AN IMPROVED DIPOLE-MOMENT MODEL FOR THE INTENSITIES OF THE VIBRATIONAL ABSORPTION OF XY4 NEAR THE LOCAL MODE LIMIT

A bond-bond coupling dipole model is discussed for the absorption of t he local-mode vibrations of XY4 (Y=H, D). In this model the interactio n between individual bonds is considered and cross terms occur in the dipole moment, The general forms of the coupling parameters alpha(ii), beta(ij), chi(ij) for XY4 are reported and their values for the molec ules (X=Si, Ge) are calculated. This model is tested with experimental intensity data for silane and germane, and the results agree. The rea son for the (3000) band of silane or (4000) band of germane being much weal;er than the (2100) band of silane or (3100) band of germane can be explained with this model. (C) 1997 Published by Elsevier Science B ,V.