Ultraviolet photoelectron spectra of rubidium halides

Energy distributions of photoelectrons from evaporated films of rubidium halides were measured in the photon energy range 10-27 eV. Density-of-states structures above the vacuum level are observed for all rubidium halides. Valence-band photoelectron spectra indicate splittings of 0.5 ±{} 0.2 and 1.0 ±{} 0.2 eV in the Br^- $4p$ and I^- $5p$ bands, respectively. Density-of-states calculations using a Slater-Koster interpolation in RbCl and a relativistic tight-binding interpolation scheme in RbBr and RbI were performed and the results are in reasonable agreement with the observed valence bandwidths and spin-orbit splittings. In the Rb⁺ $4p$ core spectra, a spin-orbit splitting of 0.9 ±{} 0.3 eV can be seen. The total width of the Rb⁺ $4p$ core spectrum of RbF is found to increase with temperature in accordance with the model of phonon broadening.