Completeness of an adiabatic expansion using reaction coordinates to describe rearrangement processes in ion–atom collisions: application to the C4+ + H system

Abstract

It is recalled that when using an adiabatic basis χi set to describe inelastic and rearrangement processes in ion–atom collisions, it is important to specify the coordinate system in which the adiabatic separation of the variables is performed. In this work, a numerical test, requiring a direct calculation of nonadiabatic matrix elements of the form , is proposed to asses the completeness of any specific finite adiabatic basis. Results are presented using a minimal basis set needed to describe the three main electron-capture channels in collisions of C4+ ions with neutral H atoms. Completeness is not obtained with any of the Jacobi coordinate systems. On the other hand, completeness of the minimal basis set is satisfactory when appropriate reaction coordinates are used.