Radiative Lifetime of the Metastable2S01State of Helium

Abstract

Two fixed, spatially separated detectors are used to measure the decay in flight of a cooled, thermal beam of pulsed metastable helium atoms. The preliminary value obtained for the radiative lifetime of the metastable $2{}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ state of helium is 20 ± 2 msec.