RECENT STUDIES OF OXYGEN-IODINE LASER

KINETICS

Azyazov V.N. and Pichugin S.Yu.P.N. Lebedev Physical Institute,Samara Branch, Russia

Heaven M.C.Emory University, Atlanta, USA

Chemical OIL (COIL) Cl2+НО2

-HCl + Cl-+О2(1 ) PО2 100 Тор,

=[О2(1)]/[O2]50 %

Discharge OIL (DOIL)

О2(Х) + е О2(1 ) + е PО2 10 Тор,

20 %

O3-SF6-N2O О2(а1 )-O(1D)-I2(или CH3I)

UV photolysis Photolytic OIL (PhOIL) О3 + hv О2(1 ) + O(1D)

PО2 1 Тор,

90 %

О2

+

-О2(1 ), О

NO2 I2

Nozzle

Resonator

О2

ENERGY LEVELS OF I, O2, I2, H2O

List of reactions that of importance in the DOIL and PhOIL

# Process Rate constant, cm3 s-1

O2(1) formation 1 O2(

3) + e O2(1) + e

EE energy exchange 23

O2(1) + I(2P3/2) O2(

3) + I(2P1/2)

O2(3) + I(2P1/2) O2(

1) + I(2P3/2)

7.8×10-11

2.6×10-11

I atoms formation 45

I2(X) + O(3P) IO+ I(2P3/2)

IO + O(3P) O2(3) + I(2P3/2)

1.4×10-10

1.5×10-10

I(2P1/2) quenching

6789

1011

I(2P1/2) + O2(1) I(2P3/2) + O2(

1)

I(2P1/2) + I2(X) I(2P3/2) + I2(X)

I(2P1/2)+ O(3P) I(2P3/2) + O(3P)

I(2P1/2)+ O3 products

I(2P1/2)+ NO2, N2O4 I(2P3/2) + NO2, N2O4

I(2P1/2)+ N2O I(2P3/2) + N2O

1.1×10-13

3.8×10-11

???

К(Т)?

O3 formation121314

O2 + O2 + O(3P) O3 + O2

O(3P) + O(3P) + O2 O3 + O(3P)

O(3P) + O2 + Ar O3 + Ar

5.9×10-34 cm6/s5.9×10-34 cm6/s5.9×10-34 cm6/s

O3 removal151617

I(2P3/2) + O3 IO + O2

O2(1) + O3 O2 + O2 + O(3P)

O2(1) + O3 O2(

1) + O3

1.210-12

1.510-11

3.310-12

IO +IO reaction18

19

IO + IO O2 + 2 I(2P3/2)

IO2 + I(2P3/2)

IO + IO + M I2O2 + M

8×10-12

3.2×10-11

5.6×10-30 cm6/s

O2(a1) quenching 20 O2(

1) +O(3P) + O2 2O2 + O(3P) ?

O(3P) scavenge 21 O(3P) + NO2 O2 + NO 9.710-12

The low-pressure flow cell

apparatus with a jet-type SOG

Dependence of the I* concentration on the distance along the flow for

w=3 %, O2:N2=1:1

Quenching of O2(1) has a minimal effect

on the I2 dissociation rate

Reducing [O2(1)] by an order of magnitude caused a slight increasing of the dissociation time

0 5 10 15 20

0.0

0.5

1.0

1.5

CO2:O

2=0,92:1, P

c=2 Torr

CO2:O

2=1,4:1, P

c=2,4 Torr

CO2:O

2=1,84:1, P

c=2,8 Torr

CO2:O

2=2,3:1, P

c=3,2 Torr

CO2:O

2=2,8:1, P

c=3,7 Torr

NI*

, 1014 cm-3

L, cm

O2(1) I*

Testing role of O2(1) by addition of CO2

Role of I2(B) in the iodine dissociation

Branching fraction

8.21

dλ

dλ

I

I768

758Xb

718

480XB

Xb

XB

B=5105 s-1 , b=0.08 s-1 bb bI

I

)]([(O

(B)][I

2

B2

X

XB

387

b

cm108.3)106.1(bI

I

)]([O(B)][I 2X

XB2

I2(A, A') + O2(a) I2(1Π1u) + O2(X) I + I + O2(X), approx=100 % I2(B) + M I + I + M, < 1 %

