Reflectance Measurements on Single Crystals of PbFCl, PbFBr, and PbBr₂

Abstract

Abstract The reflectance spectra of single crystals of PbFCl and PbFBr are measured between 2.8 and 6.5 eV at 84 and 295 K. The absorption spectra are calculated by Kramers‐Kronig transformation. Peaks at 4.55 and 5.13 eV in the absorption spectra of PbFBr and PbFCI, respectively, are attributed to cation exciton transitions. In the reflectance spectra of vacuum‐cleaved single crystals of PbBr 2 , which are measured at 84 K with different polarization directions, a new fine structure is observed. An interpretation is given based on an ionic model.