The emission of an Auger electron is the predominant decay process of core-vacant states in molecules composed of light nuclei. Auger decay is thus of great importance for all scientific fields where core-vacant states play a role, in particular X-ray spectroscopies. However, modeling this process theoretically from first principles represents a challenge for quantum chemistry due to the unbound character of core-vacant states. In this work, we present a new computational approach for Auger decay rates based on the combination of complex scaling and coupled-cluster theory. As we illustrate in some applications to H2O, N2, and C6H6, our method delivers excellent results for total decay widths and branching ratios of molecular core-vacant states and does not require any a priori assumptions about the wave function of the emitted Auger electron. Our analysis shows that complex-scaled wave functions of Feshbach resonances such as core-vacant states differ in many ways from those of shape resonances.

Molecular auger decay rates from complex-variable coupled-cluster theory

ACS Spring 2022

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