Study ofNb93Levels with theMo96(p,α)Nb93Reaction

Abstract

Levels of $^{93}\mathrm{Nb}$ have been studied with the $^{96}\mathrm{Mo}(p,\ensuremath{\alpha})$ reaction at 15-MeV incident energy. Angular distributions for transitions to a dozen prominent levels below 2 MeV have been measured with 30- to 40-keV experimental resolution over ${15}^{\ensuremath{\circ}}\ensuremath{\le}{\ensuremath{\theta}}_{L}\ensuremath{\le}{150}^{\ensuremath{\circ}}$, and they have been compared with distorted-wave Born-approximation (DWBA) calculations. Angular distributions for $p\ensuremath{-}^{96}\mathrm{Mo}$ and $\ensuremath{\alpha}\ensuremath{-}^{93}\mathrm{Nb}$ elastic scattering have also been measured, and proton and $\ensuremath{\alpha}$-optical-model potential parameter sets have been determined by a search procedure. Of the three sets of $\ensuremath{\alpha}$-potential parameters, the one which best reproduced the measured ($p,\ensuremath{\alpha}$) angular distributions of known low-lying levels in $^{93}\mathrm{Nb}$ was chosen as the standard set for the rest of the ($p,\ensuremath{\alpha}$) calculations. The conventional triton-cluster form factor was used exclusively for the ($p,\ensuremath{\alpha}$) DWBA calculations which lead to ${J}^{\ensuremath{\pi}}$ assignments. A semimicroscopic form factor was used in a few test cases in order to check the sensitivity of calculations to the choice of form factor. Reliable ${J}^{\ensuremath{\pi}}$ assignments have been made for levels below 1.5 MeV based on the $j$ dependence for $l=1(p,\ensuremath{\alpha})$ transfers, as well as for higher angular momentum transfers observed in the present work; and they are in excellent agreement with those determined from recent Coulomb-excitation and $^{90}\mathrm{Zr}(\ensuremath{\alpha},p\ensuremath{\gamma})$ works. Dominant three-nucleon shell-model configurations to which the levels of interest belong have been proposed.