Science.gov

Sample records for low-energy neutron inelastic

  1. Neutron inelastic scattering measurements of low-energy phonons in the multiferroic BiFeO3

    SciTech Connect

    Schneeloch, John A.; Xu, Zhijun; Wen, Jinsheng; Gehring, P. M.; Stock, C.; Matsuda, Masaaki; Winn, Barry L.; Gu, Genda; Shapiro, Stephen M.; Birgeneau, R. J.; Ushiyama, T.; Yanagisawa, Y.; Tomioka, Y.; Ito, T.; Xu, Guangyong

    2015-02-10

    In this study, we present neutron inelastic scattering measurements of the low-energy phonons in single crystal BiFeO3. The dispersions of the three acoustic phonon modes (LA along [100], TA1 along [010], and TA2 along [110]) and two low-energy optic phonon modes (LO and TO1) have been mapped out between 300 and 700 K. Elastic constants are extracted from the phonon measurements. The energy linewidths of both TA phonons at the zone boundary clearly broaden when the system is warmed toward the magnetic ordering temperature TN=640 K. In conclusion, this suggests that the magnetic order and low-energy lattice dynamics in this multiferroic material are coupled.

  2. Neutron inelastic scattering measurements of low-energy phonons in the multiferroic BiFeO3

    DOE PAGES

    Schneeloch, John A.; Xu, Zhijun; Wen, Jinsheng; ...

    2015-02-10

    In this study, we present neutron inelastic scattering measurements of the low-energy phonons in single crystal BiFeO3. The dispersions of the three acoustic phonon modes (LA along [100], TA1 along [010], and TA2 along [110]) and two low-energy optic phonon modes (LO and TO1) have been mapped out between 300 and 700 K. Elastic constants are extracted from the phonon measurements. The energy linewidths of both TA phonons at the zone boundary clearly broaden when the system is warmed toward the magnetic ordering temperature TN=640 K. In conclusion, this suggests that the magnetic order and low-energy lattice dynamics in thismore » multiferroic material are coupled.« less

  3. Low-energy dispersion of dynamic charge stripes in La1.75Sr0.25NiO4 observed with inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Zhong, Ruidan; Tranquada, John; Gu, Genda; Reznik, Dmitry; Winn, Barry

    The dynamic stripe correlations have been the subject of intense research, owing to the possible links with high-Tc superconductivity. In light of a recently published, direct observation of charge-stripe fluctuations in La2-xSrxNiO4 using inelastic neutron scattering, we did a follow-up neutron experiment on a x=0.25 sample to characterize the low-energy dispersion of these dynamic charge stripes using the HYSPEC instrument at the Spallation Neutron Source. The scattering signals are collected in the vicinity of a charge-order peak with a large wave vector (4.4, 3, 0), where dynamic spin-stripe correlations are negligible. Mapping the low-energy charge-stripe fluctuations in a wide temperature range, we observe a finite dispersion along the stripe-modulation direction at T >=160K where the charge stripes become disordered, while the steep dispersion in the orthogonal direction is not resolved. Work at BNL supported by Office of Basic Energy Sciences, US DOE, under Contract No. DE-SC00112704.

  4. Low-energy spin excitations in (Li0.8Fe0.2)ODFeSe superconductor studied with inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Ma, Mingwei; Wang, Lichen; Bourges, Philippe; Sidis, Yvan; Danilkin, Sergey; Li, Yuan

    2017-03-01

    We report an inelastic neutron scattering study of single crystals of (Li0.8Fe0.2 )ODFeSe. Temperature-dependent low-energy spin excitations are observed near Q =(0.5 ,0.27 ,0.5 ) and equivalent wave vectors symmetrically surrounding Q =(0.5 ,0.5 ,0.5 ) in the 1-Fe Brillouin zone, consistent with a Fermi-surface-nesting description. The excitations are broadly distributed in energy, ranging from 16 to 35 meV. Upon cooling below the superconducting critical temperature (Tc), a magnetic response below twice the superconducting gap 2 ΔSC exhibits an abrupt enhancement, consistent with the notion of spin resonance, whereas the response at higher energies increases more gradually with only a weak anomaly at Tc. Our results suggest that (Li0.8Fe0.2 )ODFeSe might be on the verge of a crossover between different Cooper-pairing channels with distinct symmetries.

  5. Low energy neutrons from sun

    NASA Technical Reports Server (NTRS)

    Ahluwalia, H. S.

    1975-01-01

    Arguments are presented in support of an earlier suggestion that low-energy neutrons are likely to be more commonly produced in the solar atmosphere. It appears that protons with an energy not exceeding 100 MeV are more significant, especially those with an energy of about 10 MeV. It is also clear that in addition to the light elements C, N, O, and Ne, due attention should be paid to elements such as Mg, Si, S, Fe, etc., and their isotopes, even if they are not so abundant.-

  6. Inelastic pion scattering by /sup 13/C at low energies

    SciTech Connect

    Mitchell, J.H.

    1987-03-01

    Angular distributions for inelastically scattered pions were obtained for several states in /sup 13/C at an incident energy of 65 MeV. The data include results from both ..pi../sup +/ and ..pi../sup -/ measurements. In addition, ..pi../sup -/ measurements were made at T/sub ..pi../ = 50 MeV at one angle to give a two point fixed-q excitation function. The data are compared to theory and the data of others. As might be expected, medium corrections are shown to be considerably more important at low energies than at resonance. This is true for inelastic transitions of multipolarity 0,2 and 3. Parameters derived from an analysis of elastic pion scattering and SCX data also provide an adequate description of the inelastic transitions. The charge asymmetry in the cross sections for the 9/2/sup +/ state that was seen at resonance persists at these energies. This result is consistent with an impulse approximation treatment of the spin-flip amplitude. This is true even though the incoming energy of the pions is far below the range where the validity of an impulse treatment is expected. 65 refs., 45 figs.

  7. Cross sections for low-energy inelastic H + Na collisions

    SciTech Connect

    Belyaev, A. K.; Barklem, P. S.; Dickinson, A. S.; Gadea, F. X.

    2010-03-15

    Full quantum-scattering calculations are reported for low-energy near-threshold inelastic collision cross sections for H+Na. The calculations include transitions between all levels up to and including the ionic state (ion-pair production) for collision energies from the threshold up to 10 eV. These results are important for astrophysical modeling of spectra in stellar atmospheres. Results for the 3s-3p excitation are carefully examined using three different quantum chemistry input data sets, and large differences are found near the threshold. The differences are found to be predominantly due to differences in the radial coupling rather than potentials and are also found not to relate to differences in couplings in a simple manner. In fact, of the three input couplings, the two that are most similar give the cross sections with the largest differences. The 3s-3p cross sections show orbiting resonances which have been seen in earlier studies, while Feshbach resonances associated with closed channels were also found to be present in the low-energy cross sections for some transitions.

  8. Materials and neutronic research at the Low Energy Neutron Source

    NASA Astrophysics Data System (ADS)

    Baxter, David V.

    2016-04-01

    In the decade since the Low Energy Neutron Source (LENS) at Indiana University Center for Exploration of Energy and Matter (CEEM) produced its first neutrons, the facility has made important contributions to the international neutron scattering community. LENS employs a 13MeV proton beam at up to 4kW beam power onto one of two Be targets to produce neutrons for research in fields ranging from radiation effects in electronics to studies of the structure of fluids confined in nanoporous materials. The neutron source design at the heart of LENS facilitates relatively rapid hands-on access to most of its components which provides a foundation for a research program in experimental neutronics and affords numerous opportunities for novel educational experiences. We describe in some detail a number of the unique capabilities of this facility.

  9. Vibrationally inelastic low-energy CO/+/ - Ar collisions.

    NASA Technical Reports Server (NTRS)

    Petty, F.; Moran, T. F.

    1972-01-01

    Examination of relative differential cross sections for inelastic scattering of CO(+) by Ar with a high-resolution ion-beam apparatus in which a CO(+) beam interacts with a neutral-Ar beam, and the energy, mass, and angular distribution of scattered ions are measured. Maxima in the inelastic energy-loss spectra occur at energies corresponding to CO(+) spectroscopic vibrational spacings. Weakly inelastic processes are observed below the threshold for vibrational energy loss, corresponding to rotational excitation with the relative importance of rotational transitions increasing with decreasing energy and scattering angle.

  10. Radial Flux Distribution of Low-Energy Neutrons.

    ERIC Educational Resources Information Center

    Higinbotham, J.

    1979-01-01

    Describes an experiment designed to illustrate the basic principle involved in the process of moderation of fast neutrons by water, and the monitoring of the low-energy neutron flux using indium as a probe. (GA)

  11. Radial Flux Distribution of Low-Energy Neutrons.

    ERIC Educational Resources Information Center

    Higinbotham, J.

    1979-01-01

    Describes an experiment designed to illustrate the basic principle involved in the process of moderation of fast neutrons by water, and the monitoring of the low-energy neutron flux using indium as a probe. (GA)

  12. Strong flux of low-energy neutrons produced by thunderstorms.

    PubMed

    Gurevich, A V; Antonova, V P; Chubenko, A P; Karashtin, A N; Mitko, G G; Ptitsyn, M O; Ryabov, V A; Shepetov, A L; Shlyugaev, Yu V; Vildanova, L I; Zybin, K P

    2012-03-23

    We report here for the first time about the registration of an extraordinary high flux of low-energy neutrons generated during thunderstorms. The measured neutron count rate enhancements are directly connected with thunderstorm discharges. The low-energy neutron flux value obtained in our work is a challenge for the photonuclear channel of neutron generation in thunderstorm: the estimated value of the needed high-energy γ-ray flux is about 3 orders of magnitude higher than that one observed.

  13. Inelastic neutron scattering studies on the incommensurate-to-commensurate transformation of low energy magnetic excitations in Fe1 + δ - y(Ni / Cu) y Te1 - x Sex

    NASA Astrophysics Data System (ADS)

    Xu, Zhijun; Wen, Jinsheng; Schneeloch, John; Zhao, Yang; Matsuda, Masaaki; Ku, Wei; Liu, Xuerong; Gu, Genda; Lee, D.-H.; Birgeneau, R. J.; Tranquada, J. M.; Xu, Guangyong

    2013-03-01

    We have performed a series of neutron scattering and magnetization measurements on Fe1 + δ - y(Ni / Cu) y Te1 - x Sex system to study the interplay between magnetism and superconductivity. Both non-superconducting and superconducting samples with Tc 8 ~15K are studied. The low energy magnetic excitations of all samples at T > >Tc consist of two incommensurate vertical columns. They change to a distinctly different U-shaped dispersion at T >Tc for the superconducting samples and the transition temperature depend on the composition. On the other hand, for all non-superconducting samples, there is no clear temperature dependence, and the low energy magnetic excitations remain two columns for temperatures down to 1.5 K. Work is supported by the Office of Basic Energy Sciences, DOE.

  14. Low energy excitations of the neutron star core

    NASA Astrophysics Data System (ADS)

    Reddy, Sanjay

    2017-01-01

    I will summarize recent work on low energy excitations in cold dense matter and its implications for thermal and transport properties, and seismology of neutron stars. I argue that a low energy Lagrangian with a handful of low energy constants (LECs) provides an adequate framework for calculations. The LECs can be related to the equation of state of dense matter at zero temperature.

  15. Low-energy inelastic neutrino reactions on 4He.

    PubMed

    Gazit, Doron; Barnea, Nir

    2007-05-11

    The inelastic scattering of neutrino off 4He is calculated microscopically at energies typical for core-collapse supernova environment. The calculation is carried out with the Argonne V18 nucleon-nucleon potential and the Urbana IX three-nucleon force. Full final state interaction is included via the Lorentz integral transform method. The contribution of axial meson exchange currents to the cross sections is taken into account from effective field theory of nucleons and pions to order O(Q3).

  16. Low-Energy Inelastic Neutrino Reactions on He4

    NASA Astrophysics Data System (ADS)

    Gazit, Doron; Barnea, Nir

    2007-05-01

    The inelastic scattering of neutrino off He4 is calculated microscopically at energies typical for core-collapse supernova environment. The calculation is carried out with the Argonne V18 nucleon-nucleon potential and the Urbana IX three-nucleon force. Full final state interaction is included via the Lorentz integral transform method. The contribution of axial meson exchange currents to the cross sections is taken into account from effective field theory of nucleons and pions to order O(Q3).

  17. Low-energy electron inelastic mean free path in materials

    SciTech Connect

    Nguyen-Truong, Hieu T.

    2016-04-25

    We show that the dielectric approach can determine electron inelastic mean free paths in materials with an accuracy equivalent to those from first-principle calculations in the GW approximation of many-body theory. The present approach is an alternative for calculating the hot-electron lifetime, which is an important quantity in ultrafast electron dynamics. This approach, applied here to solid copper for electron energies below 100 eV, yields results in agreement with experimental data from time-resolved two-photon photoemission, angle-resolved photoelectron spectroscopy, and X-ray absorption fine structure measurements in the energy ranges 2–3.5, 10–15, and 60–100 eV, respectively.

  18. Elastic and inelastic low-energy electron collisions with pyrazine.

    PubMed

    Mašín, Zdeněk; Gorfinkiel, Jimena D

    2011-10-14

    We present results of ab-initio scattering calculations for electron collisions with pyrazine using the R-matrix method, carried out at various levels of approximation. We confirm the existing experimental and theoretical understanding of the three well-known π∗ shape resonances. In addition, we find numerous core-excited resonances (above 4.8 eV) and identify their most likely parent states. We also present differential cross sections, showing high sensitivity to the scattering model chosen at low energies. We make recommendations regarding the selection of models for scattering calculations with this type of targets. © 2011 American Institute of Physics

  19. Inelastic low energy electron diffraction at metal surfaces

    NASA Astrophysics Data System (ADS)

    Nazarov, V. U.; Nishigaki, S.

    2001-06-01

    The role of incident electrons penetration under a metal surface in electron energy loss spectroscopy is considered within the fully quantum-mechanical approach. The stabilized jellium model of the surface in the semi-infinite geometry and the time-dependent local density approximation for the dynamical response are used. The travel of the projectile electron inside the target metal is treated within the kinematic low energy electron diffraction theory. Confirming our simplified hard-wall reflection model results [Phys. Rev. B 59 (1999) 9866], the dramatic enhancement of the multipole plasmon peak as compared with the dipole-mode calculations is obtained for Na and Cs, which is in a qualitative agreement with the experiment. However, for K the calculation fails to explain the experiment, which discrepancy is discussed and the future improvements of the method are outlined.

  20. Parity violation in low-energy neutron-deuteron scattering

    NASA Astrophysics Data System (ADS)

    Song, Young-Ho; Lazauskas, Rimantas; Gudkov, Vladimir

    2011-01-01

    Parity-violating effects for low-energy elastic neutron deuteron scattering are calculated for Desplanques, Donoghue, and Holstein (DDH) and effective field theory types of weak potentials in a distorted-wave Born approximation, using realistic hadronic strong interaction wave functions, obtained by solving three-body Faddeev equations in configuration space. The resulting relation between physical observables and low-energy constants can be used to fix low-energy constants from experiments. Potential model dependencies of parity-violating effects are discussed.

  1. Parity violation in low-energy neutron-deuteron scattering

    SciTech Connect

    Song, Young-Ho; Gudkov, Vladimir; Lazauskas, Rimantas

    2011-01-15

    Parity-violating effects for low-energy elastic neutron deuteron scattering are calculated for Desplanques, Donoghue, and Holstein (DDH) and effective field theory types of weak potentials in a distorted-wave Born approximation, using realistic hadronic strong interaction wave functions, obtained by solving three-body Faddeev equations in configuration space. The resulting relation between physical observables and low-energy constants can be used to fix low-energy constants from experiments. Potential model dependencies of parity-violating effects are discussed.

  2. High precision neutron inelastic cross section measurements

    NASA Astrophysics Data System (ADS)

    Olacel, A.; Belloni, F.; Borcea, C.; Boromiza, M.; Dessagne, Ph.; Henning, G.; Kerveno, M.; Negret, A.; Nyman, M.; Pirovano, E.; Plompen, A.

    2017-06-01

    High precision neutron inelastic scattering cross section data are very important for the development of the new generation of nuclear reactors (Gen IV). Our experiments, performed using the GELINA neutron source and the GAINS spectrometer of the European Commission Joint Research Center, Geel, produce highly reliable and precise cross section data. We will present the details of the setup and the data analysis technique allowing production of such unique results, and we will show examples of two experimental results.

  3. Unexpected neutron/proton ratio and isospin effect in low-energy antiproton-induced reactions

    NASA Astrophysics Data System (ADS)

    Feng, Zhao-Qing

    2017-09-01

    The inclusive spectra of pre-equilibrium nucleons produced in low-energy antiproton-nucleus collisions are thoroughly investigated within the the Lanzhou quantum molecular dynamics transport approach for the first time. The reaction channels of elastic scattering, annihilation, charge exchange, and inelastic processes in antibaryon-baryon, baryon-baryon, and meson-baryon collisions have been implemented in the model. The unexpected neutron to proton yield ratios are caused from the isospin effects of pion-nucleon collisions and the symmetry energy. It is found that the π--neutron collisions enhance the neutron emission in the antiproton annihilation in a nucleus. A soft symmetry energy with the stiffness of γs=0.5 at subsaturation densities is constrained from the available data of the neutron/proton spectra.

  4. Low energy nuclear spin excitations in Ho metal investigated by high resolution neutron spectroscopy.

    PubMed

    Chatterji, Tapan; Jalarvo, Niina

    2013-04-17

    We have investigated the low energy excitations in metallic Ho by high resolution neutron spectroscopy. We found at T = 3 K clear inelastic peaks in the energy loss and energy gain sides, along with the central elastic peak. The energy of this low energy excitation, which is 26.59 ± 0.02 μeV at T = 3 K, decreased continuously and became zero at TN ≈ 130 K. By fitting the data in the temperature range 100-127.5 K with a power law we obtained the power-law exponent β = 0.37 ± 0.02, which agrees with the expected value β = 0.367 for a three-dimensional Heisenberg model. Thus the energy of the low energy excitations can be associated with the order parameter.

  5. Development of multichannel low-energy neutron spectrometer

    SciTech Connect

    Arikawa, Y. Nagai, T.; Abe, Y.; Kojima, S.; Sakata, S.; Inoue, H.; Utsugi, M.; Iwasa, Y.; Sarukura, N.; Nakai, M.; Shiraga, H.; Fujioka, S.; Azechi, H.; Murata, T.

    2014-11-15

    A multichannel low-energy neutron spectrometer for down-scattered neutron (DSN) measurements in inertial confinement fusion (ICF) experiments has been developed. Our compact-size 256-channel lithium-glass-scintillator-based spectrometer has been implemented and tested in ICF experiments with the GEKKO XII laser. We have performed time calibration of the 256-channel analog-to-digital convertor system used for DSN measurements via X-ray pulse signals. We have clearly observed the DD-primary fusion neutron signal and have successfully studied the detector's impulse response. Our detector is soon to be implemented in future ICF experiments.

  6. Development of multichannel low-energy neutron spectrometer.

    PubMed

    Arikawa, Y; Nagai, T; Abe, Y; Kojima, S; Sakata, S; Inoue, H; Utsugi, M; Iwasa, Y; Murata, T; Sarukura, N; Nakai, M; Shiraga, H; Fujioka, S; Azechi, H

    2014-11-01

    A multichannel low-energy neutron spectrometer for down-scattered neutron (DSN) measurements in inertial confinement fusion (ICF) experiments has been developed. Our compact-size 256-channel lithium-glass-scintillator-based spectrometer has been implemented and tested in ICF experiments with the GEKKO XII laser. We have performed time calibration of the 256-channel analog-to-digital convertor system used for DSN measurements via X-ray pulse signals. We have clearly observed the DD-primary fusion neutron signal and have successfully studied the detector's impulse response. Our detector is soon to be implemented in future ICF experiments.

  7. Precise neutron inelastic cross section measurements

    SciTech Connect

    Negret, Alexandru

    2012-11-20

    The design of a new generation of nuclear reactors requires the development of a very precise neutron cross section database. Ongoing experiments performed at dedicated facilities aim to the measurement of such cross sections with an unprecedented uncertainty of the order of 5% or even smaller. We give an overview of such a facility: the Gamma Array for Inelastic Neutron Scattering (GAINS) installed at the GELINA neutron source of IRMM, Belgium. Some of the most challenging difficulties of the experimental approach are emphasized and recent results are shown.

  8. A New Polyethylene Scattering Law Determined Using Inelastic Neutron Scattering

    SciTech Connect

    Lavelle, Christopher M; Liu, C; Stone, Matthew B

    2013-01-01

    Monte Carlo neutron transport codes such as MCNP rely on accurate data for nuclear physics cross-sections to produce accurate results. At low energy, this takes the form of scattering laws based on the dynamic structure factor, S (Q, E). High density polyethylene (HDPE) is frequently employed as a neutron moderator at both high and low temperatures, however the only cross-sections available are for T =300 K, and the evaluation has not been updated in quite some time. In this paper we describe inelastic neutron scattering measurements on HDPE at 5 and 300 K which are used to improve the scattering law for HDPE. We describe the experimental methods, review some of the past HDPE scattering laws, and compare computations using these models to the measured S (Q, E). The total cross-section is compared to available data, and the treatment of the carbon secondary scatterer as a free gas is assessed. We also discuss the use of the measurement itself as a scattering law via the 1 phonon approximation. We show that a scattering law computed using a more detailed model for the Generalized Density of States (GDOS) compares more favorably to this experiment, suggesting that inelastic neutron scattering can play an important role in both the development and validation of new scattering laws for Monte Carlo work.

  9. Inelastic cross sections for low-energy electrons in liquid water: exchange and correlation effects.

    PubMed

    Emfietzoglou, Dimitris; Kyriakou, Ioanna; Garcia-Molina, Rafael; Abril, Isabel; Nikjoo, Hooshang

    2013-11-01

    Low-energy electrons play a prominent role in radiation therapy and biology as they are the largest contributor to the absorbed dose. However, no tractable theory exists to describe the interaction of low-energy electrons with condensed media. This article presents a new approach to include exchange and correlation (XC) effects in inelastic electron scattering at low energies (below ∼10 keV) in the context of the dielectric theory. Specifically, an optical-data model of the dielectric response function of liquid water is developed that goes beyond the random phase approximation (RPA) by accounting for XC effects using the concept of the many-body local-field correction (LFC). It is shown that the experimental energy-loss-function of liquid water can be reproduced by including into the RPA dispersion relations XC effects (up to second order) calculated in the time-dependent local-density approximation with the addition of phonon-induced broadening in N. D. Mermin's relaxation-time approximation. Additional XC effects related to the incident and/or struck electrons are included by means of the vertex correction calculated by a modified Hubbard formula for the exchange-only LFC. Within the first Born approximation, the present XC corrections cause a significantly larger reduction (∼10-50%) to the inelastic cross section compared to the commonly used Mott and Ochkur approximations, while also yielding much better agreement with the recent experimental data for amorphous ice. The current work offers a manageable, yet rigorous, approach for including non-Born effects in the calculation of inelastic cross sections for low-energy electrons in liquid water, which due to its generality, can be easily extended to other condensed media.

  10. Status report on the Low Energy Neutron Source for 2015

    NASA Astrophysics Data System (ADS)

    Baxter, D. V.; Rinckel, T.

    2016-11-01

    The Low Energy Neutron Source at Indiana University first produced cold neutrons in April of 2005. Ten years after first reaching this milestone, the facility has three instruments in operation on its cold target station, and a second target station is devoted to thermal and fast neutron physics offers capabilities in radiation effects research (single-event effects in electronics) and radiography. Key elements in our success over these last ten years have been the diversity of activities we have been able maintain (which often involves using each of our instruments for multiple different activities), the close relationship we have developed with a number of major sources, and the focus we have had on innovation in neutron instrumentation. In this presentation, we will introduce some of the highlights from our most recent activities, provide an update on some of our technical challenges, and describe some of our ideas for the future.

  11. Deep inelastic neutron scattering in condensed hydrogen

    NASA Astrophysics Data System (ADS)

    Bafile, Ubaldo; Celli, Milva; Zoppi, Marco

    1996-02-01

    The neutron cross-section of molecular hydrogen that is measured by deep inelastic neutron scattering (DINS) is compared with two distinct models. One is a generalization of the molecular Young and Koppel model (1964) that takes into account the modification to the translational kinetic energy that is induced by quantum effects. The second model assumes a free particle wave function for the final state of the proton (C. Andreani et al., 1995). The comparison between these two models, and with the experimental results, provides information on the crossover between the molecular and atomic regime of hydrogen in DINS.

  12. Communication: Importance of rotationally inelastic processes in low-energy Penning ionization of CHF3.

    PubMed

    Jankunas, Justin; Jachymski, Krzysztof; Hapka, Michał; Osterwalder, Andreas

    2016-06-14

    Low energy reaction dynamics can strongly depend on the internal structure of the reactants. The role of rotationally inelastic processes in cold collisions involving polyatomic molecules has not been explored so far. Here we address this problem by performing a merged-beam study of the He((3)S1)+CHF3 Penning ionization reaction in a range of collision energies E/kB = 0.5-120 K. The experimental cross sections are compared with total reaction cross sections calculated within the framework of quantum defect theory. We find that the broad range of collision energies combined with the relatively small rotational constants of CHF3 makes rotationally inelastic collisions a crucial player in the total reaction dynamics. Quantitative agreement between theory and experiment is only obtained if the energy-dependent probability for rotational excitation is included in the calculations, in stark contrast to previous experiments where classical scaling laws were able to describe the results.

  13. Communication: Importance of rotationally inelastic processes in low-energy Penning ionization of CHF3

    NASA Astrophysics Data System (ADS)

    Jankunas, Justin; Jachymski, Krzysztof; Hapka, Michał; Osterwalder, Andreas

    2016-06-01

    Low energy reaction dynamics can strongly depend on the internal structure of the reactants. The role of rotationally inelastic processes in cold collisions involving polyatomic molecules has not been explored so far. Here we address this problem by performing a merged-beam study of the He(3S1)+CHF3 Penning ionization reaction in a range of collision energies E/kB = 0.5-120 K. The experimental cross sections are compared with total reaction cross sections calculated within the framework of quantum defect theory. We find that the broad range of collision energies combined with the relatively small rotational constants of CHF3 makes rotationally inelastic collisions a crucial player in the total reaction dynamics. Quantitative agreement between theory and experiment is only obtained if the energy-dependent probability for rotational excitation is included in the calculations, in stark contrast to previous experiments where classical scaling laws were able to describe the results.

  14. Materials for Low-Energy Neutron Radiation Shielding

    NASA Technical Reports Server (NTRS)

    Singleterry, Robert C., Jr.; Thibeault, Sheila A.

    2000-01-01

    Various candidate aircraft and spacecraft materials were analyzed and compared in a low-energy neutron environment using the Monte Carlo N-Particle (MCNP) transport code with an energy range up to 20 MeV. Some candidate materials have been tested in particle beams, and others seemed reasonable to analyze in this manner before deciding to test them. The two metal alloys analyzed are actual materials being designed into or used in aircraft and spacecraft today. This analysis shows that hydrogen-bearing materials have the best shielding characteristics over the metal alloys. It also shows that neutrons above 1 MeV are reflected out of the face of the slab better by larger quantities of carbon in the material. If a low-energy absorber is added to the material, fewer neutrons are transmitted through the material. Future analyses should focus on combinations of scatterers and absorbers to optimize these reaction channels and on the higher energy neutron component (above 50 MeV).

  15. Cross sections for low-energy inelastic H+Li collisions

    SciTech Connect

    Belyaev, Andrey K.; Barklem, Paul S.

    2003-12-01

    We report calculations for the low-energy near-threshold inelastic collision cross sections between the Li(2s,2p,3s,3p)+H(1s) states. Results are obtained by solving the coupled-channel equations. Order-of-magnitude estimates for higher states have been made with the multichannel Landau-Zener model. Potentials and couplings from H. Croft et al [J. Phys. B 32, 81 (1999)] are employed. The calculated cross sections are much smaller than ones predicted by the classical Thomsom atom formula currently employed in astrophysics. This result is important for the interpretation of stellar spectra.

  16. Medical applications of neutron inelastic scattering

    NASA Astrophysics Data System (ADS)

    Kehayias, Joseph J.; Banuk-Waitekus, Anathea; Valtuena, Silvia; Sheahan, Charles A.

    1999-10-01

    A sealed, D-T, pulsed neutron generator is used for the in vivo measurement of body carbon and oxygen by neutron inelastic scattering. The generator is operated at 10 KHz, at a neutron output of about 2 X 107 n/s/4(pi) . Gamma ray spectra are collected with two B4Ge3O12 crystal detectors. The measurements are used to measure fat and lean content and distribution in the body, with minimal radiation exposure (0.08 mSv). When combined with other measurements (such as total body potassium), this whole body scanning device provides us with the `quality of lean mass', a measurable outcome of treatments designed to improve nutritional status and function. The method is used in studies of human nutrition and for assessing the efficacy of new anti-obesity and anti-cachexia pharmaceuticals.

  17. Inelastic low-energy collisions of electrons with HeH+: Rovibrational excitation and dissociative recombination

    NASA Astrophysics Data System (ADS)

    Čurík, Roman; Greene, Chris H.

    2017-08-01

    Inelastic low-energy (0-1 eV) collisions of electrons with HeH+ cations are treated theoretically, with a focus on the rovibrational excitation and dissociative recombination (DR) channels. In an application of ab initio multichannel quantum defect theory, the description of both processes is based on the Born-Oppenheimer quantum defects. The quantum defects were determined using the R-matrix approach in two different frames of reference: the center-of-charge and the center-of-mass frames. The results obtained in the two reference systems, after implementing the Fano-Jungen style rovibrational frame-transformation technique, show differences in the rate of convergence for these two different frames of reference. We find good agreement with the available theoretically predicted rotationally inelastic thermal rate coefficients. Our computed DR rate also agrees well with the available experimental results. Moreover, several computational experiments shed light on the role of rotational and vibrational excitations in the indirect DR mechanism that governs the low energy HeH+ dissociation process. While the rotational excitation is several orders of magnitude more probable process at the studied collision energies, the closed-channel resonances described by the high-n, rotationally excited neutral molecules of HeH contribute very little to the dissociation probability. But the situation is very different for resonances defined by the high-n, vibrationally excited HeH molecules, which are found to dissociate with approximately 90% probability.

  18. Direct evidence for inelastic neutron 'acceleration' by {sup 177}Lu{sup m}

    SciTech Connect

    Roig, O.; Meot, V.; Rosse, B.; Belier, G.; Daugas, J.-M.; Morel, P.; Letourneau, A.; Menelle, A.

    2011-06-15

    The inelastic neutron acceleration cross section on the long-lived metastable state of {sup 177}Lu has been measured using a direct method. High-energy neutrons have been detected using a specially designed setup placed on a cold neutron beam extracted from the ORPHEE reactor in Saclay. The 146{+-}19 b inelastic neutron acceleration cross section in the ORPHEE cold neutron flux confirms the high cross section for this process on the {sup 177}Lu{sup m} isomer. The deviation from the 258{+-}58 b previously published obtained for a Maxwellian neutron flux at a 323 K temperature could be explained by the presence of a low energy resonance. Resonance parameters are deduced and discussed.

  19. Material dependence of electron inelastic mean free paths at low energies

    SciTech Connect

    Tanuma, S. ); Powell, C.J.; Penn, D.R. )

    1990-05-01

    We present and discuss electron inelastic mean free path (IMFP) data for aluminum and gold in the 50--200 eV range. These elements serve as examples of IMFP calculations that have been made for 50--2000 eV electrons in 31 materials (27 elements and 4 compounds). Substantial differences are found in the shapes of the IMFP versus energy curves for Al and Au and these can be understood in terms of the different inelastic scattering mechanisms in the two metals. The minimum IMFP value occurs at 40 eV in aluminum and at 120 eV in gold, a result which is consistent with the trends expected from free-electron IMFP calculations. This result differs, however, from that expected from the Seah and Dench attenuation length formula which shows essentially no material dependence at low energies. We have extended a general formula derived earlier to describe the calculated IMFPs over the 200--2000 eV energy range to give the IMFP dependences on material and energy from 50 to 2000 eV.

  20. Study of Low Energy Electron Inelastic Scattering Mechanisms Using Spin Sensitive Techniques

    NASA Astrophysics Data System (ADS)

    Hsu, Hongbing

    1995-01-01

    Spin sensitive electron spectroscopies were used to study low energy electron inelastic scattering from metal surfaces and thin films. In these experiments, a beam of spin polarized electrons from a GaAs source is directed on the sample surface, and the spin polarization and intensity are measured as a function of energy loss and scattering angle by a Mott electron polarimeter coupled with a concentric hemispherical energy analyzer. Systematic studies of the angular dependence of inelastically scattered electrons were conducted on a Cu(100) surface, and Mo/Cu(100), non-magnetized Fe/Cu(100), and Co/Cu(100) films. The polarization and intensity of scattered electrons were measured as function of energy loss and scattering angle. Further studies were also conducted on Ag(100) surface and amorphous Cu/Ag(100) films. From the experimental results, the angular distributions of dipole and impact scattered electrons can be determined individually and both are found to peak in the specular scattering direction. Preliminary studies were conducted on magnetized Co/Cu(100) films. The spin dependent scattering intensity asymmetry was measured, with a clearly observable peak at energy loss of ~1 eV, which coincides with the band splitting. The polarizations of secondary electrons produced by an unpolarized primary beam were also measured. The polarizations can be related to the band polarization of magnetized cobalt films.

  1. Atomic data on inelastic processes in low-energy beryllium-hydrogen collisions

    NASA Astrophysics Data System (ADS)

    Yakovleva, Svetlana A.; Voronov, Yaroslav V.; Belyaev, Andrey K.

    2016-08-01

    Aims: Inelastic processes in low-energy Be + H and Be+ + H- collisions are treated for the states from the ground and up to the ionic state with the aim to provide rate coefficients needed for non-local thermodynamic equilibrium (non-LTE) modeling of beryllium spectra in cool stellar atmospheres. Methods: The electronic molecular structure is determined by using a recently proposed model quantum approach that is based on an asymptotic method. Nonadiabatic nuclear dynamics is treated by means of multichannel formulas, based on the Landau-Zener model for nonadiabatic transition probabilities. Results: The cross sections and the rate coefficients for inelastic processes in Be + H and Be+ + H- collisions are calculated for all transitions between 13 low-lying covalent states plus the ionic state. It is shown that the highest rate coefficient values correspond to the mutual neutralization processes with the final states Be(2s3s 1S), Be(2s3p 1,3P), Be(2s3d 3D). These processes, as well as some of the excitation, de-excitation and ion-pair formation processes, are likely to be important for non-LTE modeling. Tables A.1-A.10 are also available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/593/A27

  2. Low-energy inelastic response in the superconducting phases of PrOs4Sb12

    NASA Astrophysics Data System (ADS)

    Setty, Chandan; Wang, Yuxuan; Phillips, Philip W.

    2017-08-01

    Recent ac susceptibility and polar Kerr effect measurements in the skutterudite superconductor PrOs4Sb12 (POS) (E. M. Levenson-Falk, E. R. Schemm, M. B. Maple, and A. Kapitulnik, arXiv:1609.07535) uncovered the nature of the superconducting double transition from a high-temperature, high-field, time-reversal symmetric phase (or the A phase) to a low-temperature, low-field, time-reversal symmetry-broken phase (or the B phase). Starting from a microscopic model, we derive a Ginzburg-Landau expansion relevant to POS that describes this entrance into the time-reversal symmetry-broken phase along the temperature axis. We also provide a study of the low-energy inelastic (Raman) response in both the A and B phases of POS, and seek additional signatures which could help reveal the exact form of the gap functions previously proposed in these phases. By appropriately manipulating the incoming and scattered light geometries, along with additional subtraction procedures and suitable assumptions, we show that one can access the various irreducible representations contained in the point group describing POS. We demonstrate how to use this technique on example order parameters proposed in POS. Depending on whether there exist nodes along the c axis, we find additional low-energy spectral weight within the superconducting gap in the Eg geometry, a feature that could pinpoint the location of nodes on the Fermi surface.

  3. Neutron inelastic scattering measurements on the stable isotopes of titanium

    NASA Astrophysics Data System (ADS)

    Olacel, A.; Belloni, F.; Borcea, C.; Boromiza, M.; Dessagne, P.; Henning, G.; Kerveno, M.; Negret, A.; Nyman, M.; Pirovano, E.; Plompen, A. J. M.

    2017-07-01

    The results of a neutron inelastic scattering experiment performed at the Geel Electron Linear Accelerator pulsed white neutron source of the European Commission Joint Research Centre are reported. The neutrons with energies up to 18 MeV interacted with a natTi sample and the γ rays resulting from inelastic scattering reactions on the stable isotopes were detected using the Gamma Array for Inelastic Neutron Scattering (GAINS) spectrometer. We were able to measure the γ -production cross sections for 21 transitions in the five stable Ti isotopes. From these, the level cross sections and the total inelastic cross sections were determined. Our experimental results are compared with theoretical calculations performed using the talys 1.8 code, evaluated nuclear data libraries, and also with previously reported results.

  4. Low-energy inelastic collisions of OH radicals with He atoms and D{sub 2} molecules

    SciTech Connect

    Kirste, Moritz; Scharfenberg, Ludwig; Meijer, Gerard; Meerakker, Sebastiaan Y. T. van de; Klos, Jacek; Lique, Francois; Alexander, Millard H.

    2010-10-15

    We present an experimental study on the rotational inelastic scattering of OH (X {sup 2}{Pi}{sub 3/2},J=3/2,f) radicals with He and D{sub 2} at collision energies between 100 and 500 cm{sup -1} in a crossed beam experiment. The OH radicals are state selected and velocity tuned using a Stark decelerator. Relative parity-resolved state-to-state inelastic scattering cross sections are accurately determined. These experiments complement recent low-energy collision studies between trapped OH radicals and beams of He and D{sub 2} that are sensitive to the total (elastic and inelastic) cross sections [Sawyer et al., Phys. Rev. Lett. 101, 203203 (2008)], but for which the measured cross sections could not be reproduced by theoretical calculations [Pavlovic et al., J. Phys. Chem. A 113, 14670 (2009)]. For the OH-He system, our experiments validate the inelastic cross sections determined from rigorous quantum calculations.

  5. Probing Spin Frustration in High-symmetry Magnetic Nanomolecules by Inelastic Neutron Scattering

    SciTech Connect

    Garlea, Vasile O; Nagler, Stephen E; Zarestky, Jerel L; Stassis, C.; Vaknin, D.; Kogerler, P.; McMorrow, D. F.; Niedermayer, C.; Tennant, D. A.; Lake, B.; Qiu, Y.; Exler, M.; Schnack, J.; Luban, M.

    2006-01-01

    Low temperature inelastic neutron scattering studies have been performed to characterize the low energy magnetic excitation spectrum of the magnetic nanomolecule {l_brace}Mo{sub 72}Fe{sub 30}{r_brace}. This unique highly symmetric cluster features spin frustration and is one of the largest discrete magnetic molecules studied to date by inelastic neutron scattering. The 30 s=5/2 Fe{sup III} ions, embedded in a spherical polyoxomolybdate molecule, occupy the vertices of an icosidodecahedron and are coupled via nearest-neighbor antiferromagnetic interactions. The overall energy scale of the excitation and the gross features of the temperature dependence of the observed neutron scattering are explained by a quantum model of the frustrated spin cluster. However, no satisfactory theoretical explanation is yet available for the observed magnetic field dependence.

  6. Inelastic neutron scattering in valence fluctuation compounds

    SciTech Connect

    Jon M Lawrence

    2011-02-15

    The valence fluctuation compounds are rare earth intermetallics where hybridization of the nearly-localized 4f electrons with the conduction electrons leads to incorporation of the 4f's into the itinerant states. This hybridization slows down the conduction electrons and hence gives them a heavy effective mass, justifying application of the term 'heavy Fermion' (HF) to these materials. During the project period, we grew large single crystals of several such compounds and measured their properties using both standard thermodynamic probes and state-of-the-art inelastic neutron scattering. We obtained three main results. For the intermediate valence compounds CePd{sub 3} and YbAl{sub 3}, we showed that the scattering of neutrons by the fluctuations of the 4f magnetic moment does not have the momentum dependence expected for the itinerant heavy mass state; rather, the scattering is more typical of a localized spin fluctuation. We believe that incoherent scattering localizes the excitation. For the heavy Fermion compound Ce(Ni{sub 0.935}Pd{sub 0.065}){sub 2}Ge{sub 2}, which sits at a T = 0 critical point for transformation into an antiferromagnetic (AF) phase, we showed that the scattering from the AF fluctuations does not exhibit any of the divergences that are expected at a phase transition. We speculate that alloy disorder profoundly suppresses the growth of the fluctuating AF regions, leading to short range clusters rather than regions of infinite size. Finally, we explored the applicability of key concepts used to describe the behavior of rare earth heavy Fermions to uranium based HF compounds where the 5f electrons are itinerant as opposed to localized. We found that scaling laws relating the spin fluctuation energy measured in neutron scattering to the low temperature specific heat and susceptibility are valid for the uranium compounds, once corrections are made for AF fluctuations; however, the degeneracy of the high temperature moment is smaller than expected

  7. In-situ soil carbon analysis using inelastic neutron scattering

    USDA-ARS?s Scientific Manuscript database

    In situ soil carbon analysis using inelastic neutron scattering (INS) is based on the emission of 4.43 MeV gamma rays from carbon nuclei excited by fast neutrons. This in-situ method has excellent potential for easily measuring soil carbon since it does not require soil core sampling and processing ...

  8. Mirror nuclei 3H and 3He binding energies difference and low energy parameters of neutron-neutron scattering

    NASA Astrophysics Data System (ADS)

    Babenko, V. A.; Petrov, N. M.

    2015-07-01

    A relationship between the binding energy difference for the mirror nuclei 3H and 3He and the low energy parameters of neutron-neutron and proton-proton scattering is established. The experimental values for the difference of 3H and 3He binding energies and the low-energy proton-proton scattering parameters are used to obtain the values for the neutron-neutron scattering length a nn = -18.38(55) fm and the effective range r nn = 2.84(4) fm. The calculated neutron-neutron scattering length is in good agreement with one of the two well-known and differing experimental values of this quantity.

  9. Low energy neutron background in deep underground laboratories

    NASA Astrophysics Data System (ADS)

    Best, Andreas; Görres, Joachim; Junker, Matthias; Kratz, Karl-Ludwig; Laubenstein, Matthias; Long, Alexander; Nisi, Stefano; Smith, Karl; Wiescher, Michael

    2016-03-01

    The natural neutron background influences the maximum achievable sensitivity in most deep underground nuclear, astroparticle and double-beta decay physics experiments. Reliable neutron flux numbers are an important ingredient in the design of the shielding of new large-scale experiments as well as in the analysis of experimental data. Using a portable setup of 3He counters we measured the thermal neutron flux at the Kimballton Underground Research Facility, the Soudan Underground Laboratory, on the 4100 ft and the 4850 ft levels of the Sanford Underground Research Facility, at the Waste Isolation Pilot Plant and at the Gran Sasso National Laboratory. Absolute neutron fluxes at these laboratories are presented.

  10. Large volume high-pressure cell for inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Wang, W.; Sokolov, D. A.; Huxley, A. D.; Kamenev, K. V.

    2011-07-01

    Inelastic neutron scattering measurements typically require two orders of magnitude longer data collection times and larger sample sizes than neutron diffraction studies. Inelastic neutron scattering measurements on pressurised samples are particularly challenging since standard high-pressure apparatus restricts sample volume, attenuates the incident and scattered beams, and contributes background scattering. Here, we present the design of a large volume two-layered piston-cylinder pressure cell with optimised transmission for inelastic neutron scattering experiments. The design and the materials selected for the construction of the cell enable its safe use to a pressure of 1.8 GPa with a sample volume in excess of 400 mm3. The design of the piston seal eliminates the need for a sample container, thus providing a larger sample volume and reduced absorption. The integrated electrical plug with a manganin pressure gauge offers an accurate measurement of pressure over the whole range of operational temperatures. The performance of the cell is demonstrated by an inelastic neutron scattering study of UGe2.

  11. Large volume high-pressure cell for inelastic neutron scattering.

    PubMed

    Wang, W; Sokolov, D A; Huxley, A D; Kamenev, K V

    2011-07-01

    Inelastic neutron scattering measurements typically require two orders of magnitude longer data collection times and larger sample sizes than neutron diffraction studies. Inelastic neutron scattering measurements on pressurised samples are particularly challenging since standard high-pressure apparatus restricts sample volume, attenuates the incident and scattered beams, and contributes background scattering. Here, we present the design of a large volume two-layered piston-cylinder pressure cell with optimised transmission for inelastic neutron scattering experiments. The design and the materials selected for the construction of the cell enable its safe use to a pressure of 1.8 GPa with a sample volume in excess of 400 mm(3). The design of the piston seal eliminates the need for a sample container, thus providing a larger sample volume and reduced absorption. The integrated electrical plug with a manganin pressure gauge offers an accurate measurement of pressure over the whole range of operational temperatures. The performance of the cell is demonstrated by an inelastic neutron scattering study of UGe(2).

  12. Large volume high-pressure cell for inelastic neutron scattering

    SciTech Connect

    Wang, W.; Kamenev, K. V.; Sokolov, D. A.; Huxley, A. D.

    2011-07-15

    Inelastic neutron scattering measurements typically require two orders of magnitude longer data collection times and larger sample sizes than neutron diffraction studies. Inelastic neutron scattering measurements on pressurised samples are particularly challenging since standard high-pressure apparatus restricts sample volume, attenuates the incident and scattered beams, and contributes background scattering. Here, we present the design of a large volume two-layered piston-cylinder pressure cell with optimised transmission for inelastic neutron scattering experiments. The design and the materials selected for the construction of the cell enable its safe use to a pressure of 1.8 GPa with a sample volume in excess of 400 mm{sup 3}. The design of the piston seal eliminates the need for a sample container, thus providing a larger sample volume and reduced absorption. The integrated electrical plug with a manganin pressure gauge offers an accurate measurement of pressure over the whole range of operational temperatures. The performance of the cell is demonstrated by an inelastic neutron scattering study of UGe{sub 2}.

  13. Measurements of low-energy (d,n) reactions for BNCT. Boron Neutron Capture Therapy.

    PubMed

    Colonna, N; Beaulieu, L; Phair, L; Wozniak, G J; Moretto, L G; Chu, W T; Ludewigt, B A

    1999-05-01

    Neutron yields and energy spectra have been measured for various deuteron-induced reactions at low energy. Neutrons of energy > 100 keV emitted in the 9Be(d,n)10B, 12C(d,n)13N, and 13C(d,n)14N reactions at Ed= 1.5 MeV were detected at five angles by means of liquid scintillator detectors. While low-energy neutrons were observed in all studied reactions, only 13C(d,n)14N is characterized by a relatively large yield with spectral features potentially interesting for an accelerator-based neutron source for BNCT.

  14. Inelastic scattering measurements of low energy x-ray photons by organics, soil, water, wood, and metals

    NASA Astrophysics Data System (ADS)

    Paki Amouzou, P.; Gertsenshteyn, M.; Jannson, T.; Shnitser, P.; Savant, G.

    2006-08-01

    The angular distribution of the inelastic scattering of photons at low energies (<=80 KeV) has been measured in organic material, soil, rocks, wood, steel sheet, and water. The measurements have been performed under air inside an X-ray shield cabinet using X-rays tube as a photon source and a thermoelectrically cooled CdTe detector. Measurements have been taken for both single and combined materials. The contributions of inelastic scattering of photons for the lower Z material in a given configuration have been extracted. The measured signal is primarily Compton scattering. The measured inelastic scattering contributions were compared with the calculated inelastic scattering cross sections according to the Klein-Nishina theory, updated to include a practical energy distribution of an X-ray tube beam. Relatively good agreement was found for all targets under investigation. The slight discrepancy is attributed to photoelectric effect and sample configuration. Present results may act as a guide for optimization of X-ray imaging sensors and in particular of those based on lobster eye X-ray optics suitable for cargo inspection, improvised explosives detection, non-destructive evaluation, and medical imaging.

  15. Neutron inelastic cross section measurements for natTi

    NASA Astrophysics Data System (ADS)

    Olacel, Adina; Belloni, Francesca; Borcea, Catalin; Boromiza, Marian; Dessagne, Philippe; Henning, Gregoire; Kerveno, Maëlle; Negret, Alexandru; Nyman, Markus; Pirovano, Elisa; Plompen, Arjan

    2017-09-01

    A neutron inelastic scattering experiment was performed at the GELINA (Geel Electron LINear Accelerator) neutron source of the European Commission Joint Research Centre Geel (EC-JRC Geel) with the aim of determining the reaction cross sections for the stable isotopes of natural titanium. A 235U fission chamber was used to monitor neutrons with energies up to 20 MeV. The GAINS (Gamma Array for Inelastic Neutron Scattering) spectrometer was employed to detect the γ rays resulting from the decay of the excited nuclei. We determined the γ-ray production cross sections of the first transitions in the 46,48,49,50Ti isotopes. The experimental values were compared with previous reported results and also with theoretical calculations performed with the TALYS 1.8 code using the default input parameters. Uncertainties of around 5% were obtained for the strongest observed transitions.

  16. Inelastic Neutron Scattering of Nitric Acid Hydrates

    NASA Astrophysics Data System (ADS)

    Baloh, P.; Grothe, H.; Martín-Llorente, B.; Parker, S.

