Theoretical treatment of Auger decay and related processes with non-Hermitian quantum chemistry

X-ray spectroscopies are of growing interest to different areas of chemical research. These techniques rely on the interaction of x rays with matter, which creates electronic states with core vacancies. A characteristic feature of these electronic states is their instability towards loss of electrons, which is termed Auger decay. Auger electron spectroscopy, which analyzes the emitted electron, enables a very detailed characterization of molecules and materials. However, theoretical modeling of molecular Auger electron spectra is difficult because standard electronic-structure methods are unable to describe the loss of electrons. This project aims to model experimental Auger electron spectra based on non-Hermitian quantum chemistry. The core-ionized and core-excited states that govern Auger decay shall be described using complex-variable equation-of-motion coupled-cluster methods. In particular, states above the absorption edge, which can decay through a one-electron process, shall be characterized for the first time.