The recoil-distance (or plunger) measurements of lifetimes of excited states produced in the bombardment of ${\mathrm{F}}^{19}$ by 5.5-MeV $\alpha$ particles is reported. A detailed discussion of small corrections involved in the analysis of these measurements is also p esented. The corrections discussed are due to finite velocity spread of recoils, spread in distance between the target and plunger, effects of perturbation of $\gamma$-ray angular distributions, and various efficiency and solid-angle effects. The mean lives determined are as follows: ${\mathrm{Na}}^{22*}$ (0.891 MeV): 14.4±0.7 psec; ${\mathrm{Na}}^{22*}$ (1.528 MeV): 5.0±0.7 psec; ${\mathrm{Na}}^{22*}$ (2.211 MeV): 20.8±1.0 psec; ${\mathrm{F}}^{19*}$ (1.346 MeV): 4.7±0.6 psec; and ${\mathrm{Ne}}^{22*}$ (1.275 MeV): 4.6±0.5 psec.

• Received 10 October 1968

DOI:https://doi.org/10.1103/PhysRev.178.1773