Particle-γ-Ray Angular-Correlation Study ofNi57in the ReactionNi58(He3,αγ)Ni57

The levels of ${}_{}{}^{57}{}_{}{}^{}\mathrm{Ni}$ populated in the reaction ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}({}_{}{}^3{}_{}{}^{}\mathrm{He},\alpha ){}_{}{}^{57}{}_{}{}^{}\mathrm{Ni}$ have been studied using the method of particle-$\gamma$-ray angular correlations. The $\alpha$ particles were detected at 0° with respect to the incident beam by a position-sensitive detector located at the focal point of a magnetic spectrometer. Four 7.6×10.2-cm NaI (Tl) crystals were used simultaneously to detect coincident $\gamma$ rays at angles between 90° and 160°. Using $l$ values known from previous work, the following spin-parity assignments are made for the levels indicated: $0.78 \mathrm{MeV} {\frac{5}{2}}^{-}$, $1.11 \mathrm{MeV} {\frac{1}{2}}^{-}\left({\frac{3}{2}}^{-}\right)$, $2.59 \mathrm{MeV} {\frac{7}{2}}^{-}$, $3.24 \mathrm{MeV} {\frac{7}{2}}^{-}$, $3.71 \mathrm{MeV} (\ge \frac{3}{2})$, $3.85 \mathrm{MeV} (\frac{3}{2},\frac{5}{2})$, $4.23 \mathrm{MeV} (\frac{3}{2},\frac{5}{2},\frac{7}{2})$, $4.56 \mathrm{MeV} \left(\le \frac{7}{2}\right)$, $5.22 \mathrm{MeV} {\frac{7}{2}}^{-}$, $5.56 \mathrm{MeV} {\frac{3}{2}}^{+}$, $6.00 \mathrm{MeV} {\frac{3}{2}}^{+}$, Branching ratios for the decays of these levels are presented, along with mixing rations for the stronger transitions.