal and Abnormal Effects bull bull bull bull bull bull bull bull bull bull bull bull bull bull 33

15 Variation of Photocurrent with Temperature bull 34

16 Effect on Photocurrent l)le to Applying the Light Probe to Different Parts of Crystal bull bull 36

LIST OF FIGURES

(Continued)

Figure Page

17 Variation of Photocurrent with Time or Exposshytlle bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull 38

18a Two Dimensional Dia~am of a Unit Cell or Tartaric Acid Crystal When the Top of the Crystal is Illuminated bull bull bull bull bull bull bull bull bull bull bull 41

18b Two Dimensional Diagrwm of a Unit Cell or Tartaric Acid Crystal When the Bottom of the Crystal is Illuminated bull bull bull bull bull bull bull bull bull bull bull 41

19 tdagram of a Unit Cell or Tartaric Acid Crystal bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull bull 44

20 Diagram Showing the Unit Cell in Relation to a Tartaric Acid Crystal bull bull bull bull bull bull bull bull bull bull bull 44



I INTRODUCTION

The crystal photoeffect manifested by certain

crystals consists in the production of an electric curshy

rent upon illumination without the aid or an impressed

battery The electric current may be detected by conshy

necting the metal electrodes supporting the crystal to

a galvanometer or electrometer The diagram of the conshy

nections is shown in Fig 1

This phenomenon was first observed about 1844 by

Hankel (5) who called it the actinoelectrie effect

Several workers have since used this expression but it

is rapidly being replaced by The crystal photoeffect

The latter term was first used by Dember (8) in 1931 in

reference to the electron flow in the direction of the

light transmitted through single crystals of cuprous

oxide

Very little attention was paid to this crystal

photoeffect prior to 1901 when J c Bose (2) in India

observed this effect in galena (lead sulfide) He put

this effect to practical use middotror measuring light intenshy

sity by designing his Tejometer described in us patent

2

755840 in 1901 Since then various crystals have been

found in nature which exhibit the crystal photoetfect A

list ot these is given in Table 1

TABLE 1

A List of ~oto-crystals

Name ot crystal Investigator Year

lead sulfide J c Bose (2) 1901

argentite (~S) H H Sheldon (22) and P H Geiger (11) 1922

molybdenite w w Coblentz (5) 1924

selenium R M Holmes (12) and N L Walbridge (13 1928

cuprite H Dember (89) 1931

diamond R Robertson (21) 1932

sodium chloride St Pelz (20) 1933

potassium chloride St Pelz (20) 1933

tartaric acid r r Brady and W H Moore (3) 1939

Note Sodium chloride and potassium chloride must be colored yellow with X-rays in order to show the effect

The question ot the origin of the electromotive force

1n the illuminated crystals has proved to be very puzzling

The following theories have been proposed within the last

few years

3

THE BARRIER LAYER THEORY The barrier layer theory

has proved very successfUl in explaining the behavior of

the copper oxide photo-cell and was therefore suggested as

an explanation for the crystal photoeffect In the copper

oxide cell the barrier layer is a very thin layer having

a thickness or 10-6 to 10-a em at the boundary between the

crystal surface and the electrodes This layer is of pure

cuprous oxide containing no tmpurities The rest of the

cuprous oxide has an excess of oxygen atoms The excess

oxygen atoms nearest the metal remove electrons from the

metal and thus establish an electric field in the barrier

layer Any electrons that may be released in the barrier

layer by the absorption of light will be forced out of the

oxide into the metal giving rise to a current This explashy

nation is known as Schottkys (14) barrier layer theory

According to this theory the current should be greatest 1n

the neighborhood of the boundary and should become extremely

small at a short distance away from the barrier layer

H Dember (8) proved by expertment that the barrier layer

theory failed to explain the crystal photoelectric effect

He showed that photocurrents are produced when the crystal

but not the electrode is exposed to light He also obtained

a flow of current in a single crystal of cuprite which was

free from barrier layers

4

THE LIGHT PRESSURE THEORY In the early experiments

of Dember the light was directed on the crystal perpenshy

dicular to one of the electrodes He observed that the

photo-electric current flowed in the same direction as the

light This fact led von Laue (15) to propose that the

motion of the electrons may be due to light pressure

Maxwells electro-magnetic theory of light predicts

that light should exert a pressure on any surface on whiCh

it falls The experiment of Nichols and Hull (19) proved

the existence of this light pressure It is reasonable to

assume in the present case that the electrons are acted

upon by light pressure The fact that the electrons in

Dembers (8) experiments moved in the direction of propashy

gation of the light thus finds a ready explanation Howshy

ever R Deaglio (6) still working with cuprite crystals

(from Chessy) allowed the light to fall upon a crystal

perpendicular to the line joining the two electrodes ie

parallel to the electrode faces as shown in Fig 2 He

observed no current flow when light was directed at a point

half way between the two electrodes but did obtain a curshy

rent when the light fell slightly to the left or the right

of this point and moreover these currents flowed in

opposite directions These observations are evidently

not explained by the light pressure theory

5

THE ELECTROCHEMICAL THEORY Deaglio (6) attempted

to explain his results on the basis of an electrochemical

theory He assumed that although the dark conduction is

electronic the action of the light is such as to produce

electrolytic conduction He discovered a fatigue phenomeshy

non that could be explained by this theory After a crystal

has been illuminated at constant intensity for a long time

the photocurrent was observed to fall to less than half of

its initial value According to this theory au+ ions

are transported to the cathode and deposited there as

metallic coPPer Since this copper layer absorbs a conshy

siderable amount of light the current will be decreased

appreciably

G M~nch and R St~ler (17) allowed light to fall

on a crystal through a thin open ring electrode where the

light could not be absorbed by the transported copper but

the fatigue effect persisted nevertheless The fact that

a fatigued crystal will return to its original behavior by

being kept in the dark tor several hours also contradicts

this theory Cuprite crystals from Cornwall and Tsumeb

showed no fatigue effect

DIFFUSION THEORY The theory that will now be preshy

sented has proved most satisfactory thus tar It has its

origin in a new theory or solids first suggested in a

qualitative manner by M J 0 Strutt (23) He pointed out

6

that a solution of Schrodingers wave equation in solids should lead to a number of allowable energy bands whiCh

