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Tuesday, 14 August 2012

Molecular structure and spectroscopy-MSc/PhD model question paper

1(a) What are the different types of energies possessed by a molecule? Why the translational energy of a molecule is not quantized?   (4 Marks)
(b) Write a note on dipole transitions. (4 Marks)
(c) Explain Hund’s rule with examples. (6 Marks)
(d) A gas consisting of B2 molecules is found to be paramagnetic. What pattern of molecular orbitals must apply in this case? (6 Marks)
2 (a) Distinguish between proper and improper rotations. (6 Marks)
(b) State and explain the great orthogonality theorem. (6 Marks)
(c) Explain how the infrared activity of a vibrational mode is determined? (4 Marks)
(d) What symmetry in SF6 molecule is equivalent to C4(z) C2(x)? (4 Marks)
3 (a) What is centrifugal distortion? Explain the effect of centrifugal distortion on the moment of inertia and energy of a diatomic molecule. (8 Marks)
(b) Outline the importance of the study of quadrupole hyperfine interaction in microwave spectra. (8 Marks)
(c) Determine the revolutions per second by a CO molecule when J=3. The CO bond length is 0.1131 nm. (4 Marks)
4 (a) Explain the effect of anharmonicity on the vibrational spectra of diatomic molecules. (8 Marks)
(b) Explain in detail the mull and pellet techniques used for the recording of IR specta. (8 Marks)
(c) One of the fundamental vibration modes of H2O occurs at 3652cm-1. What would be the frequency of the corresponding mode in D2O? (4 Marks)
5(a) Explain mutual exclusion principle with example. (6 Marks)
(b) Why anti-Stokes lines are less intense than stokes line? (4 Marks)
(c) Outline the advantages of surface enhanced Raman scattering over normal Raman scattering. (6 Marks)
(d) The Raman line associated with a vibrational mode which is both Raman and infrared active is found at 4600Å when excited by light of wavelength 4358 Å. Calculate the wavelength of the corresponding infrared band. (4 Marks)
6 (a) State and Explain Frank-Condon principle. (6 Marks)
(b) What is predissociation? How would you account for it? (6 Marks)
(c) Explain the method of estimation of orbital energies of molecules by photoelectron spectroscopy. (4 Marks)
(d) When 40.81 eV radiation is used to produce photoelectron spectra of neon, photoelectrons of kinetic energy 19 eV have been emitted. Evaluate the ionization energy of these electrons in kJ/mol.  (4 Marks)
7 (a) Distinguish between spin lattice and spin-spin relaxations. (6 Marks)
(b) The ESR spectrum of an unpaired electron interacting with two equivalent protons shows three lines with intensities 1:2:1. Why? (6 Marks)
(c) Explain the principle of nuclear quadrupole resonance. (4 Marks)
(d)A free electron is placed in a magnetic field of strength 1.3 T. calculate the resonance frequency if g=2.0023. (4 Marks)
8 (a) What is isomer shift? Explain with examples. (4 Marks)
(b) How crystal symmetry is understood using Mössbauer studies? (6 Marks)
(c) Outline the principle of Doppler free two-photon spectroscopy. (6 Marks)
(d) A Mossbauer nucleus 57Fe makes the transition from the excited state of energy 14.4 keV to the ground state. What is its recoil velocity? (4 Marks)

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