Molecular Spectroscopy
Second year
Hilary Term 2004
Dr Frank Schreiber and Professor Brian Howard
10 lectures
This course concerns the spectroscopy of molecules, focussing on
isolated species in the gas phase, although some of the concepts are
applicable also to condensed matter problems. Lectures 1-6 concentrate on
the excitation of rotational and vibrational motion. Primary information
from the spectra obtained includes moments of inertia and hence bond
lengths and angles, bond force constants and dissociation energies, dipole
moments and hence electron distributions. In addition, in condensed matter
information about the orientation or the environment of the molecules is of
interest. Lectures 7-10 discuss electronic excitations, both of atoms and
of molecules. This course makes strong use of the material discussed in the
Quantum Mechanics course.
Synopsis and Handouts
- Introduction Handouts
Energy levels of molecules; Born-Oppenheimer separation; interaction of
radiation with matter; absorption; emission; transition moments;
selection rules
- Rotational Spectroscopy (Microwaves) Handouts
Rotors and their symmetry; moments of inertia; isotope effects;
centrifugal distortion; selection rules; Stark effect
- Vibrational Spectroscopy (Infrared) I Handouts for both
lectures (I and II) on vibrational spectroscopy
Selection rules; anharmonicity; rotation-vibration transitions; normal
mode vs. local mode
- Vibrational Spectroscopy (Infrared) II
overtone and combination bands; vibrational modes: individual molecules
vs. molecules in condensed phases
- Raman Spectroscopy Handouts
Stokes, Anti-Stokes and
Rayleigh scattering; rotational and vibrational transitions;
selection rules; mutual exclusion in centrosymmetric molecules;
Raman vs. IR
- Selected Topics Handouts
Experimental methods; effects
of nuclear spin statistics; applications and examples
- Atomic Spectroscopy I
Resumé of atomic spectroscopy. Wavefunctions. Atomic orbitals.
Hydrogen atom. Hydrogenic atoms. Helium atom. Alkali metals (and
pseudo-1-electron) atoms. The orbital approximation. SCF procedure.
Penetration and shielding. The quantum defect. Selection rules and
spectra. Determination of ionisation energies.
- Atomic Spectroscopy II
Many electron atoms. Russell Sanders coupling and j-j coupling. Term
symbols. Hund’s rules, selection rules and spectra.
- Molecular Spectroscopy I (Electronic)
Electronic energy levels. (Born Oppenheimer separation of energies).
Potential energy curves/surfaces. Description of diatomic (linear)
molecules. Classification of electronic states. Electronic selection
rules.
- Molecular Spectroscopy II (Electronic)
Vibrational structure. Franck-Condon Principle. Rotational structure in
electronic spectroscopy. Band heads Dissociation energies. Birge-Sponer
extrapolation. Predissociation.
Problems
Books
- J M Brown, Molecular Spectroscopy (OUP Primer 55)
- P W Atkins, Physical Chemistry
- P W Atkins / R S Friedman, Molecular Quantum Mechanics
- C N Banwell / E M McCash, Fundamentals of Molecular Spectroscopy
- J M Hollas, Modern Spectroscopy
- H Haken / H C Wolf, Molecular Physics and Elements of Quantum
Chemistry
- W Demtröder, Laser Spectroscopy
Contact
Questions, comments, and corrections are highly welcome. Please contact
frank.schreiber@uni-tuebingen.de