need not necessarily overlap or even be in contact but

might be separated by a region of forbidden energy values

The solution for individual atoms gives rise to widely

separated energy states similar to those postulated by Bohr

When these individual atoms collect to form a solid

each energy state of the individual atoms breaks up into

a band of energy states If the forbidden region has a

width corresponding to a considerable fraction of an

electron-volt of energy and the band below is completely

filled with electrons the crystal will be a good electrishy

cal insulator as an electron would be unable to gain any

energy from an applied electric field unless that field

were sufficiently intense to raise its energy to that of

the empty energy band above the forbidden region It the

crystal lattice contains impurity atoms or detecta ot any

kind such as one would expect if normal atoms became disshy

placed from their normal positions in the crystal lattice

energy states for the electrons might arise 1n the forshy

bidden region Fig 3 illustrates the relative positions

ot the energy states in a crystal of this type If an

electron leaves the filled band and locates on one of

these so-called tmpurity levels a vacancy will be left

1n the filled band This vacancy is commonly referred to

7

as a hole The hole may move about in the crystal and

give rise to a resultant electrical conductivity It will

behave like a positive ion 1n many respects but of course

will not account for the transport of metal

A physical picture of the motion of a hole is not

difficult to conceive The ejection of an electron from

an atom into an impurity state leaves behind a positive

ion An electric field that may be present due to any

cause Whatever either within or without the atom will make

it highly probable that some neighboring atom will lose an

electron This electron will combine with the positive

ion The former neighboring atom will now be a positive

ion This process repeated many ttmes will constitute a

moving positive charge through the crystal not accompanied

by the motion of an atomic nucleus

J Frenkel (10) was one of the first to apply these

concepts to a theory of the crystal photoeffect For the

sake of simplicity Frenkel considered the case of a crysshy

tal illuminated by a plane sheet of light He derived an

expression for the potential difference between this plane

and any other point in the crystal Let the sheet of light

be in the yz plane passing through the origin Its equashy

tion will be x = o Assume a difference in diffusion

velocities of electrons and holes This difference will

cause a potential gradient whichwill tend to retard the

- - -

8

faster particles (electrons or holes) and accelerate the

slower ones For a steady state the rate of change of

electron or hole concentration with respect to time will

be zero but with respect to distance x it will be for

any unit volume in the crystal

d2 n D ----plusmn =9 (ElL n e)+ dX2 dX + +

where

D+ is the diffusion coefficient for the holes

n+ is the concentration or number of holes per cc

E is the electric field strength

If+ is the mobility of the holes divided bye

e is the electronic charge

The effect of the recombination of holes and alec trona is

neglected 1n this equation and the following For the

electron concentration a similar equation holds

where D ~ and n refer to electrons On the further

assumption that the field E is constant throughout the

crystal these expressions may be written

9

This equation states that the poundield set up by the difrusion

process will draw the charges out of a unit volume as fast

as they accumulate by diffusion

The effect of recombination will now be considered

In the conduction of electricity through gases it is well

known that the rate of recombination of the ions varies as

the square of their concentration If this relation were

to hold for crystals the current would increase as the

square root of the light intensity However it is an

experimental fact that under uniform illumination of the

entire crystal the current is proportional to the first

power of the light intensity Hence it is evident that

the electrons and holes in a crystal do not recombine in

the same manner as the electrons and ions in a discharge

tube where the ions first attach themselves to the walls

and then recombine on the surface The electrons or holes

may become trapped on impurities or lattice defects and

the recombination may take place at these points

Taking recombination into consideration the equation

may be written

Dplusmn d2n+---=shy Ellplusmn e

dnplusmn-shy rnplusmn = 0 (1) dx2 dx

where r is the recombination coefficient

10

The relation of the coefficients D and ~ is expressed

by Einsteins well known equation

DftL =kT (2)

where k is Boltzmanns constant and T is absolute temperashy

ture If the same concentration be assumed for electrons

and holes n_ is the s~e as n+ ~oughout the crystal

n =n =n - +

The solution of the differential equation (1) is

(3)

where a is a constant and n is the concentration in the0

crystal plane illuminated by the plane of light Substishy

tuting the value of n from equation (3) in equation (1)

a 2

Dplusmn plusmn ecdJplusmn E - r = 0 (4)

Equation (4) may be written as two separate equations

2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)

Subtracting (6) from (5) and solving for E

D - D - + middot E = Ct (7) e(l_ + ll+)

By means of (2) equation (7) becomes

ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0

write Ex = where is the potential difference between

the illuminated plane and any point in the crystal at a

distance x from this plane

Substitute these expressions in (B) after multiplying

both sides by x

Then

(9)

