USE OF RELATIVISTIC CORE POTENTIALS TO COMPUTE POTENTIAL CURVES AND LIFETIMES OF LOW-LYING STATES OF ARSENIC FLUORIDE

The effects of spin-orbit coupling and other relativistic interactions on the electronic structure of the arsenic fluoride molecule are analyzed with the aid of ab initio configuration interaction calculations based on effective core potentials. The computed results for potential curves. vibrational wavefunctions and radiative transition probabilities between various low-lying states of AsF are compared with analogous data for the fluorides of the heavier Group V(A) atoms, antimony and bismuth. Measured spin-orbit splittings for the X 3SIGMA- and A 3PI lambda-s states are accurately reproduced in the relativistic CI and computed trends in the parallel and perpendicular b0+-X transition probabilities for this group of fluorides are found to agree with the observations of Colin, Herman and Prevot. Inclusion of a semidiffuse s orbital on the fluorine atom is important in describing the sigma* MO occupied in the A 3PI and c1PI lambda-s states. Computed electric dipole moments indicate that the latter states are more strongly polarized (negative F) than their lower-energy counterparts with pi*2 electronic configurations.