Striking harmony between the nuclear shell model and new experimentalgfactors andB(E2)values of even Ni isotopes

Abstract

High precision g factors and $B(E2)$ values were obtained in measurements of the first ${2}^{+}$ states of ${}^{58\ensuremath{-}64}\mathrm{Ni}$ using the technique of projectile Coulomb excitation in combination with transient magnetic fields. The new results are well explained by large-scale shell model calculations in which, for ${}^{58\ensuremath{-}62}\mathrm{Ni},$ up to $t=5$ nucleons are excited from the ${f}_{7/2}$ shell into the remaining $\mathrm{fp}$ shell orbits. A complete calculation was carried out for ${}^{64}\mathrm{Ni}.$ The g factor of ${}^{58}\mathrm{Ni}$ is particularly surprising as it is small but definitely positive, a result which was not expected and therefore not considered in several earlier calculations. This observation can be explained by strong coupling of valence particles to an excited ${}^{56}\mathrm{Ni}$ core in accordance with recent Monte Carlo shell model calculations.