    2009-04-01

    The IPCC report 2007 underlines the particular importance of aerosol particles for the water cycle and the radiation balance, and thus for the global climate.[1] The contribution of aerosols and clouds to radiative forcing might be comparable to the most important greenhouse gases like CO2 but is comparatively less understood. Nitric acid hydrates are important constituents of solid cloud particles in the lower polar Stratosphere (Polar Stratospheric Clouds) and the upper Troposphere (Cirrus clouds). The exact phase composition of these particles is still a matter of controversial discussion.[2] Especially, metastable modifications have, as recent measurements show, a particular relevance for the atmosphere, which has been ignored up to now.[3] Spectroscopic data for their detection are urgently needed and can be gathered with laboratory models. Only recently we have recorded the FTIR and Raman spectra of all nitric acid hydrates, stable and metastable.[4,5] These data have been corroborated by X-ray diffraction measurements.[6] However, when interpreting the spectroscopic data it became evident that not all bands could be explained reasonably. Here, DFT calculations were extremely helpful,[7] but still the translational and librational bands were not fully understood. Hence, inelastic neutron scattering was employed in order to investigate this region. The INS measurements were carried out with the instrument TOSCA at the ISIS of the Rutherford Appleton Laboratory, UK. The samples were prepared ex-situ in an amorphous state and were transferred into a helium-bath-cryostat, where the sample has been annealed between 20 K and 220 K. Characteristic changes of translational and librational modes have been observed and have been correlated with phase transitions. [1] Intergovernmental Panel on Climate Change, 4th Assessment Report "Climate Change 2007: The Physical Science Basis, Summary for Policymakers", Geneva, 2007; www.ipcc.ch [2] H. Grothe, H. Tizek and I. K

  17. Benchmarking the inelastic neutron scattering soil carbon method

    USDA-ARS?s Scientific Manuscript database

    The herein described inelastic neutron scattering (INS) method of measuring soil carbon was based on a new procedure for extracting the net carbon signal (NCS) from the measured gamma spectra and determination of the average carbon weight percent (AvgCw%) in the upper soil layer (~8 cm). The NCS ext...

  18. Low energy neutron physics research with a gamma multiplicity detector

    SciTech Connect

    Block, R.C.; Slovacek, R.E.; Werner, C.J.; Moretti, B.E.; Burke, J.A.; Drindak, N.J.; Leinweber, G.

    1996-06-01

    A sixteen-segment NaI(Tl) multiplicity gamma ray detector is used at the Rensselaer Polytechnic Institute Gaerttner LINAC Laboratory for neutron cross section measurements. This detector consists of an annulus of NaI(Tl) divided into two sets of 8 pie-shaped segments, each segment optically isolated and viewed by a photomultiplier. The neutron beam passes along the axis of the detector and impinges upon a sample placed in the center. Time-of-flight data are taken as a function of the number of sections which detect a gamma and which is defined as the detected multiplicity. This detector can simultaneously acquire a neutron scattering, capture and fission data by placing suitable limits on the total detected gamma ray energy deposited in the detector. Scattering and capture measurements have been performed on samples of holmium, erbium, and tungsten and experimental results are presented. The experimental multiplicity for capture is analyzed by assuming the single particle model, stochastically calculating the gamma ray cascades from neutron capture, and transporting each gamma ray into the detector using the Monte Carlo method. The detection efficiency for neutron capture is over 90% and is relatively insensitive to different isotopes of the same element or different spins of the compound nuclear resonances. A status report on experimental and analytical activities at the Laboratory is presented.

  19. Scoping studies - photon and low energy neutron interrogation

    SciTech Connect

    Becker, G.; Harker, Y.; Jones, J.; Harmon, F.

    1997-11-01

    High energy photon interrogation of waste containers, with the aim of producing photo nuclear reactions, in specific materials, holds the potential of good penetration and rapid analysis. Compact high energy ({le} 10 MeV) photon sources in the form of electron linacs producing bremstrahlung radiation are readily available. Work with the Varitron variable energy accelerator at ISU will be described. Advantages and limitations of the technique will be discussed. Using positive ion induced neutron producing reactions, it is possible to generate neutrons in a specific energy range. By this means, variable penetration and specific reactions can be excited in the assayed material. Examples using the {sup 3}H(p,n) and {sup 7}Li(p,n) reactions as neutron sources will be discussed. 4 refs., 7 figs.

  20. Neutron-fragment and Neutron-neutron Correlations in Low-energy Fission

    SciTech Connect

    Lestone, J.P.

    2016-01-15

    A computational method has been developed to simulate neutron emission from thermal-neutron induced fission of {sup 235}U and from spontaneous fission of {sup 252}Cf. Measured pre-emission mass-yield curves, average total kinetic energies and their variances, both as functions of mass split, are used to obtain a representation of the distribution of fragment velocities. Measured average neutron multiplicities as a function of mass split and their dependence on total kinetic energy are used. Simulations can be made to reproduce measured factorial moments of neutron-multiplicity distributions with only minor empirical adjustments to some experimental inputs. The neutron-emission spectra in the rest-frame of the fragments are highly constrained by ENDF/B-VII.1 prompt-fission neutron-spectra evaluations. The n-f correlation measurements of Vorobyev et al. (2010) are consistent with predictions where all neutrons are assumed to be evaporated isotropically from the rest frame of fully accelerated fragments. Measured n-f and n-n correlations of others are a little weaker than the predictions presented here. These weaker correlations could be used to infer a weak scission-neutron source. However, the effect of neutron scattering on the experimental results must be studied in detail before moving away from a null hypothesis that all neutrons are evaporated from the fragments.

  1. An ab initio treatment of inelastic H + Ne collisions at low energy

    NASA Astrophysics Data System (ADS)

    Grosser, J.; Schnecke, A.; Voigt, H.

    1990-12-01

    On the basis of published quantum chemical data, we calculate the integral cross section for the inelastic process H(1 s) + Ne → H(2 s, 2 p) + Ne for collision energies between threshold and 1.5 keV. Though the quantum chemical data are not completely unambiguous and not so complete as desired, a reasonable agreement between experiment and theory can be achieved.

  2. High resolution measurement of neutron inelastic scattering cross-sections for 23Na

    NASA Astrophysics Data System (ADS)

    Rouki, C.; Archier, P.; Borcea, C.; De Saint Jean, C.; Drohé, J. C.; Kopecky, S.; Moens, A.; Nankov, N.; Negret, A.; Noguère, G.; Plompen, A. J. M.; Stanoiu, M.

    2012-04-01

    The neutron inelastic scattering cross-section of 23Na has been measured in response to the relevant request of the OECD-NEA High Priority Request List, which requires a target uncertainty of 4% in the energy range up to 1.35 MeV for the development of sodium-cooled fast reactors. The measurement was performed at the GELINA facility with the Gamma Array for Inelastic Neutron Scattering (GAINS), featuring eight high purity germanium detectors. The setup is installed at a 200 m flight path from the neutron source and provides high resolution measurements using the (n,n'γ)-technique. The sample was an 80 mm diameter metallic sodium disk prepared at IRMM. Transitions up to the seventh excited state were observed and the differential gamma cross-sections at 110° and 150° were measured, showing mostly isotropic gamma emission. From these the gamma production, level and inelastic cross-sections were determined for neutron energies up to 3838.9 keV. The results agree well with the existing data and the evaluated nuclear data libraries in the low energies, and provide new experimental points in the little studied region above 2 MeV. Following a detailed review of the methodology used for the gamma efficiency calibrations and flux normalization of GAINS data, an estimated total uncertainty of 2.2% was achieved for the inelastic cross-section integrals over the energy ranges 0.498-1.35 MeV and 1.35-2.23 MeV, meeting the required targets.

  3. Toward a new polyethylene scattering law determined using inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Lavelle, C. M.; Liu, C.-Y.; Stone, M. B.

    2013-05-01

    Monte Carlo neutron transport codes such as MCNP rely on accurate data for nuclear physics cross-sections to produce accurate results. At low energy, this takes the form of scattering laws based on the dynamic structure factor, S(Q,E). High density polyethylene (HDPE) is frequently employed as a neutron moderator at both high and low temperatures, however the only cross-sections available are for ambient temperatures (˜300 K), and the evaluation has not been updated in quite some time. In this paper we describe inelastic neutron scattering measurements on HDPE at 5 and 294 K which are used to improve the scattering law for HDPE. We review some of the past HDPE scattering laws, describe the experimental methods, and compare computations using these models to the measured S(Q,E). The total cross-section is compared to available data, and the treatment of the carbon secondary scatterer as a free gas is assessed. We also discuss the use of the measurement itself as a scattering law via the one phonon approximation. We show that a scattering law computed using a more detailed model for the Generalized Density of States (GDOS) compares more favorably to this experiment, suggesting that inelastic neutron scattering can play an important role in both the development and validation of new scattering laws for Monte Carlo work.

  4. Modern Techniques for Inelastic Thermal Neutron Scattering Analysis

    NASA Astrophysics Data System (ADS)

    Hawari, A. I.

    2014-04-01

    A predictive approach based on ab initio quantum mechanics and/or classical molecular dynamics simulations has been formulated to calculate the scattering law, S(κ⇀,ω), and the thermal neutron scattering cross sections of materials. In principle, these atomistic methods make it possible to generate the inelastic thermal neutron scattering cross sections of any material and to accurately reflect the physical conditions of the medium (i.e, temperature, pressure, etc.). In addition, the generated cross sections are free from assumptions such as the incoherent approximation of scattering theory and, in the case of solids, crystalline perfection. As a result, new and improved thermal neutron scattering data libraries have been generated for a variety of materials. Among these are materials used for reactor moderators and reflectors such as reactor-grade graphite and beryllium (including the coherent inelastic scattering component), silicon carbide, cold neutron media such as solid methane, and neutron beam filters such as sapphire and bismuth. Consequently, it is anticipated that the above approach will play a major role in providing the nuclear science and engineering community with its needs of thermal neutron scattering data especially when considering new materials where experimental information may be scarce or nonexistent.

  5. Inelastic scattering of neutrons and possible biological applications.

    PubMed

    Egelstaff, P A

    1976-05-01

    The field of neutron inelastic scattering has probably been developed to the stage where it can begin to help the biologist. Because essentially no experimental data have been obtained, it is difficult either to draw conclusions or to make forecasts except on the basis of general hypotheses. It seems likely, however, that the next stage is up to biologists. After reviewing those biological problems in which molecular dynamics might play an important role, they should suggest specimens of interest which can give inelastic peaks with existing spectrometers operating with 5 to 10-A neutrons at angles greater than 5degrees and with resolutions of approximately 50 mueV. These specimens may involve molecules slightly smaller and more mobile than some biologists would like, but a successful outcome might lead to the development of spectrometers capable of working in a more satisfactory range. In this event the return may well prove rewarding to the biologists.

  6. Simulation of a complete inelastic neutron scattering experiment

    NASA Astrophysics Data System (ADS)

    Edwards, H.; Lefmann, K.; Lake, B.; Nielsen, K.; Skaarup, P.

    A simulation of an inelastic neutron scattering experiment on the high-temperature superconductor La2-xSrxCuO4 is presented. The complete experiment, including sample, is simulated using an interface between the experiment control program and the simulation software package (McStas) and is compared with the experimental data. Simulating the entire experiment is an attractive alternative to the usual method of convoluting the model cross section with the resolution function, especially if the resolution function is nontrivial.

  7. Inelastic Neutron Scattering on 160Gd

    NASA Astrophysics Data System (ADS)

    Lesher, S. R.; Casarella, C.; Crider, B. P.; Ikeyama, R.; Marsh, I.; Peters, E. E.; Prados-Estévez, F. M.; Smith, M. K.; Tully, Z.; Vanhoy, J. R.; Aprahamian, A.; Yates, S. W.

    2014-03-01

    The nature of low-lying excitations, Kπ=0+ bands in deformed nuclei remain enigmatic in the field, especially in relationship to quadrupole vibrations. One method of characterizing these states beyond excitation energies is through measurements of absolute transition probabilities. In the rare earth region of deformation, there are five stable Gd isotopes, 154Gd, 156Gd, and 158Gd have been studied to obtain B(E2) values, a fourth, 160Gd is the focus of this work. We have examined 160Gd with the (n, n'γ) reaction and neutron energies up to 3.0 MeV to confirm known 0+ states.

  8. Numerical simulations for width fluctuations in compound elastic and inelastic scattering at low energies

    SciTech Connect

    Kawano, Toshihiko; Talou, Patrick

    2012-09-18

    The statistical theories - the Hauser-Feshbach model with the width fluctuation correction - play a central role in studying nuclear reactions in the fast energy region, hence the statistical model codes are essential for the nuclear data evaluations nowadays. In this paper, we revisit issues regarding the statistical model calculations in the fast energy range, such as the inclusion of the direct channels, and the energy averaged cross sections using different statistical assumptions. Although they have been discussed for a long time, we need more precise quantitative investigations to understand uncertainties coming from the models deficiencies in the fast energy range. For example, the partition of compound formation cross section into the elastic and inelastic channels depends on the elastic enhancement factor calculated from the statistical models. In addition, unitarity of S-matrix constrains this partition when the direct reactions are involved. Practically some simple assumptions, which many nuclear reaction model codes adopt, may work reasonably for the nuclear data evaluations. However, the uncertainties on the evaluated cross sections cannot go lower than the model uncertainty itself. We perform numerical simulations by generating the resonances using the R-matrix theory, and compare the energy (ensemble) averaged cross sections with the statistical theories, such as the theories of Moldauer, HRTW (Hofmann, Richert, Tepel, and Weidenmueller), KKM (Kawai-Kerman-McVoy), and GOE (Gaussian orthogonal ensemble).

  9. Neutron Spin Structure Studies and Low-Energy Tests of the Standard Model at JLab

    SciTech Connect

    Jager, Kees de

    2008-10-13

    The most recent results on the spin structure of the neutron from Hall A are presented and discussed. Then, an overview is given of various experiments planned with the 12 GeV upgrade at Jefferson Lab to provide sensitive tests of the Standard Model at relatively low energies.

  10. Measurement of inelastic cross sections for low-energy electron scattering from DNA bases

    PubMed Central

    Michaud, Marc; Bazin, Marc.; Sanche, Léon

    2013-01-01

    Purpose Determine experimentally the absolute cross sections (CS) to deposit various amount of energies into DNA bases by low-energy electron (LEE) impact. Materials and methods Electron energy loss (EEL) spectra of DNA bases are recorded for different LEE impact energies on the molecules deposited at very low coverage on an inert argon (Ar) substrate. Following their normalisation to the effective incident electron current and molecular surface number density, the EEL spectra are then fitted with multiple Gaussian functions in order to delimit the various excitation energy regions. The CS to excite a molecule into its various excitation modes are finally obtained from computing the area under the corresponding Gaussians. Results The EEL spectra and absolute CS for the electronic excitations of pyrimidine and the DNA bases thymine, adenine, and cytosine by electron impacts below 18 eV are reported for the molecules deposited at about monolayer coverage on a solid Ar substrate. Conclusions The CS for electronic excitations of DNA bases by LEE impact are found to lie within the 10−16 – 10−18 cm2 range. The large value of the total ionisation CS indicates that ionisation of DNA bases by LEE is an important dissipative process via which ionising radiation degrades and is absorbed in DNA. PMID:21615242

  11. Elastic and inelastic scattering of neutrons on 238U nucleus

    NASA Astrophysics Data System (ADS)

    Capote, R.; Trkov, A.; Sin, M.; Herman, M. W.; Soukhovitskiĩ, E. Sh.

    2014-04-01

    Advanced modelling of neutron induced reactions on the 238U nucleus is aimed at improving our knowledge of neutron scattering. Capture and fission channels are well constrained by available experimental data and neutron standard evaluation. A focus of this contribution is on elastic and inelastic scattering cross sections. The employed nuclear reaction model includes - a new rotational-vibrational dispersive optical model potential coupling the low-lying collective bands of vibrational character observed in even-even actinides; - the Engelbrecht-Weidenmüller transformation allowing for inclusion of compound-direct interference effects; - and a multi-humped fission barrier with absorption in the secondary well described within the optical model for fission. Impact of the advanced modelling on elastic and inelastic scattering cross sections including angular distributions and emission spectra is assessed both by comparison with selected microscopic experimental data and integral criticality benchmarks including measured reaction rates (e.g. JEMIMA, FLAPTOP and BIG TEN). Benchmark calculations provided feedback to improve the reaction modelling. Improvement of existing libraries will be discussed.

  12. The interpretation of polycrystalline coherent inelastic neutron scattering from aluminium

    PubMed Central

    Roach, Daniel L.; Ross, D. Keith; Gale, Julian D.; Taylor, Jon W.

    2013-01-01

    A new approach to the interpretation and analysis of coherent inelastic neutron scattering from polycrystals (poly-CINS) is presented. This article describes a simulation of the one-phonon coherent inelastic scattering from a lattice model of an arbitrary crystal system. The one-phonon component is characterized by sharp features, determined, for example, by boundaries of the (Q, ω) regions where one-phonon scattering is allowed. These features may be identified with the same features apparent in the measured total coherent inelastic cross section, the other components of which (multiphonon or multiple scattering) show no sharp features. The parameters of the model can then be relaxed to improve the fit between model and experiment. This method is of particular interest where no single crystals are available. To test the approach, the poly-CINS has been measured for polycrystalline aluminium using the MARI spectrometer (ISIS), because both lattice dynamical models and measured dispersion curves are available for this material. The models used include a simple Lennard-Jones model fitted to the elastic constants of this material plus a number of embedded atom method force fields. The agreement obtained suggests that the method demonstrated should be effective in developing models for other materials where single-crystal dispersion curves are not available. PMID:24282332

  13. Use of borated polyethylene to improve low energy response of a prompt gamma based neutron dosimeter

    NASA Astrophysics Data System (ADS)

    Priyada, P.; Ashwini, U.; Sarkar, P. K.

    2016-05-01

    The feasibility of using a combined sample of borated polyethylene and normal polyethylene to estimate neutron ambient dose equivalent from measured prompt gamma emissions is investigated theoretically to demonstrate improvements in low energy neutron dose response compared to only polyethylene. Monte Carlo simulations have been carried out using the FLUKA code to calculate the response of boron, hydrogen and carbon prompt gamma emissions to mono energetic neutrons. The weighted least square method is employed to arrive at the best linear combination of these responses that approximates the ICRP fluence to dose conversion coefficients well in the energy range of 10-8 MeV to 14 MeV. The configuration of the combined system is optimized through FLUKA simulations. The proposed method is validated theoretically with five different workplace neutron spectra with satisfactory outcome.

  14. On the production of cosmogenic nuclides by low-energy neutrons

    NASA Astrophysics Data System (ADS)

    Fanenbruck, O.; Lange, H.-J.; Michel, R.

    1994-07-01

    Monte Carlo codes describing the propagation and interaction of medium-energy particles in matter, in combination with experimental and theoretical cross sections of the underlying nuclear reactions, were successfully applied in model calculations of cosmogenic nuclide production rates. We extended these calculations to reactions of low-energy neutrons in order to allow a consistent interpretation of the entire regime of nuclear reactions involved in galactic cosmic ray (GCR) interactions. Low-energy neutron spectra were calculated for stony meteoroids and lunar surface materials by Monte Carlo techniques using the MORSE code, Emmett (1975), within the HERMES code system. Depth- and size-dependent production rates for the production of Cl-36, Ca-41, Co-60, Ni-59, Kr-80, and Kr-82 by neutron capture were derived by folding these spectra with group cross sections calculated from microscopic neutron-capture data of the evaluated neutron data file ENDF/B VI by the code NJOY. The calculations were validated by modeling the Co-60 production in an artificial stony meteoroid irradiated isotropically by 1.6 GeV protons. The new theoretical production rates were compared with earlier calculations of low-energy neutron capture by Eberhardt et al. and by Spergel et al. (n,gamma)-produced cosmogenic nuclides are sensitive indicators of meteoroid sizes. The extension of the model calculations to longlived and stable (n,gamma) products frees this method from the uncertainties caused by the short-term GCR variations that significantly affect Co-60 production rates. The new production rates are applied to the interpretation of the existing experimental data of (n,gamma) products in lunar drill cores and in meteorites.

  15. Development of deterministic transport methods for low energy neutrons for shielding in space. Final report

    SciTech Connect

    Ganapol, B.

    1993-09-01

    Transport of low energy neutrons associated with the galactic cosmic ray cascade is analyzed in this dissertation. A benchmark quality analytical algorithm is demonstrated for use with BRYNTRN, a computer program written by the High Energy Physics Division of NASA Langley Research Center, which is used to design and analyze shielding against the radiation created by the cascade. BRYNTRN uses numerical methods to solve the integral transport equations for baryons with the straight-ahead approximation, and numerical and empirical methods to generate the interaction probabilities. The straight-ahead approximation is adequate for charged particles, but not for neutrons. As NASA Langley improves BRYNTRN to include low energy neutrons, a benchmark quality solution is needed for comparison. The neutron transport algorithm demonstrated in this dissertation uses the closed-form Green's function solution to the galactic cosmic ray cascade transport equations to generate a source of neutrons. A basis function expansion for finite heterogeneous and semi-infinite homogeneous slabs with multiple energy groups and isotropic scattering is used to generate neutron fluxes resulting from the cascade. This method, called the FN method, is used to solve the neutral particle linear Boltzmann transport equation. As a demonstration of the algorithm coded in the programs MGSLAB and MGSEMI, neutron and ion fluxes are shown for a beam of fluorine ions at 1000 MeV per nucleon incident on semi-infinite and finite aluminum slabs. Also, to demonstrate that the shielding effectiveness against the radiation from the galactic cosmic ray cascade is not directly proportional to shield thickness, a graph of transmitted total neutron scalar flux versus slab thickness is shown. A simple model based on the nuclear liquid drop assumption is used to generate cross sections for the galactic cosmic ray cascade.

  16. Comparative study of ion, x-ray and neutron emission in a low energy plasma focus

    NASA Astrophysics Data System (ADS)

    Zakaullah, M.; Akhtar, Ijaz; Waheed, A.; Alamgir, Khalid; Shah, Anwar Z.; Murtaza, G.

    1998-05-01

    In a low energy (2.3 kJ) Mather-type deuterium plasma focus, neutron and x-ray emission is investigated by time integrated and time resolved detectors. CR-39 nuclear track ion detectors are employed for measuring charged particle angular distribution. Correlation of charged particles with neutron and x-ray emission is also investigated. The neutron emission profile is found to be composed of two pulses, the intensity and anisotropy of which vary with the filling pressure. The charged particle flux is maximum with high fluence anisotropy for the pressure range 2.5-3.0 mbar which is also the optimum pressure for high neutron emission with low fluence anisotropy 0963-0252/7/2/015/img9. The high neutron emission with low fluence anisotropy is attributed to the presence of trapped deuterons in an anomalous magnetic field. The relevant pressure range generates favourable conditions for plasma density and pinch filament diameter. X-ray emission is generally high at low pressure. For the pressure range of 2.5-4.0 mbar, the axial neutron detector registers a hard x-ray pulse, which may escape through a half inch thick Cu flange. These results suggest that at low pressures, the collapsing current sheath interacts with the anode end and causes intense low energy 0963-0252/7/2/015/img10 x-ray emission, but the neutron emission remains low. X-rays are dominantly Cu 0963-0252/7/2/015/img11. In the narrow pressure regime 2.5-3.0 mbar, the current sheath forms a pinch filament leading to high neutron yield with low fluence anisotropy.

  17. Neutron Scattering Study of Low Energy Magnetic Excitation in FeTeSe System

    NASA Astrophysics Data System (ADS)

    Xu, Zhijun; Wen, Jinsheng; Schneeloch, John; Matsuda, Masaaki; Christianson, A. D.; Gu, Genda; Zaliznyak, I. A.; Xu, Guangyong; Tranquada, J. M.; Birgeneau, R. J.

    2014-03-01

    We have performed neutron scattering and magnetization/transport measurements on a series of FeTe1-xSex system single crystals to study the interplay between magnetism and superconductivity. Comparing to pure FeTe1-xSex compounds, extra Fe and Ni/Cu doping on Fe-site can change physics properties of these samples, including resistivity, magnetization and superconducting properties. Our neutron scattering studies also show the Fe-site doping change low energy magnetic spectrum, including the magnetic excitations intensity, position and magnetic correlation length in these samples. On the other hand, the temperature dependence of the low energy magnetic fluctuations are also found to be different depending on the composition. This work is supported by the Office of Basic Energy Sciences, DOE.

  18. Digital data acquisition for the Low Energy Neutron Detector Array (LENDA)

    NASA Astrophysics Data System (ADS)

    Lipschutz, S.; Zegers, R. G. T.; Hill, J.; Liddick, S. N.; Noji, S.; Prokop, C. J.; Scott, M.; Solt, M.; Sullivan, C.; Tompkins, J.

    2016-04-01

    A digital data acquisition system (DDAS) has been implemented for the Low Energy Neutron Detector Array (LENDA). LENDA is an array of 24 BC-408 plastic-scintillator bars designed to measure low-energy neutrons with kinetic energies in the range of 100 keV-10 MeV from (p,n)-type charge-exchange reactions. Compared to the previous data acquisition (DAQ) system for LENDA, DDAS offers the possibility to lower the neutron detection threshold, increase the overall neutron-detection efficiency, decrease the dead time of the system, and allow for easy expansion of the array. The system utilized in this work was XIA's Digital Gamma Finder Pixie-16 250 MHz digitizers. A detector-limited timing resolution of 400 ps was achieved for a single LENDA bar. Using DDAS, the neutron detection threshold of the system was reduced compared to the previous analog system, now reaching below 100 keV. The new DAQ system was successfully used in a recent charge-exchange experiment using the 16C(p,n) reaction at the National Superconducting Cyclotron Laboratory (NSCL).

  19. Investigating anomalous thermal expansion of copper halides by inelastic neutron scattering and ab initio phonon calculations.

    PubMed

    Gopakumar, Abhijith M; Gupta, M K; Mittal, R; Rols, S; Chaplot, S L

    2017-05-17

    We investigate the detailed lattice dynamics of copper halides, CuX (X = Cl, Br, and I), using neutron inelastic scattering measurements and ab initio calculations aimed at a comparative study of their thermal expansion behavior. We identify the low energy phonons which soften with pressure and are responsible for negative thermal expansion. The eigenvector analysis of these modes suggests that softening of the transverse-acoustic modes would lead to NTE in these compounds. The calculations are in very good agreement with our measurements of phonon spectra and thermal expansion behavior as reported in the literature. Our calculations at high pressure further reveal that a large difference in negative thermal expansion behavior in these compounds is associated with the difference in the unit cell volume.

  20. Inelastic Neutron Scattering and Magnetisation Investigation of an Exchange-Coupled Dy2 SMM

    NASA Astrophysics Data System (ADS)

    Baker, Michael L.; Zhang, Qing; Sarachik, Myriam P.; Kent, Andrew D.; Chen, Yizhang; Butch, Nicholas; Pineda, Eufemio M.; McInnes, Eric

    The strong spin orbit coupling and weak crystal field energies of simple exchange-coupled rare earth SMMs makes the precise evaluation of their magnetic properties nontrivial. Here we report a detailed investigation of the single molecule magnet hqH2Dy2(hq)4(NO3)3MeOH. Inelastic neutron scattering is used to obtain direct access to several low energy crystal field excitations. The INS results display several features that are not found in earlier FIR absorption experiments, while other features found in the latter are absent. Based on the effective point charge model, numerical calculations are currently underway to resolve these apparent discrepancies using complementary magnetisation measurements to resolve the exchange between Dy ions. Work supported by ARO W911NF-13-1-1025 (CCNY) and NSF-DMR-1309202 (NYU).

  1. Fast Neutron Inelastic Scattering Cross Sections in THORIUM-232.

    NASA Astrophysics Data System (ADS)

    Ciarcia, Christopher Albert

    Fast neutron inelastic scattering cross sections for levels between 700-1550-keV excitation energy in the actinide nucleus, ('232)Th, have been measured using the (n,n') time-of-flight technique. Two series of measurements were undertaken using neutrons with a typical energy spread of 8-10 keV, generated by the ('7)Li(p,n)('7)Be reaction. These measurments for 125(DEGREES)-differential scattering cross sections were performed over the incident neutron energy regions of (i) 0.950-1.550 MeV, in 50-keV intervals with the time-of-flight spectrometer optimized to detect 0.200 -0.400-MeV scattered neutrons and (ii) 1.200-2.000 MeV, in 100-keV intervals with the time-of-flight spectrometer optimized to detect 0.400-0.800-MeV scattered neutrons. Over these scattered energy regions, an overall energy resolution of less than 15 keV was maintained. The relative neutron fluence was determined for each individual measurement, by positioning the main detector at 0(DEGREES) to view the primary neutron flux. Relative normalization was achieved by measuring the direct neutron flux from the lithium target with a fixed overhead monitor detector in both measurements. Main detector response was determined by comparison with a ('235)U fission chamber of known efficiency. Techniques for unfolding the complicated spectra obtained from these (n,n') studies were developed, employing user interactive computer codes to (i) generate simulated scattered neutron group response functions, (ii) subtract background effects from the measured spectra, (iii) approximate the background subtracted spectra in a weighted least-squares fashion by a superposition of response functions and (iv) make corrections for neutron absorption, finite scatterer size effects and multiple neutron scattering. Support codes consisting of graphics interaction packages, data file manipulation and transfer utility routines were created to assist in the spectral analysis procedure. Excitation function and angular distribution

  2. Compensated bismuth-loaded plastic scintillators for neutron detection using low-energy pseudo-spectroscopy

    NASA Astrophysics Data System (ADS)

    Dumazert, Jonathan; Coulon, Romain; Bertrand, Guillaume H. V.; Normand, Stéphane; Méchin, Laurence; Hamel, Matthieu

    2016-05-01

    Gadolinium-covered modified plastic scintillators show a high potential for the deployment of cost-effective neutron detectors. Taking advantage of the low-energy photon and electron signature of thermal neutron captures in gadolinium-155 and gadolinium-157 however requires a background correction. In order to display a trustable rate, dual compensation schemes appear as an alternative to Pulse Shape Discrimination. This paper presents the application of such a compensation scheme to a two-bismuth loaded plastic scintillator system. A detection scintillator interacts with incident photon and fast neutron radiations and is covered with a gadolinium converter to become thermal neutron-sensitive as well. In the meantime, an identical compensation scintillator, covered with terbium, solely interacts with the photon and fast neutron part of incident radiations. After the acquisition and the treatment of the counting signals from both sensors, a hypothesis test determines whether the resulting count rate after subtraction falls into statistical fluctuations or provides a robust image of neutron activity. A laboratory prototype is tested under both photon and neutron radiations, allowing us to investigate the performance of the overall compensation system. The study reveals satisfactory results in terms of robustness to a cesium-137 background and in terms of sensitivity in presence of a californium-252 source.

  3. PANDORA, a large volume low-energy neutron detector with real-time neutron-gamma discrimination

    NASA Astrophysics Data System (ADS)

    Stuhl, L.; Sasano, M.; Yako, K.; Yasuda, J.; Baba, H.; Ota, S.; Uesaka, T.

    2017-09-01

    The PANDORA (Particle Analyzer Neutron Detector Of Real-time Acquisition) system, which was developed for use in inverse kinematics experiments with unstable isotope beams, is a neutron detector based on a plastic scintillator coupled to a digital readout. PANDORA can be used for any reaction study involving the emission of low energy neutrons (100 keV-10 MeV) where background suppression and an increased signal-to-noise ratio are crucial. The digital readout system provides an opportunity for pulse shape discrimination (PSD) of the detected particles as well as intelligent triggering based on PSD. The figure of merit results of PANDORA are compared to the data in literature. Using PANDORA, 91 ± 1% of all detected neutrons can be separated, while 91 ± 1% of the detected gamma rays can be excluded, reducing the gamma ray background by one order of magnitude.

  4. Development of deterministic transport methods for low energy neutrons for shielding in space

    NASA Technical Reports Server (NTRS)

    Ganapol, Barry

    1993-01-01

    Transport of low energy neutrons associated with the galactic cosmic ray cascade is analyzed in this dissertation. A benchmark quality analytical algorithm is demonstrated for use with BRYNTRN, a computer program written by the High Energy Physics Division of NASA Langley Research Center, which is used to design and analyze shielding against the radiation created by the cascade. BRYNTRN uses numerical methods to solve the integral transport equations for baryons with the straight-ahead approximation, and numerical and empirical methods to generate the interaction probabilities. The straight-ahead approximation is adequate for charged particles, but not for neutrons. As NASA Langley improves BRYNTRN to include low energy neutrons, a benchmark quality solution is needed for comparison. The neutron transport algorithm demonstrated in this dissertation uses the closed-form Green's function solution to the galactic cosmic ray cascade transport equations to generate a source of neutrons. A basis function expansion for finite heterogeneous and semi-infinite homogeneous slabs with multiple energy groups and isotropic scattering is used to generate neutron fluxes resulting from the cascade. This method, called the FN method, is used to solve the neutral particle linear Boltzmann transport equation. As a demonstration of the algorithm coded in the programs MGSLAB and MGSEMI, neutron and ion fluxes are shown for a beam of fluorine ions at 1000 MeV per nucleon incident on semi-infinite and finite aluminum slabs. Also, to demonstrate that the shielding effectiveness against the radiation from the galactic cosmic ray cascade is not directly proportional to shield thickness, a graph of transmitted total neutron scalar flux versus slab thickness is shown. A simple model based on the nuclear liquid drop assumption is used to generate cross sections for the galactic cosmic ray cascade. The ENDF/B V database is used to generate the total and scattering cross sections for neutrons in

  5. Development of deterministic transport methods for low energy neutrons for shielding in space

    NASA Astrophysics Data System (ADS)

    Ganapol, Barry

    1993-09-01

    Transport of low energy neutrons associated with the galactic cosmic ray cascade is analyzed in this dissertation. A benchmark quality analytical algorithm is demonstrated for use with BRYNTRN, a computer program written by the High Energy Physics Division of NASA Langley Research Center, which is used to design and analyze shielding against the radiation created by the cascade. BRYNTRN uses numerical methods to solve the integral transport equations for baryons with the straight-ahead approximation, and numerical and empirical methods to generate the interaction probabilities. The straight-ahead approximation is adequate for charged particles, but not for neutrons. As NASA Langley improves BRYNTRN to include low energy neutrons, a benchmark quality solution is needed for comparison. The neutron transport algorithm demonstrated in this dissertation uses the closed-form Green's function solution to the galactic cosmic ray cascade transport equations to generate a source of neutrons. A basis function expansion for finite heterogeneous and semi-infinite homogeneous slabs with multiple energy groups and isotropic scattering is used to generate neutron fluxes resulting from the cascade. This method, called the FN method, is used to solve the neutral particle linear Boltzmann transport equation. As a demonstration of the algorithm coded in the programs MGSLAB and MGSEMI, neutron and ion fluxes are shown for a beam of fluorine ions at 1000 MeV per nucleon incident on semi-infinite and finite aluminum slabs. Also, to demonstrate that the shielding effectiveness against the radiation from the galactic cosmic ray cascade is not directly proportional to shield thickness, a graph of transmitted total neutron scalar flux versus slab thickness is shown. A simple model based on the nuclear liquid drop assumption is used to generate cross sections for the galactic cosmic ray cascade. The ENDF/B V database is used to generate the total and scattering cross sections for neutrons in

  6. Performance of the Versatile Array of Neutron Detectors at Low Energy (VANDLE)

    SciTech Connect

    Peters, W. A.; Ilyushkin, S.; Madurga, M.; Matei, C.; Paulauskas, S. V.; Grzywacz, R. K.; Bardayan, D. W.; Brune, C. R.; Allen, J.; Allen, J. M.; Bergstrom, Z.; Blackmon, J.; Brewer, N. T.; Cizewski, J. A.; Copp, P.; Howard, M. E.; Ikeyama, R.; Kozub, R. L.; Manning, B.; Massey, T. N.; Matos, M.; Merino, E.; O'Malley, P. D.; Raiola, F.; Reingold, C. S.; Sarazin, F.; Spassova, I.; Taylor, S.; Walter, D.

    2016-08-26

    The Versatile Array of Neutron Detectors at Low Energy (VANDLE) is a new, highly efficient plastic-scintillator array constructed for decay and transfer reaction experimental setups that require neutron detection. The versatile and modular design allows for customizable experimental setups including beta-delayed neutron spectroscopy and (d,n) transfer reactions in normal and inverse kinematics. The neutron energy and prompt-photon discrimination is determined through the time of flight technique. Fully digital data acquisition electronics and integrated triggering logic enables some VANDLE modules to achieve an intrinsic efficiency over 70% for 300-keV neutrons, measured through two different methods. A custom Geant4 simulation models aspects of the detector array and the experimental setups to determine efficiency and detector response. Lastly, a low detection threshold, due to the trigger logic and digitizing data acquisition, allowed us to measure the light-yield response curve from elastically scattered carbon nuclei inside the scintillating plastic from incident neutrons with kinetic energies below 2 MeV.

  7. Performance of the Versatile Array of Neutron Detectors at Low Energy (VANDLE)

    DOE PAGES

    Peters, W. A.; Ilyushkin, S.; Madurga, M.; ...

    2016-08-26

    The Versatile Array of Neutron Detectors at Low Energy (VANDLE) is a new, highly efficient plastic-scintillator array constructed for decay and transfer reaction experimental setups that require neutron detection. The versatile and modular design allows for customizable experimental setups including beta-delayed neutron spectroscopy and (d,n) transfer reactions in normal and inverse kinematics. The neutron energy and prompt-photon discrimination is determined through the time of flight technique. Fully digital data acquisition electronics and integrated triggering logic enables some VANDLE modules to achieve an intrinsic efficiency over 70% for 300-keV neutrons, measured through two different methods. A custom Geant4 simulation models aspectsmore » of the detector array and the experimental setups to determine efficiency and detector response. Lastly, a low detection threshold, due to the trigger logic and digitizing data acquisition, allowed us to measure the light-yield response curve from elastically scattered carbon nuclei inside the scintillating plastic from incident neutrons with kinetic energies below 2 MeV.« less

  8. Performance of the Versatile Array of Neutron Detectors at Low Energy (VANDLE)

    SciTech Connect

    Peters, W. A.; Ilyushkin, S.; Madurga, M.; Matei, C.; Paulauskas, S. V.; Grzywacz, R. K.; Bardayan, D. W.; Brune, C. R.; Allen, J.; Allen, J. M.; Bergstrom, Z.; Blackmon, J.; Brewer, N. T.; Cizewski, J. A.; Copp, P.; Howard, M. E.; Ikeyama, R.; Kozub, R. L.; Manning, B.; Massey, T. N.; Matos, M.; Merino, E.; O'Malley, P. D.; Raiola, F.; Reingold, C. S.; Sarazin, F.; Spassova, I.; Taylor, S.; Walter, D.

    2016-08-26

    The Versatile Array of Neutron Detectors at Low Energy (VANDLE) is a new, highly efficient plastic-scintillator array constructed for decay and transfer reaction experimental setups that require neutron detection. The versatile and modular design allows for customizable experimental setups including beta-delayed neutron spectroscopy and (d,n) transfer reactions in normal and inverse kinematics. The neutron energy and prompt-photon discrimination is determined through the time of flight technique. Fully digital data acquisition electronics and integrated triggering logic enables some VANDLE modules to achieve an intrinsic efficiency over 70% for 300-keV neutrons, measured through two different methods. A custom Geant4 simulation models aspects of the detector array and the experimental setups to determine efficiency and detector response. Lastly, a low detection threshold, due to the trigger logic and digitizing data acquisition, allowed us to measure the light-yield response curve from elastically scattered carbon nuclei inside the scintillating plastic from incident neutrons with kinetic energies below 2 MeV.

  9. Performance of the Versatile Array of Neutron Detectors at Low Energy (VANDLE)

    NASA Astrophysics Data System (ADS)

    Peters, W. A.; Ilyushkin, S.; Madurga, M.; Matei, C.; Paulauskas, S. V.; Grzywacz, R. K.; Bardayan, D. W.; Brune, C. R.; Allen, J.; Allen, J. M.; Bergstrom, Z.; Blackmon, J.; Brewer, N. T.; Cizewski, J. A.; Copp, P.; Howard, M. E.; Ikeyama, R.; Kozub, R. L.; Manning, B.; Massey, T. N.; Matos, M.; Merino, E.; O'Malley, P. D.; Raiola, F.; Reingold, C. S.; Sarazin, F.; Spassova, I.; Taylor, S.; Walter, D.

    2016-11-01

    The Versatile Array of Neutron Detectors at Low Energy (VANDLE) is a new, highly efficient plastic-scintillator array constructed for decay and transfer reaction experimental setups that require neutron detection. The versatile and modular design allows for customizable experimental setups including beta-delayed neutron spectroscopy and (d,n) transfer reactions in normal and inverse kinematics. The neutron energy and prompt-photon discrimination is determined through the time of flight technique. Fully digital data acquisition electronics and integrated triggering logic enables some VANDLE modules to achieve an intrinsic efficiency over 70% for 300-keV neutrons, measured through two different methods. A custom GEANT4 simulation models aspects of the detector array and the experimental setups to determine efficiency and detector response. A low detection threshold, due to the trigger logic and digitizing data acquisition, allowed us to measure the light-yield response curve from elastically scattered carbon nuclei inside the scintillating plastic from incident neutrons with kinetic energies below 2 MeV.

  10. Investigating the response of Micromegas detector to low-energy neutrons using Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Khezripour, S.; Negarestani, A.; Rezaie, M. R.

    2017-08-01

    Micromegas detector has recently been used for high-energy neutron (HEN) detection, but the aim of this research is to investigate the response of the Micromegas detector to low-energy neutron (LEN). For this purpose, a Micromegas detector (with air, P10, BF3, 3He and Ar/BF3 mixture) was optimized for the detection of 60 keV neutrons using the MCNP (Monte Carlo N Particle) code. The simulation results show that the optimum thickness of the cathode is 1 mm and the optimum of microgrid location is 100 μm above the anode. The output current of this detector for Ar (3%) + BF3 (97%) mixture is greater than the other ones. This mixture is considered as the appropriate gas for the Micromegas neutron detector providing the output current for 60 keV neutrons at the level of 97.8 nA per neutron. Consecuently, this detector can be introduced as LEN detector.

  11. Density of states in solid deuterium: Inelastic neutron scattering study

    SciTech Connect

    Frei, A.; Gutsmiedl, E.; Morkel, C.; Mueller, A. R.; Paul, S.; Urban, M.; Schober, H.; Rols, S.; Unruh, T.; Hoelzel, M.

    2009-08-01

    The dynamics of solid deuterium (sD{sub 2}) is studied by means of inelastic scattering (coherent and incoherent) of thermal and cold neutrons at different temperatures and para-ortho ratios. In this paper, the results for the generalized density of states (GDOS) are presented and discussed. The measurements were performed at the thermal neutron time-of-flight (TOF) instrument IN4 at ILL Grenoble and at the cold neutron TOF instrument TOFTOF at FRM II Garching. The GDOS comprises besides the hcp phonon excitations of the sD{sub 2} the rotational transitions J=0{yields}1 and J=1{yields}2. The intensities of these rotational excitations depend strongly on the ortho-D{sub 2} molecule concentration c{sub o} in sD{sub 2}. Above E=10 meV there are still strong excitations, which very likely may originate from higher-energy damped optical phonons and multiphonon contributions. A method for separating the one-phonon and multiphonon contributions to the density of states will be presented and discussed.

  12. Observation of boson peaks by inelastic neutron scattering in polyolefins

    SciTech Connect

    Annis, B.K.; Lohse, D.J.; Trouw, F.

    1999-07-01

    Inelastic neutron scattering was used to probe the nature of the boson peak in atactic polypropylene (aPP), head-to-head polypropylene (hhPP), polyisobutylene (PIB) and a 1/1 mass ratio hhPP/PIB blend. Atactic polypropylene is among the most {open_quotes}fragile{close_quotes} of glass formers and was found to have a shoulder rather than the distinctive peak exhibited by the other three polymers. This difference is already apparent at 15 K where relaxations are not expected to occur. The results suggest that the fragility of hhPP is intermediate between aPP and PIB. Within this group of polymers which have similar chemical structures the position of the boson peak appears to correlate with the glass transition temperature and the cohesive energy density. The possibility of a correlation with chain stiffness as expressed by the characteristic ratio is also discussed. {copyright} {ital 1999 American Institute of Physics.}

  13. Design of low-energy neutron beams for boron neutron capture synovectomy

    NASA Astrophysics Data System (ADS)

    Yanch, Jacquelyn C.; Shefer, Ruth E.; Binello, E.

    1997-02-01

    A novel application of the 10B(n, (alpha) )7Li nuclear reaction for the treatment of rheumatoid arthritis is under development. this application, called Boron Neutron Capture Synovectomy (BNCS), is briefly described here and the differences between BNCS and Boron Neutron Capture Therapy (BNCT) are discussed in detail. These differences lead to substantially altered demands on neutron beam design for each therapy application. In this paper the considerations for neutron beam design for the treatment of arthritic joints via BNCS are discussed, and comparisons with the design requirements for BNCT are made. This is followed by a description of potential moderator/reflector assemblies that are calculated to produce intense, high- quality neutron beams based on the 7Li(p,n) accelerator- based reactions. Total therapy time and therapeutic ratios are given as a function of both moderator length and boron concentration. Finally, a means of carrying out multi- directional irradiations of arthritic joints is proposed.

  14. Neutron Transport Models and Methods for HZETRN and Coupling to Low Energy Light Ion Transport

    NASA Technical Reports Server (NTRS)

    Blattnig, S.R.; Slaba, T.C.; Heinbockel, J.H.

    2008-01-01

    Exposure estimates inside space vehicles, surface habitats, and high altitude aircraft exposed to space radiation are highly influenced by secondary neutron production. The deterministic transport code HZETRN has been identified as a reliable and efficient tool for such studies, but improvements to the underlying transport models and numerical methods are still necessary. In this paper, the forward-backward (FB) and directionally coupled forward-backward (DC) neutron transport models are derived, numerical methods for the FB model are reviewed, and a computationally efficient numerical solution is presented for the DC model. Both models are compared to the Monte Carlo codes HETCHEDS and FLUKA, and the DC model is shown to agree closely with the Monte Carlo results. Finally, it is found in the development of either model that the decoupling of low energy neutrons from the light ion (A<4) transport procedure adversely affects low energy light ion fluence spectra and exposure quantities. A first order correction is presented to resolve the problem, and it is shown to be both accurate and efficient.

  15. Neutron Transport Models and Methods for HZETRN and Coupling to Low Energy Light Ion Transport

    NASA Technical Reports Server (NTRS)

    Blattnig, S.R.; Slaba, T.C.; Heinbockel, J.H.

    2008-01-01

    Exposure estimates inside space vehicles, surface habitats, and high altitude aircraft exposed to space radiation are highly influenced by secondary neutron production. The deterministic transport code HZETRN has been identified as a reliable and efficient tool for such studies, but improvements to the underlying transport models and numerical methods are still necessary. In this paper, the forward-backward (FB) and directionally coupled forward-backward (DC) neutron transport models are derived, numerical methods for the FB model are reviewed, and a computationally efficient numerical solution is presented for the DC model. Both models are compared to the Monte Carlo codes HETCHEDS and FLUKA, and the DC model is shown to agree closely with the Monte Carlo results. Finally, it is found in the development of either model that the decoupling of low energy neutrons from the light ion (A<4) transport procedure adversely affects low energy light ion fluence spectra and exposure quantities. A first order correction is presented to resolve the problem, and it is shown to be both accurate and efficient.

  16. Low-energy beam transport studies supporting the spallation neutron source 1-MW beam operationa)

    NASA Astrophysics Data System (ADS)

    Han, B. X.; Kalvas, T.; Tarvainen, O.; Welton, R. F.; Murray, S. N.; Pennisi, T. R.; Santana, M.; Stockli, M. P.

    2012-02-01

    The H- injector consisting of a cesium enhanced RF-driven ion source and a 2-lens electrostatic low-energy beam transport (LEBT) system supports the spallation neutron source 1 MW beam operation with ˜38 mA beam current in the linac at 60 Hz with a pulse length of up to ˜1.0 ms. In this work, two important issues associated with the low-energy beam transport are discussed: (1) inconsistent dependence of the post-radio frequency quadrupole accelerator beam current on the ion source tilt angle and (2) high power beam losses on the LEBT electrodes under some off-nominal conditions compromising their reliability.

  17. Scintillation efficiency of liquid argon in low energy neutron-argon scattering

    NASA Astrophysics Data System (ADS)

    Creus, W.; Allkofer, Y.; Amsler, C.; Ferella, A. D.; Rochet, J.; Scotto-Lavina, L.; Walter, M.

    2015-08-01

    Experiments searching for weak interacting massive particles with noble gases such as liquid argon require very low detection thresholds for nuclear recoils. A determination of the scintillation efficiency is crucial to quantify the response of the detector at low energy. We report the results obtained with a small liquid argon cell using a monoenergetic neutron beam produced by a deuterium-deuterium fusion source. The light yield relative to electrons was measured for six argon recoil energies between 11 and 120 keV at zero electric drift field.

