Study of Gaseous Impurity Elements in Cavities with Use of Positrons and Positronium

在金属和半导体中，存在由高能粒子轰击引起或在样品制备过程中产生的空穴。在硅酸盐化合物（沸石和海泡石）中存在结构空腔。由于这些空穴在物理、机械和化学性质上的重要作用，如重辐照金属的尺寸稳定性和合成沸石的催化行为，这些空穴一直是基础研究的对象。特别是其中气态元素分子的状态和行为。1）钒正电子ACAR中空穴（空隙）中的正电子素（湮没辐射的角相关）和寿命测量已经在中子辐照的钒样品上进行，并控制氧或碳的杂质含量。已经表明，可能在空隙内表面上的氧杂质对空隙的污染导致Ps的形成，但不导致Ps的形成。 ...更多信息 h碳杂质。从窄组分的退火行为，由于para-Ps，Ps的形成增加与退火温度高达600 ℃，但随后随着温度的升高而减少。这表明氧杂质在高达600 ℃的温度下偏析到空隙表面，然后分解到基质中。寿命实验表明，Ps的正-对位转化速率非常快，且具有很大的温度依赖性。2）沸石和海泡石中的正电子湮没。本文用正电子湮没ACAR方法测量了系列合成沸石粉和天然海泡石单纤维。所有样品在ACAR曲线的顶部处显示出明显的窄对-Ps峰。通过一个简单的模型计算，发现Ps原子以自由粒子的形式存在于MS-3A沸石的α-笼和海泡石的一维空穴通道中.用正电子湮没方法研究了中子辐照镍、不锈钢和石墨中的空穴。少

In metals and semiconductors, there are cavities which are induced by bombardment of high energy particle or produced during sample preparation processes. In silicate compounds (zeolites and sepiolite) there are structural cavities. These cavities have been object of basic research because of their important roles in physical, mechanical and chemical properties such as dimensional stability of heavily irradiated metals, and catalytic behavior of synthetic zeolites.In this study positrons are used to investigate the interiors of cavities, especially state and behavior of gaseous element molecules within them.1) Positronium in cavities (voids) in vanadium Positron ACAR (angular correlation of annihilation radiation) and life measurements have been done on neutron-irradiated vanadium samples with controlled impurity contents of oxygen or carbon. It has been shown that contamination of voids with oxygen impurities, presumably on the void internal surface, leads to Ps formation, but not wit … More h carbon impurities. From the annealing behavior of narrow component due to para-Ps, the Ps formation increases with annealing temperature up to 600 ﾟC but subsequently decreases with increasing the temperature. This suggests that segregation of oxygen impurities onto the void surface up to 600 ﾟC followed by resolution into the matrix. Lifetime experiments shows a very rapid Ps ortho-para conversion rate and its large temperature dependence.2)Positron annihilation in zeolites and sepiolite. Positron annihilation ACAR measurements have been carried out for series of synthetic zeolite powders and single fibers of natural sepiolite. All of the samples showed marked narrow para-Ps peaks af the top of the ACAR curves. From a simple model calculation, the Ps atoms are found to exist as free particle in the structural cavities, such as the alpha-cages in the MS-3A zeolite and the 1-dimensional cavity channel in sepiolite. Oxygen molecules influence motion and reactions of Ps in these cavities.Cavities in neutron-irradiated nickel and stainless steel and in graphite have been studied by positron annihilation method. Less