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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
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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
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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
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Telescope
Focal Plane
Slit
Spectrograph
SpectrographSpectrograph
collimator
Dispersing element
camera
detector
8/3/2019 Introduction to Spectroscopy_JGH Lec
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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
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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
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2 slit interference
Constructive
Destructive
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Types of Spectra:
Nebulae
Stars
Hot,
Opaquemedia
8/3/2019 Introduction to Spectroscopy_JGH Lec
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EMR
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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
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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)
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N o. of molecular vibrations:
Where : n = no. of atoms
C3H8
= 3(11) - 6
= 27
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F undamental vibrations
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Linear CO2
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F or CH 2 groups
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Other linear molecules
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Hooke¶s L
aw
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Harmonic oscillator
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E nergy curve of a vibrating bond:
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T
he I R
spectrum:
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A
nimations:
Introduction to IR spectroscopy
The theory of IR spectroscopy
Sample IR spectra of molecules
E:\Organic Chemistry Software\PC_IR _ Tutor
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octane
CH3CH2CH2CH2CH2CH2CH2CH3
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8/3/2019 Introduction to Spectroscopy_JGH Lec
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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