Mgnch and St~ler (16 18) reported that for pure

laboratory grown cuprous oxide crystals no crystal photoshy

effect was observed but that it was found in cuprous oxide

crystals occurring in nature and containing a slight trace

of impurities Mench explained these results by the assumption that the mobilities of electrons and holes are

identical when there are no impurities This is borne out

by equation (9) for if~+=~- ~ = 0

For semi-conductors the mobility of the electrons is

much greater than that of the holes Therefore the fracshy

tion II - tJ to-_ bull + =1 Jl_+tJ+

Equation (9) then can be written

n qgt = ~ ln 2 (10)e n

12

It is interesting to note that except for the constant

ke this equation happens to be exactly the s~e as that

for the electromotive force of a galvanic concentration

cell

This theory shows how an electromotive force can be

set up 1n a crystal by the absorption of light It also

predicts how the crystal photoeffect should vary with

temperature The concepts used in this theory will later

be applied to the results obtained by the author 1n the

study of tartaric acid crystals

-------------------

13

T

Fig 1 l ~Light

Circuit for Crystal Photoeffect

(Longitudinal illumination) -E~~ ~

G

Fig 2 Circuit for

Crystal Photoeffect (Transverse illumination)

Fig 3 Energy Level Diagram

for Crystals

Emptyband

Impurity -----r------shy level

~~F~~d

14

II APPARATUS AND MATERIAL

The expertmental set-up used 1n this investigation

is similar to that used by Brady and Moore (3) A photoshy

graph is given 1n Fig 5 and a diagram of connections 1n

Fig 4 The amplifying circuit was originally designed by

DuBridge and Brown (4 and employs an FP-54 electrometer

tube As this tube and the amplifying circuit are extremeshy

ly sensitive to stnay fields the tube and the resistance

R are enclosed in a cylindrical brass case The rest of

the amplifying circuit and the storage battery (12 volt

Willard type Syrig are mounted in a copper box The

type HS Leeds and Northrup galvanometer G 1n the diagram)

was connected to the circuit by grounded Shielded conducshy

tors

The crystal holder H consists of two parallel brass

disks with the crystal between them all held together by

spring pressure (P Fig 6) This holder is mounted in an

insulated chamber with provision for changing the temperashy

ture from room temperature to 150degC The outer wall of the

chamber is a tin can about 5 inchamp - in diameter and the

inner wall a 3 inch brass tube The space between as

shown in Fig 6 is partly filled with an asbestos boiler

cement and partly by the heating coil packed in asbestos

The coil is in series with a rheostat an ammeter and a

SmboL Explapation Symbol Explanation

c crystal R1 resistance 50 ohms

E 12-volt d c source resistance 50 ohms~ G galvanometer resistance 4000 ohms~ H crystal holder R4 resistance 2000 ohms

milliammeter resistance 50 ohmsIf R5

L light source Rs galvanometer shunt resistance

R resistance 102500 megohms s1 switch

resistance 10000 ohms switchRo s2 R resistance 50 obms T FP-54 vacuum tube

0

T 8

s

-----~-11 I I I I ~+--- s2

E

Fig 4 A Complete Circuit for Crystal Photoeffect with FP-54 Amplifier

Fig 5 General View of the Apparatus

c

Smbol Explanation

crystal

E cement

H heating coil

M space for cooling agent

N space for water vapor absorbing agent

p spring

s sulfur

T thermometer

w water

T

Fig 6 Diagram Showing the Cross-section of the Crystal Holder

20

110 volt AC source A rough calibration curve (Fig 7)

