A COMPARATIVE-ANALYSIS OF 2 METHODS FOR THE CALCULATION OF ELECTRIC-FIELD-INDUCED PERTURBATIONS TO MOLECULAR VIBRATION

Two common methods of accounting for electric-field-induced perturbati ons to molecular vibration are analyzed and compared. The first method is based on a perturbation-theoretic treatment and the second on a fi nite-field treatment. The relationship between the two, which is not i mmediately apparent, is made by developing an algebraic formalism for the latter. Some of the higher-order terms in this development are doc umented here for the first time. As well as considering vibrational di pole polarizabilities and hyperpolarizabilities, we also make mention of the vibrational Stark effect.