Electron-impact ionization of Fe⁸⁺

Institute of Theoretical Physics and Astronomy, Vilnius University, Saulėtekio av. 3, 10257 Vilnius, Lithuania
e-mail: ausra.kyniene@tfai.vu.lt

Received: 3 July 2018
Accepted: 29 January 2019

Abstract

Electron-impact ionization cross sections and Maxwellian rate coefficients are presented for the Fe⁸⁺ ion by considering processes from the ground and metastable levels. The lifetimes of the levels for the 3s² 3p⁵ 3d configuration were analysed using the extended basis of interacting configurations. Convergence of the cross sections for the indirect process due to excitations to the high-nl subshells was investigated. We demonstrate that excitations to the subshells with orbital quantum number l = 3 with subsequent autoionization dominate up to electron energies of ∼700 eV for the ground and metastable levels. Modelling of theoretical cross sections obtained for the ground and metastable levels to produce the best fit to the measurements shows that 15% of ions reach the reaction zone in the metastable state. The obtained results contradict the previous work that showed ∼30% for the metastable fraction.