Nature of the 9/2+ band in odd-mass neutron-rich Cr nuclei

Neutron-rich Cr and Fe isotopes with N≈35 are soft near the ground state. The shape of the low-lying 9/2+ state at 0.503 MeV in the odd-mass 59Cr thus becomes a particular issue in understanding the role of the neutron g9/2 intruder orbital in this nucleus, and in this mass region in general. We apply the projected shell model and compare the calculated results between the two assumed basis deformations that are deduced with the spectroscopic quadrupole moment of the 9/2+ state obtained from the spherical shell model calculation. By studying moment of inertia, B(E2), and g factor values, it is concluded that different from its ground state, the 59Cr 9/2+ state has a stable prolate shape, consistent with the isotopes 55,57Cr and the isotone 61Fe.