X-ray photoelectron-spectroscopy study of oxides of the transuranium elements Np, Pu, Am, Cm, Bk, and Cf

Abstract

Systematic x-ray photoelectron spectroscopy (XPS) measurements are reported for both core and valence electrons for oxides of the actinides thorium, uranium, neptunium, plutonium, americum, curium, berkelium, and californium. The XPS spectra of the localized $5f$ electron states were compared to the appropriate multiplet calculations for the neutral atom. Agreement between theory and experiment was generally good but substantial solid-state broadening of the oxide spectra limited the capability for comparing detailed spectral features. Binding energies of several prominent core lines are systematically presented as a function of atomic number for the series of actinide oxides. Comparisons are made between the measured energies and the corresponding calculated energies reported by other investigators. Anomalous core-level spectra (most notably the $5d\text{'}\mathrm{s}$), which probably result from coupling of the hole-state magnetic moment with the moment of the unfilled $5f$ shell, are presented.