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Background: The nucleon-nucleus dispersive optical model (DOM) has been successful in providing good fits to scattering data and in making valuable predictions for bound-state properties in single- and double-closed shell nuclei. However, the generalizability of the DOM remains an ongoing issue. Purpose: We investigate the DOM in the continuum and bound-state regions of the open-shell, self-conjugate nuclei 28Si and 32S. We collect new differential cross section and analyzing power data for elastic scattering at incident neutron energies between 8.0 and 18.9 MeV. Methods: The measurements were conducted using a pulsed deuteron beam, the ²He(d,rc)³He source reaction, and time-of-flight techniques. All data were corrected for finite-geometry effects. Phenomenological DOM potentials were tailored to fit the differential and total cross section data, and then extrapolated to the bound-state regions. The DOM bound-state predictions were then compared to experimental data available for single-particle energies, occupation probabilities, root-mean-square radii, and spectroscopic factors. Results: The DOM bound-state predictions are in only fair agreement with experimental data and with USD shell-model predictions. Similar results are found after converting our neutron DOMs into proton DOMs. We investigate the separate effects of the dispersive surface and volume potential components on occupation probability and find that the volume component leads to a uniform depletion of the hole states, while the surface component acts mainly to deplete the valence orbitals. We compare these results to those of a variational multiparticle multihole configuration mixing {mp-mh CM) calculation using the Gogny DIS effective force. Conclusions: We find that the phenomenological DOM, which was originally designed for spherical nuclei, show certain deficiencies when applied to open-shell nuclei and suggest possible avenues of improvement. We also find that the predictions of occupation probability by the DOM using the dispersive surface component are similar to those by the mp-mh CM. This lends support to the interpretation that the surface absorption in the optical model originates from particle-vibration couplings, that is, long-range correlations. [ABSTRACT FROM AUTHOR]

Background: High-accuracy and self-consistent fission product yield (FPY) data are needed to advance microscopic/macroscopic descriptions of the nuclear fission process, to improve the predictive power of phenomenological models, and for applications in nuclear energy, nuclear forensics, and homeland security. Purpose: In a collaboration between the Triangle Universities Nuclear Laboratory (TUNL), Los Alamos National Laboratory (LANL), and Lawrence Livermore National Laboratory (LLNL), the dependence of a number of cumulative FPYs on the incoming neutron energy has been measured and unexpected energy dependencies of certain fission products have been reported [M. E. Gooden, Nucl. Data Sheets 131, 319 (2016)]. To investigate whether this observation is unique to neutron-induced fission, a program has been initiated to measure FPYs in photon-induced fission. Method: The photon-induced FPYs were measured by a combination of fission counting using a specially designed dual-fission chamber and γ-ray counting. The measurements were carried out with a monoenergetic photon beam at the HIγS facility. Gamma-ray counting of the activated targets was performed with well-shielded high-purity germanium (HPGe) detectors over a period of two months after irradiation to properly identify the decay history of fission products. Results: We report on our photofission product yield measurements on 235U, 238U, and 239Pu using a monoenergetic photon beam of Eγ=13MeV. More than 40 fission products were uniquely identified, and their yield values were computed. The use of the fission chamber with post-activation measurements has provided absolute fission product yield data with minimal uncertainties. Conclusion: The photon-induced cumulative fission product yields of 235U, 238U, and 239Pu are compared with previous photon- and neutron-induced fission measurements. In the near future data will be obtained at lower and higher photon energies. [ABSTRACT FROM AUTHOR]

This paper reports the results of the first measurements of the differential cross section of the 80Se(γ,n)79Se reaction with a linearly polarized gamma-ray (γ-ray) beam. The cross section was measured at three incident γ-ray beam energies: 15.6, 15.8, and 16.0 MeV, with a beam energy spread of 3.0% full width at half-maximum (FWHM). The differential cross section for the excitation spectrum in 79Se was measured at two scattering angles in the plane of the beam polarization: θ=90° and 135°, and at one angle in the plane perpendicular to the plane of polarization: θ=90°. The total photoneutron cross sections determined from these data are between 0.8 and 1.3 standard deviations smaller than previously published results. The excitation spectra measured in this work were fit with a Hauser-Feshbach model. Better fits to the data were obtained with a constant-temperature formulation of the nuclear level density (NLD) than with a Fermi-gas NLD model. The parameters for the constant-temperature NLD model obtained in this work are consistent with those obtained for medium-mass nuclei in previous studies. [ABSTRACT FROM AUTHOR]

