Ab initio treatment of molecular Coster-Kronig decay using complex-scaled equation-of-motion coupled-cluster theory

TL;DR

This paper extends complex-scaled equation-of-motion coupled-cluster theory to accurately model molecular Coster-Kronig decay, providing detailed spectra and decay widths for argon and hydrogen sulfide, highlighting the importance of spin-orbit coupling.

Contribution

It introduces a novel ab initio method for Coster-Kronig decay using complex scaling, improving spectral predictions and revealing the impact of spin-orbit coupling.

Findings

Spectra agree well with experimental data

Discrepancies in branching ratios highlight spin-orbit effects

Method accurately computes decay widths and ionization energies

Abstract

Vacancies in the L1 shell of atoms and molecules can decay non-radiatively via Coster-Kronig decay whereby the vacancy is filled by an electron from the L2,3 shell while a second electron is emitted into the ionization continuum. This process is akin to Auger decay, but in contrast to Auger electrons, Coster-Kronig electrons have rather low kinetic energies of less than 50 eV. In the present work, we extend recently introduced methods for the construction of molecular Auger spectra that are based on complex-scaled equation-of-motion coupled-cluster theory to Coster-Kronig decay. We compute ionization energies as well as total and partial decay widths for the 2s-1 states of argon and hydrogen sulfide and construct the L1L2,3M Coster-Kronig and L1MM Auger spectra of these species. Whereas our final spectra are in good agreement with the available experimental and theoretical data, substantial disagreements are found for various branching ratios suggesting that spin-orbit coupling makes a major impact on Coster-Kronig decay already in the third period of the periodic table.