Positronium in a Liquid Phase: Formation, Bubble State and Chemical Reactions

Abstract

This chapter reviews the following items: 1. Energy deposition and track structure of fast positrons: ionization slowing down, number of ion-electron pairs, typical sizes, thermalization, electrostatic interaction between e + and its blob, effect of local heating;2. Positronium formation in condensed media: the Ore model, quasifree Ps state, intratrack mechanism of Ps formation;3. Fast intratrack diffusion-controlled reactions: Ps oxidation and ortho-para conversion by radiolytic products, reaction rate constants, interpretation of the PAL spectra in water at different temperatures; 4. Ps bubble models. "Non-point" positronium: wave function, energy contributions, relationship between the pick-off annihilation rate and the bubble radius.

Track Effects in Positronium Formation

“…Herer c is the product of the initial number of ionelectron pairs in the blob, n 0 ≈ 30−40 [3,6], by the reaction radius of the Ps formation, R ep . A rough comparison with experiment, Fig.…”

“…[2,3]. Therefore, sometimes it is fairly difficult to figure out common features of this pro- * corresponding author; e-mail: stepanov@itep.ru cess even in neat media.…”

Formation of Quasi-Free and Bubble Positronium States in Water and Aqueous Solutions

“…Our viewpoint is different. Firstly, we take it that the thermalization of subionizing e + and eproceeds rather fast (fractions of ps), qf-Ps being formed from the thermalized particles [9]. The qf-Ps produced cannot have a kinetic energy much higher than its binding energy (E b ) in a dielectric continuum (E b~R y/2ε 2 = 1.7 eV), otherwise, it might just break up because of interaction of e + and ewith the environment, while qf-Ps moves through a medium.…”

Generalized balance equations for charged particle transport via localized and delocalized states: Mobility, generalized Einstein relations, and fractional transport

“…Physically, this fundamentally slower transport can arise due to the presence of trapped (localised) states, causing the temporary immobilisation of particles [2]. Some examples include charge carrier trapping in local imperfections of organic semiconductors [2,3], electron trapping in bubble states within liquid neon and liquid helium [4][5][6], ion trapping in liquid xenon [7][8][9][10], positronium trapping in bubbles [11][12][13] and positron annihilation on induced clusters [14]. Trapped states also exist in organic-inorganic metal-halide perovskites and influence the delocalised nature of transport in these materials [15].…”