We have measured the mean lives of two levels in Rb ii by exciting them selectively in fast beams of metastable ${\mathrm{Rb}}^{+}$ ions with radiation from an argon-ion laser, and observing their time-resolved decay downstream. The results are for $5p\frac{3}{2}{\left[\frac{1}{2}\right]}_1$, 8.04 ± 0.08 nsec, and for $5p\frac{1}{2}{\left[\frac{1}{2}\right]}_1$, 6.9 ± 0.2 nsec. We describe some of the systematic errors that must be minimized in order that the accuracies obtained by this method approach or surpass those obtained by other means. Our results show clearly that advanced calculational methods are necessary in order to take full advantage of the experimental accuracy.

• Received 14 April 1975

DOI:https://doi.org/10.1103/PhysRevA.12.987