Spectroscopy and Statistical Thermodynamics

Pre requisite: Interaction of electromagnetic radiation with matter. Characterization of

electromagnetic radiation, quantisation of energy, regions of the spectrum

Representation of spectra, basic elements of practical spectroscopy, signal-to-noise ratio – resolving power, line width – natural line broadening,Doppler broadening, Heisenberg uncertainty principle; intensity of spectral lines –transition probability, population of states, path length of sample; Born-Oppenheimer approximation; rotational, vibrational and electronic energy levels in molecules; transition moment, selection rules, Fourier Transform methods (IR and NMR)

Interaction of electromagnetic radiation with molecules and various types of spectra; Born-

Oppenheimer approximation.

Rotation spectroscopy: Selection rules, intensities of spectral lines, determination of bond

lengths of diatomic and linear triatomic molecules, isotopic substitution.

Vibrational spectroscopy: Classical equation of vibration, computation of force constant, amplitude of diatomic molecular vibrations, anharmonicity, Morse potential, dissociation energies, fundamental frequencies, overtones, hot bands, degrees of freedom for polyatomic molecules, modes of vibration, concept of group frequencies.

Raman spectroscopy: Qualitative treatment of Rotational Raman effect; Effect of nuclear spin,

Vibrational Raman spectra, Stokes and anti-Stokes lines; their intensity difference,

Electronic spectroscopy: Franck-Condon principle, electronic transitions, singlet and triplet states, fluorescence and phosphorescence, dissociation and predissociation.

Introduction, quantum mechanical aspects, common terms- canonical ensemble, occupation number, statistical weight factor, configuration, phase space, macroscopic state, microscopic; state, system, assembly and ensemble; statistical equilibrium, Boltzmann distribution law,  type of statistics, Bose-Einstein statistics, Fermi-Dirac  statistics.

Partition Function :Molecular partition function for an ideal gas, translational partition function, rotational partition function, vibrational partition function, electronic partition function, nuclear partition function

Internal energy, enthalpy, entropy, helmholtz function, pressure, Gibbs functions, residual entropy, chemical potential, heat capacity of mono and diatomic gases.