Low-spin excitations in Zr97

Abstract

The main goal of this work is the determination of spins and parities of excited states in $^{97}\mathrm{Zr}$, among others the 2264.3-keV level, which had previously been tentatively reported as the $11/{2}^{\ensuremath{-}}$ excitation corresponding to the ${h}_{11/2}$ neutron orbital. Low-spin excited states in $^{97}\mathrm{Zr}$ were populated via the cold-neutron capture reaction. The $\ensuremath{\gamma}$ rays emitted following the reaction were measured using the highly efficient array of high-purity germanium detectors, EXILL, at the Institut-Laue-Langevin (ILL), Grenoble. The primary $\ensuremath{\gamma}$ rays deexciting the capture state in $^{97}\mathrm{Zr}$ were identified for the first time. The new, precise neutron binding energy in $^{97}\mathrm{Zr}$ of 5569.15(4) keV differs significantly from the value reported in the literature. The previously reported level scheme has been amended by several new low-spin levels. The ($n,\ensuremath{\gamma}$) data were complemented by a measurement of the ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of $^{97}\mathrm{Y}$ at the Lohengrin fission-fragment separator of the ILL, and the observation of the ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of $^{97}\mathrm{Y}$ populated in neutron-induced fission of $^{235}\mathrm{U}$ and measured using the EXILL Ge array. The combined data allowed unique spin-parity assignments for many levels in $^{97}\mathrm{Zr}$. The 2264.3-keV level, with a new spin-parity assignment of $9/{2}^{+}$, may correspond to the $\ensuremath{\nu}{g}_{9/2}$ extruder orbital.