Lifetimes and Fine Structure of the Metastable Autoionizing(1s2s2p)PJ4States of the Negative Helium Ion

The decay of the differentially metastable autoionizing $\mathrm{}\left(1s2s2p\right)\mathrm{}{}_{}{}^4{}_{}{}^{}P_J^{}{}_{}{}^{}$ states of the ${}_{}{}^4{}_{}{}^{}\mathrm{He}_{}^{-}{}_{}{}^{}$ ion has been studied by time-of-flight techniques in an axial magnetic field, and Zeeman quenching has been observed. Two distinct lifetime components (11 μsec, 210 μsec) have been identified in a 100-eV beam with an axial field of 400 G. The zero-field lifetimes obtained from these and other measurements are 11 ± 5 μsec for $J=\frac{1}{2}$, $\frac{3}{2}$, and 345 ± 90 μsec for $J=\frac{5}{2}$. The $\frac{5}{2}-\frac{3}{2}$ fine-structure interval is estimated to be 0.050 ± 0.015 ${\mathrm{cm}}^{-1\mathrm{}}$.