Study of Nuclear States inNi60by Inelastic Electron Scattering

Inelastic scattering of electrons from ${}_{}{}^{60}{}_{}{}^{}\mathrm{Ni}$ was studied with an over-all energy resolution of 0.1% by the use of 183- and 250-MeV electron beams from the Tohoku 300-MeV linear accelerator. Peaks were found at 1.33 ($2^{+}$), 2.16 ($2^{+}$), 2.50 ($4^{+}$), 3.13 ($4^{+}$), 3.67 ($4^{+}$), 4.04 ($3^{-}$), 4.85 ($2^{+}$, $4^{+}$), 5.05 ($4^{+}$, $6^{+}$), 6.20 ($3^{-}$), 6.85 ($2^{+}$, $5^{-}$), and 7.05 MeV ($3^{-}$). The data were analyzed in Born approximation, using the Helm model to determine multipolarities and reduced transition probabilities. Distorted-wave calculations were also carried out for the 1.33-, 2.50-, and 4.04-MeV states. A striking feature of the present study is the discovery of the collective ($G=11\mathrm{}$) $6^{+}$ state at 5.05 MeV. The energies and transition probabilities of low-lying states were compared with the predictions of a recently developed theory based on the shell model.