  18. Prominent Role of Spin-Orbit Coupling in FeSe Revealed by Inelastic Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Ma, Mingwei; Bourges, Philippe; Sidis, Yvan; Xu, Yang; Li, Shiyan; Hu, Biaoyan; Li, Jiarui; Wang, Fa; Li, Yuan

    2017-04-01

    In most existing theories for iron-based superconductors, spin-orbit coupling (SOC) has been assumed to be insignificant. Here, we use spin-polarized inelastic neutron scattering to show that collective low-energy spin excitations in the orthorhombic (or "nematic") phase of FeSe possess nearly no in-plane component. Such spin-space anisotropy is present over an energy range greater than the superconducting gap 2 Δsc and gets fully inherited in the superconducting state, resulting in a c -axis polarized "spin resonance" without any noticeable isotropic spectral-weight rearrangement related to the superconductivity, which is distinct from observations in the superconducting iron pnictides. The contrast between the strong suppression of long-range magnetic order in FeSe and the persisting large spin-space anisotropy, which cannot be explained microscopically by introducing single-ion anisotropy into local-moment spin models, demonstrates the importance of SOC in an itinerant-electron description of the low-energy spin excitations. Our result helps to elucidate the nearby magnetic instabilities and the debated interplay between spin and orbital degrees of freedom in FeSe. The prominent role of SOC also implies a possible unusual nature of the superconducting state.

  19. Parametrization of low-energy cross sections for nonresonant neutron capture

    SciTech Connect

    Wang Chengbin; Cisse, Ousmane I.; Baye, Daniel

    2009-09-15

    The nonresonant component of radiative neutron capture reactions is parametrized at low energies by a polynomial of second degree. The potential model is first used to reproduce experimental data below 1 MeV with the help of spectroscopic factors. The fits are found sensitive to the scattering length of the initial s or p waves. The coefficients of a Taylor expansion are then calculated by resolution of the Schroedinger equation and its energy derivatives at energy zero. Such theory-guided parametrizations are derived for neutron capture by {sup 7}Li, {sup 12}C, {sup 14}C, {sup 16}O, and {sup 18}O. When the capture proceeds from the s wave to a weakly bound state, a Pade-like parametrization better approximates the potential-model results.

  20. Compact turnkey focussing neutron guide system for inelastic scattering investigations

    NASA Astrophysics Data System (ADS)

    Brandl, G.; Georgii, R.; Dunsiger, S. R.; Tsurkan, V.; Loidl, A.; Adams, T.; Pfleiderer, C.; Böni, P.

    2015-12-01

    We demonstrate the performance of a compact neutron guide module which boosts the intensity in inelastic neutron scattering experiments by approximately a factor of 40. The module consists of two housings containing truly curved elliptic focussing guide elements, positioned before and after the sample. The advantage of the module lies in the ease with which it may be reproducibly mounted on a spectrometer within a few hours, on the same timescale as conventional sample environments. It is particularly well suited for samples with a volume of a few mm3, thus enabling the investigation of materials which to date would have been considered prohibitively small or samples exposed to extreme environments, where there are space constraints. We benchmark the excellent performance of the module by measurements of the structural and magnetic excitations in single crystals of model systems. In particular, we report the phonon dispersion in the simple element lead. We also determine the magnon dispersion in the spinel ZnCr2Se4 (V = 12.5 mm3), where strong magnetic diffuse scattering at low temperatures evolves into distinct helical order.

  1. Compact turnkey focussing neutron guide system for inelastic scattering investigations

    SciTech Connect

    Brandl, G.; Georgii, R.; Dunsiger, S. R.; Tsurkan, V.; Loidl, A.; Adams, T.; Pfleiderer, C.; Böni, P.

    2015-12-21

    We demonstrate the performance of a compact neutron guide module which boosts the intensity in inelastic neutron scattering experiments by approximately a factor of 40. The module consists of two housings containing truly curved elliptic focussing guide elements, positioned before and after the sample. The advantage of the module lies in the ease with which it may be reproducibly mounted on a spectrometer within a few hours, on the same timescale as conventional sample environments. It is particularly well suited for samples with a volume of a few mm{sup 3}, thus enabling the investigation of materials which to date would have been considered prohibitively small or samples exposed to extreme environments, where there are space constraints. We benchmark the excellent performance of the module by measurements of the structural and magnetic excitations in single crystals of model systems. In particular, we report the phonon dispersion in the simple element lead. We also determine the magnon dispersion in the spinel ZnCr{sub 2}Se{sub 4} (V = 12.5 mm{sup 3}), where strong magnetic diffuse scattering at low temperatures evolves into distinct helical order.

  2. A computer code for predicting gamma production cross sections by neutron inelastic scattering from light nuclei

    NASA Technical Reports Server (NTRS)

    George, M. C.

    1972-01-01

    Gamma-ray production cross section by the inelastic scattering of neutrons from light nuclei are considered. The applicability of optical model potential is discussed. Based on experimental data, a cascade approach is developed to calculate the inelastic gamma production cross sections. In the case of O-16 using computer code LINGAP in conjunction with ABACUS-2; results are compared with reported values.

  3. DOSIMETRIC response of a REM-500 in low energy neutron fields typical of nuclear power plants.

    PubMed

    Aslam; Matysiak, W; Atanackovic, J; Waker, A J

    2012-06-01

    This study investigates the response of a REM-500 to assess neutron quality factor and dose equivalent in low energy neutron fields, which are commonly encountered in the workplace environment of nuclear power stations. The McMaster University 3 MV Van de Graaff accelerator facility was used to measure the response of the instrument in monoenergetic neutron fields in the energy range 51 to 727 keV by bombarding a thin LiF target with 1.93-2.50 MeV protons. The energy distribution of the neutron fields produced in the facility was measured by a (3)He filled gas ionization chamber. The MCA mode of the REM-500 instrument was used to collect lineal energy distributions at varying neutron energies and to calculate the frequency and dose-mean lineal energies. The effective quality factor, Q-, was also calculated using the values of Q(y)listed in the REM-500 operation manual and compared with those of ICRP 60. The authors observed a continuously increasing trend in y - F, y-D, and Q-with an increase in neutron energy. It is interesting to note that standard tissue equivalent proportional counters (TEPCs) filled with tissue equivalent(TE) gas give rise to a similar trend for these microdosimetric quantities of interest in the same energy range; however, the averages calculated in this study are larger by about 15%compared to a TEPC filled with propane-based TE gas probably because of the larger stopping power of protons in propane compared to TE gas. These somewhat larger event sizes did not result in any significant increase in the Q-compared to those obtained from a TEPC filled with TE gas and were found to be in good agreement with other measurements reported earlier at corresponding neutron energies. The instrument quality factor response, R(Q), defined as the ratio of measured quality factor to the calculated quality factor in an ICRU tissue sphere,was found to vary with neutron energy. The instrument response,R(Q), was ~0.6 at 727 keV, which deteriorates further to

  4. Phonon dynamics and inelastic neutron scattering of sodium niobate

    NASA Astrophysics Data System (ADS)

    Mishra, S. K.; Gupta, M. K.; Mittal, R.; Zbiri, M.; Rols, S.; Schober, H.; Chaplot, S. L.

    2014-05-01

    Sodium niobate (NaNbO3) exhibits an extremely complex sequence of structural phase transitions in the perovskite family and therefore provides an excellent model system for understanding the mechanism of structural phase transitions. We report temperature dependence of inelastic neutron scattering measurements of phonon densities of states in sodium niobate. The measurements are carried out in various crystallographic phases of this material at various temperatures from 300 to 1048 K. The phonon spectra exhibit peaks centered on 19, 37, 51, 70, and 105 meV. Interestingly, the peak near 70 meV shifts significantly towards lower energy with increasing temperature, while the other peaks do not exhibit any appreciable shift. The phonon spectra at 783 K show prominent change and become more diffusive as compared to those at 303 K. In order to better analyze these features, we have performed first-principles lattice dynamics calculations based on the density functional theory. The computed phonon density of states is found to be in good agreement with the experimental data. Based on our calculation we are able to assign the characteristic Raman modes in the antiferroelectric phase, which are due to the folding of the T (ω = 95 cm-1) and Δ (ω = 129 cm-1) points of the cubic Brillouin zone, to the A1g symmetry.

  5. Two-neutron "halo" from the low-energy limit of neutron-neutron interaction: Applications to drip-line nuclei 22C and 24O

    NASA Astrophysics Data System (ADS)

    Suzuki, Toshio; Otsuka, Takaharu; Yuan, Cenxi; Alahari, Navin

    2016-02-01

    The formation of two-neutron "halo", a low-density far-extended surface of weakly-bound two neutrons, is described using the neutron-neutron (nn) interaction fixed at the low-energy nn scattering limit. This method is tested for loosely-bound two neutrons in 24O, where a good agreement with experimental data is found. It is applied to halo neutrons in 22C in two ways: with the 20C core being closed or correlated (due to excitations from the closed core). This nn interaction is shown to be strong enough to produce a two-neutron halo in both cases, locating 22C on the drip line, while 21C remains unbound. A unique relation between the two neutron separation energy, S2n, and the radius of neutron halo is presented. New predictions for S2n and the radius of neutron halo are given for 22C. The appearance of Efimov states is also discussed.

  6. Triaxiality of neutron-rich 84,86,88Ge from low-energy nuclear spectra

    NASA Astrophysics Data System (ADS)

    Lettmann, M.; Werner, V.; Pietralla, N.; Doornenbal, P.; Obertelli, A.; Rodríguez, T. R.; Sieja, K.; Authelet, G.; Baba, H.; Calvet, D.; Château, F.; Chen, S.; Corsi, A.; Delbart, A.; Gheller, J.-M.; Giganon, A.; Gillibert, A.; Lapoux, V.; Motobayashi, T.; Niikura, M.; Paul, N.; Roussé, J.-Y.; Sakurai, H.; Santamaria, C.; Steppenbeck, D.; Taniuchi, R.; Uesaka, T.; Ando, T.; Arici, T.; Blazhev, A.; Browne, F.; Bruce, A.; Caroll, R. J.; Chung, L. X.; Cortés, M. L.; Dewald, M.; Ding, B.; Flavigny, F.; Franchoo, S.; Górska, M.; Gottardo, A.; Jungclaus, A.; Lee, J.; Linh, B. D.; Liu, J.; Liu, Z.; Lizarazo, C.; Momiyama, S.; Moschner, K.; Nagamine, S.; Nakatsuka, N.; Nita, C.; Nobs, C. R.; Olivier, L.; Patel, Z.; Podolyák, Zs.; Rudigier, M.; Saito, T.; Shand, C.; Söderström, P.-A.; Stefan, I.; Vaquero, V.; Wimmer, K.; Xu, Z.

    2017-07-01

    γ -ray transitions between low-spin states of the neutron-rich 84,86,88Ge were measured by means of in-flight γ -ray spectroscopy at 270 MeV/u. Excited 61+,41,2 + , and 21,2 + states of Ge,8684 and 41+ and 21,2 + states of 88Ge were observed. Furthermore, a candidate for a 31+ state of 86Ge was identified. This state plays a key role in the discussion of ground-state triaxiality of 86Ge, along with other features of its low-energy level scheme. A new region of triaxially deformed nuclei is proposed in the Ge isotopic chain.

  7. On the idea of low-energy nuclear reactions in metallic lattices by producing neutrons from protons capturing "heavy" electrons

    NASA Astrophysics Data System (ADS)

    Tennfors, Einar

    2013-02-01

    The present article is a critical comment on Widom and Larsens speculations concerning low-energy nuclear reactions (LENR) based on spontaneous collective motion of protons in a room temperature metallic hydride lattice producing oscillating electric fields that renormalize the electron self-energy, adding significantly to the effective electron mass and enabling production of low-energy neutrons. The frequency and mean proton displacement estimated on the basis of neutron scattering from protons in palladium and applied to the Widom and Larsens model of the proton oscillations yield an electron mass enhancement less than one percent, far below the threshold for the proposed neutron production and even farther below the mass enhancement obtained by Widom and Larsen assuming a high charge density. Neutrons are not stopped by the Coulomb barrier, but the energy required for the neutron production is not low.

  8. Measuring Neutron-Proton Radiative Capture Cross-section at Low Energy

    NASA Astrophysics Data System (ADS)

    Yu, To Chin; Kovash, Michael; Matthews, June; Yang, Hongwei; Yang, Yunjie

    2015-10-01

    The experiment aims to fill in a gap in our data for the cross-section of neutron-proton radiative capture (p(n,d γ)) at energies below 500 keV. Current measurements in this energy range are scarce and inconsistent with theoretical predictions and with each other. A well-determined cross-section of the capture reaction in the low energy range is useful in nuclear physics due to its fundamental nature. The measurement is also of interest in cosmology. Big Bang Nucleosynthesis (BBN), the process by which light elements are formed in early universe, is very sensitive to the p(n,d γ) cross-section in the low energy range. The measurement enables us to put tighter constraints on the theoretical predictions of BBN. We have conducted preliminary measurements in the van de Graaff accelerator facility at the University of Kentucky. Our array of detectors consists of three plastic scintillators to serve as proton targets and deuteron detectors, and five BGO scintillators to detect γ-rays. The combination results in an over-determination of reaction kinematics that discriminates against scattering processes and other backgrounds. We have obtained some early results which show promise for the precise measurement of the p(n,d γ) cross-section.

  9. Monte-Carlo simulation of soil carbon measurements by inelastic neutron scattering

    USDA-ARS?s Scientific Manuscript database

    Measuring soil carbon is critical for assessing the potential impact of different land management practices on carbon sequestration. The inelastic neutron scattering (INS) of fast neutrons (with energy around 14 MeV) on carbon-12 nuclei produces gamma rays with energy of 4.43 MeV; this gamma flux ca...

  10. Hot background” of the mobile inelastic neutron scattering system for soil carbon analysis

    USDA-ARS?s Scientific Manuscript database

    The problem of gamma spectrum peaks identification arises when conducting soil carbon (and other elements) analysis using the mobile inelastic neutron scattering (MINS) system. Some gamma spectrum peaks could be associated with radioisotopes appearing due to neutron activation of both the MINS syste...

  11. On accelerator-based neutron sources and neutron field characterization with low energy neutron spectrometer based on position sensitive 3He counter.

    PubMed

    Murata, I; Miyamaru, H; Kato, I; Mori, Y

    2009-07-01

    The development of new neutron sources for BNCT applications, based on particle accelerators is currently underway all over the world. Though nuclear reactors were used for a long time as the only neutron source available having the requested flux levels, the accelerator-based ones have recently been investigated on the other hand due to its easy-to-use and acceptable performances. However, when using an accelerator, various secondary particles would be emitted which forms a troublesome background. Moreover, the neutrons produced have usually an energy spectrum somewhat different from the requested one and thus should be largely moderated. An additional issue to be taken into account is the patient positioning, which should be close to the neutron source, in order to take advantage of a neutron flux level high enough to limit the BNCT treatment time within 1h. This implies that, inside a relatively narrow space, neutrons should be moderated, while unnecessary secondary particles should be shielded. Considering that a background-free neutron field from an accelerator-driven neutron source dedicated to BNCT application is generally difficult to be provided, the characterization of such a neutron field will have to be clearly assessed. In the present study, a low energy neutron spectrometer has been thus designed and is now being developed to measure the accelerator-based neutron source performance. The presently proposed spectrometer is based on a (3)He proportional counter, which is 50 cm long and 5 cm in diameter, with a gas pressure of 0.5 MPa. It is quite unique that the spectrometer is set up in parallel with the incident neutron beam and a reaction depth distribution is measured by it as a position sensitive detector. Recently, a prototype detector has been developed and the signal test is now underway. In this paper, the feature of the accelerator-based neutron sources is outlined and importance of neutron field characterization is discussed. And the developed

  12. Low-energy Coulomb excitation of neutron-rich zinc isotopes

    NASA Astrophysics Data System (ADS)

    van de Walle, J.; Aksouh, F.; Behrens, T.; Bildstein, V.; Blazhev, A.; Cederkäll, J.; Clément, E.; Cocolios, T. E.; Davinson, T.; Delahaye, P.; Eberth, J.; Ekström, A.; Fedorov, D. V.; Fedosseev, V. N.; Fraile, L. M.; Franchoo, S.; Gernhauser, R.; Georgiev, G.; Habs, D.; Heyde, K.; Huber, G.; Huyse, M.; Ibrahim, F.; Ivanov, O.; Iwanicki, J.; Jolie, J.; Kester, O.; Köster, U.; Kröll, T.; Krücken, R.; Lauer, M.; Lisetskiy, A. F.; Lutter, R.; Marsh, B. A.; Mayet, P.; Niedermaier, O.; Pantea, M.; Raabe, R.; Reiter, P.; Sawicka, M.; Scheit, H.; Schrieder, G.; Schwalm, D.; Seliverstov, M. D.; Sieber, T.; Sletten, G.; Smirnova, N.; Stanoiu, M.; Stefanescu, I.; Thomas, J.-C.; Valiente-Dobón, J. J.; Duppen, P. Van; Verney, D.; Voulot, D.; Warr, N.; Weisshaar, D.; Wenander, F.; Wolf, B. H.; Zielińska, M.

    2009-01-01

    At the radioactive ion beam facility REX-ISOLDE, neutron-rich zinc isotopes were investigated using low-energy Coulomb excitation. These experiments have resulted in B(E2,21+→01+) values in Zn74-80, B(E2,41+→21+) values in Zn74,76 and the determination of the energy of the first excited 21+ states in Zn78,80. The zinc isotopes were produced by high-energy proton- (A=74,76,80) and neutron- (A=78) induced fission of U238, combined with selective laser ionization and mass separation. The isobaric beam was postaccelerated by the REX linear accelerator and Coulomb excitation was induced on a thin secondary target, which was surrounded by the MINIBALL germanium detector array. In this work, it is shown how the selective laser ionization can be used to deal with the considerable isobaric beam contamination and how a reliable normalization of the experiment can be achieved. The results for zinc isotopes and the N=50 isotones are compared to collective model predictions and state-of-the-art large-scale shell-model calculations, including a recent empirical residual interaction constructed to describe the present experimental data up to 2004 in this region of the nuclear chart.

  13. Neutron-driven collectivity in light tin isotopes: Proton inelastic scattering from 104Sn

    NASA Astrophysics Data System (ADS)

    Corsi, A.; Boissinot, S.; Obertelli, A.; Doornenbal, P.; Dupuis, M.; Lechaftois, F.; Matsushita, M.; Péru, S.; Takeuchi, S.; Wang, H.; Aoi, N.; Baba, H.; Bednarczyk, P.; Ciemala, M.; Gillibert, A.; Isobe, T.; Jungclaus, A.; Lapoux, V.; Lee, J.; Martini, M.; Matsui, K.; Motobayashi, T.; Nishimura, D.; Ota, S.; Pollacco, E.; Sakurai, H.; Santamaria, C.; Shiga, Y.; Sohler, D.; Steppenbeck, D.; Taniuchi, R.

    2015-04-01

    Inelastic scattering cross sections to individual bound excited states of 104Sn were measured at 150 MeV/u beam energy and analyzed to evaluate the contribution of neutron and proton collectivity. State-of-the-art Quasi-Particle Random Phase Approximation (QRPA) with the D1M Gogny interaction reproduces the experimental proton collectivity and our inelastic scattering cross sections once used as input for a reaction calculation together with the Jeukenne-Lejeune-Mahaux (JLM) potentials. Experimental inelastic scattering cross section decreases by 40(24)% from 112Sn to 104Sn. The present work shows that (i) proton and neutron collectivities are proportional over a large range of tin isotopes (including 104Sn), as is typical for isoscalar excitations, and (ii) the neutron collectivity dominates. It suggests that the plateau in the mass range A = 106- 112 displayed by E2 transition probabilities is driven by neutron collectivity.

  14. Investigation of Low-Energy Neutrons and Their Reaction Products in Planetary Objects

    NASA Astrophysics Data System (ADS)

    Masarik, J.; Reedy, R. C.

    1995-09-01

    High precision W, Nd, and Sm isotopic analyses [1,2] used for precise age determination of the earliest episodes of planetary differentiation require an understanding of possible contributions from neutron-capture reactions to the production of the investigated isotopes. Low-energy neutrons can also be used to study the surface composition of the planets [3,4]. Neutron-capture production profiles, which are very different from those for tracks or from nuclides made by energetic cosmic ray particles, can be used for unfolding the cosmic-ray exposure history of meteorites [5]. We did Monte Carlo numerical simulations of the influence of chemical composition, temperature and water content on neutron fluxes and production of cosmogenic isotopes. The LAHET Code System [6] was used to numerically simulate the irradiation of various objects by galactic-cosmic-ray particles and to calculate neutron fluxes and production rates of various W, Sm, Nd, Gd isotopes and 59Ni, 60Co, 36Cl, 41Ca, 80Kr and 82Kr. The advantage of these calculations is that the physical model applied to the investigation of particle production and transport uses only basic physical quantities and parameters without including any free parameters and assumptions about the neutron source term, as was necessary in older approaches [7,8]. Our simulations started by selecting the energy and direction of the primary particle that starts the particle cascade. As neutrons produced in the cascade are followed down to the thermal energies, we are able to determine the main sources of observed differences in capture rates. The calculations were validated by modeling [9] ^(60)Co [10] and 41Ca [11] measured in lunar samples. For the surface temperature variations during the lunar day, which range from about 120 K to 400 K, we found that the effect on production rates is very small. Temperature influences only relative capture rates of isotopes whose thermal capture cross sections differ from a 1/v dependence. For

  15. Crystal electric field excitations in quasicrystal approximant TbCd6 studied by inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Das, Pinaki; Flint, R.; Kong, T.; Canfield, P. C.; Kreyssig, A.; Goldman, A. I.; de Boissieu, M.; Lory, P.-F.; Beutier, G.; Hiroto, T.

    All of the known quasicrystals with local moments exhibit frustration and spin glass-like behavior at low temperature. The onset of the spin freezing temperature is believed to be affected by the crystal electric field (CEF) splitting of the local moments. The quasicrystal approximant TbCd6 and its related icosahedral quasicrystal phase, i-Tb-Cd, form a set of model systems to explore how magnetism evolves from a conventional lattice (approximant phase) to an aperiodic quasicrystal. Though TbCd6 shows long-range antiferromagnetic ordering (TN = 24 K), only spin glass like behavior is observed in i-Tb-Cd with a spin freezing temperature of TF = 6 K. To investigate further, we have performed inelastic neutron scattering measurements on powder samples of TbCd6 and observed two distinct CEF excitations at low energies which points to a high degeneracy of the CEF levels related to the Tb surrounding with almost icosahedral symmetry. Work at Ames Laboratory was supported by the DOE, BES, Division of Materials Sciences & Engineering, under Contract No. DE-AC02-07CH11358. This research used resources at Institut Laue-Langevin, France.

  16. Inelastic neutron scattering study on boson peaks of imidazolium-based ionic liquids

    SciTech Connect

    Kofu, Maiko; Inamura, Yasuhiro; Podlesnyak, Andrey A.; Ehlers, Georg; Yamamuro, Osamu; Moriya, Yosuke

    2015-07-26

    Low energy excitations of 1-alkyl-3-methylimidazolium ionic liquids (ILs) have been investigated by means of neutron spectroscopy. In the spectra of inelastic scattering, a broad excitation peak referred to as a “boson peak” appeared at 1–3 meV in all of the ILs measured. The intensity of the boson peak was enhanced at the Q positions corresponding to the diffraction peaks, reflecting the in-phase vibrational nature of the boson peak. Furthermore the boson peak energy (EBP) was insensitive to the length of the alkyl-chain but changed depending on the radius of the anion. From the correlation among EBP, the anion radius, and the glass transition temperature Tg, we conclude that both EBP and Tg in ILs are predominantly governed by the inter-ionic Coulomb interaction which is less influenced by the alkyl-chain length. Furthermore, we also found that the EBP is proportional to the inverse square root of the molecular weight as observed in molecular glasses.

  17. Inelastic neutron scattering study on boson peaks of imidazolium-based ionic liquids

    DOE PAGES

    Kofu, Maiko; Inamura, Yasuhiro; Podlesnyak, Andrey A.; ...

    2015-07-26

    Low energy excitations of 1-alkyl-3-methylimidazolium ionic liquids (ILs) have been investigated by means of neutron spectroscopy. In the spectra of inelastic scattering, a broad excitation peak referred to as a “boson peak” appeared at 1–3 meV in all of the ILs measured. The intensity of the boson peak was enhanced at the Q positions corresponding to the diffraction peaks, reflecting the in-phase vibrational nature of the boson peak. Furthermore the boson peak energy (EBP) was insensitive to the length of the alkyl-chain but changed depending on the radius of the anion. From the correlation among EBP, the anion radius, andmore » the glass transition temperature Tg, we conclude that both EBP and Tg in ILs are predominantly governed by the inter-ionic Coulomb interaction which is less influenced by the alkyl-chain length. Furthermore, we also found that the EBP is proportional to the inverse square root of the molecular weight as observed in molecular glasses.« less

  18. Simple model of bulk and surface excitation effects to inelastic scattering in low-energy electron beam irradiation of multi-walled carbon nanotubes

    SciTech Connect

    Kyriakou, Ioanna; Emfietzoglou, Dimitris; Garcia-Molina, Rafael; Abril, Isabel; Kostarelos, Kostas

    2011-09-01

    The effect of bulk and surface excitations to inelastic scattering in low-energy electron beam irradiation of multi-walled carbon nanotubes (MWNTs) is studied using the dielectric formalism. Calculations are based on a semiempirical dielectric response function for MWCNTs determined by means of a many-pole plasmon model with parameters adjusted to available experimental spectroscopic data under theoretical sum-rule constrains. Finite-size effects are considered in the context of electron gas theory via a boundary correction term in the plasmon dispersion relations, thus, allowing a more realistic extrapolation of the electronic excitation spectrum over the whole energy-momentum plane. Energy-loss differential and total inelastic scattering cross sections as a function of electron energy and distance from the surface, valid over the energy range {approx}50-30,000 eV, are calculated with the individual contribution of bulk and surface excitations separated and analyzed for the case of normally incident and escaping electrons. The sensitivity of the results to the various approximations for the spatial dispersion of the electronic excitations is quantified. Surface excitations are shown to have a strong influence upon the shape and intensity of the energy-loss differential cross section in the near surface region whereas the general notion of a spatially invariant inelastic mean free path inside the material is found to be of good approximation.

  19. "Hot background" of the mobile inelastic neutron scattering system for soil carbon analysis.

    PubMed

    Kavetskiy, Aleksandr; Yakubova, Galina; Prior, Stephen A; Torbert, H Allen

    2016-01-01

    The problem of gamma spectrum peak identification arises when conducting soil carbon analysis using the inelastic neutron scattering (INS) system. Some spectral peaks could be associated with radioisotopes appearing due to neutron activation of both the measurement system and soil samples. The investigation of "hot background" gamma spectra from the construction materials, whole measurement system, and soil samples over time showed that activation of (28)Al isotope can contribute noticeable additions to the soil neutron stimulated gamma spectra.

  20. A method to describe inelastic gamma field distribution in neutron gamma density logging.

    PubMed

    Zhang, Feng; Zhang, Quanying; Liu, Juntao; Wang, Xinguang; Wu, He; Jia, Wenbao; Ti, Yongzhou; Qiu, Fei; Zhang, Xiaoyang

    2017-08-21

    Pulsed neutron gamma density logging (NGD) is of great significance for radioprotection and density measurement in LWD, however, the current methods have difficulty in quantitative calculation and single factor analysis for the inelastic gamma field distribution. In order to clarify the NGD mechanism, a new method is developed to describe the inelastic gamma field distribution. Based on the fast-neutron scattering and gamma attenuation, the inelastic gamma field distribution is characterized by the inelastic scattering cross section, fast-neutron scattering free path, formation density and other parameters. And the contribution of formation parameters on the field distribution is quantitatively analyzed. The results shows the contribution of density attenuation is opposite to that of inelastic scattering cross section and fast-neutron scattering free path. And as the detector-spacing increases, the density attenuation gradually plays a dominant role in the gamma field distribution, which means large detector-spacing is more favorable for the density measurement. Besides, the relationship of density sensitivity and detector spacing was studied according to this gamma field distribution, therefore, the spacing of near and far gamma ray detector is determined. The research provides theoretical guidance for the tool parameter design and density determination of pulsed neutron gamma density logging technique. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Direct observation of low energy nuclear spin excitations in HoCrO3 by high resolution neutron spectroscopy.

    PubMed

    Chatterji, T; Jalarvo, N; Kumar, C M N; Xiao, Y; Brückel, Th

    2013-07-17

    We have investigated low energy nuclear spin excitations in the strongly correlated electron compound HoCrO3. We observe clear inelastic peaks at E = 22.18 ± 0.04 μeV in both energy loss and gain sides. The energy of the inelastic peaks remains constant in the temperature range 1.5-40 K at which they are observed. The intensity of the inelastic peak increases at first with increasing temperature and then decreases at higher temperatures. The temperature dependence of the energy and intensity of the inelastic peaks is very unusual compared to that observed in other Nd, Co, V and also simple Ho compounds. Huge quasielastic scattering appears at higher temperatures presumably due to the fluctuating electronic moments of the Ho ions that get increasingly disordered at higher temperatures. The strong quasielastic scattering may also originate in the first Ho crystal-field excitations at about 1.5 meV.

  2. Inelastic neutron scattering study of phonon density of states in nanostructured Si1 xGex thermoelectrics

    SciTech Connect

    Dhital, Chetan; Abernathy, Douglas L; Zhu, Gaohua; Ren, Zhifeng; Broido, D.; Wilson, Stephen D

    2012-01-01

    Inelastic neutron scattering measurements are utilized to explore relative changes in the generalized phonon density of states of nanocrystalline Si1 xGex thermoelectric materials prepared via ball-milling and hot-pressing techniques. Dynamic signatures of Ge clustering can be inferred from the data by referencing the resulting spectra to a density functional theoretical model assuming homogeneous alloying via the virtual-crystal approximation. Comparisons are also presented between as-milled Si nanopowder and bulk, polycrystalline Si where a preferential low-energy enhancement and lifetime broadening of the phonon density of states appear in the nanopowder. Negligible differences are however observed between the phonon spectra of bulk Si andhot-pressed, nanostructured Si samples suggesting that changes to the single-phonon dynamics above 4 meV play only a secondary role in the modified heat conduction of this compound.

  3. Inelastic neutron scattering cross-section measurements on 7Li and 63,65Cu

    NASA Astrophysics Data System (ADS)

    Nyman, Markus; Belloni, Francesca; Ichinkhorloo, Dagvadorj; Pirovano, Elisa; Plompen, Arjan; Rouki, Chariklia

    2017-09-01

    The γ-ray production cross section for the 477.6-keV transition in 7Li following inelastic neutron scattering has been measured from the reaction threshold up to 18 MeV. This cross section is interesting as a possible standard for other inelastic scattering measurements. The experiment was conducted at the Geel Electron LINear Accelerator (GELINA) pulsed white neutron source with the Gamma Array for Inelastic Neutron Scattering (GAINS) spectrometer. Previous measurements of this cross section are reviewed and compared with our results. Recently, this cross section has also been calculated using the continuum discretized coupled-channels (CDCC) method. Experiments for studying neutrinoless double-β decay (2β0ν) or other very rare processes require greatly reducing the background radiation level (both intrinsic and external). Copper is a common shielding and structural material, used extensively in experiments such as COBRA, CUORE, EXO, GERDA, and MAJORANA. Understanding the background contribution arising from neutron interactions in Cu is important when searching for very weak experimental signals. Neutron inelastic scattering on natCu was investigated with GAINS. The results are compared with previous experimental data and evaluated nuclear data libraries.

  4. Advanced in-situ measurement of soil carbon content using inelastic neutron scattering

    USDA-ARS?s Scientific Manuscript database

    Measurement and mapping of natural and anthropogenic variations in soil carbon stores is a critical component of any soil resource evaluation process. Emerging modalities for soil carbon analysis in the field is the registration of gamma rays from soil under neutron irradiation. The inelastic neutro...

  5. Application of Geant4 simulation for analysis of soil carbon inelastic neutron scattering measurements

    USDA-ARS?s Scientific Manuscript database

    Inelastic neutron scattering (INS) was applied to determine soil carbon content. Due to non-uniform soil carbon depth distribution, the correlation between INS signals with some soil carbon content parameter is not obvious; however, a proportionality between INS signals and average carbon weight per...

  6. Gate-opening effect in ZIF-8: the first experimental proof using inelastic neutron scattering

    DOE PAGES

    Casco, M. E.; Cheng, Y. Q.; Daemen, L. L.; ...

    2016-01-28

    In order to understand the behavior of industrial molecular separations, the gate-opening phenomenon in ZIFs are of paramount importance. We show for the first time using in situ inelastic neutron scattering (INS) the swinging of the -CH3 groups and the imidazolate linkers in the prototypical ZIF-8 and ZIF-8@AC hybrid materials upon exposure to mild N2 pressure.

  7. Gate-opening effect in ZIF-8: the first experimental proof using inelastic neutron scattering.

    PubMed

    Casco, M E; Cheng, Y Q; Daemen, L L; Fairen-Jimenez, D; Ramos-Fernández, E V; Ramirez-Cuesta, A J; Silvestre-Albero, J

    2016-03-04

    The gate-opening phenomenon in ZIFs is of paramount importance to understand their behavior in industrial molecular separations. Here we show for the first time using in situ inelastic neutron scattering (INS) the swinging of the -CH3 groups and the imidazolate linkers in the prototypical ZIF-8 and ZIF-8@AC hybrid materials upon exposure to mild N2 pressure.

  8. Neutralization and inelastic scattering energy loss of low energy He + ions at InP(110) surfaces

    NASA Astrophysics Data System (ADS)

    Shoji, Fumiya; Kashihara, Keiichiro; Hanawa, Teruo; Oura, Kenjiro

    1990-03-01

    The InP(110)-l × 1 surface is investigated with a high-resolution low energy ion scattering system. Attention is paid to the precise measurement of energy spectra of the scattered He + ions from indium atoms on the surface at incident energies ranging from 300 to 1300 eV. The single scattering peaks are found to be composed of two components (peaks P1 and P2) of which the energies are shifted toward the low side with respect to the binary elastic collision model. The peak P2 is concluded to be due to the ions which are neutralized in the incoming path and subsequently re-ionized in the violent collision. The energy shift of the peak P1 has a continuous character, showing a gradual increase with increasing incident ion energy. Apparent neutralization is observed for the ions incident along the channel direction [10] at the (110) surface, and this is discussed in connection with the continuous energy loss.

  9. The sensitivity of LaBr3:Ce scintillation detectors to low energy neutrons: Measurement and Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Tain, J. L.; Agramunt, J.; Algora, A.; Aprahamian, A.; Cano-Ott, D.; Fraile, L. M.; Guerrero, C.; Jordan, M. D.; Mach, H.; Martinez, T.; Mendoza, E.; Mosconi, M.; Nolte, R.

    2015-02-01

    The neutron sensitivity of a cylindrical ⊘1.5 in.×1.5 in. LaBr3:Ce scintillation detector was measured using quasi-monoenergetic neutron beams in the energy range from 40 keV to 2.5 MeV. In this energy range the detector is sensitive to γ-rays generated in neutron inelastic and capture processes. The experimental energy response was compared with Monte Carlo simulations performed with the Geant4 simulation toolkit using the so-called High Precision Neutron Models. These models rely on relevant information stored in evaluated nuclear data libraries. The performance of the Geant4 Neutron Data Library as well as several standard nuclear data libraries was investigated. In the latter case this was made possible by the use of a conversion tool that allowed the direct use of the data from other libraries in Geant4. Overall it was found that there was good agreement with experiment for some of the neutron data bases like ENDF/B-VII.0 or JENDL-3.3 but not with the others such as ENDF/B-VI.8 or JEFF-3.1.

  10. Neutron halo isomers in stable nuclei and their possible application for the production of low energy, pulsed, polarized neutron beams of high intensity and high brilliance

    NASA Astrophysics Data System (ADS)

    Habs, D.; Gross, M.; Thirolf, P. G.; Böni, P.

    2011-05-01

    We propose to search for neutron halo isomers populated via γ-capture in stable nuclei with mass numbers of about A=140-180 or A=40-60, where the 4 s 1/2 or 3 s 1/2 neutron shell model state reaches zero binding energy. These halo nuclei can be produced for the first time with new γ-beams of high intensity and small band width (≤0.1%) achievable via Compton back-scattering off brilliant electron beams, thus offering a promising perspective to selectively populate these isomers with small separation energies of 1 eV to a few keV. Similar to single-neutron halo states for very light, extremely neutron-rich, radioactive nuclei (Hansen et al. in Annu. Rev. Nucl. Part. Sci. 45:591-634, 1995; Tanihata in J. Phys. G., Nucl. Part. Phys. 22:158-198, 1996; Aumann et al. in Phys. Rev. Lett. 84:35, 2000), the low neutron separation energy and short-range nuclear force allow the neutron to tunnel far out into free space much beyond the nuclear core radius. This results in prolonged half-lives of the isomers for the γ-decay back to the ground state in the 100 ps-μs range. Similar to the treatment of photodisintegration of the deuteron, the neutron release from the neutron halo isomer via a second, low-energy, intense photon beam has a known much larger cross section with a typical energy threshold behavior. In the second step, the neutrons can be released as a low-energy, pulsed, polarized neutron beam of high intensity and high brilliance, possibly being much superior to presently existing beams from reactors or spallation neutron sources.

  11. DAVE: A Comprehensive Software Suite for the Reduction, Visualization, and Analysis of Low Energy Neutron Spectroscopic Data

    PubMed Central

    Azuah, Richard Tumanjong; Kneller, Larry R.; Qiu, Yiming; Tregenna-Piggott, Philip L. W.; Brown, Craig M.; Copley, John R. D.; Dimeo, Robert M.

    2009-01-01

    National user facilities such as the NIST Center for Neutron Research (NCNR) require a significant base of software to treat the data produced by their specialized measurement instruments. There is no universally accepted and used data treatment package for the reduction, visualization, and analysis of inelastic neutron scattering data. However, we believe that the software development approach adopted at the NCNR has some key characteristics that have resulted in a successful software package called DAVE (the Data Analysis and Visualization Environment). It is developed using a high level scientific programming language, and it has been widely adopted in the United States and abroad. In this paper we describe the development approach, elements of the DAVE software suite, its usage and impact, and future directions and opportunities for development. PMID:27504233

  12. Precise calculations in simulations of the interaction of low energy neutrons with nano-dispersed media

    NASA Astrophysics Data System (ADS)

    Artem'ev, V. A.; Nezvanov, A. Yu.; Nesvizhevsky, V. V.

    2016-01-01

    We discuss properties of the interaction of slow neutrons with nano-dispersed media and their application for neutron reflectors. In order to increase the accuracy of model simulation of the interaction of neutrons with nanopowders, we perform precise quantum mechanical calculation of potential scattering of neutrons on single nanoparticles using the method of phase functions. We compare results of precise calculations with those performed within first Born approximation for nanodiamonds with the radius of 2-5 nm and for neutron energies 3 × 10-7-10-3 eV. Born approximation overestimates the probability of scattering to large angles, while the accuracy of evaluation of integral characteristics (cross sections, albedo) is acceptable. Using Monte-Carlo method, we calculate albedo of neutrons from different layers of piled up diamond nanopowder.

  13. Precise calculations in simulations of the interaction of low energy neutrons with nano-dispersed media

    SciTech Connect

    Artem’ev, V. A.; Nezvanov, A. Yu.; Nesvizhevsky, V. V.

    2016-01-15

    We discuss properties of the interaction of slow neutrons with nano-dispersed media and their application for neutron reflectors. In order to increase the accuracy of model simulation of the interaction of neutrons with nanopowders, we perform precise quantum mechanical calculation of potential scattering of neutrons on single nanoparticles using the method of phase functions. We compare results of precise calculations with those performed within first Born approximation for nanodiamonds with the radius of 2–5 nm and for neutron energies 3 × 10{sup -7}–10{sup -3} eV. Born approximation overestimates the probability of scattering to large angles, while the accuracy of evaluation of integral characteristics (cross sections, albedo) is acceptable. Using Monte-Carlo method, we calculate albedo of neutrons from different layers of piled up diamond nanopowder.

  14. Low-energy neutron flux measurement using a resonance absorption filter surrounding a lithium glass scintillator

    NASA Astrophysics Data System (ADS)

    Ghal-Eh, N.; Koohi-Fayegh, R.; Hamidi, S.

    2007-06-01

    The resonance absorption filter technique has been used to determine the thermal/epithermal neutron flux. The main idea in this technique is to use an element with a high and essentially singular resonance in the neutron absorption cross section as a filter surrounding a miniature-type lithium glass scintillator. The count with and without the filter surrounding the detector gives the number of resonance-energy neutrons. Some preliminary results and a comparison with the MCNP code are shown.

  15. The neutronic design and performance of the Indiana University Cyclotron Facility (IUCF) Low Energy Neutron Source (LENS)

    NASA Astrophysics Data System (ADS)

    Lavelle, Christopher M.

    Neutron scattering research is performed primarily at large-scale facilities. However, history has shown that smaller scale neutron scattering facilities can play a useful role in education and innovation while performing valuable materials research. This dissertation details the design and experimental validation of the LENS TMR as an example for a small scale accelerator driven neutron source. LENS achieves competitive long wavelength neutron intensities by employing a novel long pulse mode of operation, where the neutron production target is irradiated on a time scale comparable to the emission time of neutrons from the system. Monte Carlo methods have been employed to develop a design for optimal production of long wavelength neutrons from the 9Be(p,n) reaction at proton energies ranging from 7 to 13 MeV proton energy. The neutron spectrum was experimentally measured using time of flight, where it is found that the impact of the long pulse mode on energy resolution can be eliminated at sub-eV neutron energies if the emission time distribution of neutron from the system is known. The emission time distribution from the TMR system is measured using a time focussed crystal analyzer. Emission time of the fundamental cold neutron mode is found to be consistent with Monte Carlo results. The measured thermal neutron spectrum from the water reflector is found to be in agreement with Monte Carlo predictions if the scattering kernels employed are well established. It was found that the scattering kernels currently employed for cryogenic methane are inadequate for accurate prediction of the cold neutron intensity from the system. The TMR and neutronic modeling have been well characterized and the source design is flexible, such that it is possible for LENS to serve as an effective test bed for future work in neutronic development. Suggestions for improvements to the design that would allow increased neutron flux into the instruments are provided.

  16. Study of low energy neutron beam formation based on GEANT4 simulations

    NASA Astrophysics Data System (ADS)

    Avagyan, R.; Avetisyan, R.; Ivanyan, V.; Kerobyan, I.

    2017-07-01

    The possibility of obtaining thermal/epithermal energy neutron beams using external protons from cyclotron C18/18 is studied based on GEANT4 simulations. This study will be the basis of the Beam Shaped Assembly (BSA) development for future Boron Neutron Capture Therapy (BNCT). Proton induced reactions on 9Be target are considered as a neutron source, and dependence of neutron yield on target thickness is investigated. The problem of reducing the ratio of gamma to neutron yields by inserting a lead sheet after the beryllium target is studied as well. By GEANT4 modeling the optimal thicknesses of 9Be target and lead absorber are determined and the design characteristics of beam shaping assembly, including the materials and thicknesses of reflector and moderator are considered.

  17. On calibration of the response of liquid argon detectors to nuclear recoils using inelastic neutron scattering on 40Ar

    NASA Astrophysics Data System (ADS)

    Polosatkin, S.; Grishnyaev, E.; Dolgov, A.

    2014-10-01

    A method for measuring of ionization and scintillation yields in liquid argon from recoils with particular energy—8.2 keV—is proposed. The method utilizes a process of inelastic scattering of monoenergetic neutrons produced by fusion DD neutron generator. Features of kinematics of inelastic scattering result in a sufficient (fifteen times) increase in count rate of useful events relative to a traditional scheme using elastic scattering with the same recoil energy and comparable energy resolution.

  18. Low energy E0 transitions in odd-mass nuclei of the neutron deficient 180 < A < 200 region

    SciTech Connect

    Zganjar, E.F.; Kortelahti, M.O.; Wood, J.L.; Papanicolopulos, C.D.

    1987-01-01

    The region of neutron-deficient nuclei near Z = 82 and N = 104 provides the most extensive example of low-energy shape coexistence anywhere on the mass surface. It is shown that E0 and E0 admixed transitions may be used as a fingerprint to identify shape coexistence in odd-mass nuclei. It is also shown that all the known cases of low energy E0 and E0 admixed transitions in odd-mass nuclei occur where equally low-lying O/sup +/ states occur in neighboring even-even nuclei. A discussion of these and other relevant data as well as suggestions for new studies which may help to clarify and, more importantly, quantify the connection between E0 transitions and shape coexistence are presented. 60 refs., 7 figs., 4 tabs.

  19. IBIS: an inverse geometry Brillouin inelastic neutron spectrometer for the SNS.

    PubMed

    Zhao, J K Jinkui; Wildgruber, Christoph U; Robertson, Lee; Herwig, Kenneth W

    2013-02-01

    The high power target station at the Spallation Neutron Source (SNS) currently has about 20 completed neutron scattering instruments. With a broad coverage of the momentum transfer (Q)-energy (E) space, these instruments serve an extensive user community. In an effort to further expand the scientific capabilities of the SNS instrument suites, we propose a low background, inverse geometry Brillouin inelastic spectrometer for the SNS which will expand the Q-E coverage of the current instrument suite and facilitate the study of inelastic and quasi-elastic scatterings at low Q values. The possible location for the proposed instrument is either beamline 8 which views the decoupled water moderator, or beamline 14A, which views a cold, coupled super critical hydrogen moderator. The instrument parameters, optimizations, and performances at these two beamline locations are discussed.

  20. Level lifetimes and the structure of 134Xe from inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Peters, E. E.; Chakraborty, A.; Crider, B. P.; Ashley, S. F.; Elhami, E.; Hicks, S. F.; Kumar, A.; McEllistrem, M. T.; Mukhopadhyay, S.; Orce, J. N.; Prados-Estévez, F. M.; Yates, S. W.

    2017-07-01

    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 (1 h11 /22 d3 /2) configuration has also been tentatively identified for the first time in the N =80 isotones.

  1. Model for neutron total cross-section at low energies for nuclear grade graphite

    NASA Astrophysics Data System (ADS)

    Galván Josa, V. M.; Dawidowski, J.; Santisteban, J. R.; Malamud, F.; Oliveira, R. G.

    2015-04-01

    At subthermal neutron energies, polycrystalline graphite shows a large total cross-section due to small angle scattering processes. In this work, a new methodology to determine pore size distributions through the neutron transmission technique at subthermal energies is proposed and its sensitivity is compared with standard techniques. A simple model based on the form factor for spherical particles, normally used in the Small Angle Neutron Scattering technique, is employed to calculate the contribution of small angle effect to the total scattering cross-section, with the width and center of the radii distributions as free parameters in the model. Small Angle X-ray Scattering experiments were performed to compare results as a means to validate the method. The good agreement reached reveals that the neutron transmission technique is a useful tool to explore small angle scattering effects. This fact can be exploited in situations where large samples must be scanned and it is difficult to investigate them with conventional methods. It also opens the possibility to apply this method in energy-resolved neutron imaging. Also, since subthermal neutron transmission experiments are perfectly feasible in small neutron sources, the present findings open new possibilities to the work done in such kind of facilities.

  2. Experimental measurements with Monte Carlo corrections and theoretical calculations of neutron inelastic scattering cross section of 115In

    NASA Astrophysics Data System (ADS)

    Wang, Chao; Xiao, Jun; Luo, Xiaobing

    2016-10-01

    The neutron inelastic scattering cross section of 115In has been measured by the activation technique at neutron energies of 2.95, 3.94, and 5.24 MeV with the neutron capture cross sections of 197Au as an internal standard. The effects of multiple scattering and flux attenuation were corrected using the Monte Carlo code GEANT4. Based on the experimental values, the 115In neutron inelastic scattering cross sections data were theoretically calculated between the 1 and 15 MeV with the TALYS software code, the theoretical results of this study are in reasonable agreement with the available experimental results.

  3. Anomalous vibrational modes in acetanilide as studied by inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Barthes, Mariette; Eckert, Juegen; Johnson, Susanna W.; Moret, Jacques; Swanson, Basil I.; Unkefer, Clifford J.

    1992-10-01

    A study of the anomalous modes in acetanilide and five deuterated derivatives by incoherent inelastic neutron scattering is reported. These data show that the dynamics of the amide and methyl groups influence each other. In addition, the anomalous temperature behaviour of the NH out-of-plane bending mode is confirmed. These observations suggest that the self-trapping mechanism in ACN may be more complex than hitherto assumed.

  4. Gate-opening effect in ZIF-8: the first experimental proof using inelastic neutron scattering

    SciTech Connect

    Casco, M. E.; Cheng, Y. Q.; Daemen, L. L.; Fairen-Jimenez, D.; Ramos-Fernández, E. V.; Ramirez-Cuesta, A. J.; Silvestre-Albero, J.

    2016-01-28

    In order to understand the behavior of industrial molecular separations, the gate-opening phenomenon in ZIFs are of paramount importance. We show for the first time using in situ inelastic neutron scattering (INS) the swinging of the -CH3 groups and the imidazolate linkers in the prototypical ZIF-8 and ZIF-8@AC hybrid materials upon exposure to mild N2 pressure.

  5. Structure and dynamics of cadmium telluride studied by x-ray and inelastic neutron scattering

    SciTech Connect

    Niedziela, Jennifer L; Stone, Matthew B

    2014-01-01

    We present a combined study of density functional theory, x-ray diffraction, and inelastic neutron scattering examining the temperature dependent structure and lattice dynamics of commercially available cadmium telluride. A subtle change in the structure is evinced near 80~K, which manifests also in the measured phonon density of states. There is no change to the long-range ordered structure. The implications of the change in relation to structural defects are discussed.

