Dielectronic recombination on and electron-impact excitation of heliumlike argon

Abstract

We have measured cross sections for \ensuremath{\Delta}n=1 dielectronic recombination (DR) on He-like argon and found good agreement with theoretical calculations based on the Hartree-Fock atomic model. Experimental absolute cross sections were obtained by using the electron-energy dependence of yields of He-like and Li-like argon ions from the Kansas State University electron-beam ion source to measure the ratio of the DR cross section on He-like argon to the electron-impact-ionization cross section of Li-like argon and normalizing to the latter. The K x-ray emission spectra due to \ensuremath{\Delta}n=1,2 DR and n=1\ensuremath{\rightarrow}2 electron-impact excitation of He-like argon were also observed with a Si(Li) detector placed at 0\ifmmode^\circ\else\textdegree\fi{} relative to the electron-beam direction. By normalizing to the theoretical KLL integrated DR differential cross section, we obtained differential and partial differential DR cross sections and differential electron-impact excitation cross sections. We found good agreement with Hartree-Fock calculations for DR and with distorted-wave calculations for electron-impact excitation.