Abstract
We report on the observation of excited states in the niobium isotope with masses 84, 85 and 86. These nuclei lie in the shape transition region known to occur in nuclei with 35⩽
Z⩽40 and
N=45. Unambiguous identification was achieved by detecting γ-rays in coincidence with mass-separated recoils produced in heavy-ion fusion reactions. Rotational bands were observed in
84Nb and
85Nb which show decoupling schemes similar to those in the neighbouring nuclei. A rotational model was used to interpret these bands and the quasiparticle configurations involved. Two sequences of transitions were observed in
86Nb, at least one of which appears to be a rotational band.