Magnetic rotation and quasicollective structures in 58Fe: Influence of the νg9/2 orbital.

The structure of 58Fe was investigated at Gammasphere using 48Ca(13,14C,xn) fusion-evaporation reactions at a beam energy of 130 MeV. The level scheme has been revised and extended to J ∼ 17ħ and an excitation energy of 16.6 MeV. Regular band structures consisting of low-energy ΔJ = 1ħ transitions have been observed at moderate spin (J ∼ 8ħ-l5ħ) 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-£'2 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 GXPF1 A, KB3G, and FPD6 effective interactions in the fp model space. The projected shell model, with a deformed quasiparticle basis including the neutron νg9/2 orbital, was applied to interpret regular ΔJ = 2ħ band structures that extend beyond the maximum spin available for π[(f7/2)-2] ⨷ ν[(p3/2f5/2P1/2)4] configurations and exhibit features characteristic of rotational alignment. It is clear that the νg9/2 intruder orbital plays a crucial role in describing the quasirotational structures in this nucleus, even starting as low as J ∼ 5h. [ABSTRACT FROM AUTHOR]