The ionic beam—gas-target method was used to obtain intensity decay curves for some transitions of Ne I and Ne II. The mean radiative lifetimes of the upper levels were extracted by a computerized least-squares curve-fitting procedure. The lifetime of the $3p^{\prime }{}_{}{}^2{}_{}{}^{}D_{}^{\circ }{}_{}{}^{}$ level of Ne II was found in this way to be 5.2 ± 0.5 nsec. Somewhat less-reliable lifetimes were obtained for some $2p$ (Paschen notation) levels of Ne I. Those lifetimes $\tau$ in nsec are as follows: $\tau \left(2\mathrm{}{p}_1\right)=15.5\mathrm{}\pm 0.3$, $\tau \left(2\mathrm{}{p}_4\right)=24.8\mathrm{}\pm 0.7$, $\tau \left(2\mathrm{}{p}_6\right)=25.5\mathrm{}\pm 0.8$, and $\tau \left(2\mathrm{}{p}_9\right)=23.4\mathrm{}\pm 0.3$. Errors quoted for the Ne I lifetimes are standard deviations of several measurements. The error for the Ne II measurement represents a combination of statistical and possible systematic errors. Since the Ne I work may be affected by unresolved cascading, we do not claim an accuracy better than (15-20)% for those measurements. This paper completes the study of the ${\mathrm{Ne}}^{+}$ beam begun by Head and Head.

• Received 7 March 1973

DOI:https://doi.org/10.1103/PhysRevA.8.1644