Associates of Cu° atoms with anion vacancies v a+ (Cu°v a+centres) are used as luminescent detectors for the study of anion vacancy mobility in KCl crystals. It is found that near 220 K, Cu°v a+ centres may be thermally formed because of the migration of v a+ only to its neighbouring Cu° atom (i.e. the process occurs in {Cu°–v a−} pairs). An analogous process in {Cu+–v a+} pairs results in the creation of Cu+v a+ centres. After Cu+v a+ have trapped electrons released at the thermal destruction of Cu°, Cu°v a+ centres are formed. {Cu+–v a+} and {Cu+–v a+} pairs are produced at low temperatures by the transfer of an F electron onto an impurity ion in irradiation‐generated {Cu+–F} and {Cu2+–F} pairs. If the crystal contains Cu a− centres, Cu°v a+ centres may be formed at T > 370 K by the interaction of mobile VF centres, produced at a thermal dissociation of Cl3 molecular ions, with Cu a− centres. It is proposed that at T < 300 K it is not the isolated but the “associated” anion vacancy that can migrate. This process occurs in the field of some defects and needs a comparatively lower activation energy than the motion of isolated v a+. The isolated or “free” v a+ which are believed to be mobile at higher temperatures, are practically absent in X‐irradiated crystals at T > 250 K due to the interaction of v a+ with mobile cation vacancies or interstitial halide ions as well as due to the thermal association of v a+ with neighbouring lattice defects.
The spectra of thermally stimulated luminescence caused by the recombination of mobile V, centres, VF centres, and XT centre decay products with F centres are studied at temperatures from 80 t o 500 K for KCI, KCl : Sr, KBr, and KBr : Sr crystals X-irradiated a t 80 or 295 K. The recombination processes occurring near a cation vacancy are established to be accompanied by it new characteristic emission band located in a higher-energyregion as compared with the emission caused by the recombination of V g and F centres. The processes responsible for the emission are discussed.
Polarized Luminescence and EPR Study of SnS+ Centres in KCl: SnClz CrystalsBY ZH. EGEMBERDIEV (a), u. HALDRE (h), T. LEHTO (h), K. REALO (a), S. REIFMAN (b), V. SEEMAN (h), and S. ZAZUBOVICH (a) Sn3+ centres in KCl: SnC1, crystals X-irradiated at 77 K and subsequently warmed up to certain temperatures are investigated by absorption, EPR, and polarized luminescence methods in the temperature interval of 4.2 to 400 K. Three types of Sn3' centres with different thermal, optical and EPR characteristics are observed. The number of Sn3+(I) centres, having isotropic g = 2.011 and All9 = 0.641 cm-l and the 2.09 eV emission polarizcd along the C, crystal axis, reaches its maximum after warming an irradiated crystal up t o 230 K. The EPR spectrum of Sn3+(I) centresis characterized by a well-resolved superhyperfine (shf) structure of absorption lines, indicating that the Sn3+ ion has an approximately octahedral surrounding and weak perturbation along the 11111 axis. The Sn3+(I) centres are supposed to be Sn3' ions in an off-centre position. The number of Sn3+(II) centres with g = 1.997, All9 = 0.754 cm-l, All = 2.65 x T and the 1.71 eV emission polarized along the C,-axis of the crystal reaches its maximum after warming the irradiated crystal up to 280 K. The resolution of SHF lines decreases considerably as compared with that in the case of Sn3+(I) centres. I t i s assumedthat Sn3+(II) centres may be associates of Sn3+ ions with two cation vacancies. Immediately after an X-irradiation a t 77 K a small number of Sn3+(III) centres is observable. It is quite probable that Sn3+(III) centres are the associates of Sn3+ with one cation vacancy, whose structure is similar to that of Sn2+v; centres in non-irradiated crystals. C1
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.