Topography of potential-energy surfaces. Spin–orbit interaction for F + HF, Cl + HCl

Abstract

Potential-energy surfaces have been calculated for the F + HF and Cl + HCl reactions using the DIM (diatomics-in-molecules) method including spin–orbit interaction. The non-adiabatic coupling strength between the two lowest Ω= 1/2 potential-energy surfaces shows two maxima for motion along the minimum-energy pathway. One maximum occurs early in the entrance valley and the other late in the exit valley. These maxima depend more strongly on separation of the reactants or products than on motion of the H—X bond and are little altered on bending from the collinear configuration. However, rapid oscillatory motion of the H atom may enhance the non-adiabatic transition probability owing to multiple crossings of the region of interaction.