PH 4807 – SPECTROSCOPY

Date : 18-04-2012 Dept. No. Max. : 100 Marks

Time : 1:00 – 4:00

PART – A

Answer ALL questions (10×2=20)

Explain with the help of an example for symmetric top and spherical top molecule
The rotational constant of NO is 41.7201 cm^-1. Calculate the moment of inertia of the molecule.
Explain Born-Oppenheimer approximation.
Bond length of N₂ molecule is 1.0907 . Determine the position of the first rotational Raman lines in the spectrum. Given mass of ¹⁴N = 23.25 x 10 ^-27
What is double resonance?
Distinguish between sequence and progression
An NMR signal for a compound is found to be 420 Hz downward from TMS operating at 600 MHz. Calculate shift in ppm.
Write a note on C¹³ spectroscopy with reference to chemical shift.
Distinguish between photoluminescence and fluorescence spectroscopy
Difference between inelastic scattering and elastic scattering

PART – B

Answer any FOUR questions (4×7.5 = 30)

Explain with example, the effect of isotopic substitution on the pure rotational spectra of a diatomic molecule. The first rotational line of ¹²C¹⁶O is observed at 3.8425 cm^-1 and that of ¹³C¹⁶O at 3.67337 cm^-1. Calculate the atomic weight of ¹² C, assuming the mass of ¹⁶O to be 15.9949 a.m.u.
Outline the theory of Raman spectrum on the basis of i) classical theory and ii) quantum theory
With a neat diagram, explain the functioning of ESCA briefly.
What is indirect spin-spin interaction? Explain why many spectral lines are seen in the CH₃ and CHO protons of acetaldehyde?
Explain the functioning of XPES

PART – C

Answer any FOUR questions (4×12.5 =50)

Explain with theory, the spectrum of a linear diatomic molecule of rigid rotor type. Deduce the correction for non-rigid type.
a) Explain the theory of diatomic vibrating rotator on the basis of Bohr’s approximation.
b) The fundamental band of CO is centered at 2143 cm^-1 and the first overtone band at 4259 cm^-1. Calculate fundamental frequency of vibration, anhormonicity constant and zero point energy.
Give the selection rules associated with rotational fine structure of electronic vibration spectra. Explain the origin of P,Q and R bands and derive the energy expressions associated with the bands
Illustrate the decay scheme in ⁵⁷Co and ⁵⁷ With a block diagram explain the working of Mossbauer spectrometer
Explain the following electron spectroscopic techniques.
a) Auger electron (AES) and b) Fluorescence (XRF)

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