Nuclear-Reaction Studies in the Nickel Isotopes: The ${\mathrm{Ni}}^{61}(p,p^{\prime }){\mathrm{Ni}}^{61}$, ${\mathrm{Ni}}^{61}(d,d^{\prime }){\mathrm{Ni}}^{61}$, and ${\mathrm{Ni}}^{60}\mathrm{}(d,p)\mathrm{}{\mathrm{Ni}}^{61}$ Reactions

The levels of ${\mathrm{Ni}}^{61}$ have been studied with the reactions ${\mathrm{Ni}}^{61}(p,p^{\prime }){\mathrm{Ni}}^{61}$, ${\mathrm{Ni}}^{61}(d,d^{\prime }){\mathrm{Ni}}^{61}$, and ${\mathrm{Ni}}^{60}\mathrm{}(d,p)\mathrm{}{\mathrm{Ni}}^{61}$ at bombarding energies of 7.5 MeV using the MIT-ONR Van de Graaff generator and both the single-gap and multiple-gap spectrographs. The ($p,p^{\prime }$) reaction seems to be dominated by a compound-nucleus mechanism, and served as a check that we had found all the levels below 4.0 MeV in ${\mathrm{Ni}}^{61}$. However, the ($d,d^{\prime }$) transitions to several states below 1.5-MeV excitation were direct and strongly enhanced. In the ($d,p$) reaction, 197 levels were found below 7.051 MeV in ${\mathrm{Ni}}^{61}$. The stripping transitions were analyzed with the distorted-wave Born-approximation code JULIE, and resulting neutron single-particle strengths $\mathrm{}(2J+1)\mathrm{}{S}_{l_n,j}$, center-of-gravity energies $E_{l_n,j}$, and sum-rule strengths are given. Detailed angular distributions for the nonstripping ($d,p$) transitions are also given. Most of them have a distinctly oscillatory structure with respect to scattering angle and many are shown to be identical in shape to those found in the ${\mathrm{Ni}}^{58}\mathrm{}(d,p)\mathrm{}{\mathrm{Ni}}^{59}$ reaction. An averaged strength function is given for these nonstripping states, and it is discussed in terms of intermediate structure. Possible interpretations of the ($d,d^{\prime }$) and ($d,p$) results related to the collective and single-particle character of the low-lying states in ${\mathrm{Ni}}^{61}$ are presented.