A theoretical framework for computing Auger spectra that include spin-orbit interaction is presented. The framework is based on the state-interaction approach using equation-of-motion coupled-cluster wave-functions. The working equations for Auger decay rates are derived within the Feshbach-Fano formalism. The capabilities of the theory are illustrated by the calculation of L-edge Auger spectra of H2S and Ar using the Feshbach-Fano and complex basis function (CBF) approaches. The quality of the Feshbach-Fano results depends critically on the treatment of the free-electron state. In contrast to the K-edge spectra for which both plane wave and Coulomb wave treatments yield reasonable results, the Feshbach-Fano calculations yield accurate results for L-edges only when using Coulomb wave (FF-CW). The FF-CW and CBF calculations of Auger spectra in H2S and Ar agree well with each other and with the available experimental data. The results highlight the importance of spin-orbit interactions for modeling L-edge Auger spectra.
Jayadev et al. (Mon,) studied this question.