Orthopositronium annihilation and emission in mesostructured thin silica and silicalite-1 films

Abstract : Mesoporous silica films and MFI-type pure silica zeolite films were investigated using slow positrons. Detection of the 3γ annihilation fraction was used as a quick test to estimate the emission of orthopositronium (o-Ps) into vacuum. Positronium time-of-flight (TOF) spectroscopy, combined with Monte-Carlo simulation of the detection system was used to determine the energy of o-Ps emitted from the films. Evidence for an efficient o-Ps emission was found in both the mesoporous and silicalite-1. A 3γ fraction in the range of 31–36 % was found in the films with the highest o-Ps yield in each type of porous material, indicating that 40–50 % of the implanted positrons form positronium in the pore systems with very different pore sizes. Time-of-flight measurements showed that the energy of the orthopositronium emitted into vacuum is below 100 meV in the film with 2–3 nm pores at 3 keV positron energy, indicating an efficient slowing down but no complete thermalization in the porous films of 300–400 nm thickness
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https://hal.univ-lorraine.fr/hal-01941914
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Submitted on : Sunday, December 2, 2018 - 6:07:09 PM
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L. Liszkay, M.-F. Barthe, C. Corbel, P. Crivelli, P. Desgardin, et al.. Orthopositronium annihilation and emission in mesostructured thin silica and silicalite-1 films. Applied Surface Science, Elsevier, 2008, 255 (1), pp.187-190. ⟨10.1016/j.apsusc.2008.05.210⟩. ⟨hal-01941914⟩

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