  6. MCNP benchmarking of an inelastic neutron scattering system for soil carbon analysis

    NASA Astrophysics Data System (ADS)

    Doron, Oded; Wielopolski, Lucian; Mitra, Sudeep; Biegalski, Steven

    2014-01-01

    We benchmark here a Monte Carlo model simulating an inelastic neutron scattering (INS) system for quantitative analysis of carbon in soil. Specifically, we compare the simulations with experimental results of copper foils activations, INS system calibration, INS system optimization of the height above the ground and comparing pulse height distributions due to 137Cs and 60Co sources. Most of the simulations and the measurements agree better than 10%, although some of them registered discrepancies larger than 20%.

  7. Structure and dynamics of cadmium telluride studied by x-ray and inelastic neutron scattering

    SciTech Connect

    Niedziela, J. L.; Stone, M. B.

    2014-09-08

    We present a combined study of density functional theory, x-ray diffraction, and inelastic neutron scattering examining the temperature dependent structure and lattice dynamics of commercially available cadmium telluride. A subtle change in the structure is evinced near 80 K, which manifests also in the measured phonon density of states. There is no change to the long-range ordered structure. The implications of the change in relation to structural defects are discussed.

  8. Dynamics of water studied by coherent and incoherent inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Bellissent-Funel, M.-C.; Teixeira, J.

    1991-11-01

    This paper reviews the more recent results obtained on the dynamics of water by neutron scattering and shows that some information can be obtained by this technique at the microscopic level of the hydrogen bond. It also accounts for some very recent results obtained with the hydrated protein C-phycocyanin. Incoherent quasi-elastic and inelastic neutron scattering by water has been performed in a temperature range extending to the supercooled state. The analysis of the quasi-elastic spectrum separates two main components and gives two characteristic times, one of them being related to the hydrogen-bond lifetime. The inelastic spectra extend until 600 meV, i.e. covering the intramolecular vibration region, showing for the first time the stretching band. Collective excitations propagating at 3310 m s -1 have been observed by coherent inelastic neutron scattering. This result was predicted by previous computer molecular dynamics simulations of water. The data are interpreted as a manifestation of short wavelength collective modes propagating within patches of highly bonded water molecules, and distinct from the ordinary sound wave.

  9. Theory of inelastic neutron scattering in a field-induced spin-nematic state

    NASA Astrophysics Data System (ADS)

    Smerald, Andrew; Ueda, Hiroaki T.; Shannon, Nic

    2015-05-01

    We develop a theory of spin excitations in a field-induced spin-nematic state, and use it to show how a spin-nematic order can be indentified using inelastic neutron scattering. We concentrate on two-dimensional frustrated ferromagnets, for which a two-sublattice, bond-centered spin-nematic state is predicted to exist over a wide range of parameters. First, to clarify the nature of spin-excitations, we introduce a soluble spin-1 model, and use this to derive a continuum field theory, applicable to any two-sublattice spin-nematic state. We then parameterize this field theory, using diagrammatic calculations for a realistic microscopic model of a spin-1/2 frustrated ferromagnet, and show how it can be used to make predictions for inelastic neutron scattering. As an example, we show quantitative predictions for inelastic scattering of neutrons from BaCdVO(PO 4)2 , a promising candidate to realize a spin-nematic state at an achievable h ˜4 T. We show that in this material it is realistic to expect a ghostly Goldstone mode, signalling spin-nematic order, to be visible in experiment.

  10. Mutation induction and RBE of low energy neutrons in V79 cells.

    PubMed

    Kubota, N; Okada, S; Nagatomo, S; Ozawa, F; Inada, T; Hill, C K; Endo, S; Komatsu, K

    1999-12-01

    We have examined the neutron energy dependency of cell killing and mutation induction at the hprt locus in Chinese hamster V79 cells. Monoenergetic neutrons at 0.32, 0.57, and 1.2 MeV were generated at the Hiroshima University Radiobiological Research Accelerator (HIRRAC) Facility, and were used to irradiate cells. The variation in RBE with neutron energy for the end points of cell survival and hprt mutation induction was observed. When compared to 137Cs gamma-rays, all neutron energies were more effective at both cell killing and induction of mutation. Over the range of the neutron energies examined, we found that cytotoxicity increased as the energy decreased from 1.2 to 0.32 MeV. In comparison to gamma-rays, RBEs for cell lethality at 10% survival were 5.7, 6.7, and 7.6 for 1.2, 0.57, and 0.32 MeV, respectively. Mutation induction, on the other hand, was highest at 0.57 MeV with a gradual decrease at 1.2 and 0.32 MeV. RBEs for mutation induction were 9.7, 19.4, and 13.9 for 1.2, 0.57, and 0.32 MeV neutrons. We isolated independent V79 cell mutants at the hprt locus from untreated and neutron-exposed cells and determined the genetic changes underlying the mutation by multiplex polymerase chain reaction (PCR)-based exon deletion analysis. Preliminary results are suggestive of a specific relationship between deletion pattern and neutron energy.

  11. BAMBUS: a new inelastic multiplexed neutron spectrometer for PANDA

    NASA Astrophysics Data System (ADS)

    Lim, J. A.; Siemensmeyer, K.; Čermák, P.; Lake, B.; Schneidewind, A.; Inosov, D. S.

    2015-03-01

    We report on plans for a multiplexed neutron analyser option for the PANDA spectrometer. The key design concept is to have many analysers positioned to give a large coverage in the scattering plane, and multiple arcs of these analysers to measure different energy transfers simultaneously. The main goal is to bring intensity gains and improved reciprocal-space and energy mapping capabilities to the existing cold triple-axis spectrometer.

  12. Cross section for inelastic neutron ''acceleration'' by {sup 178}Hf{sup m2}

    SciTech Connect

    Karamian, S. A.; Carroll, J. J.

    2011-02-15

    The scattering of thermal neutrons from isomeric nuclei may include events in which the outgoing neutrons have increased kinetic energy. This process has been called inelastic neutron acceleration, or INNA, and occurs when the final nucleus, after emission of the neutron, is left in a state with lower energy than that of the isomer. The result, therefore, is an induced depletion of the isomer to the ground state. A cascade of several {gamma}'s must accompany the neutron emission to release the high angular momentum of the initial isomeric state. INNA was previously observed in a few cases, and the measured cross sections were only in modest agreement with theoretical estimates. The most recent measurement of an INNA cross section was {sigma}{sub INNA}=258{+-}58 b for neutron scattering by {sup 177}Lu{sup m}. In the present work, an INNA cross section of {sigma}{sub INNA}=168 {+-} 33 b was deduced from measurements of the total burnup of the high-spin, four-quasiparticle isomer {sup 178}Hf{sup m2} during irradiation by thermal neutrons. Statistical estimates for the probability of different reaction channels past neutron absorption were used in the analysis, and the deduced {sigma}{sub INNA} was compared to the theoretically predicted cross section.

  13. Low-energy neutron physics research with a gamma multiplicity detector

    NASA Astrophysics Data System (ADS)

    Block, Robert C.; Slovacek, R. E.; Werner, C. J.; Moretti, B. E.; Burke, J. A.; Drindak, N. J.; Leinweber, G.

    1997-02-01

    A sixteen-segment NaI(Tl) multiplicity gamma ray detector is used at the Rensselaer Polytechnic Institute Gaerttner LINAC Laboratory for neutron cross section measurements. This detector consists of an annulus of NaI(Tl) divided into two sets of 8 pie shaped segments, each segment optically isolate and viewed by a photomultiplier. The neutron beam passes along the axis of the detector and impinges upon a sample placed in the center. Time-of-flight data are taken as a function of the number of sections which detect a gamma and which is defined as the detected multiplicity. This detector can simultaneously acquire neutron scattering, capture and fission data by placing suitable limits on the total detected gamma ray energy deposited in the detector. Scattering and capture measurements have been performed on samples of holmium, erbium, and tungsten and experimental results are presented. The experimental multiplicity for capture is analyzed by assuming the single particle model, stochastically calculating the gamma ray cascades from neutron capture, and transporting each gamma ray into the detector using the Monte Carlo method. The detection efficiency for neutron capture is over 90 percent and is relatively insensitive to different isotopes of the same element or different spins of the compound nuclear resonances. A status report on experimental and analytical activities at the Laboratory is presented.

  14. Close-coupling calculations of low-energy inelastic and elastic processes in 4He collisions with H2: A comparative study of two potential energy surfaces

    NASA Astrophysics Data System (ADS)

    Lee, Teck-Ghee; Rochow, C.; Martin, R.; Clark, T. K.; Forrey, R. C.; Balakrishnan, N.; Stancil, P. C.; Schultz, D. R.; Dalgarno, A.; Ferland, Gary J.

    2005-01-01

    The two most recently published potential energy surfaces (PESs) for the HeH2 complex, the so-called MR (Muchnick and Russek) and BMP (Boothroyd, Martin, and Peterson) surfaces, are quantitatively evaluated and compared through the investigation of atom-diatom collision processes. The BMP surface is expected to be an improvement, approaching chemical accuracy, over all conformations of the PES compared to that of the MR surface. We found significant differences in inelastic rovibrational cross sections computed on the two surfaces for processes dominated by large changes in target rotational angular momentum. In particular, the H2(ν=1,j=0) total quenching cross section computed using the BMP potential was found to be a factor of 1000 larger than that obtained with the MR surface. A lesser discrepancy persists over a large range of energies from the ultracold to thermal and occurs for other low-lying initial rovibrational levels. The MR surface was used in previous calculations of the H2(ν=1,j=0) quenching rate coefficient and gave results in close agreement with the experimental data of Audibert et al. which were obtained for temperatures between 50 and 300 K. Examination of the rovibronic coupling matrix elements, which are obtained following a Legendre expansion of the PES, suggests that the magnitude of the anisotropy of the BMP potential is too large in the interaction region. However, cross sections for elastic and pure rotational processes obtained from the two PESs differ typically by less than a factor of 2. The small differences may be ascribed to the long-range and anharmonic components of the PESs. Exceptions occur for (ν=10,j=0) and (ν=11,j=1) where significant enhancements have been found for the low-energy quenching and elastic cross sections due to zero-energy resonances in the BMP PES which are not present in the MR potential.

  15. Elastic and inelastic neutron scattering cross sections for fission reactor applications

    NASA Astrophysics Data System (ADS)

    Hicks, S. F.; Chakraborty, A.; Combs, B.; Crider, B. P.; Downes, L.; Girgis, J.; Kersting, L. J.; Kumar, A.; Lueck, C. J.; McDonough, P. J.; McEllistrem, M. T.; Peters, E. E.; Prados-Estevz, F. M.; Schniederjan, J.; Sidwell, L.; Sigillito, A. J.; Vanhoy, J. R.; Watts, D.; Yates, S. W.

    2013-04-01

    Nuclear data important for the design and development of the next generation of light-water reactors and future fast reactors include neutron elastic and inelastic scattering cross sections on important structural materials, such as Fe, and on coolant materials, such as Na. These reaction probabilities are needed since neutron reactions impact fuel performance during irradiations and the overall efficiency of reactors. While neutron scattering cross sections from these materials are available for certain incident neutron energies, the fast neutron region, particularly above 2 MeV, has large gaps for which no measurements exist, or the existing uncertainties are large. Measurements have been made at the University of Kentucky Accelerator Laboratory to measure neutron scattering cross sections on both Fe and Na in the region where these gaps occur and to reduce the uncertainties on scattering from the ground state and first excited state of these nuclei. Results from measurements on Fe at incident neutron energies between 2 and 4 MeV will be presented and comparisons will be made to model calculations available from data evaluators.

  16. Impact of a low-energy enhancement in the gamma-ray strength function on the neutron-capture cross section

    SciTech Connect

    Larsen, A. C.; Goriely, S.

    2010-07-15

    A low-energy enhancement of the gamma-ray strength function in several light and medium-mass nuclei has been observed recently in {sup 3}He-induced reactions. The effect of this enhancement on (n,gamma) cross sections is investigated for stable and unstable neutron-rich Fe, Mo, and Cd isotopes. Our results indicate that the radiative neutron capture cross sections may increase considerably due to the low-energy enhancement when approaching the neutron drip line. This could have non-negligible consequences on r-process nucleosynthesis calculations.

  17. The silicon photomultipliers for inelastic neutron scattering at high energy transfers

    NASA Astrophysics Data System (ADS)

    Pietropaolo, Antonino

    2010-01-01

    The silicon photomultiplier (SiPM) is a photo sensor of recent technology. It is mostly used in particle physics, for example in the detection of minimum ionizing particles and/or Cherenkov radiation. Its performance is comparable to that of photomultiplier tubes (PMTs), but with advantages in terms of reduced volume and magnetic field insensitivity. In the present study, the performance of a SiPM as a readout for a γ-ray detector made of a yttrium-aluminum-perovskite (YAP) scintillation crystal is assessed for use in time of flight inelastic neutron spectroscopy at high energy transfers. This was done by performing explorative measurements at the Italian Neutron Experimental Station (INES) beam line at the ISIS spallation neutron source. The measurements, carried out in the so-called resonance detector (RD) configuration, demonstrate the suitability of the SiPM for this kind of application.

  18. Sharpening Low-Energy, Standard-Model Tests via Correlation Coefficients in Neutron {beta} Decay

    SciTech Connect

    Gardner, S.; Zhang, C.

    2001-06-18

    The correlation coefficients a , A , and B in neutron {beta} decay are proportional to the ratio of the axial-vector-to-vector weak coupling constants, g{sub A}/g{sub V} , to leading recoil order. With the advent of the next generation of neutron-decay experiments, the recoil-order corrections to these expressions become experimentally accessible, admitting a plurality of standard model (SM) tests. The measurement of both a and A , e.g., allows one to test the conserved-vector-current (CVC) hypothesis and to search for second-class currents (SCC) independently. The anticipated precision of these measurements suggests that the bounds on CVC violation and SCC from studies of nuclear {beta} decay can be qualitatively bettered.

  19. Use of a high repetition rate neutron generator for in vivo body composition measurements via neutron inelastic scattering

    SciTech Connect

    Kehayias, J.J.; Ellis, K.J.; Cohn, S.H.; Weinlein, J.H.

    1986-01-01

    A small D-T neutron generator with a high pulse rate is used for the in vivo measurement of body carbon, oxygen and hydrogen. The core of the neutron generator is a 13 cm-long Zetatron tube pulsed at a rate of 10 kHz delivering 10/sup 3/ to 10/sup 4/ neutrons per pulse. A target-current feedback system regulates the source of the accelerator to assure constant neutron output. Carbon is measured by detecting the 4.44 MeV ..gamma..-rays from inelastic scattering. The short half-life of the 4.44 MeV state of carbon requires detection of the ..gamma..-rays during the 10 ..mu..s neutron pulse. Generators with low pulsing rate were found inappropriate for carbon measurements because of their low duty-cycle (high neutron output during the pulse). In vivo measurements were performed with normal volunteers using a scanning bed facility for a dose less than 25 mrem. This technique offers medical as well as general bulk analysis applications. 8 refs., 5 figs.

  20. Elastic and Inelastic Neutron Scattering with a C7LYC Array

    NASA Astrophysics Data System (ADS)

    Wilson, G. L.; Brown, T.; Chowdhury, P.; Doucet, E.; Lister, C. J.; D'Olympia, N.; Devlin, M.; Mosby, S.

    2015-10-01

    A scintillator array of 16 1'' ×1'' Cs2LiYCl6 (CLYC) detectors has been commissioned for low energy nuclear science. Standard CLYC crystals detect both gamma rays and neutrons rays with excellent pulse shape discrimination, with thermal neutrons detected via the 6Li(n, α)t reaction. Our discovery of spectroscopy-grade response of CLYC for fast neutrons via the 35Cl(n,p) reaction, with a pulse height resolution of under 10 % in the < 8 MeV range, led to our present array of 7Li enriched C7LYC detectors, where the large thermal neutron response is essentially eliminated. While the intrinsic efficiency of C7LYC for fast neutron detection is low, the array can be placed near the target since a long TOF arm is no longer needed for neutron energy measurement, thus recovering efficiency through increased solid angle coverage. The array was recently deployed at Los Alamos to test its capability in measuring differential scattering cross sections as a function of energy for 56Fe and 238U. The incident energy from a white neutron source was measured via TOF, and the scattered neutron energy via the pulse height. Techniques, analysis and first results will be discussed. Supported by the NNSA Stewardship Science Academic Alliance Program under Grant DE-NA00013008.

  1. A study of neutron radiation quality with a tissue-equivalent proportional counter for a low-energy accelerator-based in vivo neutron activation facility.

    PubMed

    Aslam; Waker, A J

    2011-02-01

    The accelerator-based in vivo neutron activation facility at McMaster University has been used successfully for the measurement of several minor and trace elements in human hand bones due to their importance to health. Most of these in vivo measurements have been conducted at a proton beam energy (E(p)) of 2.00 MeV to optimise the activation of the selected element of interest with an effective dose of the same order as that received in chest X rays. However, measurement of other elements at the same facility requires beam energies other than 2.00 MeV. The range of energy of neutrons produced at these proton beam energies comes under the region where tissue-equivalent proportional counters (TEPCs) are known to experience difficulty in assessing the quality factor and dose equivalent. In this study, the response of TEPCs was investigated to determine the quality factor of neutron fields generated via the (7)Li(p, n)(7)Be reaction as a function of E(p) in the range 1.884-2.56 MeV at the position of hand irradiation in the facility. An interesting trend has been observed in the quality factor based on ICRP 60, Q(ICRP60), such that the maximum value was observed at E(p)=1.884 MeV (E(n)=33±16 keV) and then continued to decline with increasing E(p) until achieving a minimum value at E(p)=2.0 MeV despite a continuous increase in the mean neutron energy with E(p). This observation is contrary to what has been observed with direct fast neutrons where the quality factor was found to increase continuously with an increase in E(p) (i.e. increasing E(n)). The series of measurements conducted with thermal and fast neutron fields demonstrate that the (14)N(n, p)(14)C produced 580 keV protons in the detector play an important role in the response of the counter under 2.0 MeV proton energy (E(n) ≤ 250 keV). In contrast to the lower response of TEPCs to low-energy neutrons, the quality factor is overestimated in the range 1-2 depending on beam energy <2.0 MeV. This study provides

  2. The design of the inelastic neutron scattering mode for the Extreme Environment Diffractometer with the 26 T High Field Magnet

    NASA Astrophysics Data System (ADS)

    Bartkowiak, Maciej; Stüßer, Norbert; Prokhnenko, Oleksandr

    2015-10-01

    The Extreme Environment Diffractometer is a neutron time-of-flight instrument, designed to work with a constant-field hybrid magnet capable of reaching fields over 26 T, unprecedented in neutron science; however, the presence of the magnet imposes both spatial and technical limitations on the surrounding instrument components. In addition to the existing diffraction and small-angle neutron scattering modes, the instrument will operate also in an inelastic scattering mode, as a direct time-of-flight spectrometer. In this paper we present the Monte Carlo ray-tracing simulations, the results of which illustrate the performance of the instrument in the inelastic-scattering mode. We describe the focussing neutron guide and the chopper system of the existing instrument and the planned design for the instrument upgrade. The neutron flux, neutron spatial distribution, divergence distribution and energy resolution are calculated for standard instrument configurations.

  3. Investigating H₂ Sorption in a Fluorinated Metal-Organic Framework with Small Pores Through Molecular Simulation and Inelastic Neutron Scattering.

    PubMed

    Forrest, Katherine A; Pham, Tony; Georgiev, Peter A; Pinzan, Florian; Cioce, Christian R; Unruh, Tobias; Eckert, Juergen; Space, Brian

    2015-07-07

    Simulations of H2 sorption were performed in a metal-organic framework (MOF) consisting of Zn(2+) ions coordinated to 1,2,4-triazole and tetrafluoroterephthalate ligands (denoted [Zn(trz)(tftph)] in this work). The simulated H2 sorption isotherms reported in this work are consistent with the experimental data for the state points considered. The experimental H2 isosteric heat of adsorption (Qst) values for this MOF are approximately 8.0 kJ mol(-1) for the considered loading range, which is in the proximity of those determined from simulation. The experimental inelastic neutron scattering (INS) spectra for H2 in [Zn(trz)(tftph)] reveal at least two peaks that occur at low energies, which corresponds to high barriers to rotation for the respective sites. The most favorable sorption site in the MOF was identified from the simulations as sorption in the vicinity of a metal-coordinated H2O molecule, an exposed fluorine atom, and a carboxylate oxygen atom in a confined region in the framework. Secondary sorption was observed between the fluorine atoms of adjacent tetrafluoroterephthalate ligands. The H2 molecule at the primary sorption site in [Zn(trz)(tftph)] exhibits a rotational barrier that exceeds that for most neutral MOFs with open-metal sites according to an empirical phenomenological model, and this was further validated by calculating the rotational potential energy surface for H2 at this site.

  4. Proton calibration of low energy neutron detectors containing (6)LiF

    SciTech Connect

    Benton, E.V.; Frank, A.L.

    1995-03-01

    The purpose of the present calibrations is to measure the proton response of the detectors with accelerated beams having energies within the region of maximum intensities in the trapped proton spectrum encountered in near-Earth orbit. This response is compared with the responses of the spaceflight detectors when related to proton exposures. All of the spaceflight neutron measurements have been accompanied by TLD absorbed doses measurements in close proximity within the spacecraft. For purposes of comparison, the spaceflight TLD doses are assumed to be proton doses.

  5. Proton calibration of low energy neutron detectors containing (6)LiF

    NASA Technical Reports Server (NTRS)

    Benton, E. V.; Frank, A. L.

    1995-01-01

    The purpose of the present calibrations is to measure the proton response of the detectors with accelerated beams having energies within the region of maximum intensities in the trapped proton spectrum encountered in near-Earth orbit. This response is compared with the responses of the spaceflight detectors when related to proton exposures. All of the spaceflight neutron measurements have been accompanied by TLD absorbed doses measurements in close proximity within the spacecraft. For purposes of comparison, the spaceflight TLD doses are assumed to be proton doses.

  6. Neutron inelastic scattering in natural Cu as a background in neutrinoless double-β decay experiments

    NASA Astrophysics Data System (ADS)

    Boswell, M. S.; Elliott, S. R.; Perepelitsa, D. V.; Devlin, M.; Fotiades, N.; Nelson, R. O.; Kawano, T.; Guiseppe, V. E.

    2013-06-01

    Background: Experiments designed to study rare processes, such as neutrinoless double-β decay (0νββ), are crucial tests for physics beyond the standard model. These experiments rely on reducing the intrinsic radioactive background to unprecedented levels, while adequately shielding the detectors from external sources of radioactivity.Purpose: The purpose of this work is focused on understanding the background rates from neutron interactions in Cu shielding in regions around the Q values of many candidate 0νββ decay isotopes, as well as providing data for benchmarking Monte Carlo simulations of background events.Methods: Using the broad-spectrum neutron beam at Los Alamos Neutron Science Center, we have measured γ rays emitted from inelastic neutron scattering on natCu.Results: We extracted the level cross sections from the γ-production cross section for 46 energy levels in natCu. These level cross sections were compared with the available experimental data, as well as the ENDF/B-VII evaluation for discrete levels.Conclusions: For energy levels above 2 MeV we found significant discrepancies between the suggested level cross sections for both nuclei and our data. We found reasonable agreement between our measurement and the ENDF/B-VII evaluation for the total neutron inelastic cross section in 63Cu. Our measurement of the total neutron inelastic scattering cross section in 65Cu was 30% lower than the ENDF/B-VII evaluations, which we attribute to unobserved transitions in 65Cu. Furthermore, we found that the implementation of the ENDF/B-VII evaluation in simulations did not properly model the decay properties of the nucleus to the degree necessary for estimating backgrounds in rear-event searches. Finally, we examined the potential implications of our measurements on 0νββ measurements and found that many of the commonly studied 0νββ isotopes had Q values below the cutoff for ENDF/B-VII evaluated discrete levels in either Cu nucleus.

  7. Application of Geant4 simulation for analysis of soil carbon inelastic neutron scattering measurements.

    PubMed

    Yakubova, Galina; Kavetskiy, Aleksandr; Prior, Stephen A; Torbert, H Allen

    2016-07-01

    Inelastic neutron scattering (INS) was applied to determine soil carbon content. Due to non-uniform soil carbon depth distribution, the correlation between INS signals with some soil carbon content parameter is not obvious; however, a proportionality between INS signals and average carbon weight percent in ~10cm layer for any carbon depth profile is demonstrated using Monte-Carlo simulation (Geant4). Comparison of INS and dry combustion measurements confirms this conclusion. Thus, INS measurements give the value of this soil carbon parameter.

  8. Inelastic neutron scattering study of light-induced dynamics of a photosynthetic membrane system

    SciTech Connect

    Furrer, A.; Stoeckli, A.

    2010-01-15

    Inelastic neutron scattering was employed to study photoeffects on the molecular dynamics of membranes of the photosynthetic bacterium Rhodopseudomonas viridis. The main photoactive parts of this biomolecular system are the chlorophyll molecules whose dynamics were found to be affected under illumination by visible light in a twofold manner. First, vibrational modes are excited at energies of 12(2) and 88(21) cm{sup -1}. Second, a partial 'freezing' of rotational modes is observed at energies of 1.2(3) and 2.9(5) cm{sup -1}. These results are attributed to a possible coupling between molecular motions and particular mechanisms in the photosynthetic process.

  9. A high resolution, inelastic neutron scattering investigation of tunnelling methyl groups in aspirin

    NASA Astrophysics Data System (ADS)

    Johnson, M. R.; Frick, B.; Trommsdorff, H. P.

    1996-08-01

    The tunnel frequency of protonated methyl groups in aspirin has been measured, by inelastic neutron scattering, at 2 K, to be 1.22 μeV. This result and the temperature dependence up to 42 K are in poor agreement with NMR measurements of deuterated methyl groups which conclude that the rotational potential is purely three-fold symmetric. The discrepancy is attributed to a six-fold contribution in the rotational potential for which justification is provided by a calculation of the rotational potential based on the room temperature crystal structure.

  10. Magnetic excitations in multiferroic LuMnO3 studied by inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Lewtas, H. J.; Boothroyd, A. T.; Rotter, M.; Prabhakaran, D.; Müller, H.; Le, M. D.; Roessli, B.; Gavilano, J.; Bourges, P.

    2010-11-01

    We present data on the magnetic and magnetoelastic coupling in the hexagonal multiferroic manganite LuMnO3 from inelastic neutron scattering, magnetization, and thermal-expansion measurements. We measured the magnon dispersion along the main symmetry directions and used this data to determine the principal exchange parameters from a spin-wave model. An analysis of the magnetic anisotropy in terms of the crystal field acting on the Mn is presented. We compare the results for LuMnO3 with data on other hexagonal RMnO3 compounds.

  11. MIMAC low energy electron-recoil discrimination measured with fast neutrons

    NASA Astrophysics Data System (ADS)

    Riffard, Q.; Santos, D.; Guillaudin, O.; Bosson, G.; Bourrion, O.; Bouvier, J.; Descombes, T.; Muraz, J.-F.; Lebreton, L.; Maire, D.; Colas, P.; Giomataris, I.; Busto, J.; Fouchez, D.; Brunner, J.; Tao, C.

    2016-08-01

    MIMAC (MIcro-TPC MAtrix of Chambers) is a directional WIMP Dark Matter detector project. Direct dark matter experiments need a high level of electron/recoil discrimination to search for nuclear recoils produced by WIMP-nucleus elastic scattering. In this paper, we proposed an original method for electron event rejection based on a multivariate analysis applied to experimental data acquired using monochromatic neutron fields. This analysis shows that a 105 rejection power is reachable for electron/recoil discrimination. Moreover, the efficiency was estimated by a Monte-Carlo simulation showing that a 105 electron rejection power is reached with a 86.49 ± 0.17% nuclear recoil efficiency considering the full energy range and 94.67 ± 0.19% considering a 5 keV lower threshold.

  12. Elastic scattering, inelastic excitation, and neutron transfer for 7Li+120Sn at energies around the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Zagatto, V. A. B.; Lubian, J.; Gasques, L. R.; Alvarez, M. A. G.; Chamon, L. C.; Oliveira, J. R. B.; Alcántara-Núñez, J. A.; Medina, N. H.; Scarduelli, V.; Freitas, A.; Padron, I.; Rossi, E. S.; Shorto, J. M. B.

    2017-06-01

    Experimental angular distributions for the 7Li+120Sn elastic and inelastic (projectile and target excitations) scattering, and for the neutron stripping reaction, have been obtained at ELAB= 20 , 22, 24, and 26 MeV, covering an energy range around the Coulomb barrier (VB(LAB )≈21.4 MeV). Coupled channel and coupled reaction channel calculations were performed and both describe satisfactorily the experimental data sets. The 1/2- state 7Li inelastic excitation (using a rotational model), as well as the projectile coupling to the continuum (α plus a tritium particle) play a fundamental role on the proper description of elastic, inelastic, and transfer channels. Couplings to the one-neutron stripping channel do not significantly affect the theoretical elastic scattering angular distributions. The spectroscopic amplitudes of the transfer channel were obtained through a shell model calculation. The theoretical angular distributions for the one-neutron stripping reaction agreed with the experimental data.

  13. Low-energy neutron detector based upon lithium lanthanide borate scintillators

    DOEpatents

    Czirr, John B.

    1998-01-01

    An apparatus for detecting neutrons includes a cerium activated scintillation crystal containing .sup.10 B, with the scintillation crystal emitting light in response to .alpha. particles emitted from the .sup.10 B(n,.alpha.)Li* reaction. The apparatus also includes a gamma scintillator positioned adjacent the crystal and which generates light in response to gamma rays emitted from the decay of Li*. The apparatus further includes a first and a second light-to-electronic signal converter each positioned to respectively receive light from the crystal and the gamma scintillator, and each respectively outputting first and second electronic signals representative of .alpha. particles from the .sup.10 B(n,.alpha.)Li* reaction and gamma rays from the .sup.10 B(n,.alpha.)Li* reaction. The apparatus includes a coincidence circuit connected to receive the first and second signals and which generates a coincidence signal when the first and second signals coincide. The apparatus also includes a data analyzer for receiving an additional signal from at least one of the first and second converters, and for operating in response to the coincidence signal.

  14. Solid-state effects on thermal-neutron cross sections and on low-energy resonances

    SciTech Connect

    Harvey, J.A.; Mook, H.A.; Hill, N.W.; Shahal, O.

    1982-01-01

    The neutron total cross sections of several single crystals (Si, Cu, sapphire), several polycrystalline samples (Cu, Fe, Be, C, Bi, Ta), and a fine-powder copper sample have been measured from 0.002 to 5 eV. The Cu powder and polycrystalline Fe, Be and C data exhibit the expected abrupt changes in cross section. The cross section of the single crystal of Si is smooth with only small broad fluctuations. The data on two single Cu crystals, the sapphire crystal, cast Bi, and rolled samples of Ta and Cu have many narrow peaks approx. 10/sup -3/ eV wide. High resolution (0.3%) transmission measurements were made on the 1.057-eV resonance in /sup 240/Pu and the 0.433-eV resonance in /sup 180/Ta, both at room and low temperatures to study the effects of crystal binding. Although the changes in Doppler broadening with temperature were apparent, no asymmetries due to a recoilless contribution were observed.

  15. Neutron emission effects on final fragments mass and kinetic energy distribution from low energy fission of 34U

    NASA Astrophysics Data System (ADS)

    Montoya, M.; Rojas, J.; Lobato, I.

    2008-12-01

    The kinetic energy distribution as a function of mass of final fragments (m) from low energy fission of $^{234}U$, measured with the Lohengrin spectrometer by Belhafaf et al. presents a peak around m=108 and another around m = 122. The authors attribute the first peak to the evaporation of a large number of neutrons around the corresponding mass number; and the second peak to the distribution of the primary fragment kinetic energy. Nevertheless, the theoretical calculations related to primary distribution made by Faust et al. do not result in a peak around m = 122. In order to clarify this apparent controversy, we have made a numerical experiment in which the masses and the kinetic energy of final fragments are calculated, assuming an initial distribution of the kinetic energy without peaks on the standard deviation as function of fragment mass. As a result we obtain a pronounced peak on the standard deviation of the kinetic energy distribution around m = 109, a depletion from m = 121 to m = 129, and an small peak around m = 122, which is not as big as the measured by Belhafaf et al. Our simulation also reproduces the experimental results on the yield of the final mass, the average number of emitted neutrons as a function of the provisional mass (calculated from the values of the final kinetic energy of the complementary fragments) and the average value of fragment kinetic energy as a function of the final mass.

  16. Evidence for inelastic neutron acceleration by the {sup 177}Lu isomer

    SciTech Connect

    Roig, O.; Belier, G.; Meot, V.; Daugas, J.-M.

    2006-11-15

    The neutron burnup cross section {sigma}{sub burnup}{sup m} on the long-lived metastable state of {sup 177}Lu has been measured from a specially designed isomeric target. The Maxwellian averaged cross section obtained for this reaction on {sup 177}Lu{sup m}(J{sup {pi}}=23/2{sup -}) is {sigma}{sub burnup}{sup m}=626{+-}45 b at the reactor temperature T=323 K. The difference between the burnup cross section and the previously measured capture cross section {sigma}{sub n,{gamma}} clearly shows a possible existence of {sup 177}Lu{sup m} deexcitation via (n,n{sup '}) inelastic neutron acceleration channels. The results are interpreted in terms of a statistical approach using parameters from a deformed optical potential calculation.

  17. Penicillin's catalytic mechanism revealed by inelastic neutrons and quantum chemical theory.

    PubMed

    Mucsi, Zoltán; Chass, Gregory A; Ábrányi-Balogh, Péter; Jójárt, Balázs; Fang, De-Cai; Ramirez-Cuesta, Annibal J; Viskolcz, Béla; Csizmadia, Imre G

    2013-12-21

    Penicillin, travels through bodily fluids, targeting and acylatively inactivating enzymes responsible for cell-wall synthesis in gram-positive bacteria. Somehow, it avoids metabolic degradation remaining inactive en route. To resolve this ability to switch from a non-active, to a highly reactive form, we investigated the dynamic structure-activity relationship of penicillin by inelastic neutron spectroscopy, reaction kinetics, NMR and multi-scale theoretical modelling (QM/MM and post-HF ab initio). Results show that by a self-activating physiological pH-dependent two-step proton-mediated process, penicillin changes geometry to activate its irreversibly reactive acylation, facilitated by systemic intramolecular energy management and cooperative vibrations. This dynamic mechanism is confirmed by the first ever reported characterisation of an antibiotic by neutrons, achieved on the TOSCA instrument (ISIS facility, RAL, UK).

  18. Inelastic proton scattering as a mean for the determination of neutron and proton matrix element ratios

    NASA Astrophysics Data System (ADS)

    Alamanos, N.; Pakou, A.; Lagoyannis, A.; Musumarra, A.

    1999-12-01

    The determination of ratio of neutron over proton matrix elements by inelastic proton scattering, for 0 +→2 + transitions, is investigated via the comparison between experimental data and theoretical calculations. Calculations into the context of a macroscopic and a microscopic description are performed for a wide mass range nuclei: 18O, 30Si, 32,34S, 48Ca, 88Sr, for which these ratios were determined previously with an independent technique. At that point the choice of the theoretical model may be very critical. It is thus the purpose of this investigation to point out the most suitable model. It is found that in general both theoretical models can be employed for the reliable determination of neutron over proton matrix element ratios.

  19. Inelastic neutron scattering study of water in hydrated LTA-type zeolites.

    PubMed

    Corsaro, Carmelo; Crupi, Vincenza; Majolino, Domenico; Parker, Stewart F; Venuti, Valentina; Wanderlingh, Ulderico

    2006-01-26

    The vibrational dynamics of water molecules encapsulated in synthetic Na-A and Mg-exchanged A zeolites were studied versus temperature by inelastic neutron scattering (INS) measurements (30-1200 cm(-1)) as a function of the induced ion-exchange percentage by using the indirect geometry tof spectrometer TOSCA at the ISIS pulse neutron facility (RAL, UK). The experimental INS spectra were compared with those of ice Ih to characterize the structural changes induced by confinement on the H2O hydrogen-bonded network. We observed, after increasing the Mg2+ content, a tendency of water molecules to restore the bulklike arrangements together with more hindered dynamics. These results are confirmed by the analysis of the evaluated one-phonon amplitude-weighted proton vibrational density of states aimed, in particular, to follow the evolution of the water molecules librational mode region.

  20. Deep inelastic scattering from A=3 nuclei and the neutron structure function

    NASA Astrophysics Data System (ADS)

    Afnan, I. R.; Bissey, F.; Gomez, J.; Katramatou, A. T.; Liuti, S.; Melnitchouk, W.; Petratos, G. G.; Thomas, A. W.

    2003-09-01

    We present a comprehensive analysis of deep inelastic scattering from 3He and 3H, focusing in particular on the extraction of the free neutron structure function Fn2. Nuclear corrections are shown to cancel to within 1 2% for the isospin-weighted ratio of 3He to 3H structure functions, which leads to more than an order of magnitude improvement in the current uncertainty in the neutron to proton ratio Fn2/Fp2 at large x. Theoretical uncertainties originating from the nuclear wave function, including possible non-nucleonic components, are evaluated. Measurements of the 3He and 3H structure functions will, in addition, determine the magnitude of the EMC effect in all A⩽3 nuclei.

  1. Neutron Inelastic Scattering Measurements for Na, Ge, Zr, Mo and U

    NASA Astrophysics Data System (ADS)

    Bacquias, A.; Dessagne, Ph.; Kerveno, M.; Rudolf, G.; Plompen, A. J. M.; Drohé, J. C.; Rouki, C.; Nankov, N.; Nyman, M.; Borcea, C.; Negret, A.; Archier, P.; De Saint Jean, C.; Noguère, G.; Vaglio-Gaudard, C.; Koning, A.; Domula, A.; Zuber, K.; Leal, L. C.

    2014-05-01

    Studies for advanced reactor systems such as sodium-cooled fast reactors designed for recycling of high level waste, accelerator driven systems for transmutation, and systems envisioning the use of the Th/U fuel cycle impose tight requirements on nuclear data for accurate predictions of their operation and safety characteristics. Among the identified needs established by sensitivity studies, neutron inelastic scattering on the main structural materials and actinides and some (n,xn) cross sections for actinides feature prominently. Prompt-gamma spectroscopy and time-of-flight techniques were used to measure (n,xnγ) cross-sections of interest. Experiments were performed at the GELINA neutron time-of-flight facility of IRMM. Results for 235U and 23Na are briefly recalled; pertaining theoretical discussions are mentioned to explain observations concerning 238U. The status of studies on 76Ge, Zr and Mo is also reported.

  2. Level crossings and zero-field splitting in the {Cr8}-cubane spin-cluster studied using inelastic neutron scattering and magnetization

    SciTech Connect

    Vaknin, D.; Garlea, Vasile O; Demmel, F.; Mamontov, Eugene; Nojiri, H; Martin, Catalin; Chiorescu, Irinel; Qiu, Y.; Luban, M.; Kogerler, P.; Fielden, J.; Engelhardt, L; Rainey, C

    2010-01-01

    Inelastic neutron scattering (INS) in variable magnetic field and high-field magnetization measurements in the millikelvin temperature range were performed to gain insight into the low-energy magnetic excitation spectrum and the field-induced level crossings in the molecular spin cluster {Cr8}-cubane. These complementary techniques provide consistent estimates of the lowest level-crossing field. The overall features of the experimental data are explained using an isotropic Heisenberg model, based on three distinct exchange interactions linking the eight CrIII paramagnetic centers (spins s = 3/2), that is supplemented with a relatively large molecular magnetic anisotropy term for the lowest S = 1 multiplet. It is noted that the existence of the anisotropy is clearly evident from the magnetic field dependence of the excitations in the INS measurements, while the magnetization measurements are not sensitive to its effects.

  3. Level crossings and zero-field splitting in the {Cr8}-cubane spin cluster studied using inelastic neutron scattering and magnetization.

    PubMed

    Vaknin, D; Garlea, V O; Demmel, F; Mamontov, E; Nojiri, H; Martin, C; Chiorescu, I; Qiu, Y; Kögerler, P; Fielden, J; Engelhardt, L; Rainey, C; Luban, M

    2010-11-24

    Inelastic neutron scattering (INS) in variable magnetic field and high-field magnetization measurements in the millikelvin temperature range were performed to gain insight into the low-energy magnetic excitation spectrum and the field-induced level crossings in the molecular spin cluster {Cr(8)}-cubane. These complementary techniques provide consistent estimates of the lowest level-crossing field. The overall features of the experimental data are explained using an isotropic Heisenberg model, based on three distinct exchange interactions linking the eight Cr(III) paramagnetic centers (spins s = 3/2), that is supplemented with a relatively large molecular magnetic anisotropy term for the lowest S = 1 multiplet. It is noted that the existence of the anisotropy is clearly evident from the magnetic field dependence of the excitations in the INS measurements, while the magnetization measurements are not sensitive to its effects.

  4. Local-moment magnetism in superconducting FeTe0.35Se0.65 as seen via inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Xu, Zhijun; Wen, Jinsheng; Xu, Guangyong; Chi, Songxue; Ku, Wei; Gu, Genda; Tranquada, J. M.

    2011-08-01

    The nature of the magnetic correlations in Fe-based superconductors remains a matter of controversy. To address this issue, we use inelastic neutron scattering to characterize the strength and temperature dependence of low-energy spin fluctuations in FeTe0.35Se0.65 (Tc˜14 K). Integrating magnetic spectral weight for energies up to 12 meV, we find a substantial moment (LE˜0.07μB2/Fe)that shows little change with temperature, from below Tc to 300 K. Such behavior cannot be explained by the response of conduction electrons alone; states much farther from the Fermi energy must have an instantaneous local spin polarization. It raises interesting questions regarding the formation of the spin gap and resonance peak in the superconducting state.

  5. Optical model for low-energy neutrons on /sup 60/Ni

    SciTech Connect

    Winters, R.R.; Johnson, C.H.; MacKellar, A.D.

    1985-02-01

    A previously published s-wave scattering function for 1--450 keV neutrons on /sup 60/Ni is averaged for comparison to the scattering from an optical model potential. The scattering length R' is found to be 5.5 +- 0.03 fm at 225 keV. Averaging of the scattering function (both by integration with a normalized weight function and by use of an analytical approximation) produces shape elastic and compound nucleus cross sections which are then fitted by adjustment of the real and imaginary well depths in both spherical and vibrational optical models with a Woods-Saxon real well (r/sub 0/ = 1.21 fm, a/sub 0/ = 0.66 fm) and a surface derivative imaginary well (r/sub D/ = 1.21 fm, a/sub D/ = 0.48 fm). The fitted depths are V/sub 0/ = 48 MeV and W/sub D/ = 29 MeV for the spherical potentials, and V/sub 0/ = 50 MeV and W/sub D/ = 24 MeV for the vibrational potentials. Uncertainties are +- 5 MeV. From an upper limit on the p-wave strength function the W/sub D/ for p waves is found to be 1.5 MeV for the vibrational model. Thus, the imaginary potential is l dependent for the assumed geometry. For s waves the vibrational model gives a good fit also with W/sub D/ = 1.5 MeV and V/sub 0/ = 54.4 MeV; however, with that V/sub 0/ the 2p states are bound too deeply in /sup 61/Ni and the 3s size resonance is predicted at too low a mass.

  6. Multiferroic phase of doped delafossite CuFeO2 identified using inelastic neutron scattering

    SciTech Connect

    Haraldsen, Jason T; Ye, Feng; Fishman, Randy Scott; Fernandez-Baca, Jaime A; Yamaguchi, Y.; Kimura, K.; Kimura, T.

    2010-01-01

    Multiferroic materials allow the electric polarization to be controlled by switching the direction of magnetic ordering and consequently offer prospects for many new technological applications [1 4]. Because multiferroic behavior has been found in materials that exhibit complex (non-collinear and incommensurate) magnetic order, it is essential to know the spin arrangement of the ground states in these materials [4 9]. In many cases, elastic neutron scattering measurements alone are not sufficient to distinguish among several potential complex magnetic states. We report inelastic neutron scattering (INS) measurements that provide a distinct dynamical fingerprint for the multiferroic ground state of 3.5% Ga-doped CuFeO2. The complex ground state is stabilized by the displacement of the oxygen atoms [10], which are also responsible for the multiferroic coupling predicted by Arima [8]. By comparing the observed and calculated spectrum of spin excitations, we conclude that the magnetic ground state is a distorted screwtype spin configuration. The exchange interactions that stabilize this structure are consistent with those obtained from inelastic measurements [11, 12] on undoped CuFeO2.

  7. Hydrogen adsorption in HKUST-1: a combined inelastic neutron scattering and first-principles study

    NASA Astrophysics Data System (ADS)

    Brown, Craig M.; Liu, Yun; Yildirim, Taner; Peterson, Vanessa K.; Kepert, Cameron J.

    2009-05-01

    Hydrogen adsorption in high surface area nanoporous coordination polymers has attracted a great deal of interest in recent years due to the potential applications in energy storage. Here we present combined inelastic neutron scattering measurements and detailed first-principles calculations aimed at unraveling the nature of hydrogen adsorption in HKUST-1 (Cu3(1,3,5-benzenetricarboxylate)2), a metal-organic framework (MOF) with unsaturated metal centers. We reveal that, in this system, the major contribution to the overall binding comes from the classical Coulomb interaction which is not screened due to the open metal site; this explains the relatively high binding energies and short H2-metal distances observed in MOFs with exposed metal sites as compared to traditional ones. Despite the short distances, there is no indication of an elongation of the H-H bond for the bound H2 molecule at the metal site. We find that both the phonon and rotational energy levels of the hydrogen molecule are closely similar, making the interpretation of the inelastic neutron scattering data difficult. Finally, we show that the orientation of H2 has a surprisingly large effect on the binding potential, reducing the classical binding energy by almost 30%. The implication of these results for the development of MOF materials for better hydrogen storage is discussed.

  8. Hydrogen adsorption in HKUST-1: a combined inelastic neutron scattering and first-principles study.

    PubMed

    Brown, Craig M; Liu, Yun; Yildirim, Taner; Peterson, Vanessa K; Kepert, Cameron J

    2009-05-20

    Hydrogen adsorption in high surface area nanoporous coordination polymers has attracted a great deal of interest in recent years due to the potential applications in energy storage. Here we present combined inelastic neutron scattering measurements and detailed first-principles calculations aimed at unraveling the nature of hydrogen adsorption in HKUST-1 (Cu3(1,3,5-benzenetricarboxylate)2), a metal-organic framework (MOF) with unsaturated metal centers. We reveal that, in this system, the major contribution to the overall binding comes from the classical Coulomb interaction which is not screened due to the open metal site; this explains the relatively high binding energies and short H2-metal distances observed in MOFs with exposed metal sites as compared to traditional ones. Despite the short distances, there is no indication of an elongation of the H-H bond for the bound H2 molecule at the metal site. We find that both the phonon and rotational energy levels of the hydrogen molecule are closely similar, making the interpretation of the inelastic neutron scattering data difficult. Finally, we show that the orientation of H2 has a surprisingly large effect on the binding potential, reducing the classical binding energy by almost 30%. The implication of these results for the development of MOF materials for better hydrogen storage is discussed.

  9. Monte Carlo Calculation of Thermal Neutron Inelastic Scattering Cross Section Uncertainties by Sampling Perturbed Phonon Spectra

    NASA Astrophysics Data System (ADS)

    Holmes, Jesse Curtis

    Nuclear data libraries provide fundamental reaction information required by nuclear system simulation codes. The inclusion of data covariances in these libraries allows the user to assess uncertainties in system response parameters as a function of uncertainties in the nuclear data. Formats and procedures are currently established for representing covariances for various types of reaction data in ENDF libraries. This covariance data is typically generated utilizing experimental measurements and empirical models, consistent with the method of parent data production. However, ENDF File 7 thermal neutron scattering library data is, by convention, produced theoretically through fundamental scattering physics model calculations. Currently, there is no published covariance data for ENDF File 7 thermal libraries. Furthermore, no accepted methodology exists for quantifying or representing uncertainty information associated with this thermal library data. The quality of thermal neutron inelastic scattering cross section data can be of high importance in reactor analysis and criticality safety applications. These cross sections depend on the material's structure and dynamics. The double-differential scattering law, S(alpha, beta), tabulated in ENDF File 7 libraries contains this information. For crystalline solids, S(alpha, beta) is primarily a function of the material's phonon density of states (DOS). Published ENDF File 7 libraries are commonly produced by calculation and processing codes, such as the LEAPR module of NJOY, which utilize the phonon DOS as the fundamental input for inelastic scattering calculations to directly output an S(alpha, beta) matrix. To determine covariances for the S(alpha, beta) data generated by this process, information about uncertainties in the DOS is required. The phonon DOS may be viewed as a probability density function of atomic vibrational energy states that exist in a material. Probable variation in the shape of this spectrum may be

  10. Proposed low-energy absolute calibration of nuclear recoils in a dual-phase noble element TPC using D-D neutron scattering kinematics

    NASA Astrophysics Data System (ADS)

    Verbus, J. R.; Rhyne, C. A.; Malling, D. C.; Genecov, M.; Ghosh, S.; Moskowitz, A. G.; Chan, S.; Chapman, J. J.; de Viveiros, L.; Faham, C. H.; Fiorucci, S.; Huang, D. Q.; Pangilinan, M.; Taylor, W. C.; Gaitskell, R. J.

