Isospin purity of <i>T</i>=1 measurements in the <i>A</i>=38 nuclei studied via lifetime measurements in ³⁸K

The Doppler Shift Attenuation Method was used to measure lifetimes for levels in 38K at excitation energies of 1698, 2404, 2830, 2996, and 3671 keV, populated using the 40Ca(d, α) 38K reaction at a beam energy of 4.5 MeV. Values of 109(29), 95(22), 457(63), 130(40), and 160(50) fs, respectively, were measured and are compared with previous values obtained using different stopping powers. The matrix element for the transition between the Jπ = 2+ T=1 and 0+ T=1 states in this Tz = 0 nucleus is compared with the analogous transition in the other nuclei in the T = 1 triplet, 38Ca (Tz = −1) and 38Ar (Tz = +1), and with the results of shell-model calculations

Nuclear Structure of \u3csup\u3e76\u3c/sup\u3eGe from Inelastic Neutron Scattering Measurements and Shell Model Calculations

The low-lying, low-spin levels of 76Ge were studied with the (n,n′γ) reaction. Gamma-ray excitation function measurements were performed at incident neutron energies from 1.6 to 3.7 MeV, and γ-ray angular distributions were measured at neutron energies of 3.0 and 3.5 MeV. From these measurements, level spins, level lifetimes, γ-ray intensities, and multipole mixing ratios were determined. No evidence for a number of previously placed levels was found. Below 3.3 MeV, many new levels were identified, and the level scheme was re-evaluated. The B(E2) values support low-lying band structure. The 2+ mixed-symmetry state has been identified for the first time. A comparison of the level characteristics with large-scale shell model calculations yielded excellent agreement

Level Lifetimes and the Structure of \u3csup\u3e134\u3c/sup\u3eXe from Inelastic Neutron Scattering

The level structure of 134Xe was studied with the inelastic neutron scattering reaction followed by γ-ray detection. A number of level lifetimes were determined for the first time with the Doppler-shift attenuation method and the low-lying excited states were characterized. From this new spectroscopic information, the third excited state, a 0+ level which had only been observed in a previous inelastic neutron scattering study, was verified. Reduced transition probabilities were calculated; comparisons were drawn with a vibrational description of the nucleus and found lacking. The 3− octupole phonon has been confirmed, and the complete negative-parity multiplet resulting from the ν(1h11/22d3/2) configuration has also been tentatively identified for the first time in the N = 80 isotones

Inelastic Neutron Scattering Studies of \u3csup\u3e132,134\u3c/sup\u3eXe: Elucidating Structure in a Transitional Region and Possible Interferences for 0vββ Searches

Highly enriched (\u3e 99.9%) 132Xe and 134Xe gases were converted to solid 132XeF2 and 134XeF2 and were used as scattering samples for inelastic neutron scattering measurements at the University of Kentucky Accelerator Laboratory (UKAL). Lifetimes of levels up to 3.5MeV in excitation energy in these xenon isotopes were measured using the Doppler-shift attenuation method, allowing the determination of reduced transition probabilities. Gamma rays corresponding to new transitions and levels have been observed. In particular, tentative new excited 0+ states and associated decays have been examined in an effort to elucidate the structure of these nuclei in a transitional region, and comparisons have been drawn with models which seek to describe such nuclei, e.g., the E(5) critical-point symmetry of the IBM. Newly identified potential interferences for neutrinoless double-beta decay searches involving 136Xe are also discussed

Lifetime Measurements of Low-Spin Negative-Parity Levels in \u3csup\u3e160\u3c/sup\u3eGd

160Gd(n,n′γ) experiments were performed with accelerator-produced monoenergetic neutrons. Excitation functions at neutron energies from 1.5 to 2.8 MeV aided in the placement of γ rays in the level scheme and angular distributions at three neutron energies resulted in the determination of 28 excited-level lifetimes or limits in 160Gd, including the lifetimes of several negative-parity levels attributed to octupole vibrations

Collectivity of 0\u3csup\u3e+\u3c/sup\u3e States in \u3csup\u3e160\u3c/sup\u3eGd

Excited 0+ states in 160Gd have been examined with the (n,n′γ) reaction at incident neutron energies up to 2.8 MeV. Gamma-ray excitation functions and angular distribution measurements allow the confirmation of the existence of 0+ states at 1379.70 keV and 1558.30 keV, but we reject the assignments of additional previously suggested 0+ candidates. Limits on the level lifetimes of the observed 0+ states permit an evaluation of the collectivity of these states

0\u3csup\u3e+\u3c/sup\u3e States in \u3csup\u3e130,132\u3c/sup\u3eXe: A Search for E(5) Behavior

The level structures of 130,132Xe were studied with the inelastic neutron scattering reaction followed by γ-ray detection. Level lifetimes were measured using the Doppler-shift attenuation method and low-lying excited states in these nuclei were characterized. With a focus on the decay properties of the 0+ states, these nuclei were examined as representations of the E(5) critical-point symmetry

Studies of \u3csup\u3e54,56\u3c/sup\u3eFe Neutron Scattering Cross Sections

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

Collective Quadrupole Behavior in \u3csup\u3e106\u3c/sup\u3ePd

Excited states in 106Pd were studied with the (n,n′γ) reaction, and comprehensive information for excitations with spin ≤6ℏ was obtained. The data include level lifetimes in the femtosecond regime, spins and parities, transition multipolarities, and multipole mixing ratios, which allow the determination of reduced transition probabilities. The E2 decay strength to the low-lying states is mapped up to ≈2.4 MeV in excitation energy. The structures associated with quadrupole collectivity are elucidated and organized into bands

Probing the low-lying level structure of 94Zr through β¯ decay

223-227Low-lying states of 94Zr are populated following b- decay of 94Y, and the emitted g rays from 94Zr are detected using the 8p spectrometer composed of 20 Compton-suppressed HPGe detectors. High- statistics coincidence data have been used for the placement of very weak decay branches in the level scheme. Combining the results of level lifetimes from a previous experiment and the precisely measured branching ratio values of the weak decay branches from the present experiment, it is possible to extract the B(E2) values for all the possible decay branches from a given level. These values are helpful for proper identification of the collective and non-collective states of 94Zr. The experimental findings have been compared with predictions from shell-model calculations with a limited valence space; however, these calculations are inadequate in reproducing all of the measured spectroscopic quantities