Background: High-accuracy data are needed to advance microscopic descriptions of the nuclear fission process, to improve the predictive precision of phenomenological models, and for applications in nuclear energy and homeland security. Purpose: The main goal of this work is to provide high-accuracy cross-section data for photofission of 235U, 238U, and 239Pu in the energy range from the fission threshold to the high-energy tail of the giant dipole resonance. These new data should contribute significantly to the reduction of the systematic uncertainty in evaluated photofission cross-section databases. Method: Cross-section ratios for photofission of the big threee actinide nuclei were measured using a quasimonoenergetic photon beam and dual-fission chambers. The measurements were performed at the HIγS facility using a photon beam produced from Compton backscattering of free-electron laser light. The dual-fission chamber enabled simultaneous counting of fission events from two targets. This method allows for cross-section ratio measurements with very small systematic errors. The largest source of systematic error in the determination of the cross-section ratios is the uncertainty in the ratio of the target thicknesses. Results: We report photon-induced fission cross-section ratios for [235U(γ,f)/238U(γ,f)], [235U(γ,f)/239Pu(γ,f)], and [238U(γ,f)/239Pu(γ,f)] at photon energies from 9.0017.0 MeV. More than 20 data points were measured for each ratio, and the systematic uncertainties are less than 2%. Conclusion: The present photofission cross-section ratio data sets are compared to ratios computed from previous measurements, to the corresponding neutron-induced fission cross-section ratios, and to ratios computed from evaluated databases. The data obtained in this work for [235U(γ,f)/238U(γ,f)] are consistent with the existing data, while for [235U(γ,f)/239Pu(γ,f)] and [238U(γ,f)/239Pu(γ,f)] the present data are systematically lower. [ABSTRACT FROM AUTHOR]

Using dual-fission chambers each loaded with a thick (200-400-mg/cm²) actinide target of 235,238U or 239Pu and two thin (~10-100-μg/cm²) reference foils of the same actinide, the cumulative yields of fission products ranging from 92Sr to 147Nd have been measured at En = 8.9MeV. The ²H(d,n)³He reaction provided the quasimonoenergetic neutron beam. The experimental setup and methods used to determine the fission product yield (FPY) are described, and results for typically eight high-yield fission products are presented. Our FPYs for 235U(n,f), 238U(n,f), and 239Pu(n,f) at 8.9 MeV are compared with the existing data below 8 MeV from Glendenin et al. [Phys. Rev. C 24, 2600 (1981)], Nagy et al. [Phys. Rev. C 17, 163 (1978)], Gindler et al. [Phys. Rev. C 27, 2058 (1983)], and those of Mac Innes et al. [Nucl. Data Sheets 112, 3135 (2011)] and Laurec et al. [Nucl. Data Sheets 111, 2965 (2010)] at 14.5 and 14.7 MeV, respectively. This comparison indicates a negative slope for the energy dependence of most fission product yields obtained from 235U and 239Pu, whereas for 238U the slope issue remains unsettled. [ABSTRACT FROM AUTHOR]

The ½ → ½ superallowed mixed mirror decay of 19Ne to 19F is excellently suited for high precision studies of the weak interaction. However, there is some disagreement on the value of the half-life. In a new measurement we have determined this quantity to be T½ - 17.2832 ± 0.0051(stat) ± 0.0066(syst) s, which differs from the previous world average by 3 standard deviations. The impact of this measurement on limits for physics beyond the standard model such as the presence of tensor currents is discussed. [ABSTRACT FROM AUTHOR]

We present measurements of n-d analyzing power, Ay(θ), at En=22.5 MeV. The experiment uses a shielded neutron source which produced polarized neutrons via the ²H(d,n )3He reaction. It also uses a deuterated liquid-scintillator center detector and six pairs of liquid-scintillator neutron side detectors. Elastic neutron scattering events are identified by using time-of-flight techniques and by setting a window in the center detector pulse-height spectrum. The beam polarization is monitored by using a high-pressure helium gas cell and an additional pair of liquid-scintillator side detectors. The n-d Ay(θ) data were corrected for finite-geometry and multiple-scattering effects using a Monte Carlo simulation of the experiment. The 22.5-MeV data demonstrate that the three-nucleon analyzing power puzzle also exists at this energy. They show a significant discrepancy with predictions of high-precision nucleon-nucleon potentials alone or combined with Tucscon-Melbourne or Urbana IX three-nucleon forces, as well as currently available effective-field theory based potentials of next-to-next-to-next-to-leading order. [ABSTRACT FROM AUTHOR]

