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 anal yzed 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 probabilit ies between various low-lying states of AsF are compared with analogou s 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 l ambda-s states are accurately reproduced in the relativistic CI and co mputed trends in the parallel and perpendicular b0+-X transition proba bilities for this group of fluorides are found to agree with the obser vations of Colin, Herman and Prevot. Inclusion of a semidiffuse s orbi tal on the fluorine atom is important in describing the sigma MO occu pied in the A 3PI and c1PI lambda-s states. Computed electric dipole m oments indicate that the latter states are more strongly polarized (ne gative F) than their lower-energy counterparts with pi2 electronic co nfigurations.