Optical properties of caesium iodide in the vacuum ultraviolet

Abstract

Polished crystals of CsI were placed in an ultra-high vacuum reflectometer in which the near-normal incidence reflectivity could be measured in the spectral range from 4 to 11 eV, while the crystals were maintained at temperatures between 25 and 300K. In this energy range the optical properties are dominated by excitonic states in the material, which are found to conform in general to those predicted from the energy band system calculated by Onodera (1968), although some minor modifications are suggested by the presence of three doublets found in the reflection spectrum in the vicinity of 8 eV.