LUMINESCENCE OF DEFECT CENTERS IN HG2CL2

Luminescence in Hg2Cl2 crystals excited with UV light is investigated in the spectral region 0.8-2.25 eV. Measurements are performed on as-g rown samples and on samples previously exposed to UV light at RT. Six emission bands are found which depend on the concentration of the phot ochemical entities produced by irradiation of the crystals at RT. It i s concluded that infra-red (IR) luminescence of Hg2Cl2 originates from crystal defects. The observed emission bands are tentatively attribut ed to the emission of (HgClxBr3-x)(-) and (HgClxBr4-x)(2-) complexes f ormed with residual Br impurities. Centres responsible for IR Hg2Cl2 e missions are excited: (i) via excitons of Hg2Cl2, (ii) via excited sta tes of isolated Hg2Br2 molecules, and (iii) resonantly through the exc itation bands of defect centres.