Level and decay scheme studies inZr92andZr94via (n, n′γ) reactions

Abstract

Measurements of ($n, {n}^{\ensuremath{'}}\ensuremath{\gamma}$) excitation functions were made for incident neutron energies from 2.2 to 3.7 MeV. For $^{92}\mathrm{Zr}$, 51 transitions from 26 levels through 3472.0 keV excitation energy were observed. The $^{94}\mathrm{Zr}$ study of 20 levels through 3361.2 keV excitation energy produced 28 observed $\ensuremath{\gamma}$ rays, 12 of which were previously unidentified. Angular distributions were measured at 3.2 and 3.7 MeV bombarding energies for 24 and 39 transitions respectively in $^{92}\mathrm{Zr}$ and at 3.1 MeV for 18 transitions in $^{94}\mathrm{Zr}$. Two new levels were discovered in $^{92}\mathrm{Zr}$ at 2903.8 and 3407.9 keV. A previously reported ambiguity involving 2+ and 4+ levels in $^{94}\mathrm{Zr}$ has been resolved, revealing a 4+ level at 2329.0 keV and a 2+ level at 2365.4 keV. New levels were found in this isotope at 2507.6, 2698.0, 2825.2, and 2859.8 keV. Six unique spin or spin-parity assignments, based only on the present work, were made in $^{92}\mathrm{Zr}$(${E}_{x}$ in keV, ${J}^{\ensuremath{\pi}}$): 2339.0, 3; 2485.1, 5; 2742.6, 4; 2903.8, 0; 3056.5, 2; 3370.9, 1; and three in $^{94}\mathrm{Zr}$: 2365.4, 2; 2507.6, 3; 2603.7, (5). A ${4}^{\ensuremath{-}}$, ${5}^{\ensuremath{-}}$ excited proton doublet appears to have been found in each of the isotopes at excitation energies comparable to those for the doublet in $^{90}\mathrm{Zr}$. This suggests similar proton configurations for all three isotopes. Neutron inelastic scattering cross sections are in agreement with those from experiments employing neutron detection.NUCLEAR REACTIONS $^{92,94}\mathrm{Zr}(n, {n}^{\ensuremath{'}}\ensuremath{\gamma})$, $E=2.2\ensuremath{-}3.7$ MeV; measured ${E}_{\ensuremath{\gamma}}$, $\ensuremath{\sigma}(E; {E}_{\ensuremath{\gamma}}, 90\ifmmode^\circ\else\textdegree\fi{})$, $\ensuremath{\sigma}({E}_{\ensuremath{\gamma}}, {\ensuremath{\bigominus}}_{\ensuremath{\gamma}})$. Calculated $\ensuremath{\sigma}({n}^{\ensuremath{'}})$, $\ensuremath{\sigma}({E}_{\ensuremath{\gamma}}, {\ensuremath{\bigominus}}_{\ensuremath{\gamma}})$, with statistical model. $^{92,94}\mathrm{Zr}$ deduced levels, $\ensuremath{\sigma}({n}^{\ensuremath{'}})$, $\ensuremath{\delta}$, $J$, $\ensuremath{\pi}$, branching ratio. Enriched targets, Ge(Li) detectors, time-of-flight background suppression.