Proton and neutron g{9}/{2} alignments in the N = 46 isotones 86Zr and 87Nb

The magnetic moments of the 8 ⁺ yrast state in ⁸⁶Zr and the {17}/{2 ^-} and {21}/{2 ⁺} yrast states in ⁸⁷Nb have been measured via the IMPAD technique. The nuclei were produced in the ⁵⁸Ni( ³²S ,x p) reaction; the time-integral Larmor precessions were measured after recoil implantation into a polarised Fe foil. The g-factors are used to deduce the character of the g_{9}/{2} shell alignments within the states and their structures are interpreted with the shell model in the ( g _{9}/{2},p _{1}/{2}), single-particle space, using the Gross-Frenkel two-body matrix elements. A survey on the various alignment schemes in these neutron-deficient isotopes is given. We find that neutron-pair alignment is favoured for even-parity states in the near-spherical nuclei with N ⩾ 46 but a major component of the odd-parity {17}/{2 ₁^-} state arises from the alignment of a neutron-proton pair in the g_{9}/{2} shell coupled to an unpaired neutron in the p_{1}/{2} shell.