LONG LIFETIME OF POSITRONIUM IN LIQUID HELIUM
LONG LIFETIME OF POSITRONIUM IN LIQUID HELIUM
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DOI：
10.1103/physrev.108.167
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发表时间：
1957-01-01
期刊：
影响因子：
--
通讯作者：
FERRELL, RA
中科院分区：
文献类型：
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作者：
FERRELL, RA
Paul、Graham、Wackerle和Stump在液氦中观察到的正对电子寿命很长，这证明了拾取湮灭速率比基于平均电子密度所期望的速率小一个数量级以上。考虑到在以前的工作中已经推导出的排斥性正电子-氦交换力，这种差异被消除了。通过排斥氦原子并在液体中产生空腔或气泡，正电子原子能够避免与液体接触，从而大大延长其寿命。观察到的小拾取率归因于气泡中的饱和蒸汽。排斥交换力进一步降低了这一速率，与实验结果吻合较好。据预测，从沸点到临界点，温度每提高一度开尔文，寿命就会减少三倍。在液氮温度和0-100个大气压下氦气中的正电子寿命测量也将为该理论提供检验。
The long orthopositronium lifetime observed by Paul and Graham and Wackerle and Stump in liquid helium is evidence of a pickoff annihilation rate smaller by more than one order of magnitude than the rate to be expected on the basis of the average electron density. This discrepancy is removed by taking into account the repulsive positronium-helium exchange force already derived in previous work. By repelling the helium atoms and creating a cavity, or bubble, in the liquid, a positronium atom is able to avoid contact with the liquid and thereby greatly increase its lifetime. The small pickoff rate observed is attributed to the saturated vapor in the bubble. The repulsive exchange force further decreases this rate, and good agreement is obtained with experiment. It is predicted that increasing the temperature one degree Kelvin, from the boiling point to the critical point, will decrease the lifetime by a factor of three. Positron lifetime measurements in helium gas at liquid-nitrogen temperature and 0-100 atmospheres pressure would also provide a check on the theory.