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应用正电子湮没技术 ,测量了 PET(聚对苯二甲酸乙二脂 )在不同温度下的正电子湮没寿命谱 .使用正电子寿命谱的离散分析法 (PATFIT) ,根据正电子湮没参数随温度的变化 ,两个次级转变点 Tβ和 Tγ被确定 .利用最新发展的连续谱的分析程序 (MEL T) ,得到几种不同温度下的自由体积的分布 ,发现低温下自由体积大小 ,数量及分布并非常量 ,同时发现在极低温 (30 K)下 ,自由体积的分布很宽 .
Positron annihilation lifetime spectrum of PET (polyethylene terephthalate) at different temperatures was measured by positron annihilation technique. According to the positron annihilation (PATFIT) Tβ and Tγ of the two secondary transition points were determined.Using the latest development of the continuous spectrum analysis program (MEL T), we obtained the distribution of free volume at several different temperatures and found that the free volume size, number and The distribution is not constant, and it is found that the distribution of free volume is very wide at very low temperatures (30 K).