Dielectric Properties of KCl, KBr, and KI Single Crystals in the Extreme Ultraviolet up to 35 eV

Abstract

AbstractThe reflectance of freshly cleaved single crystals of KCl, KBr, and KI has been measured for 15° angle of incidence at room temperature for photon energies between 5 and 35 eV, using the continuous spectrum of synchrotron radiation. For photon energies from 12 to 30 eV the optical constants, the dielectric constant, and the energy loss function were determined by reflectance measurements with parallel polarized light at several angles of incidence between 15° and 75°. A prominent doublet near 20 eV is found for all potassium halides. It is assigned to excitonic transitions from the K+3p core level to the conduction band at Γ and X. Energy differences between some critical points at Γ and X are estimated by comparing the position of the fundamental doublet and the K+3p doublet.