Electronic structure of RbBr during the phase transition: X-ray absorption near-edge structure analysis

The x-ray absorption near-edge structure (XANES) at the Br and Rb K edges in the low-pressure (B1) and the high-pressure phase (B2) of RbBr has been analysed. We have used a full multiple-scattering method to investigate the structure of the RbBr conduction band. Theoretical K-edge absorption spectra obtained over a large energy interval were used to analyse the experimental data. The XANES is found to be determined by the multiple scattering of the photoelectron in a large cluster (30 or more atoms). For an energy interval up to 50 eV above the main edge, the single-scattering approximation is found to be less satisfactory. Comparative analysis of the XANES of the two different crystal phases makes it possible to examine the role of local symmetry and the characteristics of neighbouring atoms around the absorbing site as well as the conduction band of RbBr.