Electron-impact ionization of Ar9+

Abstract

We have calculated total and single differential cross sections for electron-impact ionization of Ar9+ in its ground (1s22s22p5)2p0 state by using a method that combines the distorted-wave Born approximation and the R-matrix theory. The incident and the scattered electrons are described by distorted waves, while the wavefunctions of the initial ground state of the Ar9+ ion and its final continuum state (Ar10++e-) are calculated by using the R-matrix approach. This allows us to take into account the excitation-autoionization process. Five states of the final Ar10+ ion, namely 1s22s22p43P, 1D, 1S and 1s22s2p53P0, 1P0, have been included in our calculation. Up to the 24-pole components of the interaction with the ionizing electron were included, exciting ten distinct Ar9+ continuum symmetries. The single differential cross sections exhibit considerable structure due to autoionizing resonances. Total cross sections for production of Ar10+ in each of the five states are presented for impact energies from the threshold energy at 17.6 to 100 au. Our theoretical values for the total cross section are in fair agreement with the experimental results.