Luminescence Accompanying the Recombination of Electrons with V F Centres in KCl Crystals

Processes of an optical production of V F centres (holes localized near cation vacancy) are investigated by absorption, ESR, and thermoluminescence methods. It is established that V F centres are most effectively produced in KCl: PbCl, 2 crystals X‐irradiated at 80 K and subsequently heated up to 270 K, at the recombination of optically released electrons with V 2z (Pb 2+ ) centres (molecular Cl   3 −ions associated with Pb 2+ ions). After an optical production of V F centres, the stimulation in the electronic absorption bands (K or L 2 ) results in the appearance of luminescence with a peak at 3 eV and band half‐width equal to 0.75 eV. If V F centres are previously oriented by polarized light, the 3 eV emission becomes polarized in the directions perpendicular to the molecular axis of the oriented V F centres. The 3 eV emission quenches rapidly at 237 K and its depolarization occurs at 111 K. The same emission is observed in undoped KCl crystal. It is concluded that the 3 eV emission is caused by the recombination of electrons with V F centres. The same spectrum must have the triplet emission of a self‐trapped exciton perturbed by a cation vacancy.