relating ammeter readings to temperatures was obtained by

a preliminary experiment but actual temperatures were

always read on the thermometer shown in Fig 6

Provision was also made for reducing the temperature

by placing solid carbon dioxide in the space M Calcium

chloride has to be placed in the space N to absorb moisture

No data were taken below room temperature

The crystal -holder is supported on sulphur cylinders

SS placed in a brass tube extending as shown from the sides

o~ the insulating chwmber Water jackets are provided as

shown to keep the sulphur ~rom being melted by heat conshy

ducted along the tube

The light source L Fig 4 was a 150 watt spiral

filament tungsten gas filled lamp It was focused on the I

crystal by a simple lens Stray light was prevented from

reaching the crystal by a brass tube extending from the

crystal to the lens

All the crystals used in this investigation are sinshy

gle crystals artificially grown in this laboratory by the

investigator A saturated solution of cp d-tartaric

acid crystals was made in distilled water This solution

was filtered to remove excess crystals and dust particles

Beakers containing this solution were covered and placed

in a box in an unused roam in which the temperature could

~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22

be controlled to the extent or avoiding large or ~dden

changes A sudden change or temperature will cause the

crystals to grow 1n clusters Crystallization usually

starts at the place where the surface of the solution

touches the wall of the beaker Crystals obtained from

this region are not perfect single crystals Crystals

starting at the surface and growing downward in to the solushy

tion are generally large and fairly perfect except for the

upper race The crystals which form at the bottom or the

beaker are almost always most nearly perfect The process

must be inspected from time to time to make sure that ranshy

dom clusters are not formed A photograph of one of the

crystals is shown in Fig e From external appearances

the small crystals are more nearly perfect than the larger

ones The best ones obtained bad a thickness of from one

to two millimeters

23

Fig 8 A Tartaric Acid Single Crystal

I

I b-axis----shy

I

aI

a-axis

c

q

Fig 9 Diagram of a Tartaric Acid Single Crystal Showing Crystal Faces

24

III EXPERIMENTS

According to the observations of J J Brady and

w H Moore (3) on tartaric acid crystals when light

falls on the crystal the galvanometer deflection rises

very suddenly to the maximum value and then decreases very

rapidly at first then more and more slowly until it

approaches a steady value When the light is cut off

the galvanometer deflects in the opposite direction to

approximately the same maximum value but finally apshy

proaches the initial value If the galvanometer deflecshy

tion is plotted against the time the curve will appear

as in Fig 10 This curve is characteristic of the crysshy

tal photoelectric effect The decrease in current 1n the

first part of the curve has been explained by the investishy

gators as caused by the building up of a space charge

(or polarization) within the crystal

They observed that crystals which appeared to have

flaws behaved differently from the curve shown in Fig 10

When the light was turned on such a crystal the galvanomshy

eter derlected first in one direction then quickly reversed

and reached a maximum in the opposite direction A thorough

investigation of this peculiar phenomenon was conducted by

the author It was found that a similar behavior is also

shown by all perfect clear single crystals It will be

bullbullbull-+-+shy~~ ~-4

1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26

called the abnormal effect in this thesis In contrashy

distinction the usual effect will be referred to as

normal

A The Effect of Crystal Thickness

All the perfect single crystals exist in a definite

form as Shown in Fig 8 the crystal faces being very

distinct This definite form is shown more clearly by

means of Fig 9 In crystallographic nomenclature face

a is called the ortbopinacoid face q clinodome c basalshy

pinacoid and r orthodame The crystal is symmetrical

about the b-axis the b- and c-axes are at right angles

to each other but the a-axis is perpendicular only to

the b-axis and not to the c-axis

In order to investigate the effect of thickness of

crystal on the crystal photoelectric current a particular

face of the single crystal is chosen for illumination

Face m is chosen in this case because it exists in most

of the crystals obtained and is easily distinguished

Electrodes are placed against the orthopinacoid faces and

light falls on the m faces along the b-axis If the

maximum deflection of the galvanometer reading is plotted

against the thickness of the crystals the curve appears

to be a straight line (Fig 11) showing that the photoshy

Ibull

28

electric current varies directly as the thickness of the

crystals Of the eleven crystals studied two did not

lie on the curve the reason is not known definitely but

these crystals bad probably been previously exposed to

strong illumination for a considerable time

B The Ettect of a Coat or Asuadag on the CrystalSurfaces in Contact with Electrodes

It was attempted to increase the current flow by deshy

creasing the contact resistance between the crystal and

the electrodes Aquadag a colloidal graphite is highly

conducting and seemed to be a suitable material A paste

or aquadag obtained by mixing it with a drop of distilled

water was spread over the crystal surface a The coating

appears to be dry in one or two hours but observations are

not taken until after one or two days In most cases the

deflection or the galvanometer increases after this coatshy

ing has been applied The amount of the increase 1n the

galvanometer deflection varies for different crystals

In some cases the magnitude increases two or three fold

as shown in Fig 12 This treatment was given to many

but not all of the crystals used 1n this investigation

~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30

c The Effect of Crystal Orientation

The effect of having the light fall on different faces

of the perfect clear single crystals was thoroughly invesshy

tigated Since most of the crystals obtained are thin it

is very difficult to concentrate the light on a particular

face as shown 1n Fig 9 The e face especially is so

small that the r face is also included in the Ulumination

Faces symmetrical with respect to the b-axis are

designated by unprimed and primed letters as q c and e

In this ease there are altogether six different faces

e q m qt c m

The results obt~ned show that the orientation of

the crystal 1n the light beam has a decided effect upon

the photoelectric current The current-time curves show

decided differences Fig 13 shows the values for the

six different faces of a perfect clear single crystal the

minimum thickness of which is 188mm The curves differ

not only as to the magnitude of deflection but even in

the direction of the current (curve F) Curve E shows

that the galvanometer starts middotto deflect in one direction

when face c is first illuminated then reverses in direcshy

tion reaches a maximum after a short time and gradually

decreases to a steady value This phenomenon appears in middot

all the perfect clear single cr~stals grown in this laborashy

tory Let us designate this curve as the abnormal curve

H

H-1

~Ril+

F

IH

32

This peculiar behavior was examined more closely

The face that shows the abnormal behavior and its two

neighbors were illuminated successively The deflections

for the two neighboring faces were always found to be

opposite in direction (Fig 14 A and C) The first porshy

tions of these current-time curves were plotted on an

enlarged scale The difference of these two sets of data

produce a curve having the abnormal shape B Fig 14

The experimental curve is shown in curve B These two

curves have the same shape and differ slightly in magnitude

Only one abnormality was found in each of the crystals

studied but it was not always found to occur on the same

face Other places near the intersection of the crystal

faces may show this abnormal behavior but if so it can

only be determined by building a crystal holder provided

with graduated circles and rotating the crystal through

a series of small angular steps

D The Temperature Effect

In this investigation the range of temperature extends

from 23degC to 151degC The crystal is coated with aquadag so

as to insure a low resistance contact between the crystal

surfaces and the electrodes The maximum galvanometer

reading is plotted against the temperature as shown in

Fig 15 From this curve it can be seen that the photoshy

+

fT +

+lili

35

electric current decreases rapidly with increasing temperashy

ture ~am 25degC to 50degC Above 50degC the current appears to

be zero but at 151degC there is a minute current in the opshy

posite direction This could not be traced rarther as

the crystal melts at 170degC Upon cooling the crystal

regains its original photoelectric current

E The Effect of a Light Probe Near the Electrode and at the Center of the Crystal

