Strong Electric Field Experiments on Positronium in Gases

Abstract

The increase in positronium formation on applying a dc electric field is measured using a two-photon angular correlation method as well as pulse-height analysis. In argon and in nitrogen the field dependence at pressures ranging up to 28 atmospheres is consistent with results of other investigators. In oxygen an increase by a factor of 2 is demonstrated, the field and pressure dependence having the same characteristics as for argon and nitrogen. In sulfur hexafluoride this normal increase in positronium formation is produced, requiring for given density an order of magnitude higher fields than in these other gases; also, the main features of an abnormal decrease in formation with increasing field which occurs at comparatively low fields are determined. A certain range-energy systematic effect crucial to field reversal experiments is explored empirically, and it is concluded that the earlier reported $\sigma ·\mathrm{E}$ effect for positronium can be traced in large part to this effect.