Nuclear Lifetimes of the 2815- and 3598-keV Levels ofK39

Abstract

The recoil-distance-Doppler-shift method has been used to measure the lifetimes of the 2815- and 3598-keV levels of ${}_{}{}^{39}{}_{}{}^{}\mathrm{K}$. These excited states were populated by the reaction ${}_{}{}^6{}_{}{}^{}\mathrm{Li}({}_{}{}^{35}{}_{}{}^{}\mathrm{Cl},d){}_{}{}^{39}{}_{}{}^{}\mathrm{K}$ using 68-MeV ${}_{}{}^{35}{}_{}{}^{}\mathrm{Cl}$ ions. The energies of the $\gamma$ rays from these two levels were determined with a 55-${\mathrm{cm}}^3$ Ge(Li) detector to be 783(±1), 2815(±1), and 3598(±1) keV. The mean lifetime of the 2815-keV level was measured as 79(±8) psec, and that of the 3598-keV level as 59(±4) psec. The corresponding $E3\mathrm{}$ strengths of 6.0(±0.1) and 25.5(±1.5) Weisskopf units are in very good agreement with the phonon-hole model calculations of Goode and Zambick.