Electronic structure of Gd hydrides studied by resonant Inelastic soft X-ray scattering

Spectacular changes in the optical and electrical properties were recently discovered in metal-hydride films of yttrium and lanthanum near their metal-insulator transitions: the dihydrides are excellent metals and the trihydrides are insulators and transparent in the visible part of optical spectrum. Such changes are best described by a model based on negatively charged hydrogen (H-) ions. We have studied the electronic structure of the similar Gd-H system by X-ray Absorption and Resonant Inelastic Soft X-ray Scattering (RIXS) Spectroscopies. During our measurements we found charge transfer excitations, which produce charge-transfer satellite systems. These satellites result support the view that hydrogen is an electron acceptor. (C) 2004 Elsevier B.V. All rights reserved.