# introduction to spectroscopy_jgh lec

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Introduction to OrganicSpectoscopy

Dr. Joy Granada HofilenaAugust 7, 2010

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Review of Some BasicsReview of Some Basics c = R x P

Angular resolution: U = 1.22 P / D radians

E = h R

F = L / 4 T d2

AZ, El, RA, Dec, Ecliptic, Galactic

Siderial time, Hour AngleG = 6.67 x 10-8 (c.g.s)

c = 3 x 1010 cm/sec,

k = 1.38 x 10-16

h = 6.626 x 10-27

mH ~ mproton = 1.67 x 10-24 gramsme = 0.91 x 10

-27 grams

eV = 1.602 x 10-12 erg

Luminosity of Sun = 4 x 1033 erg/sec

Mass of the Sun = 2 x 1033 grams

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Light: PR- PR = c = 2.998 x 1010 cm/s (in vacuum)

- E = hR

Photon energy (erg)

1 erg sec-1 = 10-7 Watt

h = 6.626 x 10-27 (c.g.s)

1 eV = 1.602 x 10-12 erg

- p = E / c = h / PPhoton momentum- P = h / p = h / mv deBroglie wavelength

Planck Function: BR(T)

Emission, absorption, continua

Discrete energy levels: Hydrogen

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Telescope

Focal Plane

Slit

Spectrograph

SpectrographSpectrograph

collimator

Dispersing element

camera

detector

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Refraction:Refraction:

Snells Law: n1 sin(H1) = n2 sin(H2)

H2

H1 n1

n2

n1 = refractive index in region 1

n2 = refractive index in region 2

n = c / v = Pvacuum / Pmedium

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Diffraction:Diffraction:

Light spreads as U = P / dIn the far field given by L = d2 / P

d

L

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2 slit interference

Constructive

Destructive

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Types of Spectra:

Nebulae

Stars

Hot,

Opaquemedia

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EMR

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Valence electrons

Core electrons

Atoms/molecules

E&M radiation interacts with materials becauseelectrons and molecules in materials are polarizable:

(refraction, absorption)

= n+ i k

n = refraction, k= absorption

Ions, electrons and atoms incident on materials can interact with materials because

they are either charged or can scatter from atomic cores

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Techniques and information content

Molecular

Libration

(hindered rotations)

Molecular

vibrations

Electronic

Absorption

Valence band and

shallow electronic

levels (atoms)

Deep electronic

core levels (atoms)

Microwave,

THz

Infrared,

Raman,

EELSVisible

Fluorescence

Luminescence

UV absorption

UV photoemission

Electron lossX-ray photoemission

(XPS, ESCA)

Auger Electron (AES)

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No. of molecular vibrations:

Where : n = no. of atoms

C3H8= 3(11) - 6

= 27

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Fundamental vibrations

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Linear CO2

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For CH2groups

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Other linear molecules

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HookesL

aw

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Harmonic oscillator

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Energy curve of a vibrating bond:

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T

he IR

spectrum:

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A

nimations:

Introduction to IRspectroscopy

The theory of IRspectroscopy

Sample IRspectra of molecules

E:\Organic Chemistry Software\PC_IR_Tutor

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octane

CH3CH2CH2CH2CH2CH2CH2CH3

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CH3CH2CH2CH2C CH

1-hexyne

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sec-butyl alcohol

benzyl alcohol

A Comparison of Aliphatic and Aromatic Alcohols

CH3CHCH2CH3

OH

CH2-OH