Nuclear-Structure Studies of ${\mathrm{Co}}^{55}$ and ${\mathrm{Co}}^{57}$ by Means of the ${\mathrm{Fe}}^{54,56}({\mathrm{He}}^3, d)$ Reaction

A high-resolution study of the ${\mathrm{Fe}}^{54,56}({\mathrm{He}}^3, d){\mathrm{Co}}^{55,57}$ reactions at 16.5-MeV bombarding energy was performed. Twenty-five states of ${\mathrm{Co}}^{55}$ and forty-one states of ${\mathrm{Co}}^{57}$ below 8-MeV excitation energy were identified. The angular distribution of deuterons at forward angles was measured, and with the aid of distorted-wave Born-approximation predictions, values of angular momentum transfers and spectroscopic factors were evaluated for the more intense transitions. Analog states to some of the low-lying states in ${\mathrm{Fe}}^{55}$ and ${\mathrm{Fe}}^{57}$ were identified and Coulomb displacement energies of 9.00±0.03 and 8.90±0.03 MeV were determined for the ${\mathrm{Co}}^{55}$-${\mathrm{Fe}}^{55}$ and ${\mathrm{Co}}^{57}$-${\mathrm{Fe}}^{57}$ pairs, respectively. The location of $1f_{\frac{7}{2}}$, $2p_{\frac{3}{2}}$, and $2p_{\frac{1}{2}}$ single-particle proton states by means of the "centroid method" is discussed and evaluated for the case of ${\mathrm{Co}}^{55}$.