Probing the local electronic structure in the H induced metal-insulator transition of Y

The occupied acid unoccupied valence band states of yttrium (Y) metal, Y di hydride and Y trihydride were measured by soft x-ray emission and absorptio n spectroscopy. The experiments were complemented by first principles calcu lations. Both experiments and theory reveal the metallic character of Y and YH2 whereas YH3-delta exhibits a band gap, which was experimentally determ ined to be 2.5 eV. The results reveal strong hybridization between H and Y states, causing a breakdown of the rigid band model description.