Optical studies of Tl2+ centres in X-rayed KI:Tl crystals

Abstract

The absorption spectra of KI crystals with high Tl+ concentrations (0.01–2.0 mol%) have been measured after X-ray exposure at 77 K or 120 K. A new band has been observed at 1800 nm. It is suggested, from the correlation of the 1800 nm band with the (Tl+)2, Tl0, and Tl++ bands, that the 1800 nm band is ascribed to Tl2+ centres which are formed when (Tl+)2 centres capture electrons created in the crystal by the X-ray exposure or released from Tl0 centres.