    2017-04-01

    We propose a new technique for the calibration of nuclear recoils in large noble element dual-phase time projection chambers used to search for WIMP dark matter in the local galactic halo. This technique provides an in situ measurement of the low-energy nuclear recoil response of the target media using the measured scattering angle between multiple neutron interactions within the detector volume. The low-energy reach and reduced systematics of this calibration have particular significance for the low-mass WIMP sensitivity of several leading dark matter experiments. Multiple strategies for improving this calibration technique are discussed, including the creation of a new type of quasi-monoenergetic neutron source with a minimum possible peak energy of 272 keV. We report results from a time-of-flight-based measurement of the neutron energy spectrum produced by an Adelphi Technology, Inc. DD108 neutron generator, confirming its suitability for the proposed nuclear recoil calibration.

  11. How low-energy weak reactions can constrain three-nucleon forces and the neutron-neutron scattering length.

    PubMed

    Gårdestig, A; Phillips, D R

    2006-06-16

    We show that chiral symmetry and gauge invariance enforce relations between the short-distance physics that occurs in a number of electroweak and pionic reactions on light nuclei. Within chiral perturbation theory, this is manifested via the appearance of the same axial isovector two-body contact term in pi(-)d --> nngamma, p-wave pion production in NN collisions, tritium beta decay, pp fusion, nud scattering, and the hep reaction. Using a Gamow-Teller matrix element obtained from calculations of pp fusion as input, we compute the neutron spectrum obtained in pi(-)d --> nngamma. With the short-distance physics in this process controlled from pp --> de(=)nu(e), the theoretical uncertainty in the nn scattering length extracted from pi(-)d --> nngamma is reduced by a factor larger than 3, to approximately < or = 0.05 fm.

  12. An integral test of the inelastic cross sections of Pb and Mo using measured neutron spectra

    NASA Technical Reports Server (NTRS)

    Shook, D. F.; Fieno, D.; Ford, C. H.; Wrights, G. N.

    1972-01-01

    Comparison of measurements and calculations of fast neutron spectra from a radioactive neutron source inside spheres of Mo or Pb and from a cylindrical reactor containing a thick Pb or Mo reflector are used as a test of ENDF cross sections. The sphere leakage spectra were measured at a sphere-to-spectrometer distance of 2 meters using a 54 Ci spherical Am-Be neutron source. Reactor leakage spectrum measurements were made at the surface of the ZP-1 reactor when bare, with a Pb radial reflector 21 cm thick, and with a metallic Mo radial reflector 10 cm thick. In the case of the thin Mo sphere there is agreement between the calculation and measurement. The Pb calculation is much lower than the measurement except at the highest neutron energy. Two-dimensional calculations of reactor spectra result indicate that the reactor source is reasonably well known. Significant differences in leakage spectrum shape for both Mo and Pb reflectors suggest that there are large uncertainties in the inelastic cross sections for Pb and some for Mo.

  13. Medical applications of in vivo neutron inelastic scattering and neutron activation analysis: Technical similarities to detection of explosives and contraband

    NASA Astrophysics Data System (ADS)

    Kehayias, J. J.

    2001-07-01

    Nutritional status of patients can be evaluated by monitoring changes in elemental body composition. Fast neutron activation (for N and P) and neutron inelastic scattering (for C and O) are used in vivo to assess elements characteristic of specific body compartments. There are similarities between the body composition techniques and the detection of hidden explosives and narcotics. All samples have to be examined in depth and the ratio of elements provides a "signature" of the chemical of interest. The N/H and C/O ratios measure protein and fat content in the body. Similarly, a high C/O ratio is characteristic of narcotics and a low C/O together with a strong presence of N is a signature of some explosives. The available time for medical applications is about 20 min—compared to a few seconds for the detection of explosives—but the permitted radiation exposure is limited. In vivo neutron analysis is used to measure H, O, C, N, P, Na, Cl, and Ca for the study of the mechanisms of lean tissue depletion with aging and wasting diseases, and to investigate methods of preserving function and quality of life in the elderly.

  14. A Study of the Spin Structure on the Neutron in Deep Inelastic Scattering of Polarized Electrons on Polarized Neutrons

    SciTech Connect

    Spengos, M

    2004-01-06

    The internal spin structure of the neutron, was studied in deep inelastic scattering of longitudinally polarized electrons from a polarized {sup 3}He target in the End Station A of the Stanford Linear Accelerator Center (SLAC). The spin asymmetry of the neutron was measured at energies between 19 and 26 GeV in the range 0.03 {le} x {le} 0.06 at an average Q{sup 2} of 2 (GeV/c){sup 2}. The results are in agreement with a new measurement of the asymmetry by SMC within their six times larger uncertainties. The spin dependent structure function g{sub 1}(x) for the neutron was determined from the asymmetry measurement and, its integral over x is found to be {integral}g{sub 1}{sup n}(x)dx = -0.038 {+-} 0.009. This result is 2.7 standard deviations from the Ellis-Jaffe Sum Rule and combined with the EMC results from the proton in very good agreement with the Bjorken Sum Rule. In the Quark Parton Model (QPM), in conjunction with the weak coupling constants F and D, from baryon decay, the result implies that the quarks contribute approximately 32% of the nucleon helicity. Finally, different ways of evolving the data, based on various theoretical models, is attempted and future aspects for spin physics, with emphasis at spin physics at SLAC, are discussed.

  15. Measurement of Feynman- spectra of photons and neutrons in the very forward direction in deep-inelastic scattering at HERA

    NASA Astrophysics Data System (ADS)

    Andreev, V.; Baghdasaryan, A.; Begzsuren, K.; Belousov, A.; Belov, P.; Boudry, V.; Brandt, G.; Brinkmann, M.; Brisson, V.; Britzger, D.; Buniatyan, A.; Bylinkin, A.; Bystritskaya, L.; Campbell, A. J.; Cantun Avila, K. B.; Ceccopieri, F.; Cerny, K.; Chekelian, V.; Contreras, J. G.; Dainton, J. B.; Daum, K.; Diaconu, C.; Dobre, M.; Dodonov, V.; Dossanov, A.; Eckerlin, G.; Egli, S.; Elsen, E.; Favart, L.; Fedotov, A.; Feltesse, J.; Ferencei, J.; Fleischer, M.; Fomenko, A.; Gabathuler, E.; Gayler, J.; Ghazaryan, S.; Glazov, A.; Goerlich, L.; Gogitidze, N.; Gouzevitch, M.; Grab, C.; Grebenyuk, A.; Greenshaw, T.; Grindhammer, G.; Haidt, D.; Henderson, R. C. W.; Herbst, M.; Hladkỳ, J.; Hoffmann, D.; Horisberger, R.; Hreus, T.; Huber, F.; Jacquet, M.; Janssen, X.; Jung, H.; Kapichine, M.; Kiesling, C.; Klein, M.; Kleinwort, C.; Kogler, R.; Kostka, P.; Kretzschmar, J.; Krüger, K.; Landon, M. P. J.; Lange, W.; Laycock, P.; Lebedev, A.; Levonian, S.; Lipka, K.; List, B.; List, J.; Lobodzinski, B.; Lytkin, L.; Malinovski, E.; Martyn, H.-U.; Maxfield, S. J.; Mehta, A.; Meyer, A. B.; Meyer, H.; Meyer, J.; Mikocki, S.; Morozov, A.; Müller, K.; Naumann, Th.; Newman, P. R.; Niebuhr, C.; Nowak, G.; Nowak, K.; Olsson, J. E.; Ozerov, D.; Pahl, P.; Pascaud, C.; Patel, G. D.; Perez, E.; Petrukhin, A.; Picuric, I.; Pirumov, H.; Pitzl, D.; Plačakytė, R.; Pokorny, B.; Polifka, R.; Povh, B.; Radescu, V.; Raicevic, N.; Ravdandorj, T.; Reimer, P.; Rizvi, E.; Robmann, P.; Roosen, R.; Rostovtsev, A.; Rotaru, M.; Rusakov, S.; Šálek, D.; Sankey, D. P. C.; Sauter, M.; Sauvan, E.; Schmitt, S.; Schoeffel, L.; Schöning, A.; Schultz-Coulon, H.-C.; Sefkow, F.; Shushkevich, S.; Soloviev, Y.; Sopicki, P.; South, D.; Spaskov, V.; Specka, A.; Steder, M.; Stella, B.; Straumann, U.; Sykora, T.; Thompson, P. D.; Traynor, D.; Truöl, P.; Tsakov, I.; Tseepeldorj, B.; Turnau, J.; Valkárová, A.; Vallée, C.; Van Mechelen, P.; Vazdik, Y.; Wegener, D.; Wünsch, E.; Žáček, J.; Zhang, Z.; Žlebčík, R.; Zohrabyan, H.; Zomer, F.

    2014-06-01

    Measurements of normalised cross sections for the production of photons and neutrons at very small angles with respect to the proton beam direction in deep-inelastic scattering at HERA are presented as a function of the Feynman variable and of the centre-of-mass energy of the virtual photon-proton system . The data are taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of . The measurement is restricted to photons and neutrons in the pseudorapidity range and covers the range of negative four momentum transfer squared at the positron vertex GeV, of inelasticity and of GeV. To test the Feynman scaling hypothesis the dependence of the dependent cross sections is investigated. Predictions of deep-inelastic scattering models and of models for hadronic interactions of high energy cosmic rays are compared to the measured cross sections.

  16. Combined inelastic neutron scattering and solid-state DFT study of dynamics of hydrogen atoms in trioctahedral 1 M phlogopite

    NASA Astrophysics Data System (ADS)

    Smrčok, L'ubomír; Kolesnikov, Alexander I.; Rieder, Milan

    2012-10-01

    Inelastic neutron scattering (INS) was used to study the vibrational dynamics of the hydrogen atoms in natural trioctahedral phlogopite, K0.93Na0.03(Mg2.47Fe0.22Al0.16Fe0.04Tl0.06)[Si2.84Al1.16]O10OH1.71F0.28Cl0.01, within the 50-1,000 cm-1 energy range. The INS spectra collected using direct geometry spectrometer SEQUOIA (ORNL) were interpreted by means of the solid-state DFT calculations covering both normal mode analysis and molecular dynamics. To optimize the structure and to calculate the vibrational modes under harmonic approximation, both a hybrid PBE0 and the AM05 functional were used, while the molecular dynamics calculations (60 ps/1 fs) were performed only with the computationally less-demanding AM05 functional. The main contributions to the dominant band within ~750-550 cm-1 are symmetric and antisymmetric Mg-O-H bending modes, overlapping with the skeletal stretching and bending modes causing weaker secondary movements of H atoms of inner hydroxyl groups. Signatures of the Mg-O-H bending modes appear down to ~400 cm-1, where a region of octahedra deformation modes starts. These deformations cause just shallow movements of the hydrogen atoms and are mirrored by the modes with close vibrational energies. The region from ~330 cm-1 down to the low-energy end of the spectrum portrays induced vibrations of the H atoms caused by deformation of individual polyhedra, translational vibrations of the parts of the 2:1 layer relative one to another, and librational and translational vibrations of the layer. The main difference between the INS spectrum of dioctahedral Al-muscovite and trioctahedral Mg-phlogopite is that the Mg-O-H modes are all assigned to in-plane vibrations of the respective hydrogen atoms.

  17. Combined inelastic neutron scattering and solid state DFT study of dynamics of hydrogen atoms in trioctahedral 1M phlogopite

    SciTech Connect

    Smrčok, Ľubomír; Kolesnikov, Alexander I; Rieder, Milan

    2012-01-01

    Inelastic neutron scattering (INS) was used to study vibrational dynamics of the hydrogen atoms in natural trioctahedral phlogopite, K0.93Na0.03(Mg2.47Fe0.22Al0.16Fe0.04Tl0.06)[Si2.84Al1.16]O10OH1.71F0.28Cl0.01, within the 50-1000 cm-1 energy range. The INS spectra collected using direct geometry spectrometer SEQUOIA at ORNL were interpreted by means of the solid-state DFT calculations covering both normal mode analysis and molecular dynamics. To optimize the structure and to calculate the vibrational modes under harmonic approximation both a hybrid PBE0 and the AM05 functional were used, while the molecular dynamics calculations (60ps/1fs) were performed only with the computationally less-demanding AM05 functional. The main contributions to the dominant band within ~750-550 cm-1 are symmetric and antisymmetric Mg-O-H bending modes, overlapping with the skeletal stretching and bending modes causing weaker secondary movements of H atoms of inner hydroxyl groups. Signatures of the Mg-O-H bending modes appear down to ~400 cm-1, where a region of octahedra deformation modes starts. These deformations cause just shallow movements of the hydrogen atoms and are mirrored by the modes with close vibrational energies. The region from ~330 cm-1 down to the low energy end of the spectrum portrays induced vibrations of the H atoms caused by deformation of individual polyhedra, translational vibrations of the parts of the 2:1 layer relative one to another, and librational and translational vibrations of the layer. The main difference between the INS spectrum of dioctahedral Al-muscovite and trioctahedral Mg-phlogopite is that the Mg-O-H modes are all assigned to in-plane vibrations of the respective hydrogen atoms.

  18. Miscibility gap and phonon thermodynamics of Fe-Au alloys studied by inelastic neutron scattering and nuclear-resonant inelastic x-ray scattering

    SciTech Connect

    Muñoz, Jorge A.; Fultz, Brent

    2015-07-23

    Recent measurements of the phonon spectra of several Au-rich alloys of face-centered-cubic Fe-Au using inelastic neutron scattering and nuclear-resonant inelastic x-ray scattering are summarized. The Wills-Harrison model, accounting for charge transfer upon alloying, is used to explain the observed negative excess vibrational entropy of mixing, which increases the miscibility gap temperature in the system by an estimated maximum of 550 K and we adjudicate to a charge transfer from the Fe to the Au atoms that results in an increase in the electron density in the free-electron-like states and in stronger sd-hybridization. When Au is the solvent, this softens the Fe–Fe bonds but stiffens the Au–Au and Au–Fe bonds which results in a net stiffening relative to the elemental components.

  19. Miscibility gap and phonon thermodynamics of Fe-Au alloys studied by inelastic neutron scattering and nuclear-resonant inelastic x-ray scattering

    NASA Astrophysics Data System (ADS)

    Muñoz, Jorge A.; Fultz, Brent

    2015-07-01

    Recent measurements of the phonon spectra of several Au-rich alloys of face-centered-cubic Fe-Au using inelastic neutron scattering and nuclear-resonant inelastic x-ray scattering are summarized. The Wills-Harrison model, accounting for charge transfer upon alloying, is used to explain the observed negative excess vibrational entropy of mixing, which increases the miscibility gap temperature in the system by an estimated maximum of 550 K and we adjudicate to a charge transfer from the Fe to the Au atoms that results in an increase in the electron density in the free-electron-like states and in stronger sd-hybridization. When Au is the solvent, this softens the Fe-Fe bonds but stiffens the Au-Au and Au-Fe bonds which results in a net stiffening relative to the elemental components.

  20. Lattice dynamics and molecular rotations in solid hydrogen deuteride: Inelastic neutron scattering study

    NASA Astrophysics Data System (ADS)

    Colognesi, D.; Formisano, F.; Ramirez-Cuesta, A. J.; Ulivi, L.

    2009-04-01

    In the present paper we report inelastic neutron scattering measurements on solid low-pressure hydrogen deuteride at three different temperatures (between 4.5 and 15.6 K) using the time-of-flight spectrometers BRISP at ILL (France) and TOSCA-II at ISIS, RAL (UK). The measured double-differential cross sections give access to the proton component of the HD self-inelastic structure factor. Processed BRISP data were employed to verify the applicability of the generalized Young and Koppel model to solid HD in our kinematic range and to obtain the mean-square displacement of the molecular centers of mass. In addition, a large broadening of the first two rotational peaks was observed. A reasonable result for the density of phonon states from TOSCA-II data has been obtained, although a rigorous extraction was not possible, due to the overlap among the various spectral components. The intensity loss in the extracted density of phonon states was interpreted as the effect the phonon-roton resonance in solid hydrogen deuteride. Finally the two Bose-corrected moments of the HD phonon spectrum, related to the molecular mean-square displacement and mean kinetic energy, were simulated through a path integral Monte Carlo code. The former quantity was compared to the mentioned experimental estimates.

  1. Communication: The H2@C60 inelastic neutron scattering selection rule: Expanded and explained

    NASA Astrophysics Data System (ADS)

    Poirier, Bill

    2015-09-01

    Recently [M. Xu et al., J. Chem. Phys. 139, 064309 (2013)], an unexpected selection rule was discovered for the title system, contradicting the previously held belief that inelastic neutron scattering (INS) is not subject to any selection rules. Moreover, the newly predicted forbidden transitions, which emerge only in the context of coupled H2 translation-rotation (TR) dynamics, have been confirmed experimentally. However, a simple physical understanding, e.g., based on group theory, has been heretofore lacking. This is provided in the present paper, in which we (1) derive the correct symmetry group for the H2@C60 TR Hamiltonian and eigenstates; (2) complete the INS selection rule, and show that the set of forbidden transitions is actually much larger than previously believed; and (3) evaluate previous theoretical and experimental results, in light of the new findings.

  2. Portraying entanglement between molecular qubits with four-dimensional inelastic neutron scattering

    PubMed Central

    Garlatti, E.; Guidi, T.; Ansbro, S.; Santini, P.; Amoretti, G.; Ollivier, J.; Mutka, H.; Timco, G.; Vitorica-Yrezabal, I. J.; Whitehead, G. F. S.; Winpenny, R. E. P.; Carretta, S.

    2017-01-01

    Entanglement is a crucial resource for quantum information processing and its detection and quantification is of paramount importance in many areas of current research. Weakly coupled molecular nanomagnets provide an ideal test bed for investigating entanglement between complex spin systems. However, entanglement in these systems has only been experimentally demonstrated rather indirectly by macroscopic techniques or by fitting trial model Hamiltonians to experimental data. Here we show that four-dimensional inelastic neutron scattering enables us to portray entanglement in weakly coupled molecular qubits and to quantify it. We exploit a prototype (Cr7Ni)2 supramolecular dimer as a benchmark to demonstrate the potential of this approach, which allows one to extract the concurrence in eigenstates of a dimer of molecular qubits without diagonalizing its full Hamiltonian. PMID:28216631

  3. Anomalous vibrational modes in acetanilide: A F. D. S. incoherent inelastic neutron scattering study

    SciTech Connect

    Barthes, M.; Moret, J. ); Eckert, J.; Johnson, S.W.; Swanson, B.I.; Unkefer, C.J. )

    1991-01-01

    The origin of the anomalous infra-red and Raman modes in acetanilide (C{sub 6}H{sub 5}NHCOCH{sub 3}, or ACN), remains a subject of considerable controversy. One family of theoretical models involves Davydov-like solitons nonlinear vibrational coupling, or polaronic'' localized modes. An alternative interpretation of the extra-bands in terms of a Fermi resonance was proposed and recently the existence of slightly non-degenerate hydrogen atom configurations in the H-bond was suggested as an explanation for the anomalies. In this paper we report some new results on the anomalous vibrational modes in ACN that were obtained by inelastic incoherent neutron scattering (INS).

  4. Inelastic neutron scattering study of spin-wave from single crystal BiFeO3

    NASA Astrophysics Data System (ADS)

    Xu, Guangyong; Xu, Zhijun; Wen, Jinsheng; Stone, Matthew; Gu, Genda; Shapiro, Stephen; Birgeneau, R. J.; Stock, Chris; Gehring, Peter

    2012-02-01

    BiFeO3 is one of the most promising multiferroic materials for device applications in spintronics and memory devices. There have been a number of studies on electric field tuning of antiferromagnetic domains, as well as possible E-field control of spin-waves in this material. The potential of controlling spin dynamics using electric field is extremely appealing. However, so far there have been very limited work on the direct measurements of spin-waves in BiFeO3, mostly due to lack of large size single crystals. We will present our recent inelastic neutron scattering studies on a single crystal BiFeO3, showing the full spin-wave spectrum in three-dimensions. A classical spin-wave model can be used to describe the results in details. The coupling parameters and spin-wave velocities have been obtained, and are in good agreements with those obtained in Raman measurements.

  5. A cryogenic high pressure cell for inelastic neutron scattering measurements of quantum fluids and solids

    SciTech Connect

    Carmichael, Justin R; Omar Diallo, Souleymane

    2013-01-01

    We present our new development of a high pressure cell for inelastic neutron scattering measurements of helium at ultra-low temperatures. The cell has a large sample volume of ~140 cm3, and a working pressure of ~70 bar, with a relatively thin wall-thickness (1.1 mm) - thanks to the high yield strength aluminum used in the design. Two variants of this cell have been developed; one with permanently joined components using electron-beam welding and explosion welding, methods that have little or no impact on the global heat treatment of the cell, and another with modular and interchangeable components, which include a capacitance pressure gauge, that can be sealed using traditional indium wire technique. The performance of the cell has been tested in recent measurements on superfluid liquid helium near the solidification line.

  6. Empirical Fit to Inelastic Electron-Deuteron and Electron-Neutron Resonance Region Transverse Cross Sections

    SciTech Connect

    Peter Bosted; M. E. Christy

    2007-11-08

    An empirical fit is described to measurements of inclusive inelastic electron-deuteron cross sections in the kinematic range of four-momentum transfer $0 \\le Q^2<10$ GeV$^2$ and final state invariant mass $1.2<3$ GeV. The deuteron fit relies on a fit of the ratio $R_p$ of longitudinal to transverse cross sections for the proton, and the assumption $R_p=R_n$. The underlying fit parameters describe the average cross section for proton and neutron, with a plane-wave impulse approximation (PWIA) used to fit to the deuteron data. Pseudo-data from MAID 2007 were used to constrain the average nucleon cross sections for $W<1.2$ GeV. The mean deviation of data from the fit is 3\\%, with less than 5\\% of the data points deviating from the fit by more than 10\\%.

  7. Empirical fit to inelastic electron-deuteron and electron-neutron resonance region transverse cross sections

    SciTech Connect

    Bosted, P. E.; Christy, M. E.

    2008-06-15

    An empirical fit is described to measurements of inclusive inelastic electron-deuteron cross sections in the kinematic range of four-momentum transfer 0{<=}Q{sup 2}<10 GeV{sup 2} and final state invariant mass 1.1neutron, with a plane-wave impulse approximation used to fit to the deuteron data. Additional fit parameters are used to fill in the dip between the quasi-elastic peak and the {delta}(1232) resonance. The mean deviation of data from the fit is 3%, with less than 4% of the data points deviating from the fit by more than 10%.

  8. Portraying entanglement between molecular qubits with four-dimensional inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Garlatti, E.; Guidi, T.; Ansbro, S.; Santini, P.; Amoretti, G.; Ollivier, J.; Mutka, H.; Timco, G.; Vitorica-Yrezabal, I. J.; Whitehead, G. F. S.; Winpenny, R. E. P.; Carretta, S.

    2017-02-01

    Entanglement is a crucial resource for quantum information processing and its detection and quantification is of paramount importance in many areas of current research. Weakly coupled molecular nanomagnets provide an ideal test bed for investigating entanglement between complex spin systems. However, entanglement in these systems has only been experimentally demonstrated rather indirectly by macroscopic techniques or by fitting trial model Hamiltonians to experimental data. Here we show that four-dimensional inelastic neutron scattering enables us to portray entanglement in weakly coupled molecular qubits and to quantify it. We exploit a prototype (Cr7Ni)2 supramolecular dimer as a benchmark to demonstrate the potential of this approach, which allows one to extract the concurrence in eigenstates of a dimer of molecular qubits without diagonalizing its full Hamiltonian.

  9. Study of the microdynamics of liquid lithium and lithium-hydrogen melt by inelastic neutron scattering

    SciTech Connect

    Blagoveshchenskii, N. M.; Morozov, V. A.; Novikov, A. G.; Pashnev, M. A. Savostin, V. V.; Shimkevich, A. L.

    2007-05-15

    The frequency spectra of vibrations of Li atoms at temperatures of 22, 227, 397, and 557 deg. C and the lithium-hydrogen melt (98 at % {sup 7}Li, 2 at % H) at 557 deg. C have been obtained from the experimental neutron inelastic scattering data. On the basis of the frequency spectra, the temperature dependences of the mean-square displacement of Li atoms, the mean-square amplitudes of atomic vibrations, and the velocity autocorrelation function of atoms have been calculated. The speed of sound in liquid lithium has been estimated within the Debye model. The frequency spectra of lithium-hydrogen melt and solid lithium hydride are compared. A generalized frequency spectrum of vibrations of hydrogen atoms in lithium-hydrogen melt is obtained.

  10. Inelastic neutron scattering cross section measurements for Xe,136134 of relevance to neutrinoless double-β decay searches

    NASA Astrophysics Data System (ADS)

    Peters, E. E.; Ross, T. J.; Liu, S. H.; McEllistrem, M. T.; Yates, S. W.

    2017-01-01

    Neutrinoless double-β decay (0 ν β β ) searches typically involve large-scale experiments for which backgrounds can be complex. One possible source of background near the 0 ν β β signature in the observed spectra is γ rays arising from inelastic neutron scattering from the materials composing or surrounding the detector. In relation to searches for the 0 ν β β of 136Xe to 136Ba, such as the EXO-200 and KamLAND-Zen projects, inelastic neutron scattering γ -ray production cross sections for 136Xe and 134Xe are of importance for characterizing such γ rays that may inhibit the unambiguous identification of this yet-to-be-observed process. These cross sections have been measured at the University of Kentucky Accelerator Laboratory at neutron energies from 2.5 to 4.5 MeV.

  11. Gamma ray production cross section from energetic neutron inelastic scattering for methodical improvements in planetary gamma-ray spectroscopy

    SciTech Connect

    Castaneda, C.M.; Gearhart, R.; Sanii, B.; Englert, P.A.J.; Drake, D.M.; Reedy, R.C.

    1991-12-31

    Planetary Gamma ray spectroscopy can be used to chemically analyze the top soil from planets in future planetary missions. The production from inelastic neutron interaction plays an effective role in the determination on the C and H at the surface. The gamma ray production cross section from the strongest lines excited in the neutron bombardment of Fe have been measured by the use of a time analyzed quasi-mono-energetic neutron beam and a high purity germanium detector. The results from En=6.5, 32, 43, and 65 MeV are presented.

  12. New opportunities for quasielastic and inelastic neutron scattering at steady-state sources using mechanical selection of the incident and final neutron energy

    SciTech Connect

    Mamantov, Eugene

    2015-06-12

    We propose a modification of the neutron wide-angle velocity selector (WAVES) device that enables inelastic (in particular, quasielastic) scattering measurements not relying on the neutron time-of-flight. The proposed device is highly suitable for a steady-state neutron source, somewhat similar to a triple-axis spectrometer, but with simultaneous selection of the incident and final neutron energy over a broad range of scattering momentum transfer. Both the incident and final neutron velocities are defined by the WAVES geometry and rotation frequency. The variable energy transfer is achieved through the natural variation of the velocity of the transmitted neutrons as a function of the scattering angle component out of the equatorial plane.

  13. New opportunities for quasielastic and inelastic neutron scattering at steady-state sources using mechanical selection of the incident and final neutron energy

    DOE PAGES

    Mamantov, Eugene

    2015-06-12

    We propose a modification of the neutron wide-angle velocity selector (WAVES) device that enables inelastic (in particular, quasielastic) scattering measurements not relying on the neutron time-of-flight. The proposed device is highly suitable for a steady-state neutron source, somewhat similar to a triple-axis spectrometer, but with simultaneous selection of the incident and final neutron energy over a broad range of scattering momentum transfer. Both the incident and final neutron velocities are defined by the WAVES geometry and rotation frequency. The variable energy transfer is achieved through the natural variation of the velocity of the transmitted neutrons as a function of themore » scattering angle component out of the equatorial plane.« less

  14. Inelastic neutron- and Raman-scattering studies of muscovite and vermiculite layered silicates

    SciTech Connect

    Wada, N. ); Kamitakahara, W.A. University of Maryland, College Park, Maryland National Institute of Standards and Technology, Building 235, E-151, Gaithersburg, Maryland )

    1991-01-15

    Investigations on the lattice dynamics of muscovite and vermiculite have been carried out by inelastic neutron scattering and Raman scattering. In the neutron measurements, dispersion curves for the out-of-plane and in-plane LA and TA phonons were fully obtained for muscovite, while more limited data were obtained for Mg vermiculite. Sound velocities were estimated from the slopes of the dispersion curves. Raman-scattering experiments revealed an interlayer shearing mode in Na and Sr vermiculites in the 0-water-layer hydration state. The intercalated water molecules in Na and Sr vermiculites exhibited a broad Raman feature (OH stretching vibrations) at 3450 cm{sup {minus}1} with a full width at half maximum of {similar to}300 cm{sup {minus}1}. In addition, relatively sharp Raman peaks from the inner-layer hydroxyls in the host octahedral layers were found at {similar to}3700 cm{sup {minus}1}. These peaks were sensitive to the hydration state or charge in the intercalated layer.

  15. The boson peak of amyloid fibrils: probing the softness of protein aggregates by inelastic neutron scattering.

    PubMed

    Schirò, G; Vetri, V; Andersen, C B; Natali, F; Koza, M M; Leone, M; Cupane, A

    2014-03-20

    Proteins and polypeptides are characterized by low-frequency vibrations in the terahertz regime responsible for the so-called "boson peak". The shape and position of this peak are related to the mechanical properties of peptide chains. Amyloid fibrils are ordered macromolecular assemblies, spontaneously formed in nature, characterized by unique biological and nanomechanical properties. In this work, we investigate the effects of the amyloid state and its polymorphism on the boson peak. We used inelastic neutron scattering to probe low-frequency vibrations of the glucagon polypeptide in the native state and in two different amyloid morphologies in both dry and hydrated sample states. The data show that amyloid fibril formation and hydration state affect the softness of the polypeptide not only by changing the distribution of vibrational modes but also, and most significantly, the dissipative mechanisms of collective low-frequency vibrations provided by water-protein and protein-protein interactions. We show how the morphology of the fibril is able to tune these effects. Atomic fluctuations were also measured by elastic neutron scattering. The data confirm that any effect of protein aggregation on fluctuation amplitudes is essentially due to changes in surface exposure to hydration water. The results demonstrate the importance of protein-protein and protein-water interactions in the dynamics and mechanics of amyloid fibrils.

  16. Magnetic Excitations in Transition-metal Oxides Studied by Inelastic Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Braden, M.

    2008-03-01

    Inelastic neutron scattering using a triple axis spectrometer is a very efficient tool to analyze magnetic excitations. We will discuss several recent experiments on transition-metal oxides where orbital degrees of freedom play an important role. Different kinds of experimental techniques including longitudinal and spherical polarization analysis were used in order to determine not only magnon frequencies but also polarization vectors. In layered ruthenates bands of different orbital character contribute to the magnetic excitations which are of both, ferromagnetic and antiferromagnetic, character. The orbital dependent magnetic excitations seem to play different roles in the superconducting pairing as well as in the metamagnetism . In manganates the analysis of the magnon dispersion in the charge and orbital ordered phase yields direct insight into the microscopic coupling of orbital and magnetic degrees of freedom and helps understanding, how the switching between metallic and insulating phases in manganates may occur. In multiferroic TbMnO3 the combination of our polarized neutron scattering results with the infrared measurements identifies a soft collective excitation of hybridized magnon-phonon character.

  17. Hydrogen self-dynamics in liquid H2-D2 mixtures studied through inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Colognesi, Daniele; Bafile, Ubaldo; Celli, Milva; Neumann, Martin; Orecchini, Andrea

    2015-07-01

    We have measured the dynamic structure factor of liquid para-hydrogen mixed with normal deuterium (T =20 K ) at two different concentration levels using incoherent inelastic neutron scattering. This choice has been made since the presence of D2 modifies the self-dynamics of H2 in a highly nontrivial way, acting both on its pseudophononic and its diffusive parts in a tunable way. After an accurate data reduction, recorded neutron spectra were studied through the modified Young and Koppel model and the H2 center-of-mass self-dynamics structure factor was finally extracted for the two mixtures. Some physical quantities (i.e., self-diffusion coefficient and mean kinetic energy) were determined and compared with accurate quantum calculations, which, in addition, also provided estimates of the velocity autocorrelation function for the H2 centers of mass. These estimates, in conjunction with the Gaussian approximation, were used to simulate the H2 center-of-mass self-dynamics structure factor in the same range as the experimental one. The agreement between measured and calculated spectra was globally good, but some discrepancies proved the unquestionable breakdown of the Gaussian approximation in these semiquantum systems at a level comparable to that already observed in pure liquid para-hydrogen.

  18. Evidence of hydroxyl-ion deficiency in bone apatites: an inelastic neutron-scattering study.

    PubMed

    Loong, C K; Rey, C; Kuhn, L T; Combes, C; Wu, Y; Chen, S; Glimcher, M J

    2000-06-01

    The novelty of very large neutron-scattering intensity from the nuclear-spin incoherence in hydrogen has permitted the determination of atomic motion of hydrogen in synthetic hydroxyapatite and in deproteinated isolated apatite crystals of bovine and rat bone without the interference of vibrational modes from other structural units. From an inelastic neutron-scattering experiment, we found no sharp excitations characteristic of the vibrational mode and stretch vibrations of OH ions around 80 and 450 meV (645 and 3630 cm(-1)), respectively, in the isolated, deproteinated crystals of bone apatites; such salient features were clearly seen in micron- and nanometer-size crystals of pure hydroxyapatite powders. Thus, the data provide additional definitive evidence for the lack of OH(-) ions in the crystals of bone apatite. Weak features at 160-180 and 376 meV, which are clearly observed in the apatite crystals of rat bone and possibly in adult mature bovine bone, but to a much lesser degree, but not in the synthetic hydroxyapatite, are assigned to the deformation and stretch modes of OH ions belonging to HPO(4)-like species.

  19. Measurement of 56Fe activity produced in inelastic scattering of neutrons created by cosmic muons in an iron shield.

    PubMed

    Krmar, M; Jovančević, N; Nikolić, D

    2012-01-01

    We report on the study of the intensities of several gamma lines emitted after the inelastic scattering of neutrons in (56)Fe. Neutrons were produced via nuclear processes induced by cosmic muons in the 20tons massive iron cube placed at the Earth's surface and used as a passive shield for the HPGe detector. Relative intensities of detected gamma lines are compared with the results collected in the same iron shield by the use of the (252)Cf neutrons. Assessment against the published data from neutron scattering experiments at energies up to 14MeV is also provided. It allowed us to infer the qualitative information about the average energy of muon-created neutrons in the iron shield.

  20. Estimation of low energy neutron flux (En <= 15 MeV) in India-based Neutrino Observatory cavern using Monte Carlo techniques

    NASA Astrophysics Data System (ADS)

    Dokania, N.; Singh, V.; Mathimalar, S.; Garai, A.; Nanal, V.; Pillay, R. G.; Bhushan, K. G.

    2015-12-01

    The neutron flux at low energy (En <= 15 MeV) resulting from the radioactivity of the rock in the underground cavern of the India-based Neutrino Observatory is estimated using Geant4-based Monte Carlo simulations. The neutron production rate due to the spontaneous fission of 235, 238U, 232Th and (α, n) interactions in the rock is determined employing the actual rock composition. It is shown that the total flux is equivalent to a finite size cylindrical rock (D=L=140 cm) element. The energy integrated neutron flux thus obtained at the center of the underground tunnel is 2.76 (0.47) × 10-6 n cm-2 s-1. The estimated neutron flux is of the same order (~10-6 n cm-2 s-1) as measured in other underground laboratories.

  1. Inelastic neutron scattering and molecular simulation of the dynamics of interlayer water in smectite clay minerals

    SciTech Connect

    Cygan, Randall T.; Daemen, Luke L.; Ilgen, Anastasia G.; Krumhansl, James L.; Nenoff, Tina M.

    2015-11-16

    The study of mineral–water interfaces is of great importance to a variety of applications including oil and gas extraction, gas subsurface storage, environmental contaminant treatment, and nuclear waste repositories. Understanding the fundamentals of that interface is key to the success of those applications. Confinement of water in the interlayer of smectite clay minerals provides a unique environment to examine the interactions among water molecules, interlayer cations, and clay mineral surfaces. Smectite minerals are characterized by a relatively low layer charge that allows the clay to swell with increasing water content. Montmorillonite and beidellite varieties of smectite were investigated to compare the impact of the location of layer charge on the interlayer structure and dynamics. Inelastic neutron scattering of hydrated and dehydrated cation-exchanged smectites was used to probe the dynamics of the interlayer water (200–900 cm–1 spectral region) and identify the shift in the librational edge as a function of the interlayer cation. Molecular dynamics simulations of equivalent phases and power spectra, derived from the resulting molecular trajectories, indicate a general shift in the librational behavior with interlayer cation that is generally consistent with the neutron scattering results for the monolayer hydrates. Both neutron scattering and power spectra exhibit librational structures affected by the location of layer charge and by the charge of the interlayer cation. Furthermore, divalent cations (Ba2+ and Mg2+) characterized by large hydration enthalpies typically exhibit multiple broad librational peaks compared to monovalent cations (Cs+ and Na+), which have relatively small hydration enthalpies.

  2. Inelastic neutron scattering and molecular simulation of the dynamics of interlayer water in smectite clay minerals

    DOE PAGES

    Cygan, Randall T.; Daemen, Luke L.; Ilgen, Anastasia G.; ...

    2015-11-16

    The study of mineral–water interfaces is of great importance to a variety of applications including oil and gas extraction, gas subsurface storage, environmental contaminant treatment, and nuclear waste repositories. Understanding the fundamentals of that interface is key to the success of those applications. Confinement of water in the interlayer of smectite clay minerals provides a unique environment to examine the interactions among water molecules, interlayer cations, and clay mineral surfaces. Smectite minerals are characterized by a relatively low layer charge that allows the clay to swell with increasing water content. Montmorillonite and beidellite varieties of smectite were investigated to comparemore » the impact of the location of layer charge on the interlayer structure and dynamics. Inelastic neutron scattering of hydrated and dehydrated cation-exchanged smectites was used to probe the dynamics of the interlayer water (200–900 cm–1 spectral region) and identify the shift in the librational edge as a function of the interlayer cation. Molecular dynamics simulations of equivalent phases and power spectra, derived from the resulting molecular trajectories, indicate a general shift in the librational behavior with interlayer cation that is generally consistent with the neutron scattering results for the monolayer hydrates. Both neutron scattering and power spectra exhibit librational structures affected by the location of layer charge and by the charge of the interlayer cation. Furthermore, divalent cations (Ba2+ and Mg2+) characterized by large hydration enthalpies typically exhibit multiple broad librational peaks compared to monovalent cations (Cs+ and Na+), which have relatively small hydration enthalpies.« less

  3. Design of a high-current low-energy beam transport line for an intense D-T/D-D neutron generator

    NASA Astrophysics Data System (ADS)

    Lu, Xiaolong; Wang, Junrun; Zhang, Yu; Li, Jianyi; Xia, Li; Zhang, Jie; Ding, Yanyan; Jiang, Bing; Huang, Zhiwu; Ma, Zhanwen; Wei, Zheng; Qian, Xiangping; Xu, Dapeng; Lan, Changlin; Yao, Zeen

    2016-03-01

    An intense D-T/D-D neutron generator is currently being developed at the Lanzhou University. The Cockcroft-Walton accelerator, as a part of the neutron generator, will be used to accelerate and transport the high-current low-energy beam from the duoplasmatron ion source to the rotating target. The design of a high-current low-energy beam transport (LEBT) line and the dynamics simulations of the mixed beam were carried out using the TRACK code. The results illustrate that the designed beam line facilitates smooth transportation of a deuteron beam of 40 mA, and the number of undesired ions can be reduced effectively using two apertures.

  4. Study of microdosimetric energy deposition patterns in tissue-equivalent medium due to low-energy neutron fields using a graphite-walled proportional counter.

    PubMed

    Waker, A J; Aslam

    2011-06-01

    To improve radiation protection dosimetry for low-energy neutron fields encountered in nuclear power reactor environments, there is increasing interest in modeling neutron energy deposition in metrological instruments such as tissue-equivalent proportional counters (TEPCs). Along with these computational developments, there is also a need for experimental data with which to benchmark and test the results obtained from the modeling methods developed. The experimental work described in this paper is a study of the energy deposition in tissue-equivalent (TE) medium using an in-house built graphite-walled proportional counter (GPC) filled with TE gas. The GPC is a simple model of a standard TEPC because the response of the counter at these energies is almost entirely due to the neutron interactions in the sensitive volume of the counter. Energy deposition in tissue spheres of diameter 1, 2, 4 and 8 µm was measured in low-energy neutron fields below 500 keV. We have observed a continuously increasing trend in microdosimetric averages with an increase in neutron energy. The values of these averages decrease as we increase the simulated diameter at a given neutron energy. A similar trend for these microdosimetric averages has been observed for standard TEPCs and the Rossi-type, TE, spherical wall-less counter filled with propane-based TE gas in the same energy range. This implies that at the microdosimetric level, in the neutron energy range we employed in this study, the pattern of average energy deposited by starter and insider proton recoil events in the gas is similar to those generated cumulatively by crosser and stopper events originating from the counter wall plus starter and insider recoil events originating in the sensitive volume of a TEPC.

  5. Enhancement of rare-earth-transition-metal exchange interaction in Pr2Fe17 probed by inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Magnani, N.; Carretta, S.; Amoretti, G.; Pareti, L.; Paoluzi, A.; Caciuffo, R.; Stride, J. A.

    2004-11-01

    The fundamental magnetic interactions of Pr2Fe17 are studied by inelastic neutron scattering and anisotropy field measurements. Data analysis confirms the presence of three magnetically inequivalent sites, and reveals an exceptionally large value of the exchange field. The unexpected importance of J-mixing effects in the description of the ground-state properties of Pr2Fe17 is shown, and possible applications of related compounds are envisaged.

  6. Thulium-169 neutron inelastic scattering cross section measurements via the (169)Tm(n,n'gamma) reaction

    NASA Astrophysics Data System (ADS)

    Ko, Young June

    1999-11-01

    A neutron inelastic scattering study for low-lying states of thulium-169 below 1 MeV has been pursued by the detection of gamma rays from the 169Tm(n,n'γ) reaction. The inelastic level cross sections, which are important to obtain nuclear potential parameters and to understand reaction mechanisms, were obtained in this study. Incident neutrons were generated by bombarding a metallic lithium target with protons from the Lowell Van de Graaff accelerator. A germanium detector was used for gamma-ray observation. Excitation functions were measured from 0.2 to 1 MeV in 50 keV intervals at a scattering angle of 125°. Gamma-ray production cross sections were obtained for 37 observed transitions from 16 levels. Gamma-ray angular distributions from 35° to 135°, in 10° steps were measured at a neutron energy of 750 keV. The angular distributions were fitted with Legendre polynomials of even (up to fourth) order. Neutron inelastic level cross sections were inferred from the excitation functions and the angular distributions. Because cross-section data from previous experimental or theoretical work were not available, no direct comparison with previous work was made. A comparison of the magnitude and behavior of the (n,inelastic) cross section for thulium with those of neighboring odd-A nuclei indicated reasonable agreement. A classical model for angular momentum transfer indicates that states with spin >=/(+) may be excited only through the compound nucleus process, but for states with spin <=/(-) compound nucleus and direct interaction processes may both participate in the excitation.

  7. Influence of electrode and insulator materials on the neutron emission in a low energy plasma focus device

    SciTech Connect

    Rout, R.K.; Garg, A.B.; Shyam, A.; Srinivasan, M.

    1995-12-01

    Insertion of internal impurities is one of the factors for the degradation of neutron output in plasma focus devices. In this context, neutron emission measurements were carried out in a 2.2 kJ (7.2 {mu}F, 25 kV) Mather type squirrel cage plasma focus device with various combinations of electrode and insulator materials. The neutron yield was measured by silver activation detector. The results indicate that a central electrode of low erosion rate material produces maximum neutron yield with the highest anisotropy factor. A time integrated X-ray pinhole image shows that focus corresponding to the highest neutron yield material is the most compressed. The dielectric constant of the ceramic insulators has, at best, a very weak correlation with neutron output. The nonceramic insulators like perspex, nylon, or teflon neither produce focus nor neutron.

  8. Role of nuclear couplings in the inelastic excitation of weakly-bound neutron-rich nuclei

    SciTech Connect

    Dasso, C.H.; Lenzi, S.M.; Vitturi, A.

    1996-12-31

    Much effort is presently devoted to the study of nuclear systems far from the stability line. Particular emphasis has been placed in light systems such as {sup 11}Li, {sup 8}B and others, where the very small binding energy of the last particles causes their density distribution to extend considerably outside of the remaining nuclear core. Some of the properties associated with this feature are expected to characterize also heavier systems in the vicinity of the proton or neutron drip lines. It is by now well established that low-lying concentrations of multipole strength arise from pure configurations in which a peculiar matching between the wavelength of the continuum wavefunction of the particles and the range of the weakly-bound hole states occurs. To this end the authors consider the break-up of a weakly-bound system in a heavy-ion collision and focus attention in the inelastic excitation of the low-lying part of the continuum. They make use of the fact that previous investigations have shown that the multipole response in this region is not of a collective nature and describe their excited states as pure particle-hole configurations. Since the relevant parameter determining the strength distributions is the binding energy of the last bound orbital they find it most convenient to use single-particle wavefunctions generated by a sperical square-well potential with characteristic nuclear dimensions and whose depth has been adjusted to give rise to a situation in which the last occupied neutron orbital is loosely-bound. Spin-orbit couplings are, for the present purpose, ignored. The results of this investigation clearly indicate that nuclear couplings have the predominant role in causing projectile dissociation in many circumstances, even at bombarding energies remarkably below the Coulomb barrier.

  9. ''Inelastic Neutron Scattering and Periodic Density Functional Studies of Hydrogen Bonded Structures''

    SciTech Connect

    Bruce S. Hudson

    2004-10-27

    This project is directed at a fundamental understanding of hydrogen bonding, the primary reversible interaction leading to defined geometries, networks and supramolecular aggregates formed by organic molecules. Hydrogen bonding is still not sufficiently well understood that the geometry of such supramolecular aggregates can be predicted. In the approach taken existing quantum chemical methods capable of treating periodic solids have been applied to hydrogen bonded systems of known structure. The equilibrium geometry for the given space group and packing arrangement were computed and compared to that observed. The second derivatives and normal modes of vibration will then be computed and from this inelastic neutron scattering (INS) spectra were computed using the normal mode eigenvectors to compute spectral intensities. Appropriate inclusion of spectrometer line width and shape was made in the simulation and overtones, combinations and phonon wings were be included. These computed spectra were then compared with experimental results obtained for low-temperature polycrystalline samples at INS spectrometers at several facilities. This procedure validates the computational methodology for describing these systems including both static and dynamic aspects of the material. The resulting description can be used to evaluate the relative free energies of two or more proposed structures and so ultimately to be able to predict which structure will be most stable for a given building block.

  10. Hydrogen dynamics in Ce2Fe17H5: inelastic and quasielastic neutron scattering studies

    NASA Astrophysics Data System (ADS)

    Skripov, A. V.; Mushnikov, N. V.; Terent'ev, P. B.; Gaviko, V. S.; Udovic, T. J.; Rush, J. J.

    2011-10-01

    The vibrational spectrum of hydrogen and the parameters of H jump motion in the rhombohedral Th2Zn17-type compound Ce2Fe17H5 have been studied by means of inelastic and quasielastic neutron scattering. It is found that hydrogen atoms occupying interstitial Ce2Fe2 sites participate in the fast localized jump motion over the hexagons formed by these tetrahedral sites. The H jump rate τ-1 of this localized motion is found to change from 3.9 × 109 s-1 at T = 140 K to 4.9 × 1011 s-1 at T = 350 K, and the temperature dependence of τ-1 in the range 140-350 K is well described by the Arrhenius law with the activation energy of 103±3 meV. Our results suggest that the hydrogen jump rate in Th2Zn17-type compounds strongly increases with decreasing nearest-neighbor distance between the tetrahedral sites within the hexagons. Since each such hexagon in Ce2Fe17H5 is populated by two hydrogen atoms, the jump motions of H atoms on the same hexagon should be correlated.

  11. Magnetic spectra in the tridiminished-icosahedron {Fe9} nanocluster by inelastic neutron scattering

    SciTech Connect

    Vaknin, David; Demmel, Franz

    2014-05-01

    Inelastic neutron scattering (INS) experiments under applied magnetic field at low temperatures show detailed low-lying magnetic excitations in the so-called tridiminshed iron icosahedron magnetic molecule. The magnetic molecule consists of nine iron Fe3+ (s=5/2) and three phosphorous atoms that are situated on the 12 vertices of a nearly perfect icosahedron. The three phosphorous atoms form a plane that separates the iron cluster into two weakly coupled three- and six-ion fragments, {Fe3} and {Fe6}, respectively. The magnetic field INS results exhibit an S=1/2 ground state expected from a perfect equilateral triangle of the {Fe3} triad with a powder averaged g value =2.00. Two sets of triplet excitations whose temperature and magnetic field dependence indicate an S=0 ground state with two nondegenerate S=1 states are attributed to the {Fe6} fragment. The splitting may result from a finite coupling between the two fragments, single-ion anisotropy, antisymmetric exchange couplings, or from magnetic frustration of its triangular building blocks.

