CI-RMBPT calculations of photoionization cross sections from quasi-continuum oscillator strengths

TL;DR

This paper introduces a new method to convert discrete oscillator strengths from CI-RMBPT calculations into photo-ionization cross sections, enabling accurate predictions for complex atoms with minimal code modifications.

Contribution

A novel conversion technique for CI-RMBPT oscillator strengths to photo-ionization cross sections is developed and validated on noble gases, enhancing accuracy over previous methods.

Findings

Good agreement with experimental data for Ne, Ar, Kr, Xe

RMBPT corrections significantly improve results for heavier noble gases

Method applicable to a wide range of multi-valence atoms and ions

Abstract

Many applications are in need of accurate photoionization cross-sections, especially in the case of complex atoms. Configuration-interaction relativistic many-body perturbation theory (CI-RMBPT) that has been successful in predicting atomic energies, matrix elements between discrete states, and other properties is quite promising, but it has not been applied to photo-ionization problems owing to extra complications arising from continuum states. In this paper a method that will allow the conversion of discrete CI-(R)MPBT oscillator strengths (OS) to photo-ionization cross sections with minimal modifications of the codes is introduced and CI-RMBPT cross sections of Ne, Ar, Kr, Xe are calculated. A consistent agreement with experiment is found. RMBPT corrections are particularly significant for Ar, Kr, and Xe and improve agreement with experiment compared to the particle-hole CI method. The demonstrated conversion method can be applied to CI-RMBPT photo-ionization calculations for a large number of multi-valence atoms and ions.