The structure of ${}^{58}$Fe was investigated at Gammasphere using ${}^{48}$Ca(${}^{13,14}$C,$x$$n$) fusion-evaporation reactions at a beam energy of 130 MeV. The level scheme has been revised and extended to $J\sim 17\hslash$ and an excitation energy of 16.6 MeV. Regular band structures consisting of low-energy $\Delta J=1\hslash$ transitions have been observed at moderate spin ($J\sim 8\hslash$–15$\hslash$) and are candidates for magnetic rotational bands. Self-consistent tilted-axis-cranking calculations within a relativistic mean-field theory were applied to investigate these bands and were found to reproduce the experimental results well. In other parts of the level scheme, quasirotational bands composed of stretched-$E2$ transitions have been extended to high spin, and other new bands have been identified. Positive-parity experimental states were compared to predictions of the spherical shell model using the GXPF1A, KB3G, and FPD6 effective interactions in the $fp$ model space. The projected shell model, with a deformed quasiparticle basis including the neutron $\nu g_{9/2}$ orbital, was applied to interpret regular $\Delta J=2\hslash$ band structures that extend beyond the maximum spin available for $\pi$[($f_{7/2}$)${}^{-2}$] $\otimes$ $\nu$[($p_{3/2}{f}_{5/2}{p}_{1/2}$)${}^4$] configurations and exhibit features characteristic of rotational alignment. It is clear that the $\nu g_{9/2}$ intruder orbital plays a crucial role in describing the quasirotational structures in this nucleus, even starting as low as $J\sim 5\hslash$.

• Received 22 February 2012

DOI:https://doi.org/10.1103/PhysRevC.85.044316