Properties of high-spin states in 91Nb and 91Zr via 6Li-induced reactions

The properties of high-spin states in 91Nb and 91Zr have been studied with the 88Sr(6Li, 3n)91Nb and 88Sr(6Li, p2 n)91Zr reactions. In-beam measurements with Ge(Li) and Si(Li) detectors of γ-ray excitation functions, γ-γ coincidences, γ-ray angular distributions, and pulsed beam-γ timing spectra were made to establish decay schemes, level energies, spin-parity assignments, γ-ray multipolarities, and isomeric lifetimes. All of the high-spin states involving the π1g9/2, π2p1/2, and ν2d5/2 orbitals as well as other more complicated states were identified. In particular, the theoretically predicted isomeric states in 91Nb and 91Zr were found: the vertical-bar (1g9/2)22p1/2, 17/2-> state in 91Nb is at 2035 keV with a tau = 5.42 +- 0.18 μsec, and vertical-bar (1g9/2) 22d5/2, 21/2+> state in 91Zr is at 3167 keV with a tau = 6.28 +- 0.20 μsec. The experimental energy levels and B (E2) values (E2 effective charges) obtained for these nuclei as well as those of other N = 50 and 51 nuclei are compared with recent theoretical work of Gloeckner et al