关于分子介质中三重态正子素(O-Ps)寿命 τ3的探讨

本文对o-Ps的寿命τ_3进行了探讨,认为介质的体积因素和介电性质是影响τ_3的主要因素,但也不应忽视介质分子对o-Ps的化学猝灭作用和正电子云团中活性自由基对o-Ps的顺磁猝灭作用的影响。提出了估计τ_3的半经验式。通过τ_3计算值与实验值的比较,作出某些有关介质的化学性质和正电子对介质的辐射效应等方面的预言.

On lifetime of ortho-positronium (o-Ps) in molecular substances

In this paper the lifetime of o-Ps is discussed. It is considered that the lifetime of o-Ps in condensed molecular substances depends primarily on the volume-factors and dielectric properties of materials, but the chemical and paramagnetic quenching of o-Ps by molecules and active radicals created in the spur can not be neglected, and sometimes they affect the lifetime of o-Ps considerably. A semi-empiricial formula for estimation of lifetime of o-Ps in pick-off annihilation is proposed, it is expressed as: \I\3 = K(M\I\/\T\-\S\Voi)/e\S\Zi where K=3.08(ns/cm3) is an empirical constant; s e is the dielectric constant of material; Mr and \T\ are the molecular weight and density of material respectively; Zi and Voi are the number of valence electrons and the mole excluded volume, respectively, of atom i by which the molecules of material are constituted. An empirical formula for Voi is also proposed. By comparison between calculated and experimental \I\3 values, a discussion about the influence of the free radicals in the spur and molecules of material on o-Ps lifetime is made.