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On the defect pattern evolution in sapphire irradiated by swift ions in a broad...
Gordo, P. M.; Liszkay, L.; Kajcsos, Zs.; Havancsák, K.; Skuratov, V. A.; Kögel, G.; Sperr, P.; Egger, W.; Lima, A. P. de; Marques, M. F. FerreiraSapphire samples, irradiated with swift Kr (245 MeV) ions at room temperature in a broad fluence range, were investigated using a continuous and a pulsed positron beam to study the defect structure created by the passage of the ions in depths of a few micrometers. At small doses, monovacancies were identified as dominant defects and positron trapping centres. These monovacancies are assumed to be highly concent...
Competitive positron and positronium trapping in porous media
Kajcsos, Zs.; Liszkay, L.; Duplâtre, G.; Lázár, K.; Lohonyai, L.; Varga, L.; Gordo, P. M.; Lima, A. P. de; Gil, C. Lopes de; Marques, M. F. FerreiraPositron annihilation acquired acceptance for structural investigation of solids but results in porous media--where positron lifetime spectroscopy (LT) reveals substantial Ps formation--were ambiguous. Data on zeolites lead to the conclusion that Ps trapping in competing "extended free volume" sites, inhomogeneous regions and grain boundaries occurs. Furthermore, positron trapping must also be considered. Syste...
Positron and positronium annihilation patterns in zeolites and bulk ceramics
Kajcsos, Zs.; Kosanovic', C.; Liszkay, L.; Major, P.; Lohonyai, L.; Zalán, P.; Lázár, K.; Bosnar, S.; Subotic', B.; Bosnar, D.; Havancsák, K.Positron lifetime (LT) measurements have revealed that in porous media the annihilation pattern is probably dominated by a near-saturation level trapping both for the positron and the positronium as well, which masks the contribution from the ldquofree annihilationrdquo, i.e., annihilation from delocalised positrons. In this work we compare positron lifetime spectra of crystalline zeolites with bulk ceramic mat...
Positron and positronium in porous media: zeolites
Kajcsos, Zs.; Liszkay, L.; Duplâtre, G.; Lohonyai, L.; Varga, L.; Lázár, K.; Pál-Borbély, G.; Beyer, H. K.; Caullet, P.; Patarin, J.; Lima, A. P. deCorrelations between positronium (Ps) production features and positron annihilation (PA) parameters were investigated in various zeolite samples (MFI, mordenite, Na-Y). The contribution of 3[gamma]-annihilation on data registration was closely examined. Long lifetimes up to 135 ns and triplet Ps (o-Ps) fractions up to 30% were found. Even low amounts of adsorbed gases or water drastically change the PA pattern....
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