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
![](/cms/asset/d66fc575-5ab5-4d21-84ef-38144b980f73/tmph_a_2105270_uf0001_oc.jpg)
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).