Vibrational corrections to transition properties

The vibrational contributions to second-order transition properties are con sidered in the framework of the Born-Oppenheimer approximation. It is shown that the usual formula for vibrational second-order transition matrix elem ents is incomplete and needs to be supplemented by a term of purely vibrati onal origin. This pure vibrational contribution is calculated for vibration al transition polarizabilities in LiH and BeF and found to be quite signifi cant. Its inclusion in theoretically calculated data for the Raman intensit ies appears to be necessary.