Levels ofGa69andGa71via the (n, n′γ) Reactions

Abstract

Differential cross sections for the production of $\gamma$ rays in the $\mathrm{Ga}(n, n^{\prime }\gamma )$ reactions have been measured at 90° as a function of incident energy for $0.4\le E_n\le 2.5$ MeV. Angular distributions at $E_n=0.650, 0.800, 1.50, \mathrm{and} 1.78$ MeV have also been measured. Level schemes and decay schemes including branching ratios have been determined. An earlier scheme for ${}_{}{}^{69}{}_{}{}^{}\mathrm{Ga}$ is confirmed, and two new levels are found. The level scheme of ${}_{}{}^{71}{}_{}{}^{}\mathrm{Ga}$ is defined for excitation energies below 2 MeV. From the $\gamma$-ray angular distributions and neutron inelastic scattering cross sections, spins have been determined for five levels in each isotope. When these and other measurements are combined, the following excitation energies in keV, spins, and parities result. In ${}_{}{}^{69}{}_{}{}^{}\mathrm{Ga}$: 319(${\mathrm{½}}^{-}$), $573\left({\frac{5}{2}}^{-}\right)$, $873\left({\frac{3}{2}}^{-}\right)$, 1027, $1108\left(\le \frac{5}{2}\right)$ $1334\left(\frac{7}{2}\right)$, 1527, 1724, and 1893. In ${}_{}{}^{71}{}_{}{}^{}\mathrm{Ga}$: 390(${\mathrm{½}}^{-}$), $487\left({\frac{5}{2}}^{-}\right)$, $512\left({\frac{3}{2}}^{-}\right)$, $911({\frac{1}{2}}^{-}, {\frac{3}{2}}^{-})$, $965\left(\frac{7}{2}\right)$, $1108\left({\frac{7}{2}}^{-}\right)$, 1474, 1487, $1495\left({\frac{9}{2}}^{+}\right)$, 1700, and 1750.