Spectroscopy ofNb90at high spin

Abstract

Excited states of $^{90}\mathrm{Nb}$ were investigated via prompt and delayed \ensuremath{\gamma} decays and the recoil-isomer tagging technique. The level scheme of $^{90}\mathrm{Nb}$ has been extended up to $J=19\ensuremath{\hbar}$ and ${E}_{x}=8.4$ MeV. Half-lives of the ${11}^{\ensuremath{-}}$ and $17/{2}^{\ensuremath{-}}$ isomeric levels in $^{90,91}\mathrm{Nb}$ were measured to be $0.47\ifmmode\pm\else\textpm\fi{}0.01$ and $3.3\ifmmode\pm\else\textpm\fi{}0.4$ \ensuremath{\mu}s, respectively. The results are compared with the predictions of large-basis shell model calculations. The effects of truncation of the valence model space on the calculated results are discussed.