introduction to spectroscopy_jgh lec

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 1/26

 Introduction to OrganicSpectoscopy

Dr. Joy Granada HofilenaAugust 7, 2010

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 2/26

R eview of Some BasicsR eview of Some Basics c = R x P

Angular resolution:  U = 1.22 P / D radians

206,265´ in a radian

E = h R

F = L / 4 T d2

AZ, El, R A, 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 ~ m proton = 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

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 3/26

The Physics of EM R adiationThe Physics of EM R adiation

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

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 4/26

Telescope

Focal Plane

Slit

Spectrograph

SpectrographSpectrograph

collimator 

Dispersing element

camera

detector 

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 5/26

R efraction:R efraction:

Snell¶s 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

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 6/26

Diffraction:Diffraction:

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

d

L

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 7/26

2 slit interference

Constructive

Destructive

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 8/26

Types of Spectra:

 Nebulae

Stars

Hot,

Opaquemedia

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 9/26

 EMR

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 10/26

 Materials responseto radiation or particles

Valence electrons

Core electrons

Atoms/molecules

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

(refraction, absorption)

ñ= 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

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 11/26

T echniques 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)

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 12/26

 N o. of molecular vibrations:

Where : n = no. of atoms

C3H8

= 3(11) - 6

= 27

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 13/26

 F undamental vibrations

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 14/26

 Linear CO2

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 15/26

 F or CH 2 groups

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 16/26

Other linear molecules

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 17/26

 Hooke¶s L

aw

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 18/26

 Harmonic oscillator 

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 19/26

 E nergy curve of a vibrating bond:

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 20/26

T 

he I  R

spectrum:

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 21/26

 A

nimations:

Introduction to IR spectroscopy

The theory of IR spectroscopy

Sample IR spectra of molecules

E:\Organic Chemistry Software\PC_IR  _ Tutor 

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 22/26

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 23/26

octane

CH3CH2CH2CH2CH2CH2CH2CH3

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 24/26

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 25/26

CH3CH2CH2CH2C CH

1-hexyne

8/3/2019 Introduction to Spectroscopy_JGH Lec

http://slidepdf.com/reader/full/introduction-to-spectroscopyjgh-lec 26/26

 sec-butyl alcohol 

benzyl alcohol 

A Comparison of Aliphatic and Aromatic Alcohols

CH3CHCH2CH3

OH

CH2-OH