A thick crystal or about 388mm was chosen ror this

investigation A slit about one millimeter wide was placed

~ediately in front of the crystal Fig 16 shows that

the shape of the current-time curve is not unusual When

the light probe is near the electrode the current is

slightly less than when it is at the center of the crystal

This may be caused by a slight unavoidable illumination of

an electrode

F The Fatigue Efrect

A freshly grown crystal was used to investigate

fatigue To show this phenomenon the crystal is illumishy

nated as usual and a galvanometer reading taken The

illumination is continued for several hours and galvanomshy

eter deflections taken at varying intervals but before

each deflection the illumination is discontinued for one

++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-

rpound_tttfi=H -middot

p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37

minute in order to give the space charge caused by the

light in the crystal a chance to dissipate The illumishy

nation is then resumed and a galvanometer deflection taken

immediately

Under this procedure successive galvanometer derlecshy

tions become smaller and smaller The amount of decrease

is greatest in the first hour ot exposure The curve

obtained by plotting the maximum galvanometer deflection

against the time o~ exposure is shown in Fig 17 After

this crystal had been exposed to light for several hours

and had in consequence exhibited a marked fatigue effect

it was allowed to remain in the dark for several hours in

order to determine whether or not the original sensitivity

would return After a dark period of twelve hours the

photo-current response for the same light intensity not

only exhibited no recovery but actnally showed a slight

decrease In a similar experiment with a crystal which

had been grown several months before the fatigue effect

was exhibited by a decrease of only six per cent in the

photo-current after continuous exposure to light for seven

hours This decrease is in marked contrast to that exhibshy

ited by the freshly grown crystal which showed a decrease

in photo-current of forty per cent after a six-hour exposshy

ure to the same light intensity

H+

Itshy

~

39

IV DISCUSSION

In order to correlate the observed results the varishy

ous theories which have been proposed for the crystal

photoeftect will be examined

The fact that the l~t probe when illuminating the

middle portion of the crystal but not the region near the

electrodes yielded a fairly large resultant current flow

does not support the barrier layer theory According

to this theory the current should be much greater when

the light probe illuminates the region near the electrodes

than when it strikes the middle portion of the crystal

The experfmental results indicate that the current is

greater when the middle portion of the crystal is illumishy

nated We may conclude that although the barrier layer

theory is very successfUl when applied to the cuprous

oxide photocell it cannot be used tor correlating the

results of the present experiments

The light pressure theory as proposed by von Laue

(15) is inapplicable to this experiment as the light was

incident on the crystal in a direction perpendicular to

the current flow (see Fig 2) whereas it is regarded as

parallel to the current flow in von Laues theory

The electrochemical theory of R Deaglio (8) is based

on assumptions which again are not applicable to this

40

exper1ment as the fatigue experiments he performed inshy

volved the passage of light parallel to the current flow

The diffUsion theory appears to be more usefUl than

any of the others which have been proposed for correlatshy

ing the data obtained in this experfment It is necesshy

sary however to add a very ~portant assumption in order

to explain the observations It must be assumed that there

is a particular direction in the crystal along which the

conductivity is a maxtmum This direction will be referred

to as the conductivity axis This important assumption

has a foundation in the experfments of J J Brady and

w H Moore (3) who discovered a series of equipotential

lines on one face of an illuminated tartaric acid crystal

The direction of maxtmum conductivity or current flow is

assumed to be perpendicular to these equipotential lines

To exhibit the crystal photoeffect electrons must

be able to gain energy from the absorbed light by the

photoelectric process This may result in the production

of the positive holes as well as in furnishing a supply

of free electrons

Let us suppose that the conductivity axis lies diagshy

onally across the unit crystal cell as represented in the

two dfmensional diagram of Fig 18 When light falls on

the top face as in case (a) the number of photoelectrons

released near the top will be greater than the number

41

Fig 18a Two Dimensional Diagram of a Unit Cell of Tartaric Acid Crystal When the Top of the Crystal is Illuminated

1 I

Fig 18b Two Dimensional Diagram of a Unit Cell of Tartaric Acid Crystal Nhen the

Bottom of the Crystal is Illuminated

42

released farther down 1n the crystal due to the diminished

light intensity The concentration of electrons and holes

will then be greater near the edge of the crystal where

the conductivity axis comes closer to the upper face

A difference in the concentration of charges along

this axis will account for an electromotive force in the

crystal When the crystal is illuminated on the bottom

race or the unit cell Fig 18 case (b) the concentrashy

tion of charges along the conductivity axis will be greater

on the left side instead of on the right as in case (a)

