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Elastic and inelastic neutron scattering differential cross sections and γ-ray production cross sections have been measured on 54,56Fe at several incident energies in the fast neutron region between 1.5 and 4.7 MeV. All measurements were completed at the University of Kentucky Accelerator Laboratory (UKAL) using a 7-MV Model CN Van de Graaff accelerator, along with the neutron production and neutron and γ-ray detection systems located there. The facilities at UKAL allow the investigation of both elastic and inelastic scattering with nearly mono-energetic incident neutrons. Time-of-flight techniques were used to detect the scattered neutrons for the differential cross section measurements. The measured cross sections are important for fission reactor applications and also for testing global model calculations such as those found at ENDF, since describing both the elastic and inelastic scattering is important for determining the direct and compound components of the scattering mechanism. The γ-ray production cross sections are used to determine cross sections to unresolved levels in the neutron scattering experiments. Results from our measurements and comparisons to model calculations are presented.

Inelastic neutron scattering measurements were performed at the University of Kentucky Accelerator Laboratory on enriched 76Ge and 76Se scattering samples. From measurements at incident neutron energies from 2.0 to 4.0 MeV, many new levels were identified and characterized in each nucleus; level lifetimes, transition probabilities, multipole mixing ratios, and other properties were determined. In addition, γ-ray cross sections for the 76Ge(n,n′γ) reaction were measured at neutron energies up to 5.0 MeV, with the goal of determining the cross sections of γ rays in 2040-keV region, which corresponds to the region of interest in the neutrinoless double β decay of 76Ge. Gamma rays from the three strongest branches from the 3952-keV level were observed, but the previously reported 2041-keV γ ray was not. Population cross sections across the range of incident neutron energies were determined for the 3952-keV level, resulting in a cross section of ~0.1 mb for the 2041-keV branch using the previously determined branching ratios. Beyond this, the data from these experiments indicate that previously unreported γ rays from levels in 76Ge can be found in the 2039-keV region.

The lifetime of the second 2+ state in 94Zr was redetermined by the Doppler-shift attenuation method following inelastic neutron scattering (DSAM-INS) from metallic Zr and ZrO2 samples of natural isotopic abundance. The new value for the level lifetime differs significantly from the previously published value, with the new lifetime found to be roughly twice that value. A reanalysis of the original γ-ray data from the enriched 94ZrO2 sample failed to expose the source of this discrepancy; however, powder X-ray diffraction and scanning electron microscopy performed on each scattering sample, including the enriched sample used previously, provide clues to an explanation and reveal the role of the chemical properties of the sample material in DSAM-INS lifetime determinations.

The low-spin structure of 93Nb has been studied using the (n,n’γ) reaction at neutron energies ranging from 1.5 to 2.6MeV and the 94Zr(p, 2nγ)93Nb reaction at bombarding energies from 11.5 to 19MeV. Excitation functions, lifetimes, and branching ratios were measured, and multipolarities and spin assignments were determined. The Jπ = 3/2- and 5/2- states at 1840 and 2013keV, respectively, are identified as mixed-symmetry states associated with the $\ensuremath{(2_{1,{\rm ms}}^{+}) \otimes 2_{p_{1/2}}}$ particle-core coupling. These assignments are in agreement with energy systematics, spins and parities, and the observed strong M1 transitions to the 2 p1/2 one-phonon structure. [ABSTRACT FROM AUTHOR]

The low-lying structure of 112Sn has been studied. γ-ray excitation functions, ranging from 2.5 to 4.0MeV, and angular distributions at 2.9 and 3.8MeV have been measured following the (n,n′γ) reaction to characterize the decays of the excited levels. Level lifetimes have been measured with the Doppler-shift attenuation method. Low-lying 1-, (2-), 3- and, 5- states have been identified as members of the heterogeneous quadrupole-octupole quintuplet. Decay properties and excitation energies are consistent with the structure formed by the coupling of the lowest quadrupole, 21+, and octupole, 31-, excitations. [ABSTRACT FROM AUTHOR]