Ortho-positronium localization in pores of Vycor glass at low temperature

16th International Conference on Positron Annihilation

Zaleski, Radoslaw^1

Maria Curie-Sklodowska University, Institute of Physics, Pl. M. Curie-Sklodowskiej 1, 20-031 Lublin, Poland^1

关键词: Ground energy;    Life-time distribution;    Lifetime spectroscopy;    Low temperatures;    Potential barriers;    Temperature dependence;    Thermal excitation;    Varying thickness;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/443/1/012062/pdf
DOI  :  10.1088/1742-6596/443/1/012062

来源: IOP

【 摘 要 】

An explanation of a discrepancy between the Extended Tao-Eldrup model and experimental lifetimes observed in some porous materials at low temperatures is presented. The discrepancy is expected in pores with a varying thickness. In such pores thermalized ortho-positronium (o-Ps) could locate in the widest parts, between potential barriers formed by a higher ground energy levels in the narrower parts of the pore. Such an effect can occur, if the energy, which o-Ps can obtain from thermal excitation, is not sufficient enough to pass the energy barrier (i.e., at low temperatures). As a consequence, the lifetime of a localized o-Ps is characteristic for the widest part of the pore only, and not to the averaged width, which can be observed when o-Ps has the ability to move freely along a pore. The problem is discussed basing on the temperature dependence of the results for Vycor glass obtained by o-Ps annihilation lifetime spectroscopy. Additionally to the mean lifetimes, the width of the lifetime distribution in the component is taken into account in the discussion.