Molecular Vibrations

Abstract

Elastic vibration of a molecule is another area where point groups and their representations find good applications. The symmetric structure of molecules allows classification of normal vibration modes according to irreducible representations of the symmetry group of the molecule without explicit knowledge of the force constants. In this chapter, we begin with the elementary theory of normal vibration modes, then study how group representation theory can be applied to the normal modes, and finally consider selection rules associated with infrared and Raman processes as well as interaction of electrons with atomic displacements.