Feshbach-Fano approach for calculation of Auger decay rates using equation-of-motion coupled-cluster wave functions: Numerical examples and benchmarks

W. Skomorowski and A.I. Krylov
J. Chem. Phys. , submitted (2020)

X-ray photon absorption leads to the creation of highly excited species, which often decay through the Auger process. The theoretical treatment of Auger decay is challenging because of the resonance nature of the initial core-excited or core-ionized states and the continuous nature of the ejected electron. In a companion paper (Skomorowski, Krylov, submitted to J. Chem. Phys.), we have introduced a theoretical framework for computing Auger rates based on the Feshbach-Fano approach and the equation-of-motion coupled-cluster ansatze augmented with core-valence separation. The outgoing Auger electron is described with a continuum orbital. We considered two approximate descriptions---a plane wave and a Coulomb wave with an effective charge. Here we use the developed methodology to calculate Auger transition rates in core-ionized and core-excited benchmark systems (Ne, H2O, CH4, and CO2). Comparison with available experimental spectra shows that the proposed computational scheme provides reliable ab initio predictions of the Auger spectra. The reliability, cost-efficiency, and robust computational setup of this methodology offer advantages in applications to a large variety of systems.

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