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We have measured the kinetic energy of positronium (Ps) atoms emitted into a vacuum from a porous silica film subsequent to positron bombardment, via the Doppler spread of the linewidth of the Ps 13S-23P transition. We find that the deeper in the target film that positrons are implanted the colder is the emitted Ps, an effect we attribute to cooling via(More)
Zs. Kajcsos, L. Liszkay, G. Duplâtre, L. Varga, L. Lohonyai, F. Pászti, E. Szilágyi, K. Lázár, E. Kótai, G. Pál-Borbély, H.K. Beyer, P. Caullet, J. Patarin, M.E. Azenha , P.M. Gordo, C. Lopes Gil, A.P. de Lima and M.F. Ferreira Marques KFKI Res. Inst. for Part. Nucl. Physics, P.O.B. 49, 1525 Budapest 114, Hungary Lab. Chim. Nucléaire, IReS, IN2P3/CNRS, B.P.(More)
The behavior of ortho-positronium (o-Ps) in mesoporous silica films implanted with low– energy positrons has been studied as a function of the film porous volume fraction. A lifetime spectrometer allowed determination of o-Ps annihilation decay both inside and outside of the film. A kinetic model is introduced that permits the determination of the yield and(More)
L. Liszkay * , C. Corbel, P Perez DSM/IRFU & IRAMIS, CEA Saclay F-91191 Gif-sur-Yvette Cedex, France P. Desgardin, M.-F. Barthe CNRS-CERI, 3A rue de la Férollerie, F-45071 Orléans Cedex 2, France T. Ohdaira, R. Suzuki AIST, Tsukuba, Ibaraki 305-8568, Japan P. Crivelli, U. Gendotti, A. Rubbia Institut für Teilchenphysik, ETHZ, CH-8093 Zürich, Switzerland M.(More)
Sapphire samples, irradiated with swift Kr (245 MeV) ions at room temperature in a broad fluence ra were investigated using a continuous and a pulsed positron beam to study the defect structure create the passage of the ions in depths of a fewmicrometers. At small doses, monovacancies were identifie dominant defects and positron trapping centres. These(More)
Correlations between positronium (Ps) production features and positron annihilation (PA) parameters were investigated in various zeolite samples (MFI, mordenite, Na–Y). The contribution of 3g-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(More)
We report on muonium (Mu) emission into vacuum following μ(+) implantation in mesoporous thin SiO(2) films. We obtain a yield of Mu into vacuum of (38±4)% at 250 K and (20±4)% at 100 K for 5 keV μ(+) implantation energy. From the implantation energy dependence of the Mu vacuum yield we determine the Mu diffusion constants in these films: D(Mu)(250(More)
We have performed a systematic study of magnesium doped, co-doped and annealed MOCVD GaN films by positron annihilation spectroscopy. GaN:Mg films are free of detectable vacancy defects up to [Mg] ∼ 3×10 cm, but at doping levels above 10 cm vacancies are observed. Two defects are identified: VN-MgGa pairs and vacancy clusters, where the amount of the(More)
KFKI Res. Inst. for Part. Nucl. Physics P.O.B. 49, H-1525 Budapest 114, Hungary Div. of Mater. Chem., Ruder Boskovic Institute Bijenicka 54, P.O.B. 180, Zagreb, Croatia Inst. of Isotopes, HAS, H-1525 Budapest, P.O.B. 77, Hungary Flerov Laboratory of Nuclear Reactions, Center of Applied Physics, JINR Ru-141980 Dubna, Russia Dept. of Mater. Physics, Eötvös(More)
We apply positron annihilation spectroscopy to identify V(N)-Mg(Ga) complexes as native defects in Mg-doped GaN. These defects dissociate in postgrowth annealings at 500-800 degrees C. We conclude that V(N)-Mg(Ga) complexes contribute to the electrical compensation of Mg as well as the activation of p-type conductivity in the annealing. The observation of(More)