Mass and beta decay ofAs68

Abstract

$_{33}^{68}\mathrm{As}_{35}$ was produced by the $^{58}\mathrm{Ni}(^{12}\mathrm{C}, pn)^{68}\mathrm{As}$ reaction at ${E}_{^{12}\mathrm{C}}=32 \mathrm{and} 42$ MeV. $\ensuremath{\gamma}$ rays from the decay of $^{68}\mathrm{As}$ were observed both in singles and coincidence using large Ge(Li) detectors. This work yielded a more accurate half-life for $^{68}\mathrm{As}$ (151.5 \ifmmode\pm\else\textpm\fi{} 0.9 sec) as well as the identification of several new levels in $^{68}\mathrm{Ge}$, including a low-lying ${0}^{+}$ state. The ground-state spin of $^{68}\mathrm{As}$ was determined to be ${3}^{(+)}$ and its total decay energy ${Q}_{\mathrm{EC}}$ was measured to be 8.1 \ifmmode\pm\else\textpm\fi{} 0.1 MeV. This corresponds to a mass excess of -58.9 \ifmmode\pm\else\textpm\fi{} 0.1 MeV, which is compared with various predictions. Assignments or restrictions of the spin and parity for many states observed in $^{68}\mathrm{Ge}$ have been made. The structure of $^{68}\mathrm{Ge}$ is discussed in terms of a vibrational model.RADIOACTIVITY $^{68}\mathrm{As}$; measured ${T}_{\frac{1}{2}}$, ${E}_{\ensuremath{\gamma}}$, ${I}_{\ensuremath{\gamma}}$, $\ensuremath{\gamma}\ensuremath{\gamma}$ coin, ${E}_{{\ensuremath{\beta}}^{+}}$, ${\ensuremath{\beta}}^{+}\ensuremath{\gamma}$ coin; deduced decay scheme, $log\mathrm{ft}$, ${Q}_{\mathrm{EC}}$. $^{68}\mathrm{Ge}$ deduced levels, ${J}^{\ensuremath{\pi}}$. Enriched targets, Ge(Li) detectors, plastic scintillator, intrinsic Ge detector, rabbit, helium jet.