Polarized Luminescence of Lead Ions Associated with Interstitial Radiation Defects in KCl:PbCl₂ Crsytals

Abstract

Two types of lead ion and interstitial chlorine atom associates (H,(Pb2+) centres) are found and investigated by optical methods in X-irradiated KCl:PbCI, crystals. The polarized 3.35 and 1.8 eV emission of these centres and the absorption bands near 5.55 and 4.4 eV are caused by electronic transitions in the Pb3+ ion perturbed by CIT molecular ion, which occupies a cation vacancy and an anion site. The broad absorption band at 3.7 eV is due to the transitions in the C1, ion perturbed by Pb2+. Vsing the ESR data obtained by Schoemaker et al. it is concluded that the centres with 3.35 and 1.8 eV emission are interstitial chlorine atoms trapped by Pba+ ions associated with the nearest neighbouring (Hflol(Pbz+) centres) and with the next nearest neighbouring (H~100](Pb2t) centres) cation vacancies, respectively. Lead ion and Cl, molecular ion associates (Vez(Pbz') centres) are found. The polarized 3.05 eV emission and the 4.3 eV absorption band of these centres are caused by the electronic transitions in Pb2+ ions perturbed by C1; . The broad 5.27 eV absorption band is due to the electronic transitions in the Clz ions perturbed by PbS+.It is assumed that the VZz(Pb2+) centre may be represented as a Clz molecular ion which occupies two anion and one cation sites and is associated with a Pb2+ ion located (according to Itoh et al.) a t a face-centred position as well as with an interstitial chlorine ion and cation vacancy.