Department of Physics and Astronomy, University of California, Riverside, California 92521-0413, USA.
Phys Rev Lett. 2010 Apr 30;104(17):173401. doi: 10.1103/PhysRevLett.104.173401. Epub 2010 Apr 27.
Long-lived |m|=1 positronium (Ps) atoms are produced in vacuum when high density bursts of positrons with net polarization p{0} are implanted into a porous silica film in a 2.3 T magnetic field. We observe a decrease in the |m|=1 population as the density of the incident positron beam is increased due to quenching interactions between oppositely polarized Ps atoms within the target. Saturation of this density dependent quenching indicates that the initial positron spin polarization p{0}=28+/-1%, and demonstrates the long term (10{2} s) survival of positron polarization in a Surko-type buffer gas trap. We conclude that, at high Ps densities, the minority spin component is essentially eliminated and the remaining Ps is almost entirely (approximately 96%) polarized, as required for the formation of a Ps Bose-Einstein condensate.
当具有净极化 p{0}的高密度正电子脉冲注入到磁场中的多孔硅薄膜中时，会在真空中产生长寿命|m|=1 正电子素（Ps）原子。我们观察到，随着入射正电子束密度的增加，|m|=1 种群减少，这是由于目标内相反极化的 Ps 原子之间的猝灭相互作用所致。这种密度相关猝灭的饱和表明初始正电子自旋极化 p{0}=28+/-1%，并证明了 Surko 型缓冲气体陷阱中正电子极化的长期（10{2} s）存活。我们得出结论，在高 Ps 密度下，少数自旋分量基本上被消除，并且剩余的 Ps 几乎完全（约 96%）极化，这是形成 Ps 玻色-爱因斯坦凝聚体所必需的。