  12. Excitations in a thin liquid {sup 4}He film from inelastic neutron scattering

    SciTech Connect

    Clements, B.E. |; Godfrin, H.; Krotscheck, E. |; Lauter, H.J.; Leiderer, P.; Passiouk, V. |; Tymczak, C.J.

    1996-05-01

    We perform a thorough analysis of the experimental dynamic structure function measured by inelastic neutron scattering for a low-temperature ({ital T}=0.65 K) four-layer liquid {sup 4}He film. The results are interpreted in light of recent theoretical calculations of the (nonvortex) excitations in thin liquid Bose films. The experimental system consists of four outer liquid layers, adsorbed to two solid inner {sup 4}He layers, which are themselves adsorbed to a graphite substrate. Relatively intense surface (ripplon) and bulklike modes are observed. The analysis of the experimental data gives strong evidence for still other modes and supports the long-standing theoretical predictions of layerlike modes (layer phonons) associated with excitations propagating primarily within the liquid layers comprising the film. The results of the analysis are consistent with the occurrence of level crossings between modes, and the existence of a layer modes for which the theory predicts will propagate in the vicinity of the solid-liquid interface. The theory and experiment agree on the detailed nature of the ripplon; its dispersion at low momenta, its fall off in intensity at intermediate momenta, and the level crossings at high momentum. Similar to experiment, the theory yields an intense mode in the maxon-roton region which is intrepreted as the formation of the bulklike excitation. {copyright} {ital 1996 The American Physical Society.}

  13. The total, elastic and inelastic scattering fast neutron cross sections of natural chromium

    SciTech Connect

    Guenther, P.T.; Smith, J.F.; Whalen, A.B.

    1982-12-01

    The present experimental results comprise a comprehensive intermediate resolution neutron total and scattering cross-section data base for elemental chromium over the energy range from 1.5 to 4.0 MeV. Nonetheless, due to the fluctuating nature of the cross sections involved, the definition of energy-averaged cross sections is uncertain. The consequences of these energy-dependent fluctuations and attendant complications influence the data analysis and interpretation. All finite sample total crosssection measurements result in effective cross sections that have to be corrected to yield the true energyaveraged cross sections. This was accomplished by concurrent multiple sample thickness measurements the results of which were then linearly extrapolated to the zero thickness cross section. It was noted that the resulting sample thickness correction showed marked local fluctuations necessitating an energy by energy treatment. Furthermore, the cross sections, even after averaging over wide energy intervals, retained undulations that complicated comparisons with model calculations. Quantitative comparisons of the present elastic and inelastic scattering results with those obtained at isolated energies by other authors were difficult, if not deceptive, due to persistent fluctuations.

  14. Inelastic Neutron Scattering studies of pure and Mo doped VO2

    NASA Astrophysics Data System (ADS)

    Banerjee, Arnab; Granroth, Garrett E.; Yiu, Yuen; Aczel, Adam A.; Koleshnikov, Alexander I.; Luo, Huxia; Cava, Robert J.; Nagler, Stephen E.; Princeton University Collaboration; Sequoia Team

    2014-03-01

    For the last half-century VO2 has been viewed as an archetypal system for studying the metal-insulator transition (MIT). Moreover, there is currently intense interest in this material arising from its promising use in fast energy efficient electronic devices. There are key unresolved issues connected with the origin of the MIT, including the role of magnetism arising from the S =1/2 V4+ ions. It is known that below 340 K in undoped VO2 the V ions form structural dimers in the insulating M1 monoclinic phase. Here we report the results of new inelastic neutron scattering measurements of VO2 and V0.75Mo0.25O2. Using the SEQUOIA chopper spectrometer at the SNS possible lattice and magnetic excitations for energies up to 600 meV were investigated. We discuss the results in the context of current ideas concerning the MIT in VO2. The research at ORNL is supported by the DOE BES, Division of Scientific User Facilities. Work at Princeton University is supported by the DOE grant number DE-FG02-98ER45706.

  15. Experimental inelastic neutron scattering spectrum of hydrogen hexagonal clathrate-hydrate compared with rigorous quantum simulations

    NASA Astrophysics Data System (ADS)

    Celli, Milva; Powers, Anna; Colognesi, Daniele; Xu, Minzhong; Bačić, Zlatko; Ulivi, Lorenzo

    2013-10-01

    We have performed high-resolution inelastic neutron scattering (INS) measurements on binary hydrogen clathrate hydrates exhibiting the hexagonal structure (sH). Two samples, differing only in the ortho/para fraction of hydrogen, were prepared using heavy water and methyl tert-butyl ether as the promoter in its perdeuterated form. The INS spectrum of the translation-rotation (TR) excitations of the guest H2 molecule was obtained by subtracting the very weak signal due to the D2O lattice modes. By means of a subtraction procedure, it has been possible to obtain separately the spectra of caged p-H2 and o-H2. sH clathrates are comprised of three distinct types of cages, two of which, differing in shape and size, are each occupied by one H2 molecule only. Both contribute to the measured INS spectrum which is, therefore, rather complex and challenging to assign unambiguously. To assist with the interpretation, the INS spectra are calculated accurately utilizing the quantum methodology which incorporates the coupled five-dimensional TR energy levels and wave functions of the H2 molecule confined in each type of nanocage. The computed INS spectra are highly realistic and reflect the complexity of the coupled TR dynamics of the guest H2 in the anisotropic confining environment. The simulated INS spectra of p-H2 and o-H2 in the small and medium cages are compared with the experimental data, and are indispensable for their interpretation.

  16. Measurement and {ital ab initio} modeling of the inelastic neutron scattering of solid N-methylformamide

    SciTech Connect

    Bour, P.; Tam, C.N.; Sopkova, J.; Trouw, F.R.

    1998-01-01

    Vibrational motions of solid N-methylformamide (NMF) and its N-deuterated analogue are investigated using the inelastic neutron scattering (INS) technique at 15 K. The force field for obtaining the normal vibrational modes of the crystal is based on a quantum chemical calculation and a subsequent transfer of a harmonic force field of a smaller pentameric segment to a fragment of 11 NMF molecules. Two types of hydrogen bonds present in crystalline NMF are also modeled with dimers. The distinct bonding leads to a splitting of the N-hydrogen wagging mode in the spectrum. Although the hydrogen bonding has a profound effect on vibrational frequencies, the results indicate that an occurrence of a double-well potential for bonded hydrogen proposed previously is unlikely. Instead, a limited electronic conjugation along the hydrogen bonds in crystalline NMF is observed. Unlike in previous models, we simulate the relative INS intensity of each vibrational transition separately, which leads to a substantial improvement of the overall profile of the intensity pattern. The modeling allows one to assign most of observed INS bands to vibrational modes and the overall spectral profile that reproduced by the simulation compares well with the experiment. {copyright} {ital 1998 American Institute of Physics.}

  17. Characterization of H2 binding sites in prototypical metal-organic frameworks by inelastic neutron scattering.

    PubMed

    Rowsell, Jesse L C; Eckert, Juergen; Yaghi, Omar M

    2005-10-26

    The hindered rotor transitions of H(2) adsorbed in the chemically related and prototypical porous metal-organic frameworks IRMOF-1, IRMOF-8, IRMOF-11, and MOF-177 were studied by inelastic neutron scattering to gain information on the specifics of H(2) binding in this class of adsorbents. Remarkably sharp and complex spectra of these materials signify a diversity of well-defined binding sites. Similarities in the spectral features as a function of H(2) loading and correlations with recent crystallographic studies were used to assign transitions ranging in rotational barrier from <0.04 to 0.6 kcal/mol as corresponding to localized adsorption sites on the organic and inorganic components of these frameworks. We find that binding of H(2) at the inorganic cluster sites is affected by the nature of the organic link and is strongest in IRMOF-11 in accord with our adsorption isotherm data. The sites on the organic link have lower binding energies, but a much greater capacity for increases in H(2) loading, which demonstrates their importance for hydrogen uptake by these materials.

  18. Low-energy neutral-current neutrino scattering on nuclei

    SciTech Connect

    Tsakstara, V.; Kosmas, T. S.; Wambach, J.

    2011-12-16

    Inelastic cross-sections of neutral current neutrino scattering on the {sup 40}Ar isotope, detector-medium of the ongoing ICARUS experiment, are computed in the context of the quasi-particle random phase approximation by utilizing realistic two-nucleon forces. ICARUS is a multipurpose neutrino physics experiment that includes in its objectives low-energy neutrino detection. The incoming neutrino energy range adopted in our calculations ({epsilon}{sub {nu}}{<=}100 MeV), covers the laboratory low-energy beta-beam-neutrinos and pion-muon stopped neutrino-beams operating or planned to be conducted at future neutron spallation sources. One of the main goals of these neutrino beams is to measure neutrino-nucleus cross sections at low-energies.

  19. Inelastic Neutron Scattering Study of the Specific Features of the Phase Transitions in (NH4)2WO2F4

    SciTech Connect

    Smirnov, Lev S; Kolesnikov, Alexander I; Flerov, I. N.; Laptash, N. M.

    2009-01-01

    Oxyfluoride (NH4)2WO2F4 has been studied by the inelastic neutron scattering method over a wide temperature range 10 300 K at two initial neutron energies of 15 and 60 meV. The role of tetrahedral ammonium groups in the mechanism of sequential phase transitions at T1 = 201 K and T2 = 160 K has been discussed.

  20. Application of epithermal neutron activation in multielement analysis of silicate rocks employing both coaxial Ge(Li) and low energy photon detector systems

    USGS Publications Warehouse

    Baedecker, P.A.; Rowe, J.J.; Steinnes, E.

    1977-01-01

    The instrumental activation analysis of silicate rocks using epithermal neutrons has been studied using both high resolution coaxial Ge(Li) detectors and low energy photon detectors, and applied to the determination of 23 elements in eight new U.S.G.S. standard rocks. The analytical use X-ray peaks associated with electron capture or internal conversion processes has been evaluated. Of 28 elements which can be considered to be determinable by instrumental means, the epithermal activation approach is capable of giving improved sensitivity and precision in 16 cases, over the normal INAA procedure. In eleven cases the use of the low energy photon detector is thought to show advantages over convertional coaxial Ge(Li) spectroscopy. ?? 1977 Akade??miai Kiado??.

  1. Crystal electric field excitations in the quasicrystal approximant TbCd6 studied by inelastic neutron scattering

    DOE PAGES

    Das, Pinaki; Lory, P. -F.; Flint, R.; ...

    2017-02-07

    Here, we have performed inelastic neutron scattering measurements on powder samples of the quasicrystal approximant, TbCd6, grown using isotopically enriched 112Cd. Both quasielastic scattering and distinct inelastic excitations were observed below 3 meV. The intensity of the quasielastic scattering measured in the paramag- netic phase diverges as TN ~ 22 K is approached from above. The inelastic excitations, and their evolution with temperature, are well characterized by the leading term, Bmore » $$0\\atop{2}$$O$$0\\atop{2}$$, of the crystalline electric field (CEF) level scheme for local pentagonal symmetry for the rare-earth ions [1] indicating that the Tb moment is directed primarily along the unique local pseudo-five-fold axis of the Tsai-type clusters. We also find good agreement between the inverse susceptibility determined from magnetization measurements using a magnetically diluted Tb0.05Y0.95Cd6 sample and that calculated using the CEF level scheme determined from the neutron measurements.« less

  2. Crystal electric field excitations in the quasicrystal approximant TbCd6 studied by inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Das, Pinaki; Lory, P.-F.; Flint, R.; Kong, T.; Hiroto, T.; Bud'ko, S. L.; Canfield, P. C.; de Boissieu, M.; Kreyssig, A.; Goldman, A. I.

    2017-02-01

    We have performed inelastic neutron scattering measurements on powder samples of the quasicrystal approximant, TbCd6, grown using isotopically enriched 112Cd. Both quasielastic scattering and distinct inelastic excitations were observed below 3 meV. The intensity of the quasielastic scattering measured in the paramagnetic phase diverges as TN˜22 K is approached from above. The inelastic excitations, and their evolution with temperature, are well characterized by the leading term, B20O20 , of the crystal electric field (CEF) level scheme for local pentagonal symmetry for the rare-earth ions [S. Jazbec et al., Phys. Rev. B 93, 054208 (2016), 10.1103/PhysRevB.93.054208] indicating that the Tb moment is directed primarily along the unique local pseudofivefold axis of the Tsai-type clusters. We also find good agreement between the inverse susceptibility determined from magnetization measurements using a magnetically diluted Tb0.05Y0.95Cd6 sample and that calculated using the CEF level scheme determined from the neutron measurements.

  3. New Frontier in Probing Fluid Transport in Low-Permeability Geomedia: Applications of Elastic and Inelastic Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Ding, M.; Hjelm, R.; Sussman, A. J.

    2016-12-01

    Low-permeability geomedia are prevalent in subsurface environments. They have become increasingly important in a wide range of applications such as CO2-sequestration, hydrocarbon recovery, enhanced geothermal systems, legacy waste stewardship, high-level radioactive waste disposal, and global security. The flow and transport characteristics of low-permeability geomedia are dictated by their exceedingly low permeability values ranging from 10-6 to 10-12 darcy with porosities dominated by nanoscale pores. Developing new characterization methods and robust computational models that allow estimation of transport properties of low-permeability geomedia has been identified as a critical basic research and technology development need for controlling subsurface and fluids flow. Due to its sensibility to hydrogen and flexible sample environment, neutron based elastic and inelastic scattering can, through various techniques, interrogate all the nanoscale pores in the sample whether they are fluid accessible or not, and readily characterize interfacial waters. In this presentation, we will present two studies revealing the effects of nanoscale pore confinement on fluid dynamics in geomedia. In one study, we use combined (ultra-small)/small-angle elastic neutron scatterings to probe nanoporous features responses in geological materials to transport processes. In the other study, incoherent inelastic neutron scattering was used to distingwish between intergranular pore water and fluid inclusion moisture in bedded rock salt, and to explore their thermal stablibility. Our work demonstrates that neutron based elastic and inelastic scatterings are techniques of choice for in situ probing hydrocarbon and water behavior in nanoporous materials, providing new insights into water-rock interaction and fluids transport in low-permeability geomaterials.

  4. Inelastic neutron scattering study of methyl groups rotation in some methylxanthines

    NASA Astrophysics Data System (ADS)

    Prager, M.; Pawlukojc, A.; Wischnewski, A.; Wuttke, J.

    2007-12-01

    The three isomeric dimethylxanthines and trimethylxanthine are studied by neutron spectroscopy up to energy transfers of 100meV at energy resolutions ranging from 0.7μeV to some meV. The loss of elastic intensity with increasing temperature can be modeled by quasielastic methyl rotation. The number of inequivalent methyl groups is in agreement with those of the room temperature crystal structures. Activation energies are obtained. In the case of theophylline, a doublet tunneling band is observed at 15.1 and 17.5μeV. In theobromine, a single tunneling band at 0.3μeV is found. Orientational disorder in caffeine leads to a 2.7μeV broad distribution of tunneling bands around the elastic line. At the same time, broad low energy phonon spectra characterize an orientational glassy state with weak methyl rotational potentials. Librational energies of the dimethylxanthines are clearly seen in the phonon densities of states. Rotational potentials can be derived which explain consistently all observables. While their symmetry in general is threefold, theophylline shows a close to sixfold potential reflecting a mirror symmetry.

  5. Transverse dynamics of water across the melting point: A parallel neutron and x-ray inelastic scattering study

    SciTech Connect

    Cunsolo A.; Kodituwakku C.; Bencivenga, F.; Frontzek, M.; Leu, b.M.; Said, A.H.

    2012-05-29

    Joint inelastic neutron and x-ray scattering measurements have been performed on heavy water across the melting point. The spectra bear clear evidence of low- and high-frequency inelastic shoulders related to transverse and longitudinal modes, respectively. Upon increasing the momentum transfer, the spectral shape evolves from a viscoelastic regime, where the low-frequency mode is clearly over-damped, toward an elastic one where its propagation becomes instead allowed. The crossover between the two regimes occurs whenever both the characteristic frequency and the linewidth of the low-frequency mode match the inverse of the structural relaxation time. Furthermore, we observe that the frequency of the transverse mode undergoes a discontinuity across the melting, whose extent reduces upon increasing the exchanged momentum.

  6. Measurement of the deep-inelastic spin-dependent structure functions of the proton and neutron at HERA

    SciTech Connect

    Beck, D.H.; Filippone, B.W.; Jourdan, J.; McKeown, R.D.; Milner, R.G.; Woodward, C.E.; Freedman, S.J.; Geesaman, D.F.; Holt, R.J.; Jackson, H.E.

    1988-01-01

    It is possible to measure the deep-inelastic spin-dependent structure functions g/sub 1//sup p/(x) and g/sub 1//sup n/(x) for the proton and neutron using internal polarized hydrogen, deuterium, and /sup 3/He targets of polarization 50% and thickness 10/sup 14/ to 10/sup 15/ cm/sup -2/ and the 60 mA longitudinally polarized 30 GeV electron beam in the HERA electron storage ring. The measurement of the deep-inelastic spin-structure of both isospin states of the nucleon at the same kinematics and using the same apparatus allows the Bjorken sum rule to be experimentally checked. In addition, it uniquely constrains the spin distribution of the u and d quarks as a function of x in any model of the nucleon. Possible target and detector configurations are described and an estimate of the accuracy of such a measurement is presented.

  7. Vibrational dynamics of plant light-harvesting complex LHC II investigated by quasi- and inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Golub, Maksym; Irrgang, Klaus-Dieter; Rusevich, Leonid; Pieper, Jörg

    2015-01-01

    Vibrational dynamics of the light-harvesting complex II (LHC II) from spinach was investigated by quasi- and inelastic neutron scattering (QENS and INS) at three different temperatures of 80, 160, and 285 K. QENS/INS spectra of solubilised LHC II and of the corresponding buffer solution were obtained separately and exhibit characteristic inelastic features. After subtraction of the buffer contribution, the INS spectrum of LHC II reveals a distinct Boson peak at ˜ 2.5 meV at 80 K that shifts towards lower energies if the temperature is increased to 285 K. This effect is interpreted in terms of a "softening" of the protein matrix along with the dynamical transition at ˜ 240 K. Our findings indicate that INS is a valuable method to obtain the density of vibrational states not only at cryogenic, but also at physiological temperatures.

  8. Observations of CEF-split intermultiplet transitions in optically opaque EuBa{sub 2}Cu{sub 3}O{sub 7} using inelastic neutron scattering

    SciTech Connect

    Staub, U.; Soderholm, L.; Osborn, R.; Balcar, E.; Trunov, V.

    1995-02-01

    Inelastic neutron scattering (INS) results on the intermultiplet transitions J=0 {yields} 1 and J=l {yields} 2 in optically opaque EuBa{sub 2}Cu{sub 3}O{sub 7} are reported. Whereas these multiplets are split by the crystalline electric field (CEF), their low J values are influenced to first order only by the 2 second-order (J=l) and additional fourth-order (J=2) CEF parameters. B{sub 0}{sup 2}, B{sub 2}{sup 2} and the spin-orbit coupling parameter were obtained by fitting the splitting of the J=1 multiplet and the energy separation between the J=0 and 1 multiplets. The J=0 to 1 splitting observed here is smaller than previously seen by optical spectroscopic studies on a variety of transparent, ionic compounds, necessitating fitting of the free-ion parameter. Additional spectroscopic information on the J=2 multiplet indicates that additional fitting of free ion parameters must be included to adequately model the observed low energy separation between the two lowest J-multiplets. Preliminary calculation on the Q-dependence of the CEF split J=0 to 1 transitions and the comparison with observations are presented.

  9. Role of phonons in negative thermal expansion and high pressure phase transitions in β-eucryptite: An ab-initio lattice dynamics and inelastic neutron scattering study

    NASA Astrophysics Data System (ADS)

    Singh, Baltej; Gupta, Mayanak Kumar; Mittal, Ranjan; Zbiri, Mohamed; Rols, Stephane; Patwe, Sadequa Jahedkhan; Achary, Srungarpu Nagabhusan; Schober, Helmut; Tyagi, Avesh Kumar; Chaplot, Samrath Lal

    2017-02-01

    β-Eucryptite (LiAlSiO4) shows anisotropic thermal expansion as well as one-dimensional super-ionic conductivity. We have performed the lattice dynamical calculations using ab-initio density functional theory along with inelastic neutron scattering measurements. The anisotropic stress dependence of the phonon spectrum is calculated to obtain the thermal expansion behavior along various axes. The calculations show that the Grüneisen parameters of the low-energy phonon modes around 10 meV have large negative values and govern the negative thermal expansion behavior at low temperatures along both the "a"- and "c"-axes. On the other hand, anisotropic elasticity along with anisotropic positive values of the Grüneisen parameters of the high-energy modes in the range 30-70 meV are responsible for the thermal expansion at high temperatures, which is positive in the a-b plane and negative along the c-axis. The analysis of the polarization vectors of the phonon modes sheds light on the mechanism of the anomalous thermal expansion behavior. The softening of a Γ-point mode at about 2 GPa may be related to the high-pressure phase transition.

  10. Inelastic neutron scattering study on the resonance mode in an optimally doped superconductor LaFeAsO0.92F0.08

    SciTech Connect

    Shamoto, S; Ishikado, Motoyuki; Christianson, Andrew D; Lumsden, Mark D; Wakimoto, S; Kodama, K.; Iyo, Akira; Arai, Masatoshi

    2010-01-01

    An optimally doped iron-based superconductor LaFeAsO{sub 0.92}F{sub 0.08} with T{sub c} = 29 K has been studied by inelastic powder neutron scattering. The magnetic excitation at Q = 1.15 {angstrom}{sup -1} is enhanced below T{sub c}, leading to a peak at E{sub res}-13 meV as the resonance mode, in addition to the formation of a gap at low energy below the crossover energy {Delta}{sub c}-10 meV. The peak energy at Q = 1.15 {angstrom}{sup -1} corresponds to 5.2 k{sub B}T{sub c} in good agreement with the other values of resonance mode observed in iron based superconductors. Although the phonon density of states has a peak at the same energy as the resonance mode in the present superconductor, The Q dependence is consistent with the resonance being of preominantly magnetic origin.

  11. Prompt and Delayed Inelastic Scattering Reactions from Fission Neutron PGAA - First Results of FaNGaS

    SciTech Connect

    Rossbach, M.; Randriamalala, T.; Revay, Zs.; Kudejova, P.; Soelradel, S.; Wagner, F.

    2015-07-01

    The new instrument Fast Neutron Gamma Spectroscopy (FaNGaS) has been installed at the SR10 beam line of the FRM II Research Reactor in Garching and tested successfully. Complimentary to cold neutron PGAA, with FaNGaS inelastic scattering reactions induced by fission neutrons can be studied. Gamma lines from (n,n'γ) reactions up to now have been rarely studied and no adequate compilation of the emitted gamma energies exist. In developing nondestructive analytical techniques using neutron generator based PGAA such data are badly needed for quantification of heavy metals and actinides in e.g. nuclear waste or safeguards samples. A number of elements and relevant actinides have been irradiated in the fast neutron beam SR10 at the FRM II reactor in Garching, Germany. A heavily shielded 50% eff. HPGe detector perpendicular to the beam is looking at the samples exposed to 2.3 E8 cm{sup -2}s{sup -1} fission neutrons. Prompt gamma spectra have been taken and evaluated using the available data in scattered sources. Additional gamma lines have been detected and are being compiled to create a data base for (n,n') reactions. Particular emphasis is given on actinides including {sup 238}U, {sup 232}Th, {sup 237}Np, {sup 242}Pu and {sup 241}Am. Some examples will be given and first results will be discussed in this contribution. (authors)

  12. Evaluation of the Doppler-Broadening of Gamma-Ray Spectra from Neutron Inelastic Scattering on Light Nuclei

    SciTech Connect

    Womble, Phillip C.; Barzilov, Alexander; Novikov, Ivan; Howard, Joseph; Musser, Jason

    2009-03-10

    Neutron-induced gamma-ray reactions are extensively used in the nondestructive analysis of materials and other areas where the information about the chemical composition of a substance is crucial. The common technique to find the intensity of the gamma ray is to fit gamma-ray line shape with an analytical function, for example, a Gaussian. However, the Gaussian fitting may fail if the gamma-ray peak is Doppler-broadened since this leads to the miscalculation of the area of the peak and, therefore, to misidentification of the material. Due to momentum considerations, Doppler-broadening occurs primarily with gamma rays from neutron-induced inelastic scattering reactions with light nuclei. The recoiling nucleus of interest must have excited states whose lifetimes are much smaller than the time of flight in the material. We have examined various light nuclei bombarded by 14 MeV neutrons to predict when the peak shape of a neutron-induced gamma ray emitted from these nuclei will be Doppler-broadened. We have found that nearly all the gamma rays from neutron-induced gamma-ray reactions on light elements (A<20) are Doppler-broadened with only a few exceptions. This means that utilization of resolution curves derived from isotopic sources or thermal neutron capture reactions have little value in the analysis.

  13. Neutron Scattering Study of Low Energy Magnetic Excitation in superconducting Te-vapor annealed under-doped FeTeSe

    NASA Astrophysics Data System (ADS)

    Xu, Zhijun; Yi, Ming; Xu, Guangyong; Shneeloch, J. A.; Matsuda, Masaaki; Chi, Songxue; Gu, Genda; Tranquada, J. M.; Birgeneau, R. J.

    To study the interplay between magnetism and superconductivity, we have performed neutron scattering and magnetization measurements on a Te vapor annealed single crystal Fe1 +yTe0.8Se0.2 (Tc~13K) sample. Te vapor annealed process is found to reduce/remove the excess Fe in the as-grown sample and make the under-doped originally non-superconducting sample become good superconducting sample. Our neutron scattering studies show both spin gap and spin resonance found in the Te vapor annealed superconducting sample. Comparing to commensurate spin resonance in as-grown optimal-doped sample, the spin resonance of Te annealed sample only shows up at the clearly incommensurate positions. The temperature and energy dependence of low energy magnetic excitations are also measured in the sample. This work is supported by the Office of Basic Energy Sciences, DOE.

  14. Cross section measurements for neutron inelastic scattering and the (n, 2nγ) reaction on Pb206

    DOE PAGES

    Negret, A.; Mihailescu, L. C.; Borcea, C.; ...

    2015-06-30

    We measured excitation functions for γ production associated with the neutron inelastic scattering and the (n, 2n) reactions on 206Pb from threshold up to 18 MeV for about 40 transitions. Two independent measurements were performed using different samples and acquisition systems to check consistency of the results. Moreover, the neutron flux was determined with a 235U fission chamber and a procedure that were validated against a fluence standard. For incident energy higher than the threshold for the first excited level and up to 3.5 MeV, estimates are provided for the total inelastic and level cross sections by combining the presentmore » γ production cross sections with the level and decay data of 206Pb reported in the literature. The uncertainty common to all incident energies is 3.0% allowing overall uncertainties from 3.3% to 30% depending on transition and neutron energy. Finally, the present data agree well with earlier work, but significantly expand the experimental database while comparisons with model calculations using the talys reaction code show good agreement over the full energy range.« less

  15. Development of a µ-TPC detector as a standard instrument for low-energy neutron field characterisation.

    PubMed

    Maire, D; Billard, J; Bosson, G; Bourrion, O; Guillaudin, O; Lamblin, J; Lebreton, L; Mayet, F; Médard, J; Muraz, J F; Richer, J P; Riffard, Q; Santos, D

    2014-10-01

    In order to measure the energy and fluence of neutron fields, in the energy range of 8 to 1 MeV, a new primary standard is being developed at the Institute for Radioprotection and Nuclear Safety (IRSN). This project, Micro Time Projection Chamber (µ-TPC), carried out in collaboration with the Laboratoire de Physqique Subatomique et de Cosmologie (LPSC), is based on the nucleus recoil detector principle. The measurement strategy requires track reconstruction of recoiling nuclei down to a few kiloelectronvolts, which can be achieved using a micro-pattern gaseous detector. A gas mixture, mainly isobutane, is used as an n-p converter to detect neutrons within the detection volume. Then electrons, coming from the ionisation of the gas by the proton recoil, are collected by the pixelised anode (2D projection). A self-triggered electronics system is able to perform the anode readout at a 50-MHz frequency in order to give the third dimension of the track. Then, the scattering angle is deduced from this track using algorithms. The charge collection leads to the proton energy, taking into account the ionisation quenching factor. This article emphasises the neutron energy measurements of a monoenergetic neutron field produced at 127 keV. The fluence measurement is not shown in this article. The measurements are compared with Monte Carlo simulations using realistic neutron fields and simulations of the detector response. The discrepancy between experiments and simulations is 5 keV mainly due to the calibration uncertainties of 10 %.

  16. Development of a low-energy monoenergetic neutron source for applications in low-dose radiobiological and radiochemical research.

    PubMed

    Aslam; Prestwich, W V; McNeill, F E; Waker, A J

    2003-06-01

    The McMaster University 3 MV KN Van de Graff accelerator facility primarily dedicated to in vivo neutron activation measurements has been used to produce moderate dose rates of monoenergetic fast neutrons of energy ranging from 150 to 600 keV with a small energy spread of about 25 keV (1sigma width of Gaussian) by bombarding thin lithium targets with 2.00-2.40 MeV protons. The calculated dose rate of the monoenergetic neutrons produced using thin lithium targets as functions of beam energy, target thickness, lab angle relative to beam direction, and the solid angle subtended by the sample with the target has also been reported.

  17. CHIPS_TPT models for exclusive Geant4 simulation of neutron-nuclear reactions at low energies

    NASA Astrophysics Data System (ADS)

    Kosov, Mikhail V.; Kudinov, Ilya V.; Savin, Dmitry I.

    2014-03-01

    A novel TPT code (Toolkit for Particle Transport), which is included in CHIPS_TPT physics list for Geant4 simulations, is briefly overviewed. Underlying concept of exclusive modelling is introduced and its beneficial features are illustrated with several examples. Widely used neutron Monte Carlo codes, MCNP and Geant4/HP, are based on inclusive algorithms that independently model neutron state change and secondary particles production while tracking. The exclusive approach implemented in TPT overcomes this unphysical separation and makes it possible to allow for kinematic restrictions as well as correlated emission of gamma-rays and secondaries.

  18. Inelastic neutron scattering from the spin ladder compound (VO)[sub 2]P[sub 2]O[sub 7

    SciTech Connect

    Eccleston, R.S.; Barnes, T.; Brody, J.; Johnson, J.W. Physics Division and Center for Computationally Intensive Physics, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996 Corporate Research Laboratories, Exxon Research and Engineering Company, Annandale, New Jersey 08801 )

    1994-11-07

    We present results from an inelastic neutron scattering experiment on the candidate Heisenberg spin ladder vanadyl pyrophosphate, (VO)[sub 2]P[sub 2]O[sub 7]. We find evidence for a spin-wave excitation gap of [ital E][sub gap]=3.7[plus minus]0.2 meV, at a band minimum near [ital Q]=0.8 A[sup [minus]1]. This is consistent with expectations for triplet spin waves in (VO)[sub 2]P[sub 2]O[sub 7] in the spin-ladder model, and represents the first confirmation in nature of a Heisenberg antiferromagnetic spin ladder.

  19. Inelastic-neutron-scattering studies of spin-wave excitations in the pnictides MnSb and CrSb

    SciTech Connect

    Radhakrishna, P.; Cable, J.W.

    1996-11-01

    The spin-wave dispersion relations in the ferromagnet MnSb, and the antiferromagnet CrSb, have been measured, by neutron inelastic scattering, along high-symmetry directions in reciprocal space, as a function of temperature. The effect of composition is discussed. The dispersion in CrSb is found to rise very steeply as a function of {ital q}, and a gap in the excitation spectrum occurs at {ital q}=0. The results for these itinerant electron magnetic materials are compared with previous experimental and theoretical work. {copyright} {ital 1996 The American Physical Society.}

  20. Inelastic-neutron-scattering studies of spin-wave excitations in the pnictides MnSb and CrSb

    NASA Astrophysics Data System (ADS)

    Radhakrishna, P.; Cable, J. W.

    1996-11-01

    The spin-wave dispersion relations in the ferromagnet MnSb, and the antiferromagnet CrSb, have been measured, by neutron inelastic scattering, along high-symmetry directions in reciprocal space, as a function of temperature. The effect of composition is discussed. The dispersion in CrSb is found to rise very steeply as a function of q, and a gap in the excitation spectrum occurs at q=0. The results for these itinerant electron magnetic materials are compared with previous experimental and theoretical work.

  1. Encapsulation of paclitaxel into a bio-nanocomposite. A study combining inelastic neutron scattering to thermal analysis and infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Martins, Murillo L.; Orecchini, Andrea; Aguilera, Luis; Eckert, Juergen; Embs, Jan; Matic, Aleksander; Saeki, Margarida J.; Bordallo, Heloisa N.

    2015-01-01

    The anticancer drug paclitaxel was encapsulated into a bio-nanocomposite formed by magnetic nanoparticles, chitosan and apatite. The aim of this drug carrier is to provide a new perspective against breast cancer. The dynamics of the pure and encapsulated drug were investigated in order to verify possible molecular changes caused by the encapsulation, as well as to follow which interactions may occur between paclitaxel and the composite. Fourier transformed infrared spectroscopy, thermal analysis, inelastic and quasi-elastic neutron scattering experiments were performed. These very preliminary results suggest the successful encapsulation of the drug.

  2. Ab initio calculations as a quantitative tool in the inelastic neutron scattering study of a single-molecule magnet analogue.

    PubMed

    Vonci, Michele; Giansiracusa, Marcus J; Gable, Robert W; Van den Heuvel, Willem; Latham, Kay; Moubaraki, Boujemaa; Murray, Keith S; Yu, Dehong; Mole, Richard A; Soncini, Alessandro; Boskovic, Colette

    2016-02-04

    Ab initio calculations carried out on the Tb analogue of the single-molecule magnet family Na9[Ln(W5O18)2] (Ln = Nd, Gd, Ho and Er) have allowed interpretation of the inelastic neutron scattering spectra. The combined experimental and theoretical approach sheds new light on the sensitivity of the electronic structure of the Tb(III) ground and excited states to small structural distortions from axial symmetry, thus revealing the subtle relationship between molecular geometry and magnetic properties of the two isostructural species that comprise the sample.

  3. SU-E-T-267: Construction and Evaluation of a Neutron Wall to Shield a 15 MV Linac in a Low-Energy Vault.

    PubMed

    Speiser, M; Hager, F; Foster, R; Solberg, T

    2012-06-01

    To design and quantify the shielding efficacy of an inner Borated Polyethylene (BPE)wall for a 15 MV linac in a low energy vault. A Varian TrueBeam linac with a maximum photon energy of 15 MV was installed in asmaller, preexisting vault. This vault originally housed a low-energy machine and did not havesufficient maze length recommended for neutron attenuation. Effective dose rate calculationswere performed using the Modified Kersey's Method as detailed in NCRP Report No. 151 andfound to be unacceptably high. An initial survey following the machine installation confirmedthese calculations. Rather than restrict the linac beam energy to 10 MV, BPE was investigatedas a neutron moderating addition. An inner wall and door were planned and constructed using4'×8'×1″ thick 5% BPE sheets. The resulting door and wall had 2″ of BPE; conduits and ductwork were also redesigned and shielded. A survey was conducted following construction of thewall. The vault modification reduced the expected effective dose at the vault door from 36.23to 0.010 mSv/week. As specific guidelines for vault modification are lacking, this project quantitativelydemonstrates the potential use of BPE for vault modification. Such modifications may provide alow-cost shielding solution to allow for the use of high energy modes in smaller treatment vaults. © 2012 American Association of Physicists in Medicine.

  4. Microscopic time-dependent analysis of neutrons transfers at low-energy nuclear reactions with spherical and deformed nuclei

    NASA Astrophysics Data System (ADS)

    Samarin, Viacheslav

    2014-03-01

    Time-dependent Schrödinger equation is numerically solved by difference method for external neutrons of nuclei 6He, 18O, 48Са, 238U at their grazing collisions with energies in the vicinity of a Coulomb barrier. The spin-orbital interaction and Pauli's exclusion principle were taken into consideration during the solution.

  5. Long-range interactions in the effective low-energy Hamiltonian of Sr2IrO4 : A core-to-core resonant inelastic x-ray scattering study

    NASA Astrophysics Data System (ADS)

    Agrestini, S.; Kuo, C.-Y.; Moretti Sala, M.; Hu, Z.; Kasinathan, D.; Ko, K.-T.; Glatzel, P.; Rossi, M.; Cafun, J.-D.; Kvashnina, K. O.; Matsumoto, A.; Takayama, T.; Takagi, H.; Tjeng, L. H.; Haverkort, M. W.

    2017-05-01

    We have investigated the electronic structure of Sr2IrO4 using core-to-core resonant inelastic x-ray scattering. The experimental spectra can be well reproduced using ab initio density functional theory based multiplet ligand field theory calculations, thereby validating these calculations. We found that the low-energy, effective Ir t2 g orbitals are practically degenerate in their crystal-field energy. We uncovered that Sr2IrO4 and iridates in general are negative charge transfer systems with large covalency and a substantial oxygen ligand hole character in the Ir t2 g Wannier orbitals. This has far reaching consequences, as not only the on-site crystal-field energies are determined by the long-range crystal structure, but, more significantly, magnetic exchange interactions will have long-range distance dependent anisotropies in the spin direction. These findings set constraints and show pathways for the design of d5 materials that can host compasslike magnetic interactions.

  6. Vibrational dynamics in dendridic oligoarylamines by Raman spectroscopy and incoherent inelastic neutron scattering.

    PubMed

    Kulszewicz-Bajer, Irena; Louarn, Guy; Djurado, David; Skorka, Lukasz; Szymanski, Marek; Mevellec, Jean Yves; Rols, Stephane; Pron, Adam

    2014-05-15

    Vibrational dynamics in triarylamine dendrimers was studied in a complementary way by Raman and infrared (IR) spectroscopies and incoherent inelastic neutron scattering (IINS). Three molecules were investigated, namely, unsubstituted triarylamine dendrimer of the first generation and two dendrimers of the first and second generation, substituted in the crown with butyl groups. To facilitate the assignment of the observed IR and Raman modes as well as the IINS peaks, vibrational models, based on the general valence force field method (GVFF), were calculated for all three compounds studied. A perfect consistency between the calculated and experimental results was found. Moreover, an important complementarity of the vibrational spectroscopies and IINS was established for the investigated dendrimers. The IINS peaks originating mainly from the C-H motions were not restricted by particular selection rules and only dependent on the IINS cross section. To the contrary, Raman and IR bands were imposed by the selection rules and the local geometry of the dendrimers yielding mainly C-C and C-N deformation modes with those of C-H nature of much lower intensity. Raman spectroscopy was also applied to the studies of the oxidation of dendrimers to their cationic forms. A strong Raman resonance effect was observed, since the spectra of the studied compounds, registered at different levels of their oxidation, strongly depended on the position of the excitation line with respect to their electronic spectrum. In particular, the blue (458 nm) excitation line turned out to be insensitive toward the cationic forms yielding very limited spectral information. To the contrary, the use of the red (647 nm) and infrared (1064 nm) excitation lines allowed for an unambiguous monitoring of the spectral changes in dendrimers oxidized to nominally monocationic and tricationic states. The analysis of oxidation-induced spectral changes in the tricationic state indicated that the charge storage

  7. Possibility of production of neutron-rich Zn and Ge isotopes in multinucleon transfer reactions at low energies

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Sargsyan, V. V.; Scheid, W.

    2010-02-15

    The production cross sections of new neutron-rich {sup 84,86}Zn and {sup 90,92}Ge isotopes beyond N=50 are estimated for the first time in the multinucleon transfer reactions {sup 48}Ca + {sup 238}U and {sup 48}Ca + {sup 244}Pu. The production of new isotopes in reactions with a {sup 48}Ca beam is discussed for future experiments.

  8. Chromosomal aberrations in peripheral blood lymphocytes exposed to a mixed beam of low energy neutrons and gamma radiation.

    PubMed

    Wojcik, A; Obe, G; Lisowska, H; Czub, J; Nievaart, V; Moss, R; Huiskamp, R; Sauerwein, W

    2012-09-01

    Cells exposed to thermal neutrons are simultaneously damaged by radiations with high and low linear energy transfer (LET). A question relevant for the assessment of risk of exposure to a mixed beam is whether the biological effect of both radiation types is additive or synergistic. The aim of the present investigation was to calculate whether the high and low LET components of a thermal neutron field interact when damaging cells. Human peripheral blood lymphocytes were exposed to neutrons from the HB11 beam at the Institute for Energy and Transport, Petten, Netherlands, in a 37 °C water phantom at varying depths, where the mix of high and low LET beam components differs. Chromosomal aberrations were analysed and the relative biological effectiveness (RBE) values as well as the expected contributions of protons and photons to the aberration yield were calculated based on a dose response of aberrations in lymphocytes exposed to (60)Co gamma radiation. The RBE for 10 dicentrics per 100 cells was 3 for mixed beam and 7.2 for protons. For 20 dicentrics per 100 cells the respective values were 2.4 and 5.8. Within the limitations of the experimental setup the results indicate that for this endpoint there is no synergism between the high and low LET radiations.

  9. Crystal field excitations in CeCu2Ge2: Revisited employing a single crystal and inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Loewenhaupt, Michael; Faulhaber, Enrico; Schneidewind, Astrid; Deppe, Micha; Hradil, Klaudia

    2012-04-01

    The intermetallic compound, CeCu2Ge2, is the counterpart of the heavy-fermion superconductor CeCu2Si2. CeCu2Ge2 is a magnetically ordering (TN = 4.1K) Kondo lattice with a moderate Sommerfeld coefficient of 140 mJ/ molK2. Earlier inelastic neutron measurements on a polycrystalline sample revealed a doublet ground state and a quasi-quartet excited state at 16.5 meV, although a splitting of the 4f1 (J = 5/2) ground state multiplet into 3 doublets is expected from the point symmetry of the Ce3+ ions. We performed detailed inelastic neutron scattering experiments on a single crystal at the thermal triple-axis spectrometer PUMA at FRM II for different crystallographic directions. From our results we infer that the quasi-quartet, in fact, consists of two doublets at 17.0 and 18.3 meV which exhibit a strong directional dependence of their transition matrix elements to the ground state doublet. Finally, we will present a new set of crystal field parameters.

  10. Magnetic Excitations in Polyoxotungstate-Supported Lanthanoid Single-Molecule Magnets: An Inelastic Neutron Scattering and ab Initio Study.

    PubMed

    Vonci, Michele; Giansiracusa, Marcus J; Van den Heuvel, Willem; Gable, Robert W; Moubaraki, Boujemaa; Murray, Keith S; Yu, Dehong; Mole, Richard A; Soncini, Alessandro; Boskovic, Colette

    2017-01-03

    Inelastic neutron scattering (INS) has been used to investigate the crystal field (CF) magnetic excitations of the analogs of the most representative lanthanoid-polyoxometalate single-molecule magnet family: Na9[Ln(W5O18)2] (Ln = Nd, Tb, Ho, Er). Ab initio complete active space self-consistent field/restricted active space state interaction calculations, extended also to the Dy analog, show good agreement with the experimentally determined low-lying CF levels, with accuracy better in most cases than that reported for approaches based only on simultaneous fitting to CF models of magnetic or spectroscopic data for isostructural Ln families. In this work we demonstrate the power of a combined spectroscopic and computational approach. Inelastic neutron scattering has provided direct access to CF levels, which together with the magnetometry data, were employed to benchmark the ab initio results. The ab initio determined wave functions corresponding to the CF levels were in turn employed to assign the INS transitions allowed by selection rules and interpret the observed relative intensities of the INS peaks. Ultimately, we have been able to establish the relationship between the wave function composition of the CF split Ln(III) ground multiplets and the experimentally measured magnetic and spectroscopic properties for the various analogs of the Na9[Ln(W5O18)2] family.

  11. Determination of low-energy parameters of neutron-proton scattering on the basis of modern experimental data from partial-wave analyses

    SciTech Connect

    Babenko, V. A. Petrov, N. M.

    2007-04-15

    The triplet and singlet low-energy parameters in the effective-range expansion for neutron-proton scattering are determined by using the latest experimental data on respective phase shifts from the SAID nucleon-nucleon database. The results differ markedly from the analogous parameters obtained on the basis of the phase shifts of the Nijmegen group and contradict the parameter values that are presently used as experimental ones. The values found with the aid of the phase shifts from the SAID nucleon-nucleon database for the total cross section for the scattering of zero-energy neutrons by protons, {sigma}{sub 0} = 20.426 b, and the neutron-proton coherent scattering length, f = -3.755 fm, agree perfectly with experimental cross-section values obtained by Houk, {sigma}{sub 0} = 20.436 {+-} 0.023 b, and experimental scattering-length values obtained by Houk and Wilson, f = -3.756 {+-} 0.009 fm, but they contradict cross-section values of {sigma}{sub 0} = 20.491 {+-} 0.014 b according to Dilg and coherent-scattering-length values of f = -3.7409 {+-} 0.0011 fm according to Koester and Nistler.

  12. Hydrogen molecule binding to unsaturated metal sites in metal-organic frameworks studied by neutron powder diffraction and inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Liu, Yun; Brown, Craig; Neumann, Dan; Dinca, Mircea; Long, Jeffrey; Peterson, Vanessa; Kepert, Cameron

    2007-03-01

    Metal organic framework (MOF) materials have shown considerable potential for hydrogen storage arising from very large surface areas. However, the low binding energy of hydrogen molecules limits its storage capability to very low temperatures (< 77 K), which is impractical for industrial applications. Using neutron powder diffraction (NPD), we have characterized the hydrogen adsorption sites in a selected series of MOF materials with exposed unsaturated metal ions. Direct binding between the unsaturated metal ions and hydrogen molecules is observed and responsible for the enhanced initial hydrogen adsorption enthalpy. The different metals centers in these MOFs show different binding strength and interaction distances between the hydrogen molecule and metal ions. The organic linker also affects the overall H2 binding strength. Inelastic neutron scattering spectra of H2 in these MOFs are also discussed.

  13. Inelastic neutron scattering studies of 76Ge and 76Se: relevance to elevance to neutrinoless double-β decay

    NASA Astrophysics Data System (ADS)

    Crider, B. P.; Peters, E. E.; Ross, T. J.; McEllistrem, M. T.; Prados-Estévez, F. M.; Allmond, J. M.; Vanhoy, J. R.; Yates, S. W.

    2015-05-01

    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.

  14. Inelastic neutron scattering studies of Ge-76 and Se-76: relevance to neutrinoless double-beta decay

    SciTech Connect

    Crider, Ben; Peters, Erin; Ross, T.J.; McEllistrem, M; Prados-Estevez, F.; Allmond, James M; Vanhoy, J.R.; Yates, S.W.

    2015-01-01

    Inelastic neutron scattering measurements were performed at the University of Kentucky Accelerator Laboratory on enriched Ge-76 and Se-76 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, gamma-ray cross sections for the Ge-76(n,n'gamma) reaction were measured at neutron energies up to 5.0 MeV, with the goal of determining the cross sections of gamma rays in 2040-keV region, which corresponds to the region of interest in the neutrinoless double beta decay of Ge-76. Gamma rays from the three strongest branches from the 3952-keV level were observed, but the previously reported 2041-keV gamma 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 similar to 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 gamma rays from levels in Ge-76 can be found in the 2039-keV region.

  15. Neutron capture and inelastic scattering cross sections for {sup 186}Os, {sup 187}Os, and {sup 189}Os and the Re-Os chronology

    SciTech Connect

    Segawa, M.; Nagai, Y.; Masaki, T.; Temma, Y.; Shima, T.; Mishima, K.; Igashira, M.; Goriely, S.; Koning, A.; Hilaire, S.

    2008-05-21

    We measured the neutron capture cross sections of {sup 186,187,189}Os taking for the first time their pulse height spectra for neutrons between 5 and 90 keV by means of an anti-Compton NaI(Tl) spectrometer. The neutron inelastic scattering cross section for {sup 187}Os as well as the neutron elastic scattering cross sections for {sup 186,187}Os were also observed with use of {sup 6}Li-glass scintillation detectors with a small systematic uncertainty.

  16. Low Energy Inelastic Atomic and Molecular Collisions.

    DTIC Science & Technology

    1981-04-15

    oemey A 17 mca mem ewa) atomic collisions deuterium molecular Collisions hydrogen argon .. excitation C argon Ions Ion beams LU & AinVIACt~ re- o sed a...1981). The intent of this work., described in our proposal, was toI obtain sufficient resolution of phosphorus, sulfur and argon L-x rays under single...collision, there are other intense VUV lines as well: the dominant ones observed in the 500-1100 A range were emission from the 2p excitation of neutral He

  17. Diffuse scattering and low-energy phonons in superionic conductor Cu1.8SSe

    NASA Astrophysics Data System (ADS)

    Danilkin, Sergey; Hoser, Andreas; Schweika, Werner

    2005-03-01

    The neutron diffuse and inelastic scattering were studied in the superionic α-phase of copper selenide. In neutron diffraction experiments on Cu1.85Se single crystal the diffuse scattering features were observed along [111] direction in vicinity of (400) and (422) reflections. In inelastic neutron scattering measurements performed with time-of-flight spectrometer the elastic and inelastic scattering processes were separated and a strong inelastic scattering was observed also along [111] nearby (400) and (022). This shows that diffuse scattering found in conventional diffraction experiment is mainly inelastic and most probably comes from the low-energy phonons. Such phonons with optic-like behaviour of transverse acoustic modes at q/qm> 0.2-0.4 were found earlier in α-Cu1.85Se [1]. [1] S.A. Danilkin, A.N. Skomorokhov, A. Hoser, H. Fuess, V. Rajevac, N.N. Bickulova, Crystal structure and lattice dynamics of superionic copper selenide Cu2-δSe, J. Alloys and Compounds, 2003, v. 361, p. 57-61.

