Photoemission, x-ray absorption, and inverse-photoemission studies of valence-fluctuating Sm3Se4

Ultraviolet and x-ray-photoemission spectra (XPS) as well as x-ray inverse-photoemission [bremsstrahlung isochromat spectroscopy (BIS)] and x-ray-absorption spectra of valence-fluctuating Sm3Se4 are discussed to clarify its electronic structure. The constant initial state and constant final state spectra in the Sm 4d4f excitation region are quantitatively interpreted in terms of the 4d104f54d94f6 and 4d104f64d94f7 multiplet structures. The Sm 3d absorption spectra support the bulk valence fluctuation. The d94f5 and d94f6 multiplet structures are clearly resolved in the 4d XPS spectra. The effective hybridization of the Sm 4f states with the conduction-electron states is found to be large and much different for the 3d photoemission, 4d photoemission, and 4f BIS final states, resulting in the different intensity ratio of the Sm2+ and Sm3+ signals in these spectra. In addition, the surface core-level shift of the Sm 4f5 final state is evaluated as 0.5 eV.