Principles of Spectroscopy

Uncertainty relation and natural line width, natural line broadening, doppler line broadening, pressure broadening, saturation broadening, removal of line broadening. signal-to-noise ratio, resolving power, intensity of spectral lines – transition probability, population of states, path length of sample. General components of an absorption experiment in various regions, dispersing elements, basic elements of practical spectroscopy, Born-Oppenheimer approximation: Rotational, vibrational and electronic energy levels in molecules, selection rules and their derivations, Fourier Transform methods (IR and NMR).

Classification of molecules, linear triatomic molecule, intensities, energy levels and rotational spectra of symmetric top molecules, Stark effect, nuclear and electron spin interaction, effect of external field, applications.

Vibrational energies of diatomic molecule, anharmonicity, vibrational-rotational spectroscopy, P, Q, R branches, breakdown of Born-Oppenheimer approximation, selection rules, vibrations of poly atomic molecules, normal mode of vibrations, skeletal vibrations, group frequencies, overtones, hot bands, fermi resonance bands, factors affecting the band positions and intensities.

Raman spectroscopy: Classical and quantum theories of Raman effect, molecular polarizability, selection rules, rotational Raman spectra-linear molecules, symmetric top and spherical top molecules, vibrational Raman spectra and rotational-vibrational Raman spectra of diatomic molecule, mutual exclusion principle, polarized and depolarized Raman spectra.

Resonance Raman Spectroscopy, Coherent Antistokes Raman Spectroscopy CARS (an elementary idea).

Atomic spectroscopy: Energy of atomic orbitals, vector representation of momenta and vector coupling (orbital and spin coupling), term symbols, spectra of hydrogen atom, alkali metal atoms, helium, alkaline earth metals and polyelectronic atoms.

Molecular spectroscopy: Energy levels, molecular orbitals- homonuclear and heteronuclear diatomic molecules, vibronic transitions, progression and sequences, derivation of Franck-Condon principle, dissociation and pre-dissociation. Electronic spectra of polyatomic molecules: AH₂ type molecules, formaldehyde and benzene. Emission spectra, radiative and non-radiative decay, internal conversion.

Larmor precession, mechanism of spin-spin and spin-lattice relaxations and quantitative treatment of relaxations, quantum mechanical treatment of A₂ system_, AB system and AX system, selection rules and relative intensities of lines.