Level structure ofAs74from theGe72(α,npγ)reaction

Abstract

States of $^{74}\mathrm{As}$, excited through the $^{72}\mathrm{Ge}(\ensuremath{\alpha},np\ensuremath{\gamma})$ reaction at ${E}_{\ensuremath{\alpha}}=30 \mathrm{to} 55$ MeV, were studied. Excitation functions, $\ensuremath{\gamma}$-ray angular distributions, $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidences, and $\ensuremath{\gamma}$-time distributions with respect to the beam bursts, were determined. Three excited states are identified with states previously observed with the ($p,n$) reaction. In addition, six new levels are incorporated into the level scheme. The decay pattern of these levels is rather simple. The existence of two $\ensuremath{\gamma}$-ray cascades showing quite similar energy spacings and possible spin sequence $J=7\ensuremath{\rightarrow}6\ensuremath{\rightarrow}5\ensuremath{\rightarrow}4$ which mainly feed the known ${3}^{\ensuremath{-}}$ state at 183.0 keV state is observed. A half-life ${T}_{\frac{1}{2}}=28\ifmmode\pm\else\textpm\fi{}2$ nsec of a level at 259.2 keV was determined. This is the state whose $g$ factor was previously assigned to a level at 273.8 keV.NUCLEAR REACTION $^{72}\mathrm{Ge}(\ensuremath{\alpha},np\ensuremath{\gamma})^{74}\mathrm{As}$,${E}_{\ensuremath{\alpha}}=30 \mathrm{to} 55$ MeV; measured ${E}_{\ensuremath{\gamma}}$,${I}_{\ensuremath{\gamma}}$,$\ensuremath{\gamma} (\ensuremath{\theta})$, exc. funct., $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$,$\ensuremath{\gamma}\ensuremath{-}t$ (nsec). $^{74}\mathrm{As}$ deduced levels, $J$,$\ensuremath{\pi}$,${T}_{\frac{1}{2}}$. Enriched Ge targets. Ge(Li) detectors.