Electron-impact ionization in the xenon isonuclear sequence

The distorted-wave approximation and electron-ion crossed beams have been employed to complete a theoretical and experimental study of electron-impact ionization along the Xe isonuclear sequence. Experimental results are given for Xe²⁺ through Xe⁶⁺ and the results of theoretical calculations are presented for Xe⁺ through Xe⁶⁺. The data reveal large contributions due to indirect ionization processes. Theoretical cross sections include the contributions of inner-shell excitations to autoionizing levels of the types Xeq+(4d¹⁰5s²5p^6-q)→Xeq+(4d⁹5s²5p^7-q) and Xeq+(4d¹⁰5s²5p^6-q)→Xeq+(4d⁹5s²5p^6-qnl) with nl=4f,5d,and 5f. Hartree-Fock structure calculations for the 4d⁹5s²5p^6-qnf configurations are highly term dependent and this has a pronounced effect on the magnitude and energy dependence of indirect contributions to the cross sections. Model calculations indicate that resonant-recombination double autoionization also contributes to the ionization cross sections of Xe²⁺ through Xe⁵⁺.