Positronium annihilation in silica aerogel studied by a positron age-momentum correlation technique  

作　　者：王丹妮 张兰芝 王宝义 于润升 章志明 李道武 魏龙 

机构地区：[1]Key Laboratory of Nuclear Analysis Techniques,Institute of High Energy Physics,CAS [2]Graduate University of Chinese Academy of Sciences

出　　处：《Chinese Physics C》2009年第1期81-84,共4页中国物理C（英文版）

基　　金：Supported by NSFC (10575112, 10705031, 60606011)

摘　　要：A high-performance positron age-momentum correlation （AMOC） spectrometer was newly developed. The counting rate is increased up to 200 cps much larger than the value 20 cps reported by other international groups. And at the same time, the time resolution still keeps at the international level of 220 ps. Furthermore, positronium （Ps） annihilation in silica aerogel was investigated by AMOC, which indicates： （1） Ps annihilation between the grains dominantly undergoes pick-off process and spin conversion from o-Ps to p-Ps; （2） Annealing below 400 ℃ changes the grain surface conditions, i. e. the desorption of hydrogen and the decrease of the defect centers concentration.A high-performance positron age-momentum correlation （AMOC） spectrometer was newly developed. The counting rate is increased up to 200 cps much larger than the value 20 cps reported by other international groups. And at the same time, the time resolution still keeps at the international level of 220 ps. Furthermore, positronium （Ps） annihilation in silica aerogel was investigated by AMOC, which indicates： （1） Ps annihilation between the grains dominantly undergoes pick-off process and spin conversion from o-Ps to p-Ps; （2） Annealing below 400 ℃ changes the grain surface conditions, i. e. the desorption of hydrogen and the decrease of the defect centers concentration.

关 键 词：positron age-momentum correlation positronium formation positron states silica aerogel 

分 类 号：O572.322[理学—粒子物理与原子核物理]