Revisiting the CeO Anion Photoelectron Spectrum: Resolving the Assignment and Photodetachment Mechanism of Satellite Transitions

Abstract

CeO serves as an important model system for understanding the interplay of electron correlation, spin-orbit coupling, and 4f/5d configurational mixing in lanthanide oxides. Its anion photoelectron spectrum exhibits dense electronic manifolds and multielectron shake-up processes that complicate spectral assignments and photodetachment dynamics. Here, we combine high-resolution anion photoelectron spectroscopy with spin-free and spin-orbit-coupled CASSCF+NEVPT2 calculations to characterize the electronic structure of CeO- and CeO. A binning-based data analysis approach enables observation of weak transitions hidden by spectral congestion, while multireference calculations reproduce the low-lying electronic structure and detachment energetics. On this basis, tentative assignments are proposed for the observed photoelectron features. Analysis of photodetachment selection rules, photoelectron angular distributions, and multielectron detachment channels provides additional insight into the mechanisms underlying the spectrum. These results establish a comprehensive interpretation of the CeO- photoelectron spectrum and underscore the importance of combining high-resolution spectroscopy with multireference relativistic theory for electronically complex lanthanide systems.