Electronic Structure of the Thorium Hydrides Th${\mathrm{H}}_2$ and ${\mathrm{Th}}_4$${\mathrm{H}}_{15}$

Photoelectron spectroscopy using synchrotron radiation has been used to study the electronic structure of single-phase stoichiometric Th${\mathrm{H}}_2$ and ${\mathrm{Th}}_4$ ${\mathrm{H}}_{15}$. Th-derived conduction bands are observed together with lower-lying hybridized bonding bands. For ${\mathrm{Th}}_4$ ${\mathrm{H}}_{15}$, a narrow $d$-like conduction band (∼0.6-eV full width at half-maximum) separated from other bands by a 2-eV band gap is seen. Energy-dependent cross-section measurements for the various bands have been used to determine hybridization and angular momentum character.