Channel-specific core-valence projectors for determining partial Auger decay widths

ABSTRACT

Auger decay is a relaxation process of core-vacant states in atoms and molecules, in which one valence electron fills the core vacancy while a second one is emitted. These states pose a challenge to electronic-structure theory, because they are embedded in the ionisation continuum. Recently, we showed that molecular Auger decay can be described using complex-variable coupled-cluster (CC) methods and that partial widths and branching ratios can be computed based on a decomposition of the CC energy. Here, we introduce channel-specific core-valence projectors, dubbed Auger channel projectors, as a more general technique to evaluate partial widths from complex-variable treatments. We apply this new method to core-ionised states of neon, water, ammonia and methane using CC singles and doubles (CCSD), equation-of-motion ionisation potential CCSD and configuration interaction singles (CIS) wave functions. Even though a single CIS calculation can never describe all Auger decay channels at once, we show that a combination of CIS calculations based on different reference states is able to recover partial and total decay widths from CC calculations to an excellent degree.

GRAPHICAL ABSTRACT

KEYWORDS:

• Auger decay
• electronic resonances
• coupled-cluster
• configuration interaction singles
• electronic structure

Acknowledgments

F.M. thanks Garrette Pauley Paran, Anthuan Ferino Pérez, Valentina Parravicini and Jonas Nijssen for helpful discussions about point-group symmetry and for help in verifying the implementation.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

T.-C.J. gratefully acknowledges funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (Grant Agreement No. 851766). F. M. is grateful for a Kekulé fellowship (K 208/24) by the Fonds der Chemischen Industrie.