One-dimensional metallic-dielectric photonic crystal (PC) was proposed to modify the scintillation spectrum of BaF2 crystal. For the PC of several periods of Al2O3=MgF2=Al=MgF2; the photonic band of the PC and the corresponding scintillation spectrum of the BaF2 crystal as the functions of geometrical parameters and incident angles were discussed. The band structure of the PC was optimized to achieve high transmittance for the fast emission and deep rejection for the slow emission of the BaF2 crystal. Results show that the relative suppression ratio of the slow to the fast emission reaches 50 and simultaneously the fast emission is greater than 33.3% that of the un-modified BaF2.

The defects associated with interstitial oxygen in lead tungstate crystals (PbWO4) are investigated by the relativistic self-consistent discrete variational embedded cluster method. The research work is focused on the density of states of interstitial oxygen defects and relational Frankel defects. The transition state method is used to calculate excitation energy of dierent electron orbits. Simulation results show that the existence of defects related to interstitial oxygen can diminish the bandwidth of the WO2/4 associated with interstitial oxygen could result in the absorption at 420nm.

A study on point defects in lead tungstate (PbW04) by using positron annihilation lifetime method is presented. The measurement was carried out for the cases of untreated, vacuum-annealed, oxygen- annealed and La-doped PbW04 crystals. It was found that the components T2, which reflect the positron annihilation in point defects, are different from each other for each ease. Some tentative models for the defects are discussed.