  18. Microscopic dynamics of AC{sub 60} compounds in the plastic, polymer, and dimer phases investigated by inelastic neutron scattering

    SciTech Connect

    Schober, H.; Toelle, A.; Renker, B.; Heid, R.; Gompf, F.

    1997-09-01

    We present inelastic neutron-scattering results for AC{sub 60} (A=K,Rb,Cs) compounds. The spectra of the high-temperature fcc phases strongly resemble the ones of pristine C{sub 60} in the plastic phase. At equal temperatures we find identical rotational diffusion constants for pristine C{sub 60} and Rb{sub 1}C{sub 60} (D{sub r}=2.4 10{sup 10} s{sup {minus}1} at 400 K). The changes taking place in the inelastic part of the spectra on cooling AC{sub 60} indicate the formation of strong intermolecular bonds. The buildup of intensities in the gap region separating internal and external vibrations in pure C{sub 60} is the most prominent signature of this transition. The spectra of the low-temperature phases depend on their thermal history. The differences can be explained by the formation of a polymer phase (upon slow cooling from the fcc phase) and a dimer phase (upon fast cooling), respectively. The experimental data are analyzed on the basis of lattice dynamical calculations. The density-of-states are well modeled assuming a [2+2] bond for the polymer and a single intercage bond for the dimer. Indications for different intercage bonding are also found in the internal mode spectra, which, on the other hand, react only weakly to the charge transfer. The dimer phase is metastable and converts into the polymer phase with a strongly temperature-dependent time constant. The transition from the polymer to the fcc phase is accompanied by inelastic precursor effects which are interpreted as the signature of inhomogeneities arising from plastic monomer regions embedded in the polymer phase. In the polymer phase AC{sub 60} compounds show strong anharmonic behavior in the low-temperature region. The possible connection with the metal-to-insulator transition is discussed. {copyright} {ital 1997} {ital The American Physical Society}

  19. Lattice vibrations of para-hydrogen impurities in a solid deuterium matrix: An inelastic neutron scattering study

    NASA Astrophysics Data System (ADS)

    Colognesi, D.; Celli, M.; Ramirez-Cuesta, A. J.; Zoppi, M.

    2007-11-01

    In the present study, we report inelastic neutron scattering measurements from para-hydrogen defects in solid normal deuterium at three different concentrations (between 3% and 11%) using the time-of-flight spectrometer TOSCA-II. The measured double-differential cross sections give access to the self-inelastic structure factors for the H2 centers of mass. Corrected experimental data, analyzed through the Young-Koppel model and the Gaussian approximation, are transformed into defect densities of phonon states, which come out to be broad, structured, and nearly concentration independent. Two experimentally determined Bose-corrected spectral moments are found to be in agreement with independent estimates, providing a strong validation of our data reduction procedure. Subsequently, experimental phonon spectra are compared to three calculations, namely, a simple harmonic model at infinite dilution, a more advanced harmonic model with concentration effects, and finally a lattice dynamics simulation based on self-consistent phonon and coherent potential approximations. However, while the first part of the defect spectral density, attributed to the propagating modes, turns out to be roughly explained, the localized part is properly described by none of these models, except for its mean frequency position. The large overall width appears so far impossible to be reproduced, representing a challenge for the physicists involved in quantum dynamics simulations.

  20. Communication: The H{sub 2}@C{sub 60} inelastic neutron scattering selection rule: Expanded and explained

    SciTech Connect

    Poirier, Bill

    2015-09-14

    Recently [M. Xu et al., J. Chem. Phys. 139, 064309 (2013)], an unexpected selection rule was discovered for the title system, contradicting the previously held belief that inelastic neutron scattering (INS) is not subject to any selection rules. Moreover, the newly predicted forbidden transitions, which emerge only in the context of coupled H{sub 2} translation-rotation (TR) dynamics, have been confirmed experimentally. However, a simple physical understanding, e.g., based on group theory, has been heretofore lacking. This is provided in the present paper, in which we (1) derive the correct symmetry group for the H{sub 2}@C{sub 60} TR Hamiltonian and eigenstates; (2) complete the INS selection rule, and show that the set of forbidden transitions is actually much larger than previously believed; and (3) evaluate previous theoretical and experimental results, in light of the new findings.

  1. Assignment of the Internal Vibrational Modes of C70 by Inelastic Neutron Scattering Spectroscopy and Periodic-DFT.

    PubMed

    Refson, Keith; Parker, Stewart F

    2015-10-01

    The fullerene C70 may be considered as the shortest possible nanotube capped by a hemisphere of C60 at each end. Vibrational spectroscopy is a key tool in characterising fullerenes, and C70 has been studied several times and spectral assignments proposed. Unfortunately, many of the modes are either forbidden or have very low infrared or Raman intensity, even if allowed. Inelastic neutron scattering (INS) spectroscopy is not subject to selection rules, and all the modes are allowed. We have obtained a new INS spectrum from a large sample recorded at the highest resolution available. An advantage of INS spectroscopy is that it is straightforward to calculate the spectral intensity from a model. We demonstrate that all previous assignments are incorrect in at least some respects and propose a new assignment based on periodic density functional theory (DFT) that successfully reproduces the INS, infrared, and Raman spectra.

  2. Complete assignment of the vibrational modes of C60 by inelastic neutron scattering spectroscopy and periodic-DFT.

    PubMed

    Parker, Stewart F; Bennington, Stephen M; Taylor, Jon W; Herman, Henryk; Silverwood, Ian; Albers, Peter; Refson, Keith

    2011-05-07

    In this paper we exploit the complementarity of inelastic neutron scattering (INS), infrared and Raman spectroscopies with ab initio calculations to generate an updated assignment of the vibrational modes of C(60). We have carried out periodic-DFT calculations of the high temperature face centred cubic phase modelled as the standard structure and also of the low temperature simple cubic phase, the latter for the first time. Our assignment differs from all previous work, however, it is the only one that is able to successfully reproduce the INS spectrum in terms of both transition energies and intensities. In addition to the INS spectrum we are also able to quantitatively simulate the major features of the infrared and Raman spectra in the high temperature phase and the infrared spectrum in the low temperature phase.

  3. Inelastic neutron scattering, lattice dynamics, and high-pressure phase stability of zircon-structured lanthanide orthophosphates

    SciTech Connect

    Bose, Preyoshi P.; Mittal, R; Chaplot, S L; Loong, C. K.; Boatner, Lynn A

    2010-01-01

    Inelastic neutron-scattering experiments and lattice-dynamical calculations are reported on a series of rareearth orthophosphates RPO4 R=Tm, Er, Ho, and Tb. The experimental phonon spectra for the compounds are in good agreement with our model calculations. The lattice-dynamical model is found useful for the calculation of various thermodynamic properties such as the lattice specific heat, thermal expansion, and equation of state of these compounds. The RPO4 compounds are known to transform to the scheelite body-centered tetragonal, I41 /a or monoclinic phase P21 /n at high pressures. Our calculations show that while the scheelite phase stabilizes at high pressure due to its lower volume, the monoclinic phase may occur as an intermediate phase depending on the ionic size of the R atom. The latter phase is stabilized at higher temperature at high pressure due to its high vibrational entropy. A pressure-temperature phase diagram is proposed.

  4. The application of inelastic neutron scattering to investigate the steam reforming of methane over an alumina-supported nickel catalyst

    NASA Astrophysics Data System (ADS)

    McFarlane, Andrew R.; Silverwood, Ian P.; Norris, Elizabeth L.; Ormerod, R. Mark; Frost, Christopher D.; Parker, Stewart F.; Lennon, David

    2013-12-01

    An alumina-supported nickel catalyst, previously used in methane reforming experiments employing CO2 as the oxidant, is applied here in the steam reforming variant of the process. Micro-reactor experiments are used to discern an operational window compatible with sample cells designed for inelastic neutron scattering (INS) experiments. INS spectra are recorded after 6 h reaction of a 1:1 mixture of CH4 and H2O at 898 K. Weak INS spectra are observed, indicating minimal hydrogen retention by the catalyst in this operational regime. Post-reaction, the catalyst is further characterised by powder X-ray diffraction, transmission electron microscopy and Raman scattering. In a comparable fashion to that seen for the ‘dry’ reforming experiments, the catalyst retains substantial quantities of carbon in the form of filamentous coke. The role for hydrogen incorporation by the catalyst is briefly considered.

  5. Temperature dependence of the low frequency dynamics of myoglobin. Measurement of the vibrational frequency distribution by inelastic neutron scattering.

    PubMed Central

    Cusack, S; Doster, W

    1990-01-01

    Inelastic neutron scattering spectra of myoglobin hydrated to 0.33 g water (D2O)/g protein have been measured in the low frequency range (1-150 cm-1) at various temperatures between 100 and 350 K. The spectra at low temperatures show a well-resolved maximum in the incoherent dynamic structure factor Sinc(q, omega) at approximately 25 cm-1 and no elastic broadening. This maximum becomes gradually less distinct above 180 K due to the increasing amplitude of quasielastic scattering which extends out to 30 cm-1. The vibrational frequency distribution derived independently at 100 and 180 K are very similar, suggesting harmonic behavior at these temperatures. This result has been used to separate the vibrational motion from the quasielastic motion at temperatures above 180 K. The form of the density of states of myoglobin is discussed in relation to that of other amorphous systems, to theoretical calculations of low frequency modes in proteins, and to previous observations by electron-spin relaxation of fractal-like spectral properties of proteins. The onset of quasielastic scattering above 180 K is indicative of a dynamic transition of the system and correlates with an anomalous increase in the atomic mean-squared displacements observed by Mössbauer spectroscopy (Parak, F., E. W. Knapp, and D. Kucheida. 1982. J. Mol. Biol. 161: 177-194.) and inelastic neutron scattering (Doster, W., S. Cusack, and W. Petry, 1989. Nature [Lond.]. 337: 754-756.) Similar behavior is observed for a hydrated powder of lysozyme suggesting that the low frequency dynamics of globular proteins have common features. PMID:2166599

  6. Inelastic neutron scattering investigation of magnetostructural excitations in the spin-Peierls organic system (TMTTF) 2P F6

    NASA Astrophysics Data System (ADS)

    Pouget, J. P.; Foury-Leylekian, P.; Petit, S.; Hennion, B.; Coulon, C.; Bourbonnais, C.

    2017-07-01

    One-dimensional (1D) conductors such as Bechgaard and Fabre salts are a prototypal example of correlated systems where the phase diagram is controlled by sizable electron-electron repulsions. In deuterated (TMTTF) 2P F6 , where this interaction achieves charge localization at ambient pressure on donor stacks, magnetostructural coupling plays a decisive role to stabilize a spin-Peierls (SPs) ground state at TSP=13 K . In this paper, we present the first inelastic neutron scattering investigation of SP magnetic excitations in organics. Our paper reveals the presence above TSP of sizable critical fluctuations leading to the formation of a pseudogap in the 1D antiferromagnetic (AF) S =1 /2 magnetic excitation spectrum of the donor stack, concomitant with the local formation of singlet of paired spins into dimers below TSPMF≈40 K . In addition, the inelastic neutron scattering investigation allows us also to probe the SP critical lattice dynamics and to show that at ambient pressure these dynamics are of relaxation or order-disorder type. Below TSP, our paper reveals the emergence of a two gap SP magnetic excitation spectrum towards a well-defined S =1 magnon mode and a continuum of two excitations, as theoretically predicted. Our measurements allow us to locate the ambient pressure SP phase of (TMTTF) 2P F6 in the classical (adiabatic) limit close to the classical/quantum crossover line. Then we provide arguments suggesting that pressurized (TMTTF) 2P F6 shifts to the quantum (antiadiabatic) SP gapped phase, which ends in a quantum critical point allowing the stabilization of an AF phase that competes with superconductivity at higher pressure. Finally, we propose that the magnetostructural coupling mechanism in the Fabre salts is caused by dimer charge/spin fluctuations driven by the coupling of donors with anions.

  7. Data processing workflow for time of flight polarized neutrons inelastic measurements

    NASA Astrophysics Data System (ADS)

    Savici, Andrei T.; Zaliznyak, Igor A.; Ovidiu Garlea, V.; Winn, Barry

    2017-06-01

    We discuss the data processing workflow for polarized neutron scattering measurements performed at HYSPEC [1] spectrometer at the Spallation Neutron Source, Oak Ridge National Laboratory. The effects of the focusing Heusler crystal polarizer and the wide- angle supermirror transmission polarization analyzer are added to the data processing flow of the non-polarized case. The implementation is done using the Mantid [2] software package.

  8. Data processing workflow for time of flight polarized neutrons inelastic measurements

    SciTech Connect

    Savici, Andrei T; Zaliznyak, Igor; Garlea, Vasile O; Winn, Barry L

    2017-01-01

    We discuss the data processing workflow for polarized neutron scattering measurements performed at HYSPEC spectrometer at the Spallation Neutron Source, Oak Ridge National Laboratory. The effects of the focusing Heusler crystal polarizer and the wide-angle supermirror transmission polarization analyzer are added to the data processing flow of the non-polarized case. The implementation is done using the Mantid software package.

  9. Time-of-Flight Elastic and Inelastic Neutron Scattering Studies on the Localized 4d Electron Layered Perovskite La5Mo4O16

    NASA Astrophysics Data System (ADS)

    Iida, Kazuki; Kajimoto, Ryoichi; Mizuno, Yusuke; Kamazawa, Kazuya; Inamura, Yasuhiro; Hoshikawa, Akinori; Yoshida, Yukihiko; Matsukawa, Takeshi; Ishigaki, Toru; Kawamura, Yukihiko; Ibuka, Soshi; Yokoo, Tetsuya; Itoh, Shinichi; Katsufuji, Takuro

    2017-06-01

    The magnetic structure and spin-wave excitations in the quasi-square-lattice layered perovskite compound La5Mo4O16 were studied by a combination of neutron diffraction and inelastic neutron scattering techniques using polycrystalline sample. Neutron powder diffraction refinement revealed that the magnetic structure is ferrimagnetic in the ab plane with antiferromagnetic stacking along the c-axis where the magnetic propagation vector is k = (0,0,1/2). The ordered magnetic moments are estimated to be 0.54(2)μB for Mo5+ (4d1) ions and 1.07(3)μB for Mo4+ (4d2) ions at 4 K, which are about half of the expected values. The inelastic neutron scattering results display strong easy-axis magnetic anisotropy along the c-axis due to the spin-orbit interaction in Mo ions evidenced by the spin gap at the magnetic zone center. The model Hamiltonian consisting of in-plane anisotropic exchange interactions, the interlayer exchange interaction, and easy-axis single-ion anisotropy can explain our inelastic neutron scattering data well. Strong Ising-like anisotropy and weak interlayer coupling compared with the intralayer exchange interaction can explain both the high-temperature magnetoresistance and long-time magnetization decay recently observed in La5Mo4O16.

  10. Cross sections and partial kerma factors for elastic and inelastic neutron scattering from nitrogen, oxygen and calcium at En = 21.6 MeV.

    PubMed

    Olsson, N; Ramström, E; Trostell, B

    1990-09-01

    The Studsvik high-resolution, low-background time-of-flight facility has been used to measure differential neutron scattering cross sections for nitrogen, oxygen and calcium at a neutron energy of 21.6 MeV. Angular distributions in the range 10 degrees-160 degrees have been measured for both elastic and inelastic scattering from some low-lying levels in the three nuclei. Angle-integrated cross sections have been determined by fitting Legendre polynomial expansions to the differential data. Partial kerma factors for elastic and inelastic scattering have been deduced from these fits. Analyses in terms of the spherical optical model and the distorted-wave Born approximation have provided information on potential parameters and deformations, which have been used to calculate cross sections and partial kerma factors. Comparisons have been made with other recent data sets and model predictions, as well as with the evaluated neutron data file ENDF/B-V.

  11. CdZnTe γ detector for deep inelastic neutron scattering on the VESUVIO spectrometer

    NASA Astrophysics Data System (ADS)

    Andreani, C.; D'Angelo, A.; Gorini, G.; Imberti, S.; Pietropaolo, A.; Rhodes, N. J.; Schooneveld, E. M.; Senesi, R.; Tardocchi, M.

    In this paper it is shown that solid-state cadmium-zinc-telluride (CZT) is a promising photon detector for neutron spectroscopy in a wide energy interval, ranging from thermal ( 25 meV) to epithermal ( 70 eV) neutron energies. In the present study two CZT detectors were tested as part of the inverse-geometry neutron spectrometer VESUVIO operating at the ISIS pulsed neutron source. The response of the CZT detector to photon emission from radiative neutron capture in 238U was determined by biparametric measurements of neutron time of flight and photon energy. The scattering response function F(y) from a Pb sample has been derived using both CZT and conventional 6Li-glass scintillator detectors. The former showed both an improved signal to background ratio and higher efficiency as compared to 6Li glass, allowing us to measure F(y) up to the fourth 238U absorption energy (Er=66.02 eV). Due to the small size of CZT detectors, their use is envisaged in arrays, with high spatial resolution, for neutron-scattering studies at high energy (ω>1 eV) and low wavevector (q <10 Å-1) transfers.

  12. Inelastic neutron scattering cross sections for Ge76 relevant to background in neutrinoless double- β decay experiments

    DOE PAGES

    Crider, B. P.; Peters, E. E.; Allmond, J. M.; ...

    2015-09-11

    The experimental signature in searches for the neutrinoless double- decay of 76Ge is a peak near 2039 keV in the spectrum. Given the low probability of the process, it is important that the background in this region be well understood. Moreover, inelastic scattering reactions with neutrons from muon-induced interactions and ( ,n) reactions in the surrounding materials or in the detector can provide contributions to the background. We also measured the production cross sections for rays from the 76Ge(n,n ) reaction in the 2039-keV region at incident neutron energies up to 4.9 MeV. In addition to determining that the crossmore » sections of a previously known 2040.7-keV ray from the 3952-keV level in 76 Ge are rather small, we find that a larger contribution arises from a 2037.5-keV ray which is attributed to a newly identified level at 3147 keV in 76Ge. Finally, a third contribution is also possible from another new level at 3577 keV. These results indicate that the 2039-keV region in 76Ge neutrinoless double- decay searches is more complex than was previously thought.« less

  13. Inelastic neutron scattering of the itinerant magnets Cr2Te3 and tr-Cr5Te8

    NASA Astrophysics Data System (ADS)

    Aczel, Adam; Granroth, Garrett; Ghimire, Nirmal; McGuire, Michael; Mandrus, David; Nagler, Steve

    2012-02-01

    Itinerant magnets based on transition metal chalcogenide compounds are of current interest, in part due to their relationship to the parent compounds of Fe-based superconductors. Two particularly interesting systems in this family are the chromium tellurides Cr2Te3 and trigonal (tr) Cr5Te8. These materials crystallize in layered structures with alternating partially and fully-occupied planes of Cr atoms stacked along the c-axis. Magnetization measurements along different crystallographic directions show a net ferromagnetic response and large magnetic anisotropy. In addition, the saturation moments are smaller than predicted by an ionic model; consistent with itinerant behavior. Previous neutron diffraction results for Cr2Te3 revealed an ordered moment of < 0.2 μB in the partially-occupied planes. We examined the magnetic excitations in these materials by powder neutron spectroscopy measurements using the SEQUOIA instrument at the SNS. We find similar moment sizes for the magnetic Cr atoms of both systems. However, despite their similar crystal structures, ordered moment sizes, and chemical compositions, their magnetic excitation spectra are strikingly different. We compare our data to the predictions of various models in an effort to determine the relevant exchange parameters, put constraints on their magnitudes, and understand the differences between the inelastic magnetic spectra. We find that exchange along the c-direction is critical to explain our data.

  14. Inelastic neutron scattering cross sections for 76Ge relevant to background in neutrinoless double-β decay experiments

    NASA Astrophysics Data System (ADS)

    Crider, B. P.; Peters, E. E.; Allmond, J. M.; McEllistrem, M. T.; Prados-Estévez, F. M.; Ross, T. J.; Vanhoy, J. R.; Yates, S. W.

    2015-09-01

    The experimental signature in searches for the neutrinoless double-β decay of 76Ge is a peak near 2039 keV in the spectrum. Given the low probability of the process, it is important that the background in this region be well understood. Inelastic scattering reactions with neutrons from muon-induced interactions and (α ,n ) reactions in the surrounding materials or in the detector can provide contributions to the background. We have measured the production cross sections for γ rays from the 76Ge(n ,n'γ ) reaction in the 2039-keV region at incident neutron energies up to 4.9 MeV. In addition to determining that the cross sections of a previously known 2040.7-keV γ ray from the 3952-keV level in 76Ge are rather small, we find that a larger contribution arises from a 2037.5-keV γ ray which is attributed to a newly identified level at 3147 keV in 76Ge. A third contribution is also possible from another new level at 3577 keV. These results indicate that the 2039-keV region in 76Ge neutrinoless double-β decay searches is more complex than was previously thought.

  15. Neutron transition strengths of 2{sub 1}{sup +} states in the neutron-rich oxygen isotopes determined from inelastic proton scattering

    SciTech Connect

    Nguyen Dang Chien; Khoa, Dao T.

    2009-03-15

    A coupled-channel analysis of the {sup 18,20,22}O(p,p{sup '}) data has been performed to determine the neutron transition strengths of the 2{sub 1}{sup +} states in oxygen targets, using the microscopic optical potential and inelastic form factor calculated in the folding model. A complex density- and isospin-dependent version of the CDM3Y6 interaction was constructed, based on the Brueckner-Hartree-Fock calculation of nuclear matter, for the folding model input. Given an accurate isovector density dependence of the CDM3Y6 interaction, the isoscalar ({delta}{sub 0}) and isovector ({delta}{sub 1}) deformation lengths of the 2{sub 1}{sup +} states in {sup 18,20,22}O have been extracted from the folding model analysis of the (p,p{sup '}) data. A specific N dependence of {delta}{sub 0} and {delta}{sub 1} has been established which can be linked to the neutron shell closure occurring at N approaching 16. The strongest isovector deformation was found for the 2{sub 1}{sup +} state in {sup 20}O, with {delta}{sub 1} about 2.5 times larger than {delta}{sub 0}, which indicates a strong core polarization by the valence neutrons in {sup 20}O. The ratios of the neutron/proton transition matrix elements (M{sub n}/M{sub p}) determined for the 2{sub 1}{sup +} states in {sup 18,20}O have been compared with those deduced from the mirror symmetry, using the measured B(E2) values of the 2{sub 1}{sup +} states in the proton-rich {sup 18}Ne and {sup 20}Mg nuclei, to discuss the isospin impurity in the 2{sub 1}{sup +} excitation of the A=18, T=1 and A=20, T=2 isobars.

  16. Distribution of glass transition temperatures Tg in polystyrene thin films as revealed by low-energy muon spin relaxation: A comparison with neutron reflectivity results.

    PubMed

    Kanaya, Toshiji; Ogawa, Hiroki; Kishimoto, Mizuki; Inoue, Rintaro; Suter, Andreas; Prokscha, Thomas

    2015-08-01

    In a previous paper [Phys. Rev. E 83, 021801 (2011)] we performed neutron reflectivity (NR) measurements on a five-layer polystyrene (PS) thin film consisting of alternatively stacked deuterated polystyrene (dPS) and hydrogenated polystyrene (hPS) layers (dPS/hPS/dPS/hPS/dPS, ∼100 nm thick) on a Si substrate to reveal the distribution of Tg along the depth direction. Information on the Tg distribution is very useful to understand the interesting but unusual properties of polymer thin films. However, one problem that we have to clarify is if there are effects of deuterium labeling on Tg or not. To tackle the problem we performed low-energy muon spin relaxation (μSR) measurements on the above-mentioned deuterium-labeled five-layer PS thin film as well as dPS and hPS single-layer thin films ∼100 nm thick as a function of muon implantation energy. It was found that the deuterium labeling had no significant effects on the Tg distribution, guaranteeing that we can safely discuss the unusual thin film properties based on the Tg distribution revealed by NR on the deuterium-labeled thin films. In addition, the μSR result suggested that the higher Tg near the Si substrate is due to the strong orientation of phenyl rings.

  17. STUDY MAGNETIC EXCITATIONS IN DOPED TRANSITION METAL OXIDES USING INELASTIC NEUTRON SCATTERING

    SciTech Connect

    Dai, Pengcheng

    2014-02-18

    Understanding the interplay between magnetism and superconductivity continues to be a “hot” topic in modern condensed matter physics. The discovery of high-temperature superconductivity in iron-based materials in 2008 provided an unique opportunity to compare and contrast these materials with traditional high-Tc copper oxide superconductors. Neutron scattering plays an important role in determining the dynamical spin properties in these materials. This proposal is a continuation of previous DOE supported proposal. This report summarizes the final progress we have made over from May 2005 till Aug. 2013. Overall, we continue to carry out extensive neutron scattering experiments on Fe-based materials, focusing on understanding their magnetic properties. In addition, we have established a materials laboratory at UT that has allowed us to grow these superconductors. Because neutron scattering typically demands a large amount of samples, by growing these materials in our own laboratory, we can now pursuit neutron scattering experiments over the entire electronic phase diagram, focusing on regions of interests. The material synthesis laboratory at UT was established entirely with the support of DOE funding. This not only allowed us to carry out neutron scattering experiments, but also permit us to provide samples to other US/International collaborators for studying these materials.

  18. Neutron inelastic-scattering cross sections of /sup 232/Th, /sup 233/U, /sup 235/U, /sup 238/U, /sup 239/Pu and /sup 240/Pu. [LMFBR

    SciTech Connect

    Smith, A.B.; Guenther, P.T.

    1982-01-01

    Differential-neutron-emission cross sections of /sup 232/Th, /sup 233/U, /sup 235/U, /sup 238/U, /sup 239/Pu and /sup 240/Pu are measured between approx. = 1.0 and 3.5 MeV with the angle and magnitude detail needed to provide angle-integrated emission cross sections to approx. < 3% accuracies. Emitted-neutron resolutions are quantitatively defined and vary from approx. = 0.1 to 0.35 MeV. The experimental results are corrected for fisson-neutron contributions to obtain pseudo-elastic-neutron-scattering cross sections which, together with the neutron total cross sections, define the non-elastic cross sections to within well specified energy resolutions. These results imply inelastic-neutron-scattering cross sections which are compared with comparable quantities derived from ENDF/B-V. Good general agreement is noted for /sup 232/Th, /sup 233/U, /sup 235/U and /sup 238/U inelastic-scattering values, poor agreement is observed for /sup 240/Pu, and a serious discrepancy exists in the case of /sup 239/Pu.

  19. A New On-the-Fly Sampling Method for Incoherent Inelastic Thermal Neutron Scattering Data in MCNP6

    SciTech Connect

    Pavlou, Andrew Theodore; Brown, Forrest B.; Ji, Wei

    2014-09-02

    At thermal energies, the scattering of neutrons in a system is complicated by the comparable velocities of the neutron and target, resulting in competing upscattering and downscattering events. The neutron wavelength is also similar in size to the target's interatomic spacing making the scattering process a quantum mechanical problem. Because of the complicated nature of scattering at low energies, the thermal data files in ACE format used in continuous-energy Monte Carlo codes are quite large { on the order of megabytes for a single temperature and material. In this paper, a new storage and sampling method is introduced that is orders of magnitude less in size and is used to sample scattering parameters at any temperature on-the-fly. In addition to the reduction in storage, the need to pre-generate thermal scattering data tables at fine temperatures has been eliminated. This is advantageous for multiphysics simulations which may involve temperatures not known in advance. A new module was written for MCNP6 that bypasses the current S(α,β) table lookup in favor of the new format. The new on-the-fly sampling method was tested for graphite for two benchmark problems at ten temperatures: 1) an eigenvalue test with a fuel compact of uranium oxycarbide fuel homogenized into a graphite matrix, 2) a surface current test with a \\broomstick" problem with a monoenergetic point source. The largest eigenvalue difference was 152pcm for T= 1200K. For the temperatures and incident energies chosen for the broomstick problem, the secondary neutron spectrum showed good agreement with the traditional S(α,β) sampling method. These preliminary results show that sampling thermal scattering data on-the-fly is a viable option to eliminate both the storage burden of keeping thermal data at discrete temperatures and the need to know temperatures before simulation runtime.

  20. Measurement of the structure function of the nearly free neutron using spectator tagging in inelastic 2H(e ,e'ps )X scattering with CLAS

    NASA Astrophysics Data System (ADS)

    Tkachenko, S.; Baillie, N.; Kuhn, S. E.; Zhang, J.; Arrington, J.; Bosted, P.; Bültmann, S.; Christy, M. E.; Fenker, H.; Griffioen, K. A.; Kalantarians, N.; Keppel, C. E.; Melnitchouk, W.; Tvaskis, V.; Adhikari, K. P.; Aghasyan, M.; Amaryan, M. J.; Anefalos Pereira, S.; Avakian, H.; Ball, J.; Baltzell, N. A.; Battaglieri, M.; Bedlinskiy, I.; Biselli, A. S.; Briscoe, W. J.; Brooks, W. K.; Burkert, V. D.; Carman, D. S.; Celentano, A.; Chandavar, S.; Charles, G.; Cole, P. L.; Contalbrigo, M.; Cortes, O.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Dodge, G. E.; Doughty, D.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fedotov, G.; Fleming, J. A.; Garillon, B.; Gevorgyan, N.; Ghandilyan, Y.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Golovatch, E.; Gothe, R. W.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Harrison, N.; Hattawy, M.; Hicks, K.; Ho, D.; Holtrop, M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Jo, H. S.; Keller, D.; Khandaker, M.; Kim, A.; Kim, W.; King, P. M.; Klein, A.; Klein, F. J.; Koirala, S.; Kubarovsky, V.; Kuleshov, S. V.; Lenisa, P.; Lewis, S.; Livingston, K.; Lu, H.; MacCormick, M.; MacGregor, I. J. D.; Markov, N.; Mayer, M.; McKinnon, B.; Mineeva, T.; Mirazita, M.; Mokeev, V.; Montgomery, R. A.; Moutarde, H.; Munoz Camacho, C.; Nadel-Turonski, P.; Niccolai, S.; Niculescu, G.; Niculescu, I.; Osipenko, M.; Pappalardo, L. L.; Paremuzyan, R.; Park, K.; Pasyuk, E.; Phillips, J. J.; Pisano, S.; Pogorelko, O.; Pozdniakov, S.; Price, J. W.; Procureur, S.; Protopopescu, D.; Puckett, A. J. R.; Rimal, D.; Ripani, M.; Rizzo, A.; Rosner, G.; Rossi, P.; Roy, P.; Sabatié, F.; Schott, D.; Schumacher, R. A.; Seder, E.; Senderovich, I.; Sharabian, Y. G.; Simonyan, A.; Smith, G. D.; Sober, D. I.; Sokhan, D.; Stepanyan, S.; Stepanyan, S. S.; Strauch, S.; Tang, W.; Ungaro, M.; Vlassov, A. V.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Watts, D.; Wei, X.; Weinstein, L. B.; Wood, M. H.; Zana, L.; Zonta, I.; CLAS Collaboration

    2014-04-01

    Background: Much less is known about neutron structure than that of the proton due to the absence of free neutron targets. Neutron information is usually extracted from data on nuclear targets such as deuterium, requiring corrections for nuclear binding and nucleon off-shell effects. These corrections are model dependent and have significant uncertainties, especially for large values of the Bjorken scaling variable x . As a consequence, the same data can lead to different conclusions, for example, about the behavior of the d quark distribution in the proton at large x . Purpose: The Barely Off-shell Nucleon Structure experiment at Jefferson Lab measured the inelastic electron-deuteron scattering cross section, tagging spectator protons in coincidence with the scattered electrons. This method reduces nuclear binding uncertainties significantly and has allowed for the first time a (nearly) model-independent extraction of the neutron structure function F2(x ,Q2) in the resonance and deep-inelastic regions. Method: A novel compact radial time projection chamber was built to detect protons with momentum between 70 and 150 MeV/c and over a nearly 4 π angular range. For the extraction of the free-neutron structure function F2n, spectator protons at backward angles (>100∘ relative to the momentum transfer) and with momenta below 100 MeV/c were selected, ensuring that the scattering took place on a nearly free neutron. The scattered electrons were detected with Jefferson Lab's CLAS spectrometer, with data taken at beam energies near 2, 4, and 5 GeV. Results: The extracted neutron structure function F2n and its ratio to the inclusive deuteron structure function F2d are presented in both the resonance and the deep-inelastic regions for momentum transfer squared Q2 between 0.7 and 5 GeV2/c2 , invariant mass W between 1 and 2.7 GeV/c2 , and Bjorken x between 0.25 and 0.6 (in the deep-inelastic scattering region). The dependence of the semi-inclusive cross section on the

  1. Applying Monte-Carlo simulations to optimize an inelastic neutron scattering system for soil carbon analysis

    USDA-ARS?s Scientific Manuscript database

    Computer Monte-Carlo (MC) simulations (Geant4) of neutron propagation and acquisition of gamma response from soil samples was applied to evaluate INS system performance characteristic [sensitivity, minimal detectable level (MDL)] for soil carbon measurement. The INS system model with best performanc...

  2. Magnetic Transitions in Iron Porphyrin Halides by Inelastic Neutron Scattering and Ab-initio Studies of Zero-Field Splittings

    DOE PAGES

    Stavretis, Shelby E.; Atanasov, Mihail; Podlesnyak, Andrey A.; ...

    2015-10-02

    Zero-field splitting (ZFS) parameters of nondeuterated metalloporphyrins [Fe(TPP)X] (X = F, Br, I; H2TPP = tetraphenylporphyrin) are determined by inelastic neutron scattering (INS). The ZFS values are D = 4.49(9) cm–1 for tetragonal polycrystalline [Fe(TPP)F], and D = 8.8(2) cm–1, E = 0.1(2) cm–1 and D = 13.4(6) cm–1, E = 0.3(6) cm–1 for monoclinic polycrystalline [Fe(TPP)Br] and [Fe(TPP)I], respectively. Along with our recent report of the ZFS value of D = 6.33(8) cm–1 for tetragonal polycrystalline [Fe(TPP)Cl], these data provide a rare, complete determination of ZFS parameters in a metalloporphyrin halide series. The electronic structure of [Fe(TPP)X] (X =more » F, Cl, Br, I) has been studied by multireference ab initio methods: the complete active space self-consistent field (CASSCF) and the N-electron valence perturbation theory (NEVPT2) with the aim of exploring the origin of the large and positive zero-field splitting D of the 6A1 ground state. D was calculated from wave functions of the electronic multiplets spanned by the d5 configuration of Fe(III) along with spin–orbit coupling accounted for by quasi degenerate perturbation theory. Results reproduce trends of D from inelastic neutron scattering data increasing in the order from F, Cl, Br, to I. A mapping of energy eigenvalues and eigenfunctions of the S = 3/2 excited states on ligand field theory was used to characterize the σ- and π-antibonding effects decreasing from F to I. This is in agreement with similar results deduced from ab initio calculations on CrX63- complexes and also with the spectrochemical series showing a decrease of the ligand field in the same directions. A correlation is found between the increase of D and decrease of the π- and σ-antibonding energies eλX (λ = σ, π) in the series from X = F to I. Analysis of this correlation using second-order perturbation theory expressions in terms of angular overlap parameters rationalizes the experimentally deduced trend

  3. Magnetic Transitions in Iron Porphyrin Halides by Inelastic Neutron Scattering and Ab Initio Studies of Zero-Field Splittings.

    PubMed

    Stavretis, Shelby E; Atanasov, Mihail; Podlesnyak, Andrey A; Hunter, Seth C; Neese, Frank; Xue, Zi-Ling

    2015-10-19

    Zero-field splitting (ZFS) parameters of nondeuterated metalloporphyrins [Fe(TPP)X] (X = F, Br, I; H₂TPP = tetraphenylporphyrin) have been directly determined by inelastic neutron scattering (INS). The ZFS values are D = 4.49(9) cm⁻¹ for tetragonal polycrystalline [Fe(TPP)F], and D = 8.8(2) cm⁻¹, E = 0.1(2) cm⁻¹ and D = 13.4(6) cm⁻¹, E = 0.3(6) cm⁻¹ for monoclinic polycrystalline [Fe(TPP)Br] and [Fe(TPP)I], respectively. Along with our recent report of the ZFS value of D = 6.33(8) cm⁻¹ for tetragonal polycrystalline [Fe(TPP)Cl], these data provide a rare, complete determination of ZFS parameters in a metalloporphyrin halide series. The electronic structure of [Fe(TPP)X] (X = F, Cl, Br, I) has been studied by multireference ab initio methods: the complete active space self-consistent field (CASSCF) and the N-electron valence perturbation theory (NEVPT2) with the aim of exploring the origin of the large and positive zero-field splitting D of the ⁶A₁ ground state. D was calculated from wave functions of the electronic multiplets spanned by the d⁵ configuration of Fe(III) along with spin–orbit coupling accounted for by quasi degenerate perturbation theory. Results reproduce trends of D from inelastic neutron scattering data increasing in the order from F, Cl, Br, to I. A mapping of energy eigenvalues and eigenfunctions of the S = 3/2 excited states on ligand field theory was used to characterize the σ- and π-antibonding effects decreasing from F to I. This is in agreement with similar results deduced from ab initio calculations on CrX₆³⁻ complexes and also with the spectrochemical series showing a decrease of the ligand field in the same directions. A correlation is found between the increase of D and decrease of the π- and σ-antibonding energies e(λ)(X) (λ = σ, π) in the series from X = F to I. Analysis of this correlation using second-order perturbation theory expressions in terms of angular overlap parameters rationalizes the

  4. IRiS—Exploring new frontiers in neutron-rich isotopes of the heaviest elements with a new Inelastic Reaction Isotope Separator

    NASA Astrophysics Data System (ADS)

    Dvorak, J.; Block, M.; Düllmann, Ch. E.; Heinz, S.; Herzberg, R.-D.; Schädel, M.

    2011-10-01

    A dedicated Inelastic Reaction Isotope Separator (IRiS) for multi-nucleon transfer products will be designed and installed at GSI. Research at IRiS will focus on the investigation of new neutron-rich isotopes of the heaviest elements, study of which will advance various research fields, such as nuclear chemistry, nuclear and atomic physics, as well as nuclear astrophysics. The scientific motivation for this project and the alternative design options for the separator and its main components are discussed.

  5. Nuclear structure of 76Ge from inelastic neutron scattering measurements and shell model calculations

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, S.; Crider, B. P.; Brown, B. A.; Ashley, S. F.; Chakraborty, A.; Kumar, A.; McEllistrem, M. T.; Peters, E. E.; Prados-Estévez, F. M.; Yates, S. W.

    2017-01-01

    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 (E 2 ) 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.

  6. Inelastic neutron scattering study of tetramethylpyrazine in the complex with chloranilic acid

    NASA Astrophysics Data System (ADS)

    Prager, M.; Pawlukojc, A.; Sobczyk, L.; Grech, E.; Grimm, H.

    2005-09-01

    The tunnel splitting of the methyl librational ground states in the hydrogen bonded tetramethylpyrazine-chloranilic acid (TMP-CLA) complex are determined for temperatures T<=28 K by high resolution neutron spectroscopy. Three tunnel modes are resolved at T = 2.4 K. Their relative intensities show that the crystal structure must be different from the proposed space group. Tunnelling and methyl librational modes from the measured density of states are combined into rotational potentials. There are discrepancies of activation energies calculated for these potentials and those obtained from quasielastic scattering of neutrons at T>=50 K due to structural differences in the two respective temperature regimes. Rotational potentials in TMP-CLA are significantly weaker as in pure TMP.

  7. Quasi- and inelastic neutron scattering to investigate the molecular dynamics of discotic molecules in the bulk

    NASA Astrophysics Data System (ADS)

    Krause, Christina; Zorn, Reiner; Frick, Bernhard; Schönhals, Andreas

    2015-01-01

    In- and quasielastic neutron scattering is employed to investigate both the vibrational density of states and the molecular dynamics of two homologous discotic liquid crystals (DLC) with different length of the alkyl side chain based on a triphenylene derivate. For both compounds characteristic low frequency excess contributions to the vibrational density of states are found. Therefore it is concluded that these liquid crystals show a glass-like behaviour. Elastic scans further show that in these materials a rich molecular dynamics takes place.

  8. Direct observation of electronic and nuclear ground state splitting in external magnetic field by inelastic neutron scattering on oxidized ferrocene and ferrocene containing polymers

    NASA Astrophysics Data System (ADS)

    Appel, Markus; Frick, Bernhard; Elbert, Johannes; Gallei, Markus; Stühn, Bernd

    2015-01-01

    The quantum mechanical splitting of states by interaction of a magnetic moment with an external magnetic field is well known, e.g., as Zeeman effect in optical transitions, and is also often seen in magnetic neutron scattering. We report excitations observed in inelastic neutron spectroscopy on the redox-responsive polymer poly(vinylferrocene). They are interpreted as splitting of the electronic ground state in the organometallic ferrocene units attached to the polymer chain where a magnetic moment is created by oxidation. In a second experiment using high resolution neutron backscattering spectroscopy we observe the hyperfine splitting, i.e., interaction of nuclear magnetic moments with external magnetic fields leading to sub-μeV excitations observable in incoherent neutron spin-flip scattering on hydrogen and vanadium nuclei.

  9. Unconventional superconductivity in Ba(0.6)K(0.4)Fe2As2 from inelastic neutron scattering.

    PubMed

    Christianson, A D; Goremychkin, E A; Osborn, R; Rosenkranz, S; Lumsden, M D; Malliakas, C D; Todorov, I S; Claus, H; Chung, D Y; Kanatzidis, M G; Bewley, R I; Guidi, T

    2008-12-18

    A new family of superconductors containing layers of iron arsenide has attracted considerable interest because of their high transition temperatures (T(c)), some of which are >50 K, and because of similarities with the high-T(c) copper oxide superconductors. In both the iron arsenides and the copper oxides, superconductivity arises when an antiferromagnetically ordered phase has been suppressed by chemical doping. A universal feature of the copper oxide superconductors is the existence of a resonant magnetic excitation, localized in both energy and wavevector, within the superconducting phase. This resonance, which has also been observed in several heavy-fermion superconductors, is predicted to occur when the sign of the superconducting energy gap takes opposite values on different parts of the Fermi surface, an unusual gap symmetry which implies that the electron pairing interaction is repulsive at short range. Angle-resolved photoelectron spectroscopy shows no evidence of gap anisotropy in the iron arsenides, but such measurements are insensitive to the phase of the gap on separate parts of the Fermi surface. Here we report inelastic neutron scattering observations of a magnetic resonance below T(c) in Ba(0.6)K(0.4)Fe(2)As(2), a phase-sensitive measurement demonstrating that the superconducting energy gap has unconventional symmetry in the iron arsenide superconductors.

  10. An inelastic incoherent neutron scattering study of water in small-pored zeolites and other water-bearing minerals

    NASA Astrophysics Data System (ADS)

    Line, Christina M. B.; Kearley, G. J.

    2000-05-01

    Inelastic neutron scattering spectra of the zeolites natrolite Na2Al2Si3O10 2H2O, wairakite CaAl2Si4O12 2H2O, scolecite CaAl2Si3O10 3H2O, and bikitaite Li2Al2Si4O12. 2H2O, together with the sheet silicate apophyllite KCa4Si8O20(F, OH) 8H2O, are shown here. We show clear trends across these minerals, illustrating the relative influence of hydrogen bonding and cation bonding. For some of these spectra, the bands are clearly separated, permitting a discussion of their assignments. In particular, we can identify librational bands (L) or librational edge (LE) and translational (cation-water stretch) bands (C), and by elimination can tentatively assign bands as hydrogen-bond stretch bands (H), as follows (frequencies given in meV): Natrolite: 13,18 (C) 26 (H), 64,68,87 (L); Apophyllite 17,26 (C), 35 (H) 64,79,98 (L); Scolecite 10 (C), 22,29,36,41 (H), 46 (LE); Wairakite 12 (C), 30 (LE); Bikitaite 13 (C), 22 (H), 34 (LE), 70(L). The results are compared with those for ice and are explained in terms of the nearest-neighbor environment of the water molecule.

  11. Inelastic neutron scattering study of binding of para-hydrogen in an ultra-microporous metal-organic framework

    NASA Astrophysics Data System (ADS)

    Yang, Sihai; Ramirez-Cuesta, Anibal J.; Schröder, Martin

    2014-01-01

    Metal-organic framework (MOF) materials show promise for H2 storage and it is widely predicted by computational modelling that MOFs incorporating ultra-micropores are optimal for H2 binding due to enhanced overlapping potentials. We report the investigation using inelastic neutron scattering of the interaction of H2 in an ultra-microporous MOF material showing low H2 uptake capacity. The study has revealed that adsorbed H2 at 5 K has a liquid recoil motion along the channel with very little interaction with the MOF host, consistent with the observed low uptake. The low H2 uptake is not due to incomplete activation or decomposition as the desolvated MOF shows CO2 uptake with a measured pore volume close to that of the single crystal pore volume. This study represents a unique example of surprisingly low H2 uptake within a MOF material, and complements the wide range of studies on systems showing higher uptake capacities and binding interactions.

  12. Looking inside the pores of a MCM-41 based Mo heterogeneous styrene oxidation catalyst: an inelastic neutron scattering study.

    PubMed

    Fernandes, Cristina I; Rudić, Svemir; Vaz, Pedro D; Nunes, Carla D

    2016-07-14

    Styrene oxidation mediated by a Mo-based mesoporous catalyst can yield selectively styrene oxide or benzaldehyde. Kinetic data evidenced that styrene oxide is the initial single-product formed by the catalytic Mo-mediated process. However, after some hours of reaction benzaldehyde yield rises while that of the epoxide decreases concomitantly. The mechanistic proposal pointed to a surface assisted acid-base mechanism by which styrene oxide is interconverted into benzaldehyde through over-oxidation and cleavage of the C-C bond and releases formaldehyde as well. In an attempt to gain some insight into whether this mechanistic proposal is realistic we have conducted a combined DRIFT and inelastic neutron scattering (INS) study to assess the adsorbed species at the catalyst's surface and confirm the mechanistic proposal. INS and DRIFT provided complementary insight into surface-adsorbed species by probing donor (INS) and acceptor (DRIFT) species. INS also allowed for an estimation of product selectivity by means of a Job method stressing the power of the technique.

  13. Inelastic neutron scattering study of reline: shedding light on the hydrogen bonding network of deep eutectic solvents.

    PubMed

    Araujo, C F; Coutinho, J A P; Nolasco, M M; Parker, S F; Ribeiro-Claro, P J A; Rudić, S; Soares, B I G; Vaz, P D

    2017-07-21

    The solids choline chloride and urea, mixed in a 1 : 2 molar proportion, form the iconic deep eutectic solvent "Reline". A combination of computational and vibrational spectroscopy tools, including inelastic neutron scattering (INS), have been used to probe intermolecular interactions in the eutectic mixture. Reline's experimental spectra were estimated using discrete and periodic ab initio calculations of a molecular aggregate with two choline chloride and four urea units. This is the minimum size required to achieve satisfactory agreement with experiment, as smaller clusters cannot represent all of reline's significant intermolecular interactions. The INS spectrum of reline, compared with that of pure choline chloride, reveals a displacement of chloride anions away from their preferred positions on top of choline's methyl groups, whose torsional movement becomes less hindered in the mixture. Urea, which adopts a planar (sp(2)) shape in the crystal, becomes non-planar (sp(3)) in reline, a feature herein discussed for the first time. In reline, urea molecules form a wide range of hydrogen bonds, from soft contacts to stronger associations, the latter being responsible for the deviation from ideality. The chloride's interactions with choline are largely conserved at the hydroxyl end while becoming weaker at the cationic headgroup. The interplay of soft and strong interactions confers flexibility to the newly formed hydrogen-bond network and allows the ensemble to remain liquid at room temperature.

  14. Inelastic neutron scattering, Raman, vibrational analysis with anharmonic corrections, and scaled quantum mechanical force field for polycrystalline L-alanine

    NASA Astrophysics Data System (ADS)

    Williams, Robert W.; Schlücker, Sebastian; Hudson, Bruce S.

    2008-01-01

    A scaled quantum mechanical harmonic force field (SQMFF) corrected for anharmonicity is obtained for the 23 K L-alanine crystal structure using van der Waals corrected periodic boundary condition density functional theory (DFT) calculations with the PBE functional. Scale factors are obtained with comparisons to inelastic neutron scattering (INS), Raman, and FT-IR spectra of polycrystalline L-alanine at 15-23 K. Calculated frequencies for all 153 normal modes differ from observed frequencies with a standard deviation of 6 wavenumbers. Non-bonded external k = 0 lattice modes are included, but assignments to these modes are presently ambiguous. The extension of SQMFF methodology to lattice modes is new, as are the procedures used here for providing corrections for anharmonicity and van der Waals interactions in DFT calculations on crystals. First principles Born-Oppenheimer molecular dynamics (BOMD) calculations are performed on the L-alanine crystal structure at a series of classical temperatures ranging from 23 K to 600 K. Corrections for zero-point energy (ZPE) are estimated by finding the classical temperature that reproduces the mean square displacements (MSDs) measured from the diffraction data at 23 K. External k = 0 lattice motions are weakly coupled to bonded internal modes.

