Luminescence Accompanying the Recombination of Electrons with V_F Centres in KCl Crystals

Abstract

) (a), S. ZAZUBOVICH (a), V. SEEW (b), and V. NAGIRNYI (a) Processes of an optical production of VF centres (holes localized near cation vacancy) are investigated by absorption, ESR, and thermoluminescence methods. It is established that VF centres are most effectively produced in KCI : PbCI, crystals X-irradiated at 80 K and subsequently heated up to 270 K, at the recombination of optically released electrons with Vrz(Pba+) centres (molecular C1, ions associated with Pb2+ ions). After an optical production of VF centres, the stimulation in the electronic absorption bands (K or 4) results in the appearance of luminescence with a peak at 3 eV and band half-width equal to 0.75 eV. If VF 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 r centres. The 3 eV emission quenches rapidly a t 237 K and its depolarization occurs at 111 K. The same emission is observed in undoped KC1 crystal. It is concluded that the 3 eV emission is caused by the recombination of electrons with VF centres. The same spectrum must have the triplet emission of a self-trapped exciton perturbed by a cation vacancy. ;laeTcfi n o n~p~3 a~a~ a 3 a y~e~a 1 i 3 eV B H a n p a s n e H m x , n e p n e H A m y n R p H M x M o n eo6aacm OHOJIO 237 K, a ~e n o n~p~a a u~~ ero ~~O M C X O A I Z T OHOJIO 111 K. AHaJfOrM9HOe naaysesne ~a G n~~r [ a e~c n B HeammMpo8aHno&i KCl. MOXHO ~~K~I O~H T E . , TO ~a n y~r e~n e 3 eV 0 6 y C 3 0 B J l e H O p e H o~6~~a u~e f i 3JIeKTPOHOB C VF-4eHTPaMH. AHajrOrM9HbIft CneK-T P Z l J b H b I a COCTaB n0JI;KHO IZMeTb I53JIyYeHHe aBTOJIOKaJIH30BaHHOrO 3KCHTOHa, B03-HgIIJeHHOrO HaTHOHHOfi BaKaHCHefi.