An attempt for formulating techniques of measuring sub-nanometer vacancies using positronium

通过测量正电子寿命来估计绝缘材料中自由体积空穴的大小和数量已成为可能。由于有关的物理量，即o-Ps分量的寿命τ_3和强度l_3并不是自由体积量的直接度量，因此必须找出τ_3与自由体积大小、l_3与自由体积数量之间的联系。为此，我们进行了以下调查：1)总结了o-Ps参数与自由体积特性之间的关系。已经明确的是，Ps寻找更大的洞和/或挖洞（使洞尺寸更大）。在塑化条件下，使孔尺寸变大的程度约为20%。然而，在玻璃状聚合物中，这种程度不会那么大。O-Ps强度l_3并不总是自由体积数的度量。2)将o-Ps法与其它测定自由体积的方法进行了比较。化学位移Xe-129与τ_3的相关性特别好，可作为化学位移技术的标定标准。3)测量自由体积的Ps方法已应用于一些实际情况。用Ps法测定了几种聚酰亚胺吸附外部分子（丙烯）后的自由体积态变化。测定了反渗透膜的自由体积结构。

It is becoming possible to estimate the size and number of free volume holes in insulating materials from positron lifetime measurements. Since the related physical quantities, the lifetime τ_3 and the intensity l_3 of the o-Ps component, are not the direct measure of the free volume quantities, it is imperative to work out a connection between τ_3 and the free volume size, and between l_3 and the number of them. For this purpose we have performed the following investigations ;1) The relationships between o-Ps parameters and free volume characteristics are summarized.It has been made clear that Ps seeks larger holes and/or dig holes (makes the hole size lager).The extent of making the hole size larger has been found to be approximately 20% in plasticized conditions. In glassy polymers, however, the extent will not be as large as this.O-Ps intensity l_3 is not always the measure of the number of the free volumes.2) The o-Ps method has been compared with other techniques of free volume determination. Chemical shift Xe-129 showed particularly excellent correlation with τ_3, which served as the standard for calibration of the chemical shift technique.3) The Ps method of measuring the free volumes has been applied to some practical cases.The chanse of free volume states after sorbing external molecules (propylene) was measured for several polyimides using the Ps method.The free volume structure of reverse osmosis membranes was measured.