Cross-section measurements have been made at 16 and 19 MeV in two exit-channel configurations of neutrondeuteron breakup: the space star and coplanar star. In this kinematically complete measurement, the outgoing proton and one of the neutrons were detected in coincidence and their energies were determined via timeof- flight techniques. Monte Carlo simulations based on rigorous three-nucleon Faddeev calculations using the charge-dependent-Bonn (CD-Bonn) nucleon-nucleon potential were used to compare the experimental results with theory. Large discrepancies between data and theory were found in both breakup configurations measured at both energies, suggesting deficiencies in current theoretical treatment of three-nucleon forces or in present knowledge of the neutron-neutron 1So force. [ABSTRACT FROM AUTHOR]

Models of the r process are sensitive to the production rate of 9Be because, in explosive environments rich in neutrons, α(αn, γ)9Be is the primary mechanism for bridging the stability gaps at A = 5 and A = 8. The α(αn, γ)9Be reaction represents a two-step process, consisting of α +α → 8Be followed by 8Be(n, γ)9Be. We report here on a new absolute cross-section measurement for the 9Be(γ, rc)8Be reaction conducted using a highly efficient, 3He-based neutron detector and nearly monoenergetic photon beams, covering energies from Eγ = 1.5 MeV to Eγ = 5.2 MeV, produced by the High Intensity γ-ray Source of Triangle Universities Nuclear Laboratory. In the astrophysically important threshold energy region, the present cross sections are 40% larger than those found in most previous measurements and are accurate to ±10% (95% confidence). The revised thermonuclear α(αn, γ)9Be reaction rate could have implications for the r process in explosive environments such as type II supernovae. [ABSTRACT FROM AUTHOR]

Nuclear resonance fluorescence experiments were carried out at the High-Intensity γ-ray Source facility at Triangle Universities Nuclear Laboratory to characterize the low-energy dipole structure of 238U using 100% linearly polarized photon beams from 2.0 to 6.2 MeV. 113 transitions corresponding to de-excitations to the ground state in 238U were observed and the energy, spin, parity, integrated cross section, reduced width, and branching ratio were determined for each of these identified levels. The total E1 γ-ray interaction cross section was calculated and it was deduced that the observed concentration of low-lying El transitions were excited from the low-energy tail of the giant dipole resonance and were not a pygmy dipole resonance. Comparisons were made between quasiparticle random-phase approximation calculations and the experimentally observed strength. The observed and predicted M1 strength agreed well with each other. However, there was no similar agreement for the £1 strength. [ABSTRACT FROM AUTHOR]

The 48Ca(γ,n) cross section was measured by using γ-ray beams of energies between 9.5 and 15.3 MeV generated at the Triangle Universities Nuclear Laboratory high-intensity γ-ray source. Prior to this experiment, no direct measurements had been made with γ-ray beams of sufficiently low energy spread to observe a structure in this energy range. The cross sections were measured at 34 different γ-ray energies with an enriched 48Ca target. Neutron emission is the dominant decay mechanism in the measured energy range that spans from the threshold, across the previously identified M1 strength, and up the low-energy edge of the E1 giant dipole resonance. This paper found B(M1) = 6.8 ± Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. for the 10.23-MeV resonance, a value greater than previously measured. Structures in the cross section have been observed whose magnitudes are in agreement with existing data and that are commensurate with extended random-phase approximation calculations. [ABSTRACT FROM AUTHOR]

Gamma-ray transitions in 235 U were measured using the (γ, γ′ reaction below 3 MeV. The nuclear-resonance- fluorescence experiment was carried out at the High-Intensity γ-ray Source facility using nearly monoenergetic and circularly polarized photon beams. More than 20 transitions corresponding to deexcitations to the ground state and low-lying levels in 235U were observed. The integrated cross sections to the excited levels and intensities of branching transitions were deduced. The experimental results are compared with predictions from a quasiparticle random-phase approximation in a deformed basis. [ABSTRACT FROM AUTHOR]

