THE CALCULATION OF THE CHANGE IN VIBRATIONAL FREQUENCY DUE TO CHANGES IN MASS, GEOMETRY, AND POTENTIAL CONSTANTS OF A MOLECULE

Abstract

An expression for the change in vibrational frequency in terms of changes in the kinetic and potential energy of a molecule has been derived.For numerical calculations approximations are given. The change in frequency due to configurational changes has also been estimated in a qualitative manner. Finally, an approximate relation between the frequencies observed for a certain symmetry type and those calculated by means of force constants derived from some other symmetry type is given as an aid in assigning vibrational spectra.