Considerable data have recently been collected on light zirconium isotopes. We present new measurements on ${}_{}{}^{84}{}_{}{}^{}\mathrm{Zr}$ and some unpublished results on ${}_{}{}^{82}{}_{}{}^{}\mathrm{Zr}$. We have performed calculations on ${}_{}{}^{82,84,86}{}_{}{}^{}\mathrm{Zr}$ using an extension to the IBM which allows a collective core to couple to up to four unpaired fermions (two broken pairs). The role of vibrational collectivity is clear in the N=44 and N=46 nuclei, but collective rotation becomes the dominant mode below N=44. The relative positions of the neutron and proton Fermi surfaces are crucial in determining the complexity of the decay path down the yrast states, being dominated by proton configurations for N≤44 but showing strong competition between neutron and proton structures when N>44.

• Received 11 June 1993

DOI:https://doi.org/10.1103/PhysRevC.48.2607