This will result in current flows of opposite direction

in the two cases In both cases the ~ceumulation of charges

at the boundaries between the crystal and the electrodes

will result in a decrease of current with time Because

of the difference in arrangement of the atoms at opposite

ends of the conductivity axis in contact with the electrodes

it is to be expected that the variation middotor the current with

time will depend on the direction of current flow

From the X-ray analysis of tartaric acid crystals by

w T Astbury (1) a very definite picture of the unit cell

bas been obtained The crystal belongs to the monoclinic

system the unit cell has the following dfmensionss

a =770A b =604A and c =620A The axes b and c are

perpendicular to each other and a is perpendicular to b

but makes an angle of 100deg17 with c The unit cell is shown

43

diagrwmmatically in Fig 19 The X-ray analysis shows

that there are two molecules to a unit cell The single

crystal is composed of a large number or unit cells Fig

20 shows the unit cell properly oriented with respect to

the single crystal The face c or the single crystal is

formed by the top surfaces of a large number of unit cells

The crystal faces m mbull q and qt are not parallel to the

sides of the unit cell The a-axis lies 1n the same plane

as the q and q faces

The expertmental results indicate that the direction

of current flow is the same for illumination of faces c

q m and qt When face m is illuminated the current

flows 1n the opposite direction to that produced by the

illumination of face c The conductivity axis as already

indicated has been assumed to lie in the unit cell as

shown in Fig 19 Bearing in mind the direction of the

conductivity axis the direction of current flow may be

predicted when any particular race is illuminated When

light is sent along the c-axis toward the c face the conshy

centration of charges due to light absorption will be

greatest at one electrode while the greatest charge conshy

centration tor light sent along the b-axia is near the

other electrode The inclination of the conductivity axis

relative to the direction of light propagation is 1n opposhy

site directions in the two cases indicating that flow of

44

Fig 19 Diagram of a Unit Cell of Tartaric Acid Crystal

Fig 20 Diagram Showing the Unit Cell in Relation to a Tartaric Acid Crystal

45

the currents should also be opposite

Fig 14 illustrates how the abnormal effect results

from the superposition of two current-time curves obtained

by illuminating two crystal faces which yield opposite

currents Curve A was obtained by illuminating the c-face

Curve C was obtained by illuminating the m face and Curve

B was the observed abnormal effect obtained from the illumishy

nation of the q-face B is the resultant of curves A and

c As it is difficult to obtain accurate readings in Short

time intervals it is entirely possible that the difference

between curves B and B is due to experimental error

From these results it may be expected that there will

be an abnormal effect when the beam of light falls upon a

particular portion of the crystal lying somewhere between

two faces that yield oppositely directed currents This

was therefore sought and found experimentally The direcshy

tion of light propagation was held constant while the crysshy

tal was rotated very carefully so as to explore the region

between faces m and c

However since the crystal faces are not always formed

exactly parallel to the electrodes but may have their unit

cells tilted slightly from this condition of parallelism

thus changing slightly the direction of the conductivity

axis with respect to the crystal faces it may be and it

46

was so found experimentally that the abnormal effect does

not always occur at exactly corresponding points in difshy

ferent crystals

The diffusion theory in its stmplest form indicates

that there should be a decrease in the crystal photocurrent

with increase in temperature This prediction is in accord

with the experimental results from 23deg0 to 50deg0 At higher

temperatures the current becomes too small to detect It

is reasonable to suppose that the mobility of the electrons

and holes would approach each other for the higher temperashy

tures and the concentration theory indicates that the

electromotive force would be zero under these conditions

In equation (9) if~- a~+ the potential difference= 0

The fact that the initial current response increases

as a linear fUnction of the thickness of the crystal may

be explained on the basis of increased light absorption

Just as impurities in the crystal give rise to intershy

mediate energy states so also normal atoms if displaced

tram their normal positions during the growth of the crysshy

tals may be regarded as giving rise to energy states beshy

tween a filled and an empty band (impurity levels Fig 3)

The fUrther assumption is then in order that the displaced

atoms may be brought back to their normal positions by the

passage of a current through the crystal These assumptions

are sufficient to account for the results observed when

47

studying the fatigue effect A decrease 1n the number of

impurity levels represents a decrease in the possible numshy

ber of holes and consequently a decrease 1n the observed

current Thermal agitation at room temperature may also

aid the displaced atams to return to their normal posishy

tions this accounts for the fact that old crystals show

a much smaller fatigue effect than those freshly grown

48

V CONCLUSIONS

From the experimental facts and the correlation obshy

tained the following conclusions may be drawn

1 d-Tartaric acid single crystals exhibit a crystal

photoeffeet

2 Hole conductivity as well as electron conductivity

exists in the crystals

3 There is a particular direction in the unit cell

along which the conductivity is a maximum This direction

is named the conductivity axis

4 The conductivity axis is perpendicular to the equishy

potential lines reported by J J Brady and W H Moore

5 The fact that the current flow is in one direction

for the illumination of a particular face and in the opposhy

site direction for the illumination of another face is a

result of the particular direction of the conductivity

axis in the unit cell

6 The exceedingly puzzling fact that the current may

start out in one direction and then decrease to zero and

rise to a maximum in the opposite direction is due to the

superposition of the effects trom two neighboring faces

49

BIBLIOGRAPHY

1 Astbury w T The crystalline structure and propershyties of tartaric acid Proc Roy Soc Ser A 102506-528 1924

2 Bose J c US Patent 755840 filed Sept 30 1901 issued March 29 1904

3 Brady J J and Moore W H Actinoelectric effects in tartaric acid crystals Phys Rev 55308-311 1939

4 Brown H and DuBridge L A An tmproved dc amplishyfying circuit Rev Sci Inst 4532-536 1933

5 Coblentz w w Some new thermoelectrical and actinoshyelectrical properties of molybdenite Scientific Papers of Nat Bur of Standards No 486 April 1924

6 Deaglio R Photoelectric effect for single crystalsof cuprite Zeits bull f Phys - 83179-183 1933 (Cit) Photoelectric effect in monocrystals of cuprite Phys Zeits 36144-147 1935

7 Dember H Electron strewm produced by light Phys Zeits 33207-208 1932

8 Dember H Photoelectric emf in cuprous oxide crystals Phys Zeits 32554-556 1931

9 Dember H Crystal photoelectric cell Phys Zeits 32856-858 1931

10 Frenkel J Conduction in poor electronic conductors Nature 132312-313 1933

11 Geiger P H Spectro-raquobotoelectrical effects in argentite The production of an electromotive force by illumination Phys Rev 22461-469 1923

