Papers by Keyword: Positronium Formation

Abstract: Here we discuss the e⁺ fate from its injection into a liquid till its annihilation, namely: 1) energy losses and track structure of fast positrons. Parameters of the terminal e⁺ blob; 2) electric interaction between blob constituents; 3) picosecond stage: hot (epithermal), quasi-free (dry), solvated (hydrated) e^- and e⁺, capture of hot particles by a scavenger; 4) positronium formation in condensed matter: the Ore model, the diffusion-recombination model, formation of quasi-free Ps and Ps in a bubble, a “non-point” positronium; 5) application of an external magnetic field, mixing of ortho- and para-Ps states, R(H)-parameter, Ps contactdensity; 6) diffusion-controlled reactions involving Ps (oxidation and ortho-para conversion) at nanosecond stage, temperature dependence of the reaction rate constants.

Abstract: In porous media, positron annihilation techniques (PAT) revealed the existence of annihilation modi with long lifetimes connected to structural and extrastructural free volumes acting as trapping centres for o-Ps. Our aim in this work was to study the influence of the synthesis applied for the production of the zeolite framework and the correlation between the trapping pattern and crystallization progress. PAT lifetime (LT) measurements were performed in silicalite-1 samples in various stages of crystallization and a large change was observed in the long components. The results are discussed in connection to the crystallization and the availability of free volume.