Possible coexistence of magnetic and antimagnetic rotations in Ni61

Abstract

The high-spin spectroscopy of $^{61}\mathrm{Ni}$ has been studied by the fusion-evaporation reaction $^{54}\mathrm{Cr}(^{11}\mathrm{B},4n)^{61}\mathrm{Ni}$ at a beam energy of 54 MeV. One dipole band and one quadrupole band in $^{61}\mathrm{Ni}$ are established for the first time. They can be respectively taken as candidates of magnetic and antimagnetic rotational bands based on the comparison with the well-known cases in $^{110}\mathrm{Cd}$ and the calculations of the classical particles-plus-rotor model. These two new bands are further investigated by the microscopic tilted axis cranking covariant density functional theory with configurations $\ensuremath{\pi}[{(1{f}_{7/2})}^{\ensuremath{-}1}{(fp)}^{1}]\ensuremath{\bigotimes}\ensuremath{\nu}[{(1{g}_{9/2})}^{1}{(fp)}^{4}]$ and $\ensuremath{\pi}[{(1{f}_{7/2})}^{\ensuremath{-}2}{(fp)}^{2}]\ensuremath{\bigotimes}\ensuremath{\nu}[{(1{g}_{9/2})}^{1}{(fp)}^{4}]$, respectively, and good agreement between experiment and calculation is obtained. By examining the angular-momentum coupling, the dipole band is characterized by the shears mechanism whereas the quadrupole band is characterized by the two-shears-like mechanism. This study provides evidence for possible coexistence of magnetic and antimagnetic rotations in the $A\ensuremath{\approx}60$ mass region.