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

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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.