The R-matrix method for electron impact ionisation

Abstract

The R-matrix method has been extended to enable electron impact ionisation processes to be studied. A 'fast' ionising electron is described by a distorted wave and both the initial target state as well as the continuum state consisting of the final ion and a 'slow' ejected electron, are expanded in terms of an R-matrix basis. The method is programmed for a general atomic system and some test calculations for total cross sections including ionisation plus simultaneous excitation are presented for electron impact ionisation of neutral helium.