Metastable-Atom Population of Fast, Neutral Helium Beams

Abstract
The fraction of metastable He(2S3) atoms formed by electron-capture neutralization of (25-90)-keV He+ ions in H2 gas or sodium vapor has been measured by using photon-particle coincidence techniques. The true metastable-atom populations measured by such techniques differ from apparent metastable-atom populations measured by the beam-attenuation technique. The consequences to existing experimental collision cross sections involving He(2S3) are discussed.