Methods, algorithms and computer codes for calculation of electron-impact excitation parameters

TL;DR

This paper presents computer codes developed at Vilnius University for calculating electron-impact excitation parameters in ions, using multireference wavefunctions and different relativistic approaches, validated against known data.

Contribution

Introduction of two versions of electron scattering codes employing configuration interaction and Breit-Pauli approximation for complex ions, ensuring consistent data for plasma modeling.

Findings

Codes produce results consistent with experimental data

Accuracy validated for hydrogen, helium, lithium, and tungsten ions

Different relativistic approaches compared for improved precision

Abstract

We describe the computer codes, developed at Vilnius University, for the calculation of electron-impact excitation cross sections, collision strengths, and excitation rates in the plane-wave Born approximation. These codes utilize the multireference atomic wavefunctions which are also adopted to calculate radiative transition parameters of complex many-electron ions. This leads to consistent data sets suitable in plasma modelling codes. Two versions of electron scattering codes are considered in the present work, both of them employing configuration interaction method for inclusion of correlation effects and Breit-Pauli approximation to account for relativistic effects. These versions differ only by one-electron radial orbitals, where the first one employs the non-relativistic numerical radial orbitals, while another version uses the quasirelativistic radial orbitals. The accuracy of produced results is assessed by comparing radiative transition and electron-impact excitation data for neutral hydrogen, helium and lithium atoms as well as highly-charged tungsten ions with theoretical and experimental data available from other sources.