Conventional shell-model calculations of the iron isotopes with $A=56-60\mathrm{}$ are discussed. The calculated level spectra are in good agreement with experiment. The calculations of $E2\mathrm{}$ observables are in reasonable agreement with experiment when added effective charges of $1.0e$ are used for both neutrons and protons. The neutron effective charge is significantly different from one appropriate ($1.9e$) for ${}_{}{}^{56}{}_{}{}^{}\mathrm{Ni}$. There is a strong state dependence in the effective $M1\mathrm{}$ operator, and calculations of $M1\mathrm{}$ observables are in general disagreement with experiment. An analysis of the structure of ground-state bands and yrast levels is made in terms of a simple rotational model. In all even isotopes, the intrinsic quadrupole moments in the ground-state "band" shrink dramatically with increasing $J$. There is evidence of a band crossing in all three even isotopes, but no evidence is found for an abrupt shape change in the ground-state bands of these nuclei. It is concluded that no simple rotational model gives a good description of the low-lying states of the iron isotopes.

NUCLEAR STRUCTURE ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{59}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{60}{}_{}{}^{}\mathrm{Fe}$, calculated levels. ${}_{}{}^{56}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{58}{}_{}{}^{}\mathrm{Fe}$, ${}_{}{}^{60}{}_{}{}^{}\mathrm{Fe}$, calculated $B\left(M1\mathrm{}\right)\mathrm{}$, $B\left(E2\mathrm{}\right)\mathrm{}$, $\mu$, branching ratios. Shell model, Vervier interaction, Horie-Ogawa interaction, effective operators. Comparison with experiment and rotational model.

• Received 17 April 1979

DOI:https://doi.org/10.1103/PhysRevC.20.830