An experimental study of the decay of the He-ion

The decay in flight of He - ions has been studied under field free conditions. Measurements with He - beams of energies between 2 and 30 keV in flight tubes from 0.1 to 1.7 m long have established the existence of two components with greatly different lifetimes present in approximately equal proportions in the beam. The lifetime of the long lived component appears to be comparable with that predicted theoretically for the 4 P 5/2 state while the second component, which dominates the observed decay, has a lifetime of 9 -3 +5 mu s.