12 Holmes R M and Rooney A B Thermoelectric power of selenium crystals Phys Rev 311126 1928

13 Holmes R M and Walbridge N L A photo-emf in single crystals of selenium Phys Rev 32281 1929

50

14 Lange B Photo-elements Reinhold Publishing Corpshyoration 1938 (Cit) Schottky w Conduction and photoelectric effects 1n blocking layers Phys Zeits 32833-842 1931

15 Laue v M (Cit) Phys Zeits 32858 1931 n16 Monch G Theory of crystal photoelectric effect Zeits f Phys 91264-271 1934

n17 Monch G and Stuhler R Photoelectric effect for single crystals of cuprite Zeits f Phys 85131-134 1933

18 Monch G and Stuhler R Crystal photoelectric effect Zeits f Phys 91253-263 1934

19 Nichols E F and Hull G F Preliminary communicashytion on the pressure of heat and light radiation Phys Rev 13307-320 1901

20 Pelz s Photoelectric effect in colored rock-salt Akad Wiss Wien Ber 142509-522 1933

21 Robertson R Fox J J and Martin A E Photoshyconductivity of d~onds Nature 129579 1932 (Cit) Two types of diamond Phil Trans of Roy Soc s A 232463-535 1934

22 Sheldon H H and Geiger P H The production of an emf on closed circuit by a light effect on argentite Proc Nat middotAcad Amer 8161-163 1922

23 Strutt M J o Eddy currents in an ellipticalcylinder Ann d Phys 84485 1927

- - - -

fin^Jo frofesson)


AN ABSTNACT OF TIE TIIE8IS OF

-9Fgq 5rtl-l-gt - - ror trre -EljD-- - - 1r - -[ssfa-sshy( ttarae ) ( Degree ) ( ua5 or )

Date Ehe s ls pne senteaJhf l-- -1-q4-1- - - shy11s1--lllrs--cgurtgl-ampo-tqette-gt--19-Qtegttt1q-tc-l-rgtsl9--shy

-c-rurltlrl

Abstnact Approved

By neana of a eensltlve eunrent lneasurng devloe oonshyueotod la senles rlth a d-tertarlc aeld cnystall a flor of ounnont can bo detected rhen tbc c4yetal ls lllunlnatedl rltblleht fron an ordlnary tungsten ftlaent larap lfre cunrent rosponse ls greatly deBendont ou the onlentatlon of tho orTsshytal rlth neapeot to the dlneetlon of the lnoldent bcan ofItght Uogt of the cnystal faces glve a ourront rccponse upon lllumlnatton rlrlsb rlses napldly to a naxtnuu Just aftor tJee 1lgbt 1g trrrned oar then decrcageg and flael3y neaobes a ooastant ya1ue |l|hls type of reeponso ls callcQnlhe nortaleffect

lllhere are oentain neglons of the cr1rstaI horeven Chtohglve e cuJplrent flor rlrlcb gtantg out ln ono dfupectloa Justaftcn the llgpt ls turtred oa deeneasss naplclly rlth the ttne of lllrutnatloa and tben florE ln the opposlte dlneetlonEhls ls ealled the abnomal effeot It ts found that thls abnoraal effect alrays ocours rhen a polnt (srall neglon) ls tlhmlnated tbet LLog betseen tro regtons rhose nomel ounnent flors eno opBosltely dllrected Iho Buporposltlm of ths tro nomel orurncnt-ttne rosBonso onrYes glvoe a nesu1taut rhloh agneor rlth the obsenved abnomal rosponso rlthll the expenlshyuental error

A study ras uade of the verlatioa of pbotoounent dth taperature betveen 23oC end 15100 llhe crnrent ras found to hecrease rapidIy as tbe tcn1renature ras raleed fp 25oC to SOoC et rbloh point tbe orrrnent becaoe too mall to mealurolt 151oC a maII rovorro onpreat ras noted

Palntlag tbe onystal faoes drlch mede oonteot lth the eleetrodes r][th iaguidagi resuted la aa lncroase tn Bbotoshyourent

- 2 shy




IDPROVEDT







ACKNOWLEDGMENT









~LE OF CONTENTS

Part Page

















bull bull

bull bull bull

LIST OF FIGURES

Figure Page

















LIST OF FIGURES

(Continued)

Figure Page








I INTRODUCTION















oxide






2




TABLE 1
















few years

3

























4

























5













appreciably













6

























7


























- - -

8







where












9




















may be written




10



DftL =kT (2)




n =n =n - +


(3)




a 2



2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)




ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










- 2 shy




IDPROVEDT







ACKNOWLEDGMENT









~LE OF CONTENTS

Part Page

















bull bull

bull bull bull

LIST OF FIGURES

Figure Page

















LIST OF FIGURES

(Continued)

Figure Page








I INTRODUCTION















oxide






2




TABLE 1
















few years

3

























4

























5













appreciably













6

























7


























- - -

8







where












9




















may be written




10



DftL =kT (2)




n =n =n - +


(3)




a 2



2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)




ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










IDPROVEDT







ACKNOWLEDGMENT









~LE OF CONTENTS

Part Page

















bull bull

bull bull bull

LIST OF FIGURES

Figure Page

















LIST OF FIGURES

(Continued)

Figure Page








I INTRODUCTION















oxide






2




TABLE 1
















few years

3

























4

























5













appreciably













6

























7


























- - -

8







where












9




















may be written




10



DftL =kT (2)




n =n =n - +


(3)




a 2



2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)




ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










ACKNOWLEDGMENT









~LE OF CONTENTS

Part Page

















bull bull

bull bull bull

LIST OF FIGURES

Figure Page

















LIST OF FIGURES

(Continued)

