Vibrational spectroscopy of diatomic molecules in static electric fields: An a b i n i t i o study of HF

Abstract

For the specific case of the hydrogen fluoride molecule, a detailed determination of the vibrational effects on molecular electrical properties has been made for the lowest four vibrational states. Electrical properties at fixed H–F distances obtained from correlated and SCF-level ab initio treatments were used along with an ab initio potential energy curve to describe the vibrating system. Using numerical vibrational wave functions, the electrical properties of the low-lying vibrational states were rigorously calculated by finite differences and these are compared with values obtained with certain approximate means. One and two-photon, dipole, and quadrupole absorption cross sections were calculated in the same manner. The extensive incorporation of electrical properties and the detailed treatment of the vibrational states provides certain fundamentally new information on (i) the role of vibrational motion in dipole and other types of transitions, and (ii) the effect of external electrical fields on vibrational effects.