Potential energy surfaces for F-H-2 and Cl-H-2: Long-range interactions and nonadiabatic couplings

The intermediate and long-range behavior of the three lowest doublet potent ial energy surfaces for the F(P-2(j))H-2 and Cl(P-2(j))-H-2 systems has bee n studied, using a harmonic expansion of the potential, where the dependenc e on the relative orientation of the half-filled orbital of the open-shell atom and the molecular axis has been given in terms of bipolar spherical ha rmonics, whereas the coefficients modulate the effect of the variation of t he intermolecular distance. The contribution of van der Waals, electrostati c, and charge-transfer interactions to the strength and the intermolecular distance dependence of each radial term are derived from previous molecular beam scattering experiments and from correlation formulas. The latter prov ide the link of these quantities to basic properties of the interacting par tners. Besides describing elastic and inelastic channels, these surfaces al so provide accurate information on the entrance channel for reactions.