Abstract
The reflection spectra of RbCl, RbBr and RbI single crystals were investigated for temperatures between 300K and 8K in order to study excitations from the Rb+4p level (+ 4p level. They are discussed in the light of predictions of a recent model for the Rb+ 4p excitons based on ligand field theory. The continuum transitions associated with the valence band and the Rb+ 4p level show characteristic structure which is compared with calculations of the joint density of states.