COIL active medium luminescence spectra in the visible range recorded with a resolution of 1 nm at Pc = 2.3 Torr, I2 =0.5%, N2:O2=1:1

Estimation of excitation probabilitiesfrom Barnault et al. measurements

I*+ I2 I+I2(X,v)

v -excitation probability of v-th

vibrational level

m≤v≤n=

v250.110<v230.9 (0 for dashed curve)

Standard dissociation model with v25 0.1 can not provide observed dissociation rates in COIL medium. About 20 molecules of O2(a) consumed to dissociate one I2 molecule if standard model is predominant dissociation pathway.

n

mvv

Pump-probe technique used to study OIL kinetics

Monochromator Ge

Digital Oscilloscope

Nd/YAG Pumped Dye Laser

Delay Generator

Pump

Fluorescence cell

I2+Ar

Light baffles

Quenching gas

Excimer laser

Rate of I2(A') quenching (Rq) depends on CO2 partial pressure РСО2 at PAr=50 Torr, РI2=0.013 Torr

and T=300 K

KCO2 = 8.510-13 cm3/s KAr = 2.710-14 cm3/s

KO2 = 6 10-12 cm3/s

KI2 = 4.810-11 cm3/s

N2O,NO2 or O3

Pump

193 or 248 nm

Powermeter

1268 nm filter

Ge photo-detector

O2(1) formation:

N2O +193 nm O(1D) + N2

O(1D) + N2O N2 + O2(1) ?

O(3P) + NO2 NO + O2(1) ?

O3 +248 nm O(1D) + O2(1)

O2(1) O2(3)+1268 nm

Branching fraction for O2(1) from O(1D)+N2O & O(3P)+N2O

3O

O2N

193

248a, I

I

E

E08.3

Typical temporal profiles of the 1268 nm emission intensities for the N2O photolysis experiment (IN2O) –PN2O=207 Torr, PAr=407 Torr and for the O3 photolysis experiment (IO3)- PN2=755 Torr, PAr=1.3 Torr

#IN2O

mV

IO3 mV E193

mJ

E248

mJ

a

12345

0.150.150.140.140.11

0.350.350.330.510.33

14.415.814.21611

11.211.211.218.411.2

1.030.941.030.971.05

YieldO(1D) + N2O N2 + O2(1) 100 %

O(3P) + NO2 NO + O2(1) <10 %

Quenching I(2P1/2) by О(3Р), О3

N2O + 193 нм N2 + O(1D)

O(1D) + N2O N2 + O2(1) NO + NO

O3 +248 nm O(1D) + O2(1)

O(1D) + CO2(N2) O(3P) + CO2(N2)

I2(X) + O(3P) IO+ I(2P3/2)IO + O(3P) O2(

3) +I(2P3/2)I(2P3/2) + O2(1) I(2P1/2) + O2(

3) I(2P1/2) + O(3P) I(2P3/2) +О(3P)I(2P1/2) + O3 products

I(2P1/2 ) I(2P3/2 )+ h (= 1315 nm)

Dashed lines are calculations at KO=1.210-11 cm3/sKO3=1.810-12 cm3/s

0.0000 0.0001

0.00

0.01

0.02

0.55

0.33

0.22

0.13

Time, sec

PO3

/Torr

=248 nm

E=22 mJ/cm2

0.067

Quenching I(2P1/2) by NO2, N2O4 & N2OCF3I + h (248 nm) CF3 + I(2P1/2) NO2=2.85x10-19 cm2

NO2 + h (248 nm) O + NO NO2=2x10-20 cm2

N2O4 + h (248 nm) NO2+ NO2 N2O4= 80NO2

O+ NO+NO2

KN2O4= (3.70.5)×10-13 cm3/sKNO2= (2.90.3)×10-15 cm3/sKN2O= (1.30.1)×10-15 cm3/s

0 20 40 60 80

0,0000

0,0005

0,0010

0,0015

t, sec

Em

isso

n in

tens

ity

at

268

nm

PAr

=92 Torr, PO2

=680 Torr

PAr

=200 Torr, PO2

=573 Torr

PAr

=305 Torr, PO2

=467 Torr

PAr

=250Torr, PO2

=521 Torr

calcul. calcul. calcul. calcul.

