“…Ce can be found in the 4+ formal oxidation state in some nonmolecular, extended solids such as Cs 2 CeCl 6 and other binary halides, − CeO 2 , Ce(SO 4 ) 2 , and [NH 4 ] 2 [Ce(NO 3 ) 6 ], , among others . These materials have been the subject of numerous synchrotron-radiation-based spectroscopy experiments, including X-ray photoelectron spectroscopy, resonant inelastic X-ray scattering, and X-ray absorption (XAS) spectroscopies at the Ce L 3 -, ,,− M 5,4 -, ,,− and N 5,4 -edges, as well as ligand K-edges. , Some of these studies have presented evidence for the importance of both 4f- and 5d-orbital contributions to the covalency in Ce bonding. ,,− Extended solids including CeO 2 have also served as important test cases for evaluating whether accurate theoretical methodology can treat the 4f electrons simply as part of the core or whether a more demanding approach should be followed that allows the 4f electrons to delocalize and participate in bonding. − Ce intermetallics have been at the forefront of condensed matter physics and development of the Anderson impurity model for heavy Fermion systems and Kondo insulators . For example, Ce L 3 - and M 5,4 -edge X-ray absorption near-edge structure (XANES) spectroscopic investigations of CeRu 3 , CeRh 3 , and CePt 3 have provided evidence for 4f-electron delocalization, ,,, and L 3 -edge investigations of intermetallics such as CeCoIn 5 have led to a new understanding of their remarkable magnetic and superconducting properties. − The pace of synthetic, experimental, and theoretical progress has been impeded recently because of sample purity concerns, u...…”