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

The structure of Fe-58 was investigated at Gammasphere using Ca-48(C-13,C-14,xn) fusion-evaporation reactions at a beam energy of 130 MeV. The level scheme has been revised and extended to J similar to 17 (h) over bar and an excitation energy of 16.6 MeV. Regular band structures consisting of low-energy Delta J = 1 (h) over bar transitions have been observed at moderate spin (J similar to 8 (h) over bar -15 (h) over bar) 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 (h) over barh band structures that extend beyond the maximum spin available for pi left perpendicular(f(7/2))(-2)right perpendicular circle times nu left perpendicular(p(3/2)f(5/2)p(1/2))(4)right perpendicular 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 similar to 5 (h) over bar.