Luminescence of LaBr_3: Ce,Hf Crystals under Photon Excitation in the Ultraviolet, Vacuum Ultraviolet, and X-Ray Ranges

摘要

This study has been carried out using synchrotron radiation, time-resolved luminescence ultraviolet and vacuum ultraviolet spectroscopy, optical absorption spectroscopy, and thermal activation spectroscopy. It has been found that, in scintillation spectrometric crystals LaBr_3: Ce,Hf characterized by a low hygroscopicity, along with Ce~(3+) centers in regular lattice sites, there are Ce~(3+) centers located in the vicinity of the defects of the crystal structure. It has also been found that the studied crystals exhibit photoluminescence (PL) of new point defects responsible for a broad band at wavelengths of 500-600 nm in the PL spectra. The minimum energy of interband transitions in LaBr_3 is estimated as E_g ~ 6.2 eV. The effect of multiplication of electronic excitations has been observed in the range of PL excitation energies higher than 13 eV (more than 2E_g). Thermal activation studies have revealed channels of electronic excitation energy transfer to Ce~(3+) impurity centers.