Effect of hydrogenation on the electronic state of metallic La hydrides probed by X-ray absorption spectroscopy at the La L-edges

We have investigated the effect of hydrogenation on La 5d and 6p electronic states in metallic LaHx (x = 0.0, 2.0, 2.3, and 2.6) by X-ray absorption near edge structure at the La L-edges. As the hydrogen content x increases from 0 to 2.6, white-line intensity at the La L2,3-edges shows a remarkable increase in the range of x>2.0. This is interpreted as the increase in La 5d hole induced by interstitial H atoms on the octahedral sites. On the other hand, the shoulder structure at the La L1-edge disappears in the process of x = 0.0rightarrow;2.0, indicating that the p-d hybridization is weakened by H atoms on the tetrahedral sites. This study demonstrates that H atoms on the two interstitial H sites provide different contribution to the modification of the electronic states.