Temporal emission intensity of O2(1) at PO3=2.4 Torr, Ptot=773 Torr. Dashed lines are calculations at K=1.1x10-31 cm6/s.

0 20 40 60 80

0,000

0,001

t, sec

PAr

= 0 Torr, PO2

= 762 Torr

PAr

= 108 Torr, PO2

= 654Torr

PAr

= 249 Torr, PO2

= 513 Torr

calcul. calcul. calcul.

Em

issi

on in

ten

sity

at

600

nm

NO2 emission intensity near to 600 nm at PO3=2.4 Torr, PN2O=2.8 Torr, Ptot=762 Torr

Quenching of O2(a1) in the presence О2 and O(3P)

O3 +h(248 nm) O(1D) + O2(1) O(3P) + O2(X)O2(1) O2(3)+ h (1268 nm)

O(3P) + O2(1) + O2 O(3P) + 2O2

Conclusions

Standard dissociation model with v25 0.1 can not provide observed dissociation rates in COIL medium. About 20 molecules of O2(a) consumed to dissociate one I2 molecule if standard model is predominant dissociation pathway.

The total excitation probabilities of I2(X,v) in

reaction I* + I2 I + I2(X,v>10) are v25 0.1

and 10<v<25 0.9

I2(B) and takes a minor part in iodine dissociation and O2(b) does not play a noticeable role in I2(B) formationI2 dissociation pathway involving O2(b) state is not major channel

Measured kinetic constants:

I2(A) + CO2 I2(X) + CO2 (8.50.9)10-13 cm3/s

I2(A) + O2 I2(X) + O2 (6.00.6)10-12 cm3/s

I2(A) + I2 I2(X) + I2 (4.80.9)10-11 cm3/s

I2(A) + Ar I2(X) + Ar (2.70.3)10-14 cm3/s

О2(b) + CO2 О2(а) + CO2 (6.10.5)10-13 cm3/s

О2(b) + O3 products (1.90.2)10-11 cm3/s

I(2P1/2) + O(3P) I + O(3P) (1.2±0.1)10-11 cm3/s

I(2P1/2) + O3 products (1.8±0.4)10-12 cm3/s

I(2P1/2) + NO2 I + NO2 (2.9±0.3)10-15 cm3/s

I(2P1/2) + N2O4 I + N2O4 (3.7±0.5)10-13 cm3/s

I(2P1/2) + N2O I + N2 O (1.3±0.1)10-15 cm3/s

O2(a1) + O(3P) + O2 O(3P) + 2O2 (1.1±0.2)10-31 cm6/s

Yield of O2(a1) in reactionsO(1D) + N2O N2 + O2(

3) or O2(1) - 1±0.12

O(3P or 1D) + NO2 NО + O2(3) or O2(1) - < 0.1

Conclusions

O2(a,v=3)+I2(X)O2(X)+2I (97)O2(a,v=1)+I2(X,v15)O2(X)+2I (102)O2(a,v=2)+I2(X,v8) O2(X)+2I (103)O2(b) + I2(X) O2(X) + 2I (21)

Developed I2 dissociation model

I* + I2 I + I2(10<v<25) (33)I2(10<v<25)+O2(a)O2(X)+I2(A’,A)

(101)

O2(a,v=1)+I2(X)O2(X)+I2(A’) (95)O2(a,v=2)+I2(X)O2(X)+I2(A) (96)O2(a)+I2(A’,A) O2(X)+2I (25)

Potential energy curves of I2. The red and blue arrows show the excitation pathways of energy states lying bellow and above the I2 dissociation limit, respectively. The inscriptions above arrows denote the reaction producing excitation

Heidner et al. modelO2(a)+I2(X)O2(X)+ I2(20<v<45) (32)I2(20<v<45)+O2(a)O2(X)+2I (34) I* + I2 I + I2(25<v<45) (33)

Conclusions

A model that involves excitation of I2(A’,A) byreactionsO2(a,v=1)+I2(X)O2(X)+I2(A’) (95)O2(a,v=2)+I2(X)O2(X)+I2(A) (96)O2(a)+I2(A’,A) O2(X)+2I (25)I* + I2 I + I2(10<v<25) (33)I2(10<v<25)+O2(a)O2(X)+I2(A’,A) (101)yields results that are in reasonableagreement with the flow tube experiments.