Luminescence of Lead Ion Centers in Cadmium Iodide Single Crystals

Abstract

Emission and excitation spectra of the luminescence associated with Pb 2+ centers in CdI 2 layered crystals have been investigated. Excitation in the absorption band of the center induces an emission band with fine vibrational structures at the energy near the absorption band, and a broad emission band with large Stokes shift. Measurements of the decay time and time-resolved emission spectra reveal that the former band consists of two parts originating from ( 3 E u , 3 A 2u ) and 3 A 1u states of Pb 2+ with D 3d symmetry. The low energy broad band is ascribed to the emission from a relaxed state of excitons of CdI 2 perturbed by Pb 2+ . Thermally activated transfer of energy is found to take place from the excited states of Pb 2+ into the perturbed exciton state.