NEAR-INFRARED LUMINESCENCE OF HG2CL3

Luminescence in Hg2Cl2 crystals excited with UV light or X-rays is inv estigated in the near infra-red (NIR) spectral region up to 1000 nm. M easurements are performed on as-grown samples and on samples previousl y exposed to UV light or X-rays at RT. Three types of luminescence cen tres denoted A, B, and C are identified, the luminescence of which dep ends on the concentration of the photochemical products induced by irr adiation of the crystals at RT. Thermoluminescence of Hg2Cl2 is observ ed for the first time. The glow emission is found in the NIR range, to o. It is due to radiative transitions in centres A and B. It is conclu ded that the NIR luminescence of Hg2Cl2 is not an intrinsic emission b ut originates from crystal defects. Moreover, luminescence of free exc itons in Hg2Cl2 is not observed even at 4.2 K and strong excitation wi th X-rays or UV light.