RES structure of Bi3+ centres in KCl:Bi,S and CaO:Bi crystals

Emission, excitation, and polarization spectra as well as decay kinetics are studied at 4.2 to 500 K for the luminescence of Bi3+ centres in two crystals (KCl and CaO) with strongly different electron-phonon interaction. It is concluded that three bands at approximate to 2.5, 3.11, and approximate to 1.5 eV, observed in the emission spectrum of the kCl:Bi, S crystal belong to the same centre, but arise from states of different origin; The splitting of the 2.5 eV band, caused by the presence of a defect (S2-) near a Bi3+ ion is detected. Besides the well-known tripler 3.3 and 3.1 eV bands, a new 4.15 eV emission is found in CaO:Bi crystal: which is ascribed to transitions from the singlet excited state of the Bi3+ ion. The structure and the parameters of the relaxed excited states are determined and the models of the corresponding Bi3+ centres are discussed.