Figure Page








I INTRODUCTION















oxide






2




TABLE 1
















few years

3

























4

























5













appreciably













6

























7


























- - -

8







where












9




















may be written




10



DftL =kT (2)




n =n =n - +


(3)




a 2



2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)




ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










~LE OF CONTENTS

Part Page

















bull bull

bull bull bull

LIST OF FIGURES

Figure Page

















LIST OF FIGURES

(Continued)

Figure Page








I INTRODUCTION















oxide






2




TABLE 1
















few years

3

























4

























5













appreciably













6

























7


























- - -

8







where












9




















may be written




10



DftL =kT (2)




n =n =n - +


(3)




a 2



2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)




ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










bull bull

bull bull bull

LIST OF FIGURES

Figure Page

















LIST OF FIGURES

(Continued)

Figure Page








I INTRODUCTION















oxide






2




TABLE 1
















few years

3

























4

























5













appreciably













6

























7


























- - -

8







where












9




















may be written




10



DftL =kT (2)




n =n =n - +


(3)




a 2



2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)




ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










LIST OF FIGURES

(Continued)

Figure Page








I INTRODUCTION















oxide






2




TABLE 1
















few years

3

























4

























5













appreciably













6

























7


























- - -

8







where












9




















may be written




10



DftL =kT (2)




n =n =n - +


(3)




a 2



2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)




ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50












I INTRODUCTION















oxide






2




TABLE 1
















few years

3

























4

























5













appreciably













6

























7


























- - -

8







where












9




















may be written




10



DftL =kT (2)




n =n =n - +


(3)




a 2



2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)




ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










2




TABLE 1
















few years

3

























4

























5













appreciably













6

























7


























- - -

8







where












9




















may be written




10



DftL =kT (2)




n =n =n - +


(3)




a 2



2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)




ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










3

























4

























5













appreciably













6

























7


























- - -

8







where












9




















may be written




10



DftL =kT (2)




n =n =n - +


(3)




a 2



2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)




ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










4

























5













appreciably













6

























7


























- - -

8







where












9




















may be written




10



DftL =kT (2)




n =n =n - +


(3)




a 2



2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)




ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










5













appreciably













6

























7


























- - -

8







where












9




















may be written




10



DftL =kT (2)




n =n =n - +


(3)




a 2



2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)




ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










6

























7


























- - -

8







where












9




















may be written




10



DftL =kT (2)




n =n =n - +


(3)




a 2



2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)




ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










7


























- - -

8







where












9




















may be written




10



DftL =kT (2)




n =n =n - +


(3)




a 2



2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)




ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










- - -

8







where












9




















may be written




10



DftL =kT (2)




n =n =n - +


(3)




a 2



2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)




ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










9




















may be written




10



DftL =kT (2)




n =n =n - +


(3)




a 2



2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)




ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










10



DftL =kT (2)




n =n =n - +


(3)




a 2



2 a D+ + eal+E - r = 0 (5)

2a n_ - eall_E - r = 0 (6)




ll - E =kT - + a (8) e ll_+IJ+

11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










11

From (3) ax = 1n (n n)0





both sides by x

Then

(9)












n qgt = ~ ln 2 (10)e n

12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










12




cell







-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










-------------------

13

T

Fig 1 l ~Light



G

Fig 2 Circuit for



for Crystals

Emptyband


~~F~~d

14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










14














tors


















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50

















0

T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










T 8

s

-----~-11 I I I I ~+--- s2

E



c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50











c

Smbol Explanation

crystal

E cement

H heating coil



p spring

s sulfur

T thermometer

w water

T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










T


20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










20


















crystal to the lens








~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










~

~~~

Rt-4 ~~middot +~

4 ~--_

j

~_~

bull--tshy

22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










22
















to two millimeters

23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










23


I

I b-axis----shy

I

aI

a-axis

c

q


24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










24

III EXPERIMENTS

























1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50











1=-~shy~~~~ -~f

~~~~bull _r---

middot _fu~ ~ 1

1 bull+

-+t

~F

~Hi]=

f l~

26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










26



normal





















Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










Ibull

28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










28





















~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










~

_ ~-

~ ~ ~ ~~-~ -~ -

_

-shy

--~-+1 ~

1

ir-

1-hpound-tplusmnrii

ir-r _-nEr_

_ -

- Llmiddot~

+shy

IHshy

=J

TtF

-

I+ It

30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










30











e q m qt c m















H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










H

H-1

~Ril+

F

IH

32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










32

























+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










+

fT +

+lili

35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










35















an electrode








++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










++

~4

+-J ++

ttrt

-1

tplusmn

~Sill

plusmn_ ~ -t

~

~if

li ~

~

~ 1

~--B middot~

Jtshytplusmn

4

-r-

t

1-5

f+1irt ~12

+-dshy

t~middot ll

middot--=~ ~rmiddot

titr E ~~~~

middot---=1i +

Ibull

t -r~

bshy

~~

lff~ ~_r

r

imiddot

~

f1

p

mrr

H-


p +

+

l71middot~

__ jj -Hf+ _

+tl n

t-t_115- -~-

~ifj +l

tl -1

m~

+-[

q +

i~if~ ~ -

~

middot ttl

tJtplusmnt1

lgt-JH

-m

~

f+l

uiIJ

37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










37




immediately





















H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










H+

Itshy

~

39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










39

IV DISCUSSION
























40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










40




















of free electrons






41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










41


1 I



42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










42


























43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










43


























44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










44



45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










45

























46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










46



ferent crystals























47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










47








48

V CONCLUSIONS




photoeffeet

















49

BIBLIOGRAPHY














50










48

V CONCLUSIONS




photoeffeet

















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the crystal photoeffect in

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