In this course, molecular spectroscopy techniques which study interactions of electromagnetic radiation (ranging from microwave to X-ray frequencies) with molecules will be explained.

Optical properties of molecules and their study will be highlighted with magnetic properties and interactions forming another full fledged course.

In the microwave region, molecular rotational spectra under various rigid rotor approximations such as symmetric, spherical and asymmetric tops will be considered in detail following which the failure of rigid rotor model will be discussed. In the infrared region, molecular vibrational motion will be studied in detail. Both harmonic and anharmonic models will be included.

Normal modes of molecular vibration will be analysed using molecular point group theory. Spectra due to scattering of light which forms an important complement to absorption spectroscopy and known as Raman effect and rotational-vibrational Raman spectra will be explained.

In the visible and uv region, electronic spectra of polyatomic molecules will be analyzed. Electronic spectra are very rich and complicated to analyze and a few basic concepts such as Jablonski diagram, Jahn-Teller and Renner-Teller effect will be examined.

In the UV and X-ray region, elementary concepts of photoelectron, Auger and X-ray fluorescence and their application to surface chemistry will be introduced. Spectroscopic techniques for characterizing surfaces will be covered as a separate topic in the NPTEL project.

Module No.

Topic/s

Lectures

1

Introduction to electromagnetic radiation and its interaction with atoms and molecules - absorption, emission, stimulated emission, time dependent quantum mechanics, line broadening and line widths.

5

2

Angular momentum in quantum mechanics and molecular rotation, Euler angles, operators associated with rotations, molecular rotational (microwave) spectroscopy - diatomic molecules, centrifugal effects, spin statistics, line intensities and dipole moments. Polyatomic molecular rotational spectroscopy, centrifugal distortion, asymmetric tops, selection rules.

5-8

3

Diatomic molecular vibrational spectroscopy, Harmonic and anharmonic vibrations, wave functions, selection rules, Morse oscillator, vibrational motion in polyatomic molecules- normal modes, visualization of normal modes of polyatomic molecules, the Wilson F matrix, internal coordinates, Wilson GF matrix, diagonalization.

8-10

4

Group theory -The symmetry of normal modes of vibrations. Direct product representations selection rules. An introduction to molecular symmetry groups (permutation- inversion groups). Vibrational analysis of benzene as an example to illustrate principles of group theory.

5-8

5

Raman spectroscopy. Theory of Rayleigh and Raman scattering, classical and quantum models. Rotational Raman effect and an analysis of molecular electric polarization tensor –vibrational Raman effect. Rotational-vibrational transitions from both IR spectroscopy and Raman spectroscopy.

5

6

Electronic spectroscopy of diatomic and polyatomic molecules. Vector coupling of angular momenta. Russell- Saunders and J - J coupling. Molecular term symbols.

The Franck - Condon principle, Deslanders tables and dissociation energies. Symmetry of diatomic levels and parity (Gerade / Ungerade). Walsh‘s rules in qualitative MO. Theory. Huckel MO theory. Jahn - Teller and Renner - Teller effects. Non - radiative Transitions and Jablonski diagram.

6-8

7

Photoelectron, Auger and X-ray fluorescence spectroscopy. Introduction and a few examples.

3-4

8

Laser spectroscopy and applications, Introduction to lasers, molecular beams. Optical pumping and double resonance. Quantum beats, photon echoes and free induction decay, applications in laser induced chemical reactions and coherent control, femtosecond chemistry and laser Raman spectroscopy.

3-5

Introductory Quantum mechanics as can be found in the NPTEL site. In particular, postulates of quantum mechanics, elementary and exactly solvable model systems, harmonic oscillator Schrodinger equation and details of its solution, familiarity with separation of variables and simplification of hydrogen atom Schrodinger equation and its solution, an understanding of the mathematical properties of hydrogen atomic orbitals, Legendre, Hermite and Laguerre polynomials.

Elementary matrix algebra and calculation of eigenvalues and eigenvectors of Hermitian and unitary matrices, inverses of matrices.

Born-Oppenheimer approximation and perturbation and variation method. Elementary group theory ( molecular symmetry and construction of character tables for molecular point groups using
Great Orthogonality theorem).

The list here is merely suggestive and possibly representative. There are many other good books and course materials as well.

P. F. Bernath, Spectra of Atoms and Molecules (Second Edition), Oxford University Press, 2005.

I. N. Levine, Molecular Spectroscopy, Wliey-Interscience, New York, 1975.

E. B. Wilson Jr., J. C. Decius and P. C. Cross, Molecular Vibrations, Dover Publications, New York, 1980

J. M. Hollas, Modern Spectroscopy (Fourth Edition), John Wiley & Sons, New York, 2004.

J. I. Steinfeld, Molecules and Radiation, Dover, New York, 1986.

D. C. Harris and M. D. Bertolucci, Symmetry and Spectroscopy: An Introduction to Vibrational and Electronic Spectroscopy, Dover, New York, 1989

H. W. Kroto, Molecular Rotation Spectra, Dover, New York, 2003

W. Demtroder, Laser Spectroscopy (Third Edition), Springer, Berlin, 2003.

Helene Lefebvre-Brion and R. W. Field, The Spectra and Dynamics of Diatomic Molecules, Elsevier, Amsterdam, 2004

J. R. Lakowicz, Principles of Fluorescence Spectroscopy, Kluwer Academic, New York, 1999.

W. Gordy and R. L. Cook, Microwave Molecular Spectra, Wiley, New York, 1984.

Important: Please enable javascript in your browser and download Adobe Flash player to view this site
Site Maintained by Web Studio, IIT Madras. Contact Webmaster: nptel@iitm.ac.in