An ab initio study of the potential energy surfaces for the collision between a Cs atom and an I_2 molecule

摘要

For the Cs + I_2 collision system, a systematic theoretical study is first reported using the ab initio method. Three of eight possible channels are considered. The nonadiabatic coupling between the covalent state and the ionic one is calculated from different angles, especially the T-shape collision. The complete ion-pair formation potential energy surfaces of the T-shape collision in two electronic states (ionic ~2B_2 state and covalent ~2A, state) and the reactive surface of the linear collision are constructed at the QCISD(T)/SDD level. The main features of potential energy surfaces, such as the minimum energy reaction path, the crossing radius (R_c), and energy minimum geometries, are analyzed. The cross section of this titled system is calculated based on the harpoon mechanism and compared with the available experimental data and those obtained for the M + I_2 (M = Li, Na) systems.