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
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).