Properties of low-energy dipole states in 232Th have been investigated with the nuclear resonance fluorescence technique. The present work used monoenergetic γ-ray beams at energies of 2-4 MeV from the high-intensity γ-ray source at Triangle Universities Nuclear Laboratory. Over 40 transitions corresponding to deexcitation to the ground state and first excited state were observed for the first time. Excitation energies, integrated cross sections, decay widths, branching ratios, and transition strengths for those states in 232Th were determined and compared with quasiparticle random-phase-approximation calculations. A large number of E1 transitions were observed for the first time in actinide nuclei with summed strength of 3.28(69)×10-3 e2 fm2. The observed summed M1 strength of 4.26(63)μN2 is in good agreement with the other actinides and with the systematics of the scissors mode in deformed rare-earth nuclei. [ABSTRACT FROM AUTHOR]

We report on new measurements establishing the existence of low-lying isomeric states in ^{136}Cs using γ rays produced in ^{136}Xe(p,n)^{136}Cs reactions. Two states with O(100)  ns lifetimes are placed in the decay sequence of the ^{136}Cs levels that are populated in charged-current interactions of solar neutrinos and fermionic dark matter with ^{136}Xe. Xenon-based experiments can therefore exploit a delayed-coincidence tag of these interactions, greatly suppressing backgrounds to enable spectroscopic studies of solar neutrinos and dark matter.

We report new measurements of the ratio of the electric form factor to the magnetic form factor of the neutron, G(n)(E)/G(n)(M), obtained via recoil polarimetry from the quasielastic 2H(e-->,e(')n-->)1H reaction at Q2 values of 0.45, 1.13, and 1.45 (GeV/c)(2) with relative statistical uncertainties of 7.6% and 8.4% at the two higher Q2 points, which points have never been achieved in polarization measurements.

Cotton and snap bean were selected for a multi-year, multi-state regional (south-eastern USA) research project to evaluate the efficacy of both commercial and experimental bacterial and fungal biological control agents for the management of damping-off diseases. The goal for this portion of the project was to determine the viability and stability of biological agents after application to seed. The biological seed treatments used included: (1) Bacillaceae bacteria, (2) non-Bacillaceae bacteria, (3) the fungus Trichoderma and (4) the fungus Beauveria bassiana. Seed assays were conducted to evaluate the following application factors: short-term (< or = 3 months) stability after seed treatment; quality (i.e. isolate purity); compatibility with chemical pesticides and other biocontrol agents; application uniformity between years and plant species. For the bacterial treatments, the Bacillaceae genera (Bacillus and Paenibacillus) maintained the greatest population of bacteria per seed, the best viability over time and the best application uniformity across years and seed type. The non-Bacillaceae genera Burkholderia and Pseudomonas had the least viability and uniformity. Although Beauveria bassiana was only evaluated one year, the seed fungal populations were high and uniform. The seed fungal populations and uniformity for the Trichoderma isolates were more variable, except for the commercial product T-22. However, this product was contaminated with a Streptomyces isolate in both the years that it was evaluated. The study demonstrated that Bacillaceae can be mixed with Trichoderma isolates or with numerous pesticides to provide an integrated pest control/growth enhancement package.

We have measured the transverse asymmetry A(T') in 3He(e,e(')) quasielastic scattering in Hall A at Jefferson Laboratory with high precision for Q2 values from 0.1 to 0.6 (GeV/c)(2). The neutron magnetic form factor G(n)(M) was extracted based on Faddeev calculations for Q2 = 0.1 and 0.2 (GeV/c)(2) with an experimental uncertainty of less than 2%.

The role of extracellular chitinase in the biocontrol activity of Trichoderma virens was examined using genetically manipulated strains of this fungus. The T. virens strains in which the chitinase gene (cht42) was disrupted (KO) or constitutively over-expressed (COE) were constructed through genetic transformation. The resulting transformants were stable and showed patterns similar to the wild-type (WT) strain with respect to growth rate, sporulation, antibiotic production, colonization efficiency on cotton roots and growth/survival in soil. Biocontrol activity of the KO and COE strains were significantly decreased and enhanced, respectively against cotton seedling disease incited by Rhizoctonia solani when compared with the WT strain.