X-ray photoelectron spectroscopy studies of the electronic structure of the dihydrides and trihydrides of lanthanum and cerium

We analysed the valence band and the 3d and 4d core levels of LaHx (x = 0, 2.2, 2.9) and CeHx (x = 0, 2.1, 2.9) using X-ray photoelectron spectroscopy. A hydrogen-induced band around 5 eV is observed in all the hydrides. The density of states at EF is considerably reduced in the dihydrides and vanishes completely in the trihydrides in agreement with the transition from metallic to non-metallic behaviour. The cerium 4f level appears at 2 eV and is separated from the hydrogen-induced band for both cerium hydrides. The character and occupancy of the 4f levels of cerium is almost conserved in the hydrides as is confirmed by measurements of the magnetic susceptibility. The 3d core levels are shifted by 1.3 eV (LaH2.2), 2.9 eV (LaH2.9), 1.9 eV (CeH2.1) and 2.1 eV (CeH2.9) and exhibit intense satellites on the low binding energy side.