On the influence of electron mobilities on the yields of formation of positronium in liquids: New I3 measurements and Monte Carlo simulations

Abstract

We study the formation of positronium (Ps) at the end of the radiation tracks generated by the passage of energetic positrons in various liquids. We focus particularly on the possible influence of the thermal electron mobility μ(e−) on this process. To this end, we present a compilation of experimental data of the probability of ortho-Ps formation I3 and μ(e−) in 51 pure liquids at room temperature. We also present new measurements of I3 as a function of temperature for n-hexane, 2,2-dimethylbutane, tetramethylsilane, and tetramethylstannane from the melting point up to 294 K. Those results are compared to the variation of μ(e−) with temperature which can be found in the literature. Finally, we use Monte Carlo simulation techniques to perform a sensitivity study in which we evaluate the relative contributions of various physicochemical properties of the liquids (such as the mean thermalization distances of e+ and e−, their thermal mobilities, the dielectric constant, and the temperature) on the values of I3. A review of previous works on this question is also given.