Relaxed excited states origin and structure in lead-doped caesium bromide

Absorption, emission and excitation spectra, polarization and decay kinetic s of luminescence and their temperature dependences have been studied at 4. 2-300 K for several CsBr:Pb samples with various lead concentrations. The o rigin and structure of the relaxed excited states responsible for the 3.33, 2.8 and 2.43 eV emission bands have been discussed. It has been concluded that the relaxed excited state model proposed for Tl+-doped caesium halides and CsCl:Pb is not valid in case of CsBr:Pb. To establish the origin of th e relaxed excited states in a CsBr:Pb crystal, the luminescence characteris tics of CsBr:Pb have been compared with those reported for Cs4PbBr6, PbBr2 and CsPbBr3 bulk crystals. It has been assumed that owing to a strong inter action between Pb2+ and Br- ions, the molecular-like states, which are simi lar to the excited levels of some stable lead-related compounds, are respon sible for the luminescence of CsBr:Pb crystals.