COUPLED WAVEPACKETS STUDY OF THE DYNAMICS OF A MODEL ION-MOLECULE CHARGE-EXCHANGE

The dynamics of the ion-molecule charge exchange process A + BC+ --> A(+) + BC is investigated in a semiclassical framework. The treatment makes use of a semiclassical approximation whereby the collisional motion evolves along a classical trajectory, whereas the vibrational wavefunctions associated with each electronic state are treated quantally. The wavefunctions are defined over a grid and their time evolution is handled numerically. Besides its ability to solve the collision equations, the wavepacket method is shown to provide a useful physical picture of the collision. The goal of this paper is to put forward the basic characteristics of charge exchange processes in term of coupled wavepackets dynamics. In order to do that, a very simple model case has been investigated in the frame of the impact parameter approximation. This model provides deep physical insight into the dynamics of the process, especially in the intermediate energy domain where the non-adiabatic transitions are neither vertical, nor horizontal.