The luminescence of crystals which were excited with ultra-violet light was investigated within the spectral range of 0.8 to 2.25eV. Measurements were performed on as-grown samples and on samples which had previously been exposed to ultra-violet light at room temperature. Six emission bands were found which depended upon the concentrations of the photochemical entities which were produced by irradiation at room temperature. It was concluded that the infra-red luminescence originated from crystal defects. The observed emission bands were tentatively attributed to the emission of (HgClxBr3-x)- and (HgClxBr4-x)2- complexes which formed from residual Br impurities. It was suggested that the centers which were responsible for the infra-red emissions involved excitons of Hg2Cl2, excited states of isolated Hg2Br2 molecules, and resonance of the excitation bands of defect centers.

Z.Bryknar, P.Peka, A.Konáková, J.Král, H.J.Schulz: Radiation Effects and Defects in Solids, 1995, 134, 447-51