Study of the interactions between positronium and atoms or molecules

我们研究了（1）电子偶素散射过程中的自旋轨道相互作用和（2）电子偶素的拾取湮灭。结果如下。(1)由Mitroy和Novikov预言的正电子偶素与原子的自旋轨道相互作用已经在实验上被探测到。采用新开发的正电子寿命装置，采用数字处理。我们发现，当外加磁场为1.0T时，1atm的氦气中未受磁扰动的正电子偶素的寿命显著降低。这种下降是由于自旋-轨道相互作用引起的Ps自旋转换。由于这种相互作用，ortho-Ps的湮灭截面已被确定为Mitroy和Novikov预期的三倍大。(2)本文对正电子偶素在19种气体中的拾取湮没进行了系统的研究。标准化的碰撞湮灭率^1 Z_的值<eff>为0.1-2.31。当<eff>其它气体的值低于0.73时，氘（1.25）和CH_3I（2.31）的^1Z_（？）用自旋-轨道相互作用解释了π的值。CH_3I仍在研究中。N_2O的值与其它气体的值相似，但据报道，N_2O的值很高。

We have studied (1) spin orbit interaction during positronium scattering, and (2) pickoff annihilation of positronium. The results are as follows.(1) Spin-orbit interaction of positronium with atoms, predicted by Mitroy and Novikov, has been detected experimentally. Newly developed positron lifetime apparatus employing digital processing was used. We have found that the lifetime of the magnetically unperturbed ortho-positronium in Xe gas of 1 atm decreases significantly when a magnetic field of 1.0 T is applied. This decrease is attributed to the Ps spin conversion caused by the spin-orbit interaction during the positronium-Xe collision. The annihilation cross section of ortho-Ps due to this interaction has been determined to be three times as large as that expected by Mitroy and Novikov.(2) Systematic study of the pick-off annihilation of ortho-positronium in 19 gases was performed. The values of the normalized collisional annihilation-rate, ^1Z_<eff>, have been measured to be 0.1-2.31. The ^1Z_<eff> for Xe (1.25) and CH_3I (2.31) are exceptionally large while the values for the other gases are below 0.73. The value for Xe is explained in terms of the spin-orbit interaction. CH_3I is still under investigation. The value for N_2O, which was reported to be anomalously high, has been revealed to be similar to those of the other gases.