SUPPRESSION OF THE SLOW COMPONENT OF BAF2 CRYSTAL BY INTRODUCTION OF SRF2 AND MGF2 CRYSTALS

The emission spectrum, the time dependence of the luminescence, the light output, the excitation and the reflectance spectra have been measured for pure BaF2 crystal, for BaF2:Sr crystals with Sr2+ concentrations of 2 and 5 mol% and for BaF2:MgF2 crystal with a mole mixing ratio of 1:2. The measurements have been made by using synchrotron orbital radiation and high-energy electrons produced by gamma-rays. It is shown that the BaF2, BaF2:Sr and BaF2:MgF2 crystals have a fast component luminescence with decay times around 0.90 ns. The slow and fast components luminescence of the BaF, crystal are suppressed by the introduction of Sr2+ and Mg2+ ions. It is, however, clearly seen that the suppression of the slow component is more effective than that of the fast component, especially in the BaF2:MgF2 crystal. The Sr2+ and Mg2+ ions act as electron trapping centers, preventing the formation of self-trapped excitons by electron-hole pairs, that is the slow component.