Lifetime of the2S1State of He

Abstract

A traveling Auger detector is used to measure the attenuation of a cooled thermal beam of He $2{}_{}{}^1{}_{}{}^{}S$ atoms in a vacuum of 1×${10}^{-8\mathrm{}}$ Torr. Its velocity is determined by a time-of-flight technique. The lifetime obtained is (38 ± 8)×${10}^{-3\mathrm{}}$ sec.