Theoretical studies of non-adiabatic processes in ion–molecule collisions: Ar+(2PJ)+ CO

Abstract

State-to-state cross-sections have been calculated for collisions of Ar⁺(²P_J) with CO at a relative energy of 2 eV. Charge transfer, fine-structure transitions and vibrational excitation processes have been observed. The computations have been made by means of the vibronic semiclassical method recently used by Parlant and Gislason for N₂⁺+ Ar collisions. The translational motion is treated classically, and the time-dependent Schrödinger equation is solved exactly for the vibronic states of the system. The potential-energy surfaces utilized are semiempirical, while the electronic couplings have been calculated by the method developed by Archirel and Levy. The charge-transfer couplings are found to be strongly anisotropic. Because of this anisotropy, the body-fixed approximation successfully used for the(ArN₂)⁺ system has been removed for studying Ar⁺+ CO collisions. The results for the total charge-transfer cross-section are in good agreement with experimental data. The populations of the CO⁺ product states appear to represent a compromise between energy resonance and Franck–Condon factors. In addition, the calculations show an unexpected participation of the A state of CO⁺.