${}^{58}\mathrm{Co}$: Structure of an odd-odd nucleus in the pf shell

High-spin states in the odd-odd ${}^{58}\mathrm{Co}$ nucleus have been studied with the fusion-evaporation reaction ${}^{51}\mathrm{V}$ (${}^{10}\mathrm{B}$,$p2n$) using the γ-spectrometer Saci-Perere. Thirty-six new excited states up to spin ${11}^{+}$ and an excitation energy of 8.0 MeV have been observed, which are connected by 46 γ-ray transitions. Transition probabilities for 14 excited states were measured through the Doppler-shift attenuation method. The results are compared with shell-model calculations using the GXPF1 effective interaction, developed for use in the pf shell. These results were interpreted by considering particle-hole excitations with respect to the doubly magic $N=Z=28$ core.

Figure 1

γ-ray spectrum from the ${}^{10}\mathrm{B}$ on ${}^{51}\mathrm{V}$ (thin target experiment at $E=33$ MeV) gated on the 321-keV low-lying transition of the ${}^{58}\mathrm{Co}$ nucleus, and on protons detected by the SACI array. The γ rays, with energy indicated in keV, were assigned to the ${}^{58}\mathrm{Co}$ nucleus. The symbol ${}^{*}$refer to the ${}^{57}\mathrm{Co}$ γ-ray lines.

Figure 2

The partial level scheme of ${}^{58}\mathrm{Co}$ obtained from the present work.

Figure 3

γ-ray spectrum from the ${}^{10}\mathrm{B}$ on ${}^{51}\mathrm{V}$ (thin target experiment at $E=33$ MeV) gated on the 1992-keV low-lying transition of the ${}^{58}\mathrm{Co}$ nucleus, and on protons detected by the SACI array. These γ rays were assigned to the ${}^{58}\mathrm{Co}$ nucleus.

Figure 4

γ-ray spectrum from the ${}^{10}\mathrm{B}$ on ${}^{51}\mathrm{V}$ (thin target experiment at $E=33$ MeV) gated on the sum of 578- and 944-keV low-lying transitions of the ${}^{58}\mathrm{Co}$ nucleus, and on protons detected by the SACI array. These γ rays were assigned to the ${}^{58}\mathrm{Co}$ nucleus.

Figure 5

Line-shape analysis for the $7^{+}\to 5^{+}$ 1555-keV (top) and $7^{+}\to 6^{+}$ 505-keV (bottom) transitions, observed at ${101}^{°}$ and ${37}^{°}$, with a gate at 321 keV.

Figure 6

Line-shape analysis for the $6^{+}\to 5^{+}$ 1050-keV transition, depopulating the 1425-keV state, with a gate at 321 keV (top), and the $6^{+}\to 5^{+}$ 1051-keV transition, depopulating the 1076-keV state, with a gate at 1238 keV (bottom), both observed at ${101}^{°}$ and ${37}^{°}$.

Figure 7

Line-shape analysis for the $8^{+}\to 7^{+}$ 1465-keV transition observed at ${101}^{°}$ and ${37}^{°}$ and gated on the 505-keV transition.

Figure 8

Experimental and theoretical decay schemes for the excited states with spin 7.

Figure 9

Comparison between experimental and theoretical excited states in ${}^{58}\mathrm{Co}$.