On the possible existence of a long-lived doublet state of He^-

Abstract

The metastable fraction of a He beam produced by electric-field detachment from He- ions has been measured by the beam- attenuation technique in the energy range from 20 to 700 keV. It is shown that H2 as an attenuation gas gives the correct metastable fraction. The data further suggest the existence of a long-lived ( approximately 10 mu s) bound doublet state of He-.