Lifetime Measurements of Excited States inK38

Excitation energies and mean lives of levels in ${}_{}{}^{38}{}_{}{}^{}\mathrm{K}$ up to 3.85 MeV, excited in the ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}(d,\alpha \gamma ){}_{}{}^{38}{}_{}{}^{}\mathrm{K}$ reaction at $E_d=4.421\mathrm{}$ MeV, have been measured using the Doppler-shift attenuation method. The $\gamma$ rays were detected at 31.7 and 121.7° in coincidence with $\alpha$ particles detected in an annular detector with an average angle of 169°. The following mean lifetimes were found (excitation energy in keV, lifetimes in fsec): 459, > 4000; 1698, 65 ± 17; 2401, 90 ± 25; 2613, ${9000}_{-2000\mathrm{}}^{+7000\mathrm{}}$; 2646, > 12000; 2829, 280 ± 70; 2870, 4500 ± 1200; 2993, 220 ± 50; 3315, 2450 ± 420; 3342, < 55; 3668, < 150; 3725, < 120; 3849, < 55. Several spin-parity restrictions made in earlier work have been made stricter on the basis of these results.