Lifetimes ofK39Excited States

The mean lifetimes of nine levels in ${}_{}{}^{39}{}_{}{}^{}\mathrm{K}$ up to 4.12 MeV in excitation have been measured by the Doppler-shift-attenuation method. The levels were populated by the ${}_{}{}^{39}{}_{}{}^{}\mathrm{K}(p,p^{\prime }\gamma ){}_{}{}^{39}{}_{}{}^{}\mathrm{K}$ reaction at proton energies of 6.47 and 6.67 MeV. $\gamma$ rays were detected in a 30-${\mathrm{cm}}^3$ coaxial Ge(Li) detector at 30 and 135° to the beam direction in coincidence with protons scattered between 164-174°. Transition strengths have been calculated for the first four excited states, and the results are compared with predictions of the weak-coupling model and a phonon-hole coupling model. The weak-coupling model is shown to underestimate $E2$, $M2$, and $E3$ strengths, while the phonon-hole coupling model predicts enhanced $E3$ strengths.