Study of the Level Structure ofNi60from (p, p′γ) Angular Distributions

Abstract

Measurements of ${\mathrm{Ni}}^{60}(p, p^{\prime }\gamma )$ angular distributions have been made for incident proton energies of 5 to 7 MeV, using a 99.0% enriched ${\mathrm{Ni}}^{60}$ target 3.9 mg/${\mathrm{cm}}^2$ thick. The $\gamma$-ray spectra become quite complex at 7 MeV, with transitions from most of the ${\mathrm{Ni}}^{60}$ states up to 4-MeV excitation being present. The angular distributions remain essentially the same at various energies after correction for cascade feeding. The earlier tentative $0^{+}$ assignment for the 2.29-MeV level now appears to be correct, since the angular distribution of the 0.95-MeV $\gamma$ ray is isotropic (±4%) and the ($p, p^{\prime }$) cross section is in good agreement with Hauser-Feshbach theory. From its observed angular distribution, a 0.47-MeV cascade (2.63→2.16 MeV) has been identified as a $3^{+}(M1, E2)2^{+}$ transition essentially pure $E2\mathrm{}$ in character. The angular distribution of the 1.79-MeV cascade from the 3.12-MeV level agrees with the prediction for a $2^{+}(M1, E2)2^{+}$ transition with a mixing ratio of $\delta =0.24\mathrm{}\pm 0.06$, in accord with a previous determination from the decay of ${\mathrm{Cu}}^{60}$. The present work indicates the following level scheme for ${\mathrm{Ni}}^{60}$: 1.33($2^{+}$), 2.16($2^{+}$), 2.29($0^{+}$), 2.50($4^{+}$), 2.63($3^{+}$), and 3.12($2^{+}$); 3.19(1) and 3.39(3 or 2) MeV.