  15. An inelastic neutron scattering and NIR-FT Raman spectroscopy study of chloroform and trichloroethylene in faujasites

    SciTech Connect

    Davidson, A.M.; Mellot, C.F.; Eckert, J.; Cheetham, A.K.

    2000-01-27

    Molecular information about the nature and the strength of the interactions between chloroform and trichloroethylene (TCE) sorbates and siliceous FAU, NaY, and NaX zeolites was obtained by inelastic neutron scattering (INS) and Raman spectroscopies. The spectral features of the two sorbates differ in terms of their frequencies, splittings, and line widths from the ones of chloroform and TCE molecules in the gas phase. In conjunction with the authors simulation results, these differences are rationalized by assuming that, in siliceous FAU, the two sorbates undergo a nondissociative adsorption involving the formation of an H{sub sorbate}{hor{underscore}ellipsis}O{sub framework} hydrogen bond and Cl{sub sorbate}{hor{underscore}ellipsis}O{sub framework} van der Waals interactions, whereas in NaY and NaX, additional Cl{sub sorbate}{hor{underscore}ellipsis}Na{sup +} electrostatic interactions are involved. Interestingly, no {pi}/Na{sup +} interaction takes place for TCE. These findings, which are in agreement with previous calorimetric and simulation results, confirm that the strength of the sorbate/zeolite interactions is correlated to the basicity of the zeolite and therefore increases in the sequence siliceous FAU < NaY < NaX, following the sequence of the heats of adsorption.

  16. Structure of kaolinite and influence of stacking faults: reconciling theory and experiment using inelastic neutron scattering analysis.

    PubMed

    White, Claire E; Kearley, Gordon J; Provis, John L; Riley, Daniel P

    2013-05-21

    The structure of kaolinite at the atomic level, including the effect of stacking faults, is investigated using inelastic neutron scattering (INS) spectroscopy and density functional theory (DFT) calculations. The vibrational dynamics of the standard crystal structure of kaolinite, calculated using DFT (VASP) with normal mode analysis, gives good agreement with the experimental INS data except for distinct discrepancies, especially for the low frequency modes (200-400 cm(-1)). By generating several types of stacking faults (shifts in the a,b plane for one kaolinite layer relative to the adjacent layer), it is seen that these low frequency modes are affected, specifically through the emergence of longer hydrogen bonds (O-H⋯O) in one of the models corresponding to a stacking fault of -0.3151a - 0.3151b. The small residual disagreement between observed and calculated INS is assigned to quantum effects (which are not taken into account in the DFT calculations), in the form of translational tunneling of the proton in the hydrogen bonds, which lead to a softening of the low frequency modes. DFT-based molecular dynamics simulations show that anharmonicity does not play an important role in the structural dynamics of kaolinite.

  17. Search for a reliable nucleic acid force field using neutron inelastic scattering and quantum mechanical calculations: Bases, nucleosides and nucleotides

    SciTech Connect

    Leulliot, Nicolas; Ghomi, Mahmoud; Jobic, Herve

    1999-06-15

    Neutron inelastic scattering (NIS), IR and Raman spectra of the RNA constituents: bases, nucleosides and nucleotides have been analyzed. The complementary aspects of these different experimental techniques makes them especially powerful for assigning the vibrational modes of the molecules of interest. Geometry optimization and harmonic force field calculations of these molecules have been undertaken by quantum mechanical calculations at several theoretical levels: Hartree-Fock (HF), Moller-plesset second-order perturbation (MP2) and Density Functional Theory (DFT). In all cases, it has been shown that HF calculations lead to insufficient results for assigning accurately the intramolecular vibrational modes. In the case of the nucleic bases, these discrepancies could be satisfactorily removed by introducing the correlation effects at MP2 level. However, the application of the MP2 procedure to the large size molecules such as nucleosides and nucleotides is absolutely impossible, taking into account the prohibitive computational time needed. On the basis of our results, the calculations at DFT levels using B3LYP exchange and correlation functional appear to be a cost-effective alternative in obtaining a reliable force field for the whole set of nucleic acid constituents.

  18. Applying Monte-Carlo simulations to optimize an inelastic neutron scattering system for soil carbon analysis.

    PubMed

    Yakubova, Galina; Kavetskiy, Aleksandr; Prior, Stephen A; Torbert, H Allen

    2017-10-01

    Computer Monte-Carlo (MC) simulations (Geant4) of neutron propagation and acquisition of gamma response from soil samples was applied to evaluate INS system performance characteristic [minimal detectible level (MDL), sensitivity] for soil carbon measurement. The INS system model with best performance characteristics was determined based on MC simulation results. Measurements of MDL using an experimental prototype based on this model demonstrated good agreement with simulated data. This prototype will be used as the base engineering design for a new INS system. Copyright © 2017. Published by Elsevier Ltd.

  19. Validation of the U-238 inelastic scattering neutron cross section through the EXCALIBUR dedicated experiment

    NASA Astrophysics Data System (ADS)

    Leconte, Pierre; Bernard, David

    2017-09-01

    EXCALIBUR is an integral transmission experiment based on the fast neutron source produced by the bare highly enriched fast burst reactor CALIBAN, located in CEA/DAM Valduc (France). Two experimental campaigns have been performed, one using a sphere of diameter 17 cm and one using two cylinders of 17 cm diameter 9 cm height, both made of metallic Uranium 238. A set of 15 different dosimeters with specific threshold energies have been employed to provide information on the neutron flux attenuation as a function of incident energy. Measurements uncertainties are typically in the range of 0.5-3% (1σ). The analysis of these experiments is performed with the TRIPOLI4 continuous energy Monte Carlo code. A calculation benchmark with validated simplifications is defined in order to improve the statistical convergence under 2%. Various 238U evaluations have been tested: JEFF-3.1.1, ENDF/B-VII.1 and the IB36 evaluation from IAEA. A sensitivity analysis is presented to identify the contribution of each reaction cross section to the integral transmission rate. This feedback may be of interest for the international effort on 238U, through the CIELO project.

  20. Measurements of the differential cross sections for elastic and inelastic scattering of 14-MeV neutrons in natural chromium, iron, nickel, and niobium

    SciTech Connect

    Christodoulou, E.G. . Dept. of Radiology); Tsirliganis, N.C. . Dept. of Electrical Engineering and Electronics); Knoll, G.F. . Dept. of Nuclear Engineering and Radiological Sciences)

    1999-07-01

    The time-of-flight technique was used with the ring scattering geometry in a laboratory with low neutron-scattering background to measure the angular distributions of the cross sections for elastic and inelastic scattering of 14-MeV neutrons in natural chromium, iron, nickel, and niobium. Specifically for inelastic scattering, the measurements included the 1.43- and 4.56-MeV levels of [sup 52]Cr; the 0.85-, (2.94 to 3.12)-, and (4.46 to 4.51)-MeV level groups of [sup 56]Fe; the 1.33-MeV level of [sup 60]Ni combined with the 1.45-MeV level of [sup 58]Ni; and the 4.48-MeV level of [sup 58]Ni. Pulses of neutrons with time width of 0.9 to 1.1 ns were produced via the D-T reaction in a 150-keV linear accelerator, with average intensities of 9 [times] 10[sup 8] n/s. The scattering angles ranged from [approximately]16 to [approximately]160 deg, with a typical step of [approximately]10 deg. The overall uncertainty for the elastic scattering cross section was in the range of 7 to 10% for all materials, except around the minima of the angular distribution for niobium. The uncertainties for the inelastic scattering cross sections were estimated to be between 8 and 24%. The measured angular distributions were compared with the evaluations in the ENDF/B-VI, JENDL-3, CENDL-2, BROND-2, and JEF-2 nuclear data libraries. For elastic scattering, there are no significant discrepancies in general, neither among the evaluations nor between the present data and the evaluations. For the inelastic scattering there are substantial discrepancies both in shape and magnitude among the evaluations (when available) as well as between the present data and the evaluations.

  1. Subnanosecond Dynamics of Proteins in Solution: MD Simulations and Inelastic Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Tarek, M.; Tobias, D. J.

    In summary, while classical MD simulations using current generation force fields have allowed us to reproduce quite well the dynamics of proteins in a variety of environments, as probed by neutron scattering data, the full potential of such calculations has not yet been fully exploited. We have illustrated some examples where simulations can be used to provide support for the models used by experimentalists, and others where it is clear that further work is needed to extract the maximum information from QENS spectra. At any rate, it is crucial that simulations and experiments on such complex systems go hand in hand, so that "raw data" may be compared side-by-side, and all the pitfalls, both in the simulation protocols and the experimental data analysis, may be identified and overcome.

  2. Angular distribution of 4.43-MeV γ-rays produced in inelastic scattering of 14.1-MeV neutrons by 12C nuclei

    NASA Astrophysics Data System (ADS)

    Bystritsky, V. M.; Grozdanov, D. N.; Zontikov, A. O.; Kopach, Yu. N.; Rogov, Yu. N.; Ruskov, I. N.; Sadovsky, A. B.; Skoy, V. R.; Barmakov, Yu. N.; Bogolyubov, E. P.; Ryzhkov, V. I.; Yurkov, D. I.

    2016-07-01

    The work is devoted to measuring the angular distribution of 4.43-MeV γ-rays produced in inelastic scattering of 14.1-MeV neutrons by 12C nuclei. A portable ING-27 neutron generator (designed and fabricated at VNIIA, Moscow) with a built-in 64-pixel silicon α-detector was used as a source of tagged neutrons. The γ-rays of characteristic nuclear radiation from 12C were detected with a spectrometric system that consisted of 22 γ-detectors based on NaI(Tl) crystals arranged around the carbon target. The measured angular distribution of 4.43-MeV γ-rays is analyzed and compared with the results of other published experimental works.

  3. Magnetic Transitions in Iron Porphyrin Halides by Inelastic Neutron Scattering and Ab-initio Studies of Zero-Field Splittings

    SciTech Connect

    Stavretis, Shelby E.; Atanasov, Mihail; Podlesnyak, Andrey A.; Hunter, Seth C.; Neese, Frank; Xue, Zi-Ling

    2015-10-02

    Zero-field splitting (ZFS) parameters of nondeuterated metalloporphyrins [Fe(TPP)X] (X = F, Br, I; H2TPP = tetraphenylporphyrin) are determined by inelastic neutron scattering (INS). The ZFS values are D = 4.49(9) cm–1 for tetragonal polycrystalline [Fe(TPP)F], and D = 8.8(2) cm–1, E = 0.1(2) cm–1 and D = 13.4(6) cm–1, E = 0.3(6) cm–1 for monoclinic polycrystalline [Fe(TPP)Br] and [Fe(TPP)I], respectively. Along with our recent report of the ZFS value of D = 6.33(8) cm–1 for tetragonal polycrystalline [Fe(TPP)Cl], these data provide a rare, complete determination of ZFS parameters in a metalloporphyrin halide series. The electronic structure of [Fe(TPP)X] (X = F, Cl, Br, I) has been studied by multireference ab initio methods: the complete active space self-consistent field (CASSCF) and the N-electron valence perturbation theory (NEVPT2) with the aim of exploring the origin of the large and positive zero-field splitting D of the 6A1 ground state. D was calculated from wave functions of the electronic multiplets spanned by the d5 configuration of Fe(III) along with spin–orbit coupling accounted for by quasi degenerate perturbation theory. Results reproduce trends of D from inelastic neutron scattering data increasing in the order from F, Cl, Br, to I. A mapping of energy eigenvalues and eigenfunctions of the S = 3/2 excited states on ligand field theory was used to characterize the σ- and π-antibonding effects decreasing from F to I. This is in agreement with similar results deduced from ab initio calculations on CrX63- complexes and also with the spectrochemical series showing a decrease of the ligand field in the same directions. A correlation is found between the increase of D and decrease of the π- and σ-antibonding energies eλX (λ = σ, π) in the series from X = F to I. Analysis of this

  4. Inelastic and Quasielastic Neutron Scattering in PbMg1/3Nb2/3O3 Above the Burns Temperature

    SciTech Connect

    Burkovsky, R.; Shapiro, S.; Vakhrushev, S.B.; Ivanov, A.; Hirota, K.; Matsuura, M.

    2010-12-01

    We present here the results of the study of the true paraelectric phase of PMN via neutron inelastic and quasielastic scattering. Inelastic data for two different Brillouin Zones were treated simultaneously in terms of the 2-mode approach for the lowest TO mode. We have confirmed that 2-mode description allows removing the contradictions between the temperature dependences of the soft-mode frequency and the dielectric susceptibility existing in the single mode model. The diffuse scattering was mapped in three Brillouin zones and substantial anisotropy of the 2-d intensity distribution was found that was not reported before. Treatment of data in terms of Huang scattering produced satisfactory description of the experimental data. It is shown that broad satellite peaks close to the main Bragg reflections in our case can be described in terms of instrumental resolution.

  5. A Monte Carlo Library Least Square approach in the Neutron Inelastic-scattering and Thermal-capture Analysis (NISTA) process in bulk coal samples

    NASA Astrophysics Data System (ADS)

    Reyhancan, Iskender Atilla; Ebrahimi, Alborz; Çolak, Üner; Erduran, M. Nizamettin; Angin, Nergis

    2017-01-01

    A new Monte-Carlo Library Least Square (MCLLS) approach for treating non-linear radiation analysis problem in Neutron Inelastic-scattering and Thermal-capture Analysis (NISTA) was developed. 14 MeV neutrons were produced by a neutron generator via the 3H (2H , n) 4He reaction. The prompt gamma ray spectra from bulk samples of seven different materials were measured by a Bismuth Germanate (BGO) gamma detection system. Polyethylene was used as neutron moderator along with iron and lead as neutron and gamma ray shielding, respectively. The gamma detection system was equipped with a list mode data acquisition system which streams spectroscopy data directly to the computer, event-by-event. A GEANT4 simulation toolkit was used for generating the single-element libraries of all the elements of interest. These libraries were then used in a Linear Library Least Square (LLLS) approach with an unknown experimental sample spectrum to fit it with the calculated elemental libraries. GEANT4 simulation results were also used for the selection of the neutron shielding material.

  6. Neutron transfer versus inelastic surface vibrations in the enhancement of sub-barrier fusion excitation function data and the energy dependent Woods-Saxon potential

    NASA Astrophysics Data System (ADS)

    Singh Gautam, Manjeet

    2015-02-01

    This work deeply analyzed the relative importance of the neutron transfer channels and inelastic surface vibrations of colliding nuclei in the sub-barrier fusion enhancement of various heavy ion systems using an energy dependent Woods-Saxon potential (EDWSP) model in conjunction with a one-dimensional Wong formula and the coupled channel formulation using the code CCFULL. The multi-phonon vibrational states of colliding nuclei and the nucleon transfer channels are found to be dominant internal degrees of freedom. The coupling between the relative motion of reactants and these relevant channels produces anomalously large sub-barrier fusion enhancement over the expectations of the one-dimensional barrier penetration model. In some cases, the influence of neutron transfer dominates over the couplings to low lying surface vibrational states of collision partners. Furthermore, the effects of coupling to inelastic surface excitations and the impact of neutron transfer channels with positive ground state Q-values are imitated due to energy dependence in the Woods-Saxon potential. In the EDWSP model calculations, a wide range for the diffuseness parameter, which is much larger than the value extracted from the elastic scattering data, is needed to account for the observed fusion enhancement in the close vicinity of the Coulomb barrier.

  7. New insights into the compressibility and high-pressure stability of Ni(CN)2: a combined study of neutron diffraction, Raman spectroscopy, and inelastic neutron scattering.

    PubMed

    Mishra, Sanjay K; Mittal, Ranjan; Zbiri, Mohamed; Rao, Rekha; Goel, Prabhatasree; Hibble, Simon J; Chippindale, Ann M; Hansen, Thomas; Schober, Helmut; Chaplot, Samrath L

    2016-02-03

    Nickel cyanide is a layered material showing markedly anisotropic behaviour. High-pressure neutron diffraction measurements show that at pressures up to 20.1 kbar, compressibility is much higher in the direction perpendicular to the layers, c, than in the plane of the strongly chemically bonded metal-cyanide sheets. Detailed examination of the behaviour of the tetragonal lattice parameters, a and c, as a function of pressure reveal regions in which large changes in slope occur, for example, in c(P) at 1 kbar. The experimental pressure dependence of the volume data is fitted to a bulk modulus, B0, of 1050 (20) kbar over the pressure range 0-1 kbar, and to 124 (2) kbar over the range 1-20.1 kbar. Raman spectroscopy measurements yield additional information on how the structure and bonding in the Ni(CN)2 layers change with pressure and show that a phase change occurs at about 1 kbar. The new high-pressure phase, (Phase PII), has ordered cyanide groups with sheets of D4h symmetry containing Ni(CN)4 and Ni(NC)4 groups. The Raman spectrum of phase PII closely resembles that of the related layered compound, Cu1/2Ni1/2(CN)2, which has previously been shown to contain ordered C≡N groups. The phase change, PI to PII, is also observed in inelastic neutron scattering studies which show significant changes occurring in the phonon spectra as the pressure is raised from 0.3 to 1.5 kbar. These changes reflect the large reduction in the interlayer spacing which occurs as Phase PI transforms to Phase PII and the consequent increase in difficulty for out-of-plane atomic motions. Unlike other cyanide materials e.g. Zn(CN)2 and Ag3Co(CN)6, which show an amorphization and/or a decomposition at much lower pressures (~100 kbar), Ni(CN)2 can be recovered after pressurising to 200 kbar, albeit in a more ordered form.

  8. Confirming a Predicted Selection Rule in Inelastic Neutron Scattering Spectroscopy: The Quantum Translator-Rotator H2 Entrapped Inside C60

    NASA Astrophysics Data System (ADS)

    Xu, Minzhong; Jiménez-Ruiz, Mónica; Johnson, Mark R.; Rols, Stéphane; Ye, Shufeng; Carravetta, Marina; Denning, Mark S.; Lei, Xuegong; Bačić, Zlatko; Horsewill, Anthony J.

    2014-09-01

    We report an inelastic neutron scattering (INS) study of a H2 molecule encapsulated inside the fullerene C60 which confirms the recently predicted selection rule, the first to be established for the INS spectroscopy of aperiodic, discrete molecular compounds. Several transitions from the ground state of para-H2 to certain excited translation-rotation states, forbidden according to the selection rule, are systematically absent from the INS spectra, thus validating the selection rule with a high degree of confidence. Its confirmation sets a precedent, as it runs counter to the widely held view that the INS spectroscopy of molecular compounds is not subject to any selection rules.

  9. Angular distribution measurement of gamma rays from inelastic neutron scattering on 56Fe at the nELBE time-of-flight facility

    NASA Astrophysics Data System (ADS)

    Dietz, Mirco; Bemmerer, Daniel; Beyer, Roland; Gohl, Stefan; Junghans, Arnd R.; Kögler, Toni; Massarczyk, Ralph; Müller, Stefan E.; Schwengner, Ronald; Szücs, Tamás; Takacs, Marcell P.; Wagner, Andreas; Wagner, Louis

    2017-09-01

    Inelastic neutron scattering from 56Fe was studied at the nELBE time-of-flight facility. The incoming neutron energy ranges from 100 keV to 10 MeV in the fast neutron spectrum, where high precision nuclear data are needed. A detector setup has been installed to investigate the γ-ray angular distributions. It contains five HPGe and five LaBr3 detectors positioned at 30, 55, 90, 125 and 150 degrees relative to the beam axis. The intrinsic and the neutron induced background from the setup was subtracted by cyclical measurements with and without the natural Fe-target. Corrections for extended source efficiency and gamma-self-absorption, inside the target, were done using GEANT4 simulations. The angular distributions measured with the HPGe detectors are compared with earlier data. High neutron energy resolution up to a few keV was obtained with the LaBr3 detectors due to their much better time resolution.

  10. Carbonate-Bridged Lanthanoid Triangles: Single-Molecule Magnet Behavior, Inelastic Neutron Scattering, and Ab Initio Studies.

    PubMed

    Giansiracusa, Marcus J; Vonci, Michele; Van den Heuvel, Willem; Gable, Robert W; Moubaraki, Boujemaa; Murray, Keith S; Yu, Dehong; Mole, Richard A; Soncini, Alessandro; Boskovic, Colette

    2016-06-06

    Optimization of literature synthetic procedures has afforded, in moderate yield, homogeneous and crystalline samples of the five analogues Na11[{RE(OH2)}3CO3(PW9O34)2] (1-RE; RE = Y, Tb, Dy, Ho, and Er). Phase-transfer methods have allowed isolation of the mixed salts (Et4N)9Na2[{RE(OH2)}3CO3(PW9O34)2] (2-RE; RE = Y and Er). The isostructural polyanions in these compounds are comprised of a triangular arrangement of trivalent rare-earth ions bridged by a μ3-carbonate ligand and sandwiched between two trilacunary Keggin {PW9O34} polyoxometalate ligands. Alternating-current (ac) magnetic susceptibility studies of 1-Dy, 1-Er, and 2-Er reveal the onset of frequency dependence for the out-of-phase susceptibility in the presence of an applied magnetic field at the lowest measured temperatures. Inelastic neutron scattering (INS) spectra of 1-Ho and 1-Er exhibit transitions between the lowest-lying crystal-field (CF) split states of the respective J = 8 and (15)/2 ground-state spin-orbit multiplets of the Ho(III) and Er(III) ions. Complementary ab initio calculations performed for these two analogues allow excellent reproduction of the experimental magnetic susceptibility and low-temperature magnetization data and are in reasonable agreement with the experimental INS data. The ab initio calculations reveal that the slight difference in coordination environments of the three Ln(III) ions in each complex gives rise to differences in the CF splitting that are not insignificant. This theoretical result is consistent with the observation of multiple relaxation processes by ac magnetic susceptibility and the broadness of the measured INS peaks. The ab initio calculations also indicate substantial mixing of the MJ contributions to the CF split energy levels of each Ln(III) ion. Calculations indicate that the CF ground states of the Ho(III) centers in 1-Ho are predominantly comprised of contributions from small MJ, while those of the Er(III) centers in 1-Er are predominantly

  11. Development and testing of a deuterium gas target assembly for neutron production via the H-2(d,n)He-3 reaction at a low-energy accelerator facility

    SciTech Connect

    Feautrier, D.; Smith, D.L.

    1992-03-01

    This report describes the development and testing of a deuterium gas target intended for use at a low-energy accelerator facility to produce neutrons for basic research and various nuclear applications. The principle source reaction is H-2(d,n)He-3. It produces a nearly mono-energetic group of neutrons. However, a lower-energy continuum neutron spectrum is produced by the H-2(d;n,p)H-2 reaction and also by deuterons which strike various components in the target assembly. The present target is designed to achieve the following objectives: (1) minimize unwanted background neutron production from the target assembly, (2) provide a relatively low level of residual long-term activity within the target components, (3) have the capacity to dissipate up to 150 watts of beam power with good target longevity, and (4) possess a relatively modest target mass in order to minimize neutron scattering from the target components. The basic physical principles that have to be considered in designing an accelerator target are discussed and the major engineering features of this particular target design are outlined. The results of initial performance tests on this target are documented and some conclusions concerning the viability of the target design are presented.

  12. Nucleus Z=126 with magic neutron number N=184 may be related to the measured Maruhn-Greiner maximum at A/2=155 from compound nuclei at low energy nuclear reactions

    NASA Astrophysics Data System (ADS)

    Prelas, M. A.; Hora, H.; Miley, G. H.

    2014-07-01

    Evaluation of nuclear binding energies from theory close to available measurements of a very high number of superheavy elements (SHE) based on α-decay energies Qα, arrived at a closing shell with a significant neutron number 184. Within the option of several discussed magic numbers for protons of around 120, Bagge's numbers 126 and 184 fit well and are supported by the element generation measurements by low energy nuclear reactions (LENR) discovered in deuterium loaded host metals. These measurements were showing a Maruhn-Greiner maximum from fission of compound nuclei in an excited state with double magic numbers for mutual confirmation.

  13. Test of the consistency of various linearized semiclassical initial value time correlation functions in application to inelastic neutron scattering from liquid para-hydrogen

    SciTech Connect

    Miller, William; Liu, Jian; Miller, William H.

    2008-03-15

    The linearized approximation to the semiclassical initial value representation (LSC-IVR) is used to calculate time correlation functions relevant to the incoherent dynamic structure factor for inelastic neutron scattering from liquid para-hydrogen at 14 K. Various time correlations functions were used which, if evaluated exactly, would give identical results, but they do not because the LSC-IVR is approximate. Some of the correlation functions involve only linear operators, and others involve non-linear operators. The consistency of the results obtained with the various time correlation functions thus provides a useful test of the accuracy of the LSC-IVR approximation and its ability to treat correlation functions involving both linear and nonlinear operators in realistic anharmonic systems. The good agreement of the results obtained from different correlation functions, their excellent behavior in the spectral moment tests based on the exact moment constraints, and their semi-quantitative agreement with the inelastic neutron scattering experimental data all suggest that the LSC-IVR is indeed a good short-time approximation for quantum mechanical correlation functions.

  14. Unitarization and low-energy scattering data

    NASA Astrophysics Data System (ADS)

    Magalhães, P. C.; Robilotta, M. R.

    2014-07-01

    A procedure based on the well-known K-matrix formalism is presented, which makes patterns in inelastic regions of low-energy scattering data considerably more transparent. It relies on the use of an empirical kernel, obtained by eliminating elastic loops from the experimental amplitude. This allows structures associated with resonances, such as locations, widths, and heights, to become visible with the naked eye. The method is illustrated with a study of the P-wave Kπ amplitude.

  15. High-energy magnetic excitations in overdoped La2-xSrxCuO4 studied by neutron and resonant inelastic X-ray scattering

    DOE PAGES

    Wakimoto, S.; Ishii, K.; Kimura, H.; ...

    2015-05-21

    We have performed neutron inelastic scattering and resonant inelastic x-ray scattering (RIXS) at the Cu-L3 edge to study high-energy magnetic excitations at energy transfers of more than 100 meV for overdoped La2₋xSrxCuO4 with x=0.25 (Tc=15 K) and x=0.30 (nonsuperconducting) using identical single-crystal samples for the two techniques. From constant-energy slices of neutron-scattering cross sections, we have identified magnetic excitations up to ~250 meV for x=0.25. Although the width in the momentum direction is large, the peak positions along the (π,π) direction agree with the dispersion relation of the spin wave in the nondoped La2CuO4 (LCO), which is consistent with themore » previous RIXS results of cuprate superconductors. Using RIXS at the Cu-L3 edge, we have measured the dispersion relations of the so-called paramagnon mode along both (π,π) and (π,0) directions. Although in both directions the neutron and RIXS data connect with each other and the paramagnon along (π,0) agrees well with the LCO spin-wave dispersion, the paramagnon in the (π,π) direction probed by RIXS appears to be less dispersive and the excitation energy is lower than the spin wave of LCO near (π/2,π/2). Thus, our results indicate consistency between neutron inelastic scattering and RIXS, and elucidate the entire magnetic excitation in the (π,π) direction by the complementary use of two probes. The polarization dependence of the RIXS profiles indicates that appreciable charge excitations exist in the same energy range of magnetic excitations, reflecting the itinerant character of the overdoped sample. Lastly, we find a possible anisotropy in the charge excitation intensity might explain the apparent differences in the paramagnon dispersion in the (π,π) direction as detected by the x-ray scattering.« less

  16. STARS/LiBerACE: Segmented silicon and high-purity germanium detector arrays for low-energy nuclear reaction and structure studies

    NASA Astrophysics Data System (ADS)

    Lesher, S. R.; Phair, L.; Bernstein, L. A.; Bleuel, D. L.; Burke, J. T.; Church, J. A.; Fallon, P.; Gibelin, J.; Scielzo, N. D.; Wiedeking, M.

    2010-09-01

    The Silicon Telescope Array for Reaction Studies (STARS) consists of large-area annular double-sided silicon detectors for charged-particle identification. The Livermore Berkeley Array for Collaborative Experiments (LiBerACE) is an array of six Compton-suppressed high-purity germanium Clover detectors for efficient detection of γ-rays. These detector arrays are versatile tools for studies of neutron-induced reaction cross-sections, fission, light neutron-rich nuclei, and other low-energy nuclear physics topics through transfer, fusion, incomplete-fusion, and inelastic-scattering reactions. The STARS and LiBerACE arrays and typical experimental configurations are described in detail.

  17. Staggered magnetization and low-energy magnon dispersion in the multiferroic skyrmion host Cu2OSeO3

    NASA Astrophysics Data System (ADS)

    Marcus, Guy G.; Trump, Benjamin A.; Kindervater, Jonas; Jones, Lacy L.; Stone, Matthew B.; McQueen, Tyrel M.; Broholm, Collin L.

    We present neutron diffraction and inelastic scattering of the insulating helimagnet, Cu2OSeO3 which provide evidence for staggered magnetization and elucidate the associated low-energy magnon spectrum. The modulation wavelength of approximately λ ~ 50 nm detected at antiferromagnetic Bragg points is of the same length scale as previously reported for the skyrmion lattice. This superstructure evidences the composite nature of the spin-1 tetrahedra that form the topological magnetic structure of the material. To understand the interplay of ferrimagnetism and long wavelength modulated magnetism, we have performed inelastic neutron scattering on a co-aligned sample of chemical vapor transport grown single crystals. We shall present the low-energy magnon dispersion and infer an effective spin Hamiltonian to account for the long-wavelength, low-energy magnetism of Cu2OSeO3. The work at IQM was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Material Sciences and Engineering, under Grant No. DEFG02-08ER46544. GGM also acknowledges support from the NSF-GRFP Grant No. DGE-1232825.

  18. Coupling of laser excitation and inelastic neutron scattering: attempt to probe the dynamics of light-induced C-phycocyanin dynamics.

    PubMed

    Combet, Sophie; Pieper, Jörg; Coneggo, Frédéric; Ambroise, Jean-Pierre; Bellissent-Funel, Marie-Claire; Zanotti, Jean-Marc

    2008-06-01

    Excitation energy transfer (EET) in light-harvesting antennae is a highly efficient key event in photosynthesis, where light-induced dynamics of the antenna pigment-protein complexes may play a functional role. So far, however, the relationship between EET and protein dynamics remains unknown. C-phycocyanin (C-PC) is the main pigment/protein complex present in the cyanobacterial antenna, called "phycobilisome". The aim of the present study was to investigate light-induced C-PC internal thermal motions (ps timescale) measured by inelastic neutron scattering. To synchronize the beginning of the laser flash (6 ns duration) with that of the neutron test pulse ( approximately 87 micros duration), we developed a novel type of "time-resolved" experimental setup on MIBEMOL time-of-flight neutron spectrometer (LLB, France). Data acquisition has been modified to get quasi-simultaneously "light" and "dark" measurements (with and without laser, respectively) and eliminate many spurious effects that could occur on the sample during the experiment. The study was carried out on concentrated C-PC ( approximately 135 g/L protein in D(2)O phosphate buffer), contained in an aluminium/sapphire sample holder (almost "transparent" for neutrons) and homogeneously illuminated inside an "integrating sphere". We observed very similar incoherent dynamical structure factors of C-PC with or without light. The vibrational density of states showed two very slightly increased vibrational modes with light, at approximately 30 and approximately 50 meV ( approximately 240 and approximately 400 cm(-1), respectively). These effects have to be verified by further experiments before probing any temporal evolution, by introducing a time delay between the laser flash and the neutron test pulse.

  19. Molecular and Vibrational Dynamics in the Cholesterol-Lowering Agent Lovastatin: Solid-State NMR, Inelastic Neutron Scattering, and Periodic DFT Study.

    PubMed

    Bilski, Paweł; Drużbicki, Kacper; Jenczyk, Jacek; Mielcarek, Jadwiga; Wąsicki, Jan

    2017-04-06

    Molecular and vibrational dynamics of a widely used cholesterol-lowering agent, lovastatin, have been studied by combining nuclear magnetic resonance relaxation experiments ((1)H NMR) with inelastic neutron scattering (INS) and periodic density functional theory modeling (plane-wave DFT). According to a complementary experimental study, lovastatin shows no phase transitions down to cryogenic conditions, while a progressive, stepwise activation of several molecular motions is observed below room temperature. The molecular packing and intermolecular forces were analyzed theoretically, supported by a (13)C NMR study and further correlated with observed molecular dynamics. The NMR relaxation experiments combined with theoretical calculations disclose that molecular dynamics in solid lovastatin is related to methyl group motions and conformational disorder in the methylbutanoate fragment. This is precisely assigned and analyzed quantitatively from both experimental and theoretical perspectives. The neutron vibrational spectroscopy further corroborates that the methyl rotors have a classical nature. In addition to the intramolecular reorientations, the vibrational dynamics was analyzed with an emphasis on the low-wavenumber range. For the first time, the terahertz response of lovastatin was studied by confronting neutron and optical techniques and clearly illustrating their complementarity. The consistent picture of the molecular dynamics is provided, which may support further considerations on alternative drug formulations and the amorphization tendency in this important lipid-lowering drug.

  20. Zinc-induced modification of the dynamical magnetic susceptibility in the superconducting state of YBa{sub 2}Cu{sub 3}O{sub 6+}{sub {ital x}} as revealed by inelastic neutron scattering

    SciTech Connect

    Sidis, Y.; Bourges, P.; Hennion, B.; Regnault, L.P.; Villeneuve, R.; Collin, G.; Marucco, J.F.

    1996-03-01

    Inelastic-neutron-scattering measurements have been performed to determine the imaginary part of the dynamical susceptibility, {chi}{double_prime}({ital Q},{omega}), of a YBa{sub 2}(Cu{sub 1{minus}{ital y}}Zn{sub {ital y}}){sub 3}O{sub 6.97} sample exhibiting a superconducting transition at {ital T}{sub {ital c}}=69 K. Zinc substitution induces striking modifications of the energy dependence of {chi}{double_prime}({ital Q},{omega}) but magnetic fluctuations remain peaked at the antiferromagnetic wave vector, {ital Q}{sub AF}, at all investigated energies. In the superconducting state of the zinc-free compound, {chi}{double_prime}({ital Q},{omega}) is restricted to a narrow energy range, {h_bar}{omega}=33{endash}47 meV, displaying a {ital spin} {ital gap} at {ital E}{sub {ital G}}=33 meV and a resonant enhancement at {ital E}{sub {tau}}=39 meV, both features vanishing upon heating up above {ital T}{sub {ital c}}. In the {ital y}=0.02 substituted sample in the superconducting state, there is still an energy band in the range 32{endash}47 meV but no clear resonance, and a signal is now observed in the low energy range, though the line shape of {chi}{double_prime}({ital Q},{omega}) indicates some reminiscence of the spin gap of the pure compound. {copyright} {ital 1996 The American Physical Society.}

  1. Intercomparison of Monte Carlo radiation transport codes to model TEPC response in low-energy neutron and gamma-ray fields.

    PubMed

    Ali, F; Waker, A J; Waller, E J

    2014-10-01

    Tissue-equivalent proportional counters (TEPC) can potentially be used as a portable and personal dosemeter in mixed neutron and gamma-ray fields, but what hinders this use is their typically large physical size. To formulate compact TEPC designs, the use of a Monte Carlo transport code is necessary to predict the performance of compact designs in these fields. To perform this modelling, three candidate codes were assessed: MCNPX 2.7.E, FLUKA 2011.2 and PHITS 2.24. In each code, benchmark simulations were performed involving the irradiation of a 5-in. TEPC with monoenergetic neutron fields and a 4-in. wall-less TEPC with monoenergetic gamma-ray fields. The frequency and dose mean lineal energies and dose distributions calculated from each code were compared with experimentally determined data. For the neutron benchmark simulations, PHITS produces data closest to the experimental values and for the gamma-ray benchmark simulations, FLUKA yields data closest to the experimentally determined quantities.

  2. Statistical Hauser-Feshbach theory with width-fluctuation correction including direct reaction channels for neutron-induced reactions at low energies

    NASA Astrophysics Data System (ADS)

    Kawano, T.; Capote, R.; Hilaire, S.; Chau Huu-Tai, P.

    2016-07-01

    A model to calculate particle-induced reaction cross sections with statistical Hauser-Feshbach theory including direct reactions is given. The energy average of the scattering matrix from the coupled-channels optical model is diagonalized by the transformation proposed by Engelbrecht and Weidenmüller [C. A. Engelbrecht and H. A. Weidenmüller, Phys. Rev. C 8, 859 (1973), 10.1103/PhysRevC.8.859]. The ensemble average of S -matrix elements in the diagonalized channel space is approximated by a model of Moldauer [P. A. Moldauer, Phys. Rev. C 12, 744 (1975), 10.1103/PhysRevC.12.744] using the newly parametrized channel degree-of-freedom νa to better describe the Gaussian orthogonal ensemble (GOE) reference calculations. The Moldauer approximation is confirmed by a Monte Carlo study using a randomly generated S matrix, as well as the GOE threefold integration formula. The method proposed is applied to the 238U(n ,n' ) cross-section calculation in the fast-energy range, showing an enhancement in the inelastic scattering cross sections.

  3. Mixed quantum/classical approach to OH-stretch inelastic incoherent neutron scattering spectroscopy for ambient and supercooled liquid water and ice Ih.

    PubMed

    Shi, L; Skinner, J L

    2015-07-07

    OH-stretch inelastic incoherent neutron scattering (IINS) has been measured to determine the vibrational density of states (VDOS) in the OH-stretch region for liquid water, supercooled water, and ice Ih, providing complementary information to IR and Raman spectroscopies about hydrogen bonding in these phases. In this work, we extend the combined electronic-structure/molecular-dynamics (ES/MD) method, originally developed by Skinner and co-workers to simulate OH-stretch IR and Raman spectra, to the calculation of IINS spectra with small k values. The agreement between theory and experiment in the limit k → 0 is reasonable, further validating the reliability of the ES/MD method in simulating OH-stretch spectroscopy in condensed phases. The connections and differences between IINS and IR spectra are analyzed to illustrate the advantages of IINS over IR in estimating the OH-stretch VDOS.

  4. Mixed quantum/classical approach to OH-stretch inelastic incoherent neutron scattering spectroscopy for ambient and supercooled liquid water and ice Ih

    SciTech Connect

    Shi, L.; Skinner, J. L.

    2015-07-07

    OH-stretch inelastic incoherent neutron scattering (IINS) has been measured to determine the vibrational density of states (VDOS) in the OH-stretch region for liquid water, supercooled water, and ice Ih, providing complementary information to IR and Raman spectroscopies about hydrogen bonding in these phases. In this work, we extend the combined electronic-structure/molecular-dynamics (ES/MD) method, originally developed by Skinner and co-workers to simulate OH-stretch IR and Raman spectra, to the calculation of IINS spectra with small k values. The agreement between theory and experiment in the limit k → 0 is reasonable, further validating the reliability of the ES/MD method in simulating OH-stretch spectroscopy in condensed phases. The connections and differences between IINS and IR spectra are analyzed to illustrate the advantages of IINS over IR in estimating the OH-stretch VDOS.

  5. Crystal field splittings of PrX 2 compounds (X=Pt, Rh, Ir, Ru, Ni) studied by inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Greidanus, F. J. A. M.; De Jongh, L. J.; Huiskamp, W. J.; Furrer, A.; Buschow, K. H. J.

    1983-01-01

    Neutron inelastic scattering experiments have been performed on polycrystalline samples of the cubic Laves phase compounds PrX 2(X=Pt, Rh, Ir, Ni). Measurements in the paramagnetic state yield LLW parameters 0.6< x<1 and W<0. In this region various levels cross at an x value 0.86 and as a consequence the electronic ground state in the paramagnetic regime is either the singlet Γ 1, or the non-magnetic doublet Γ 3. Measurements in the ferromagnetic state support these conclusions. The crystal-field parameters obtained can be used in model calculations of some macroscopic quantities, in particular the specific heat and the spontaneous magnetization. The variation of the x values in the present series of Laves phase compounds evidences the presence of a contribution by conduction electrons to the crystal field.

  6. Molecular aluminum hydrides identified by inelastic neutron scattering during H2 regeneration of catalyst-doped NaAlH4.

    PubMed

    Fu, Qi Jia; Ramirez-Cuesta, A J; Tsang, Shik Chi

    2006-01-19

    Catalyst-doped sodium aluminum hydrides have been intensively studied as solid hydrogen carriers for onboard proton-exchange membrane (PEM) fuel cells. Although the importance of catalyst choice in enhancing kinetics for both hydrogen uptake and release of this hydride material has long been recognized, the nature of the active species and the mechanism of catalytic action are unclear. We have shown by inelastic neutron scattering (INS) spectroscopy that a volatile molecular aluminum hydride is formed during the early stage of H2 regeneration of a depleted, catalyst-doped sodium aluminum hydride. Computational modeling of the INS spectra suggested the formation of AlH3 and oligomers (AlH3)n (Al2H6, Al3H9, and Al4H12 clusters), which are pertinent to the mechanism of hydrogen storage. This paper demonstrates, for the first time, the existence of these volatile species.

  7. Inelastic neutron scattering studies of 132,134Xe: Elucidating structure in a transitional region and possible interferences for 0vββ searches

    NASA Astrophysics Data System (ADS)

    Peters, E. E.; Ross, T. J.; Crider, B. P.; Ashley, S. F.; Chakraborty, A.; Hennek, M. D.; Kumar, A.; Liu, S. H.; McEllistrem, M. T.; Prados-Estévez, F. M.; Thrasher, J. S.; Yates, S. W.

    2015-05-01

    Highly enriched (> 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.

  8. Mixed quantum/classical approach to OH-stretch inelastic incoherent neutron scattering spectroscopy for ambient and supercooled liquid water and ice Ih

    NASA Astrophysics Data System (ADS)

    Shi, L.; Skinner, J. L.

    2015-07-01

    OH-stretch inelastic incoherent neutron scattering (IINS) has been measured to determine the vibrational density of states (VDOS) in the OH-stretch region for liquid water, supercooled water, and ice Ih, providing complementary information to IR and Raman spectroscopies about hydrogen bonding in these phases. In this work, we extend the combined electronic-structure/molecular-dynamics (ES/MD) method, originally developed by Skinner and co-workers to simulate OH-stretch IR and Raman spectra, to the calculation of IINS spectra with small k values. The agreement between theory and experiment in the limit k → 0 is reasonable, further validating the reliability of the ES/MD method in simulating OH-stretch spectroscopy in condensed phases. The connections and differences between IINS and IR spectra are analyzed to illustrate the advantages of IINS over IR in estimating the OH-stretch VDOS.

  9. Study of a solid state microdosemeter based on a monolithic silicon telescope: irradiations with low-energy neutrons and direct comparison with a cylindrical TEPC.

    PubMed

    Agosteo, S; Colautti, P; Fanton, I; Fazzi, A; Introini, M V; Moro, D; Pola, A; Varoli, V

    2011-02-01

    A silicon device based on the monolithic silicon telescope technology coupled to a tissue-equivalent converter was proposed and investigated for solid state microdosimetry. The detector is constituted by a ΔE stage about 2 µm in thickness geometrically segmented in a matrix of micrometric diodes and a residual-energy measurement stage E about 500 µm in thickness. Each thin diode has a cylindrical sensitive volume 9 µm in nominal diameter, similar to that of a cylindrical tissue-equivalent proportional counter (TEPC). The silicon device and a cylindrical TEPC were irradiated in the same experimental conditions with quasi-monoenergetic neutrons of energy between 0.64 and 2.3 MeV at the INFN-Legnaro National Laboratories (LNL-INFN, Legnaro, Italy). The aim was to study the capability of the silicon-based system of reproducing microdosimetric spectra similar to those measured by a reference microdosemeter. The TEPC was set in order to simulate a tissue site about 2 μm in diameter. The spectra of the energy imparted to the ▵E stage of the silicon telescope were corrected for tissue-equivalence through an optimized procedure that exploits the information from the residual energy measurement stage E. A geometrical correction based on parametric criteria for shape-equivalence was also applied. The agreement between the dose distributions of lineal energy and the corresponding mean values is satisfactory at each neutron energy considered.

  10. Role of scalar dibaryon and f0(500 ) in the isovector channel of low-energy neutron-proton scattering

    NASA Astrophysics Data System (ADS)

    Deinet, Werner; Teilab, Khaled; Giacosa, Francesco; Rischke, Dirk H.

    2016-10-01

    We calculate the total and the differential cross section for n p scattering at low energies in the isospin I =1 channel within the so-called extended linear sigma model. This model contains conventional (pseudo)scalar and (axial-)vector mesons, as well as the nucleon and its chiral partner within the mirror assignment. In order to obtain good agreement with experimental data analysis results we need to consider two additional resonances: the lightest scalar state f0(500 ) and a dibaryon state with quantum numbers I =1 ,JP=0+ (also known as S10 resonance). The resonance f0(500 ) is coupled to nucleons in a chirally invariant way through the mirror assignment and is crucial for a qualitatively correct description of the shape of the differential cross section. On the other hand, the dibaryon is exchanged in the s channel and is responsible of the large cross section close to threshold. We compare our results to data analysis results performed by the said program of the CNS Data Analysis Center (in the following "said results").

  11. From bare interactions, low-energy constants, and unitary gas to nuclear density functionals without free parameters: Application to neutron matter

    NASA Astrophysics Data System (ADS)

    Lacroix, Denis; Boulet, Antoine; Grasso, Marcella; Yang, C.-J.

    2017-05-01

    We further progress along the line of Ref. [D. Lacroix, Phys. Rev. A 94, 043614 (2016), 10.1103/PhysRevA.94.043614] where a functional for Fermi systems with anomalously large s -wave scattering length as was proposed that has no free parameters. The functional is designed to correctly reproduce the unitary limit in Fermi gases together with the leading-order contributions in the s - and p -wave channels at low density. The functional is shown to be predictive up to densities ˜0.01 fm-3 that is much higher densities compared to the Lee-Yang functional, valid for ρ <10-6 fm-3. The form of the functional retained in this work is further motivated. It is shown that the new functional corresponds to an expansion of the energy in (askF) and (rekF) to all orders, where re is the effective range and kF is the Fermi momentum. One conclusion from the present work is that, except in the extremely low-density regime, nuclear systems can be treated perturbatively in -(askF) -1 with respect to the unitary limit. Starting from the functional, we introduce density-dependent scales and show that scales associated with the bare interaction are strongly renormalized by medium effects. As a consequence, some of the scales at play around saturation are dominated by the unitary gas properties and not directly by low-energy constants. For instance, we show that the scale in the s -wave channel around saturation is proportional to the so-called Bertsch parameter ξ0 and becomes independent of as. We also point out that these scales are of the same order of magnitude than those empirically obtained in the Skyrme energy density functional. We finally propose a slight modification of the functional such that it becomes accurate up to the saturation density ρ ≃0.16 fm-3.

  12. Magnetic properties of nano-scale hematite, α-Fe2O3, studied by time-of-flight inelastic neutron spectroscopy.

    PubMed

    Hill, Adrian H; Jacobsen, Henrik; Stewart, J Ross; Jiao, Feng; Jensen, Niels P; Holm, Sonja L; Mutka, Hannu; Seydel, Tilo; Harrison, Andrew; Lefmann, Kim

    2014-01-28

    Samples of nanoscale hematite, α-Fe2O3, with different surface geometries and properties have been studied with inelastic time-of-flight neutron scattering. The 15 nm diameter nanoparticles previously shown to have two collective magnetic excitation modes in separate triple-axis neutron scattering studies have been studied in further detail using the advantage of a large detector area, high resolution, and large energy transfer range of the IN5 TOF spectrometer. A mesoporous hematite sample has also been studied, showing similarities to that of the nanoparticle sample and bulk α-Fe2O3. Analysis of these modes provides temperature dependence of the magnetic anisotropy coefficient along the c-axis, κ1. This is shown to remain negative throughout the temperature range studied in both samples, providing an explanation for the previously observed suppression of the Morin transition in the mesoporous material. The values of this anisotropy coefficient are found to lie between those of bulk and nano-particulate samples, showing the hybrid nature of the mesoporous 3-dimensional structure.

  13. Magnetic properties of nano-scale hematite, α-Fe{sub 2}O{sub 3}, studied by time-of-flight inelastic neutron spectroscopy

    SciTech Connect

    Hill, Adrian H.; Jacobsen, Henrik Holm, Sonja L.; Lefmann, Kim; Stewart, J. Ross; Jiao, Feng; Jensen, Niels P.; Mutka, Hannu; Seydel, Tilo; Harrison, Andrew

    2014-01-28

    Samples of nanoscale hematite, α-Fe{sub 2}O{sub 3}, with different surface geometries and properties have been studied with inelastic time-of-flight neutron scattering. The 15 nm diameter nanoparticles previously shown to have two collective magnetic excitation modes in separate triple-axis neutron scattering studies have been studied in further detail using the advantage of a large detector area, high resolution, and large energy transfer range of the IN5 TOF spectrometer. A mesoporous hematite sample has also been studied, showing similarities to that of the nanoparticle sample and bulk α-Fe{sub 2}O{sub 3}. Analysis of these modes provides temperature dependence of the magnetic anisotropy coefficient along the c-axis, κ{sub 1}. This is shown to remain negative throughout the temperature range studied in both samples, providing an explanation for the previously observed suppression of the Morin transition in the mesoporous material. The values of this anisotropy coefficient are found to lie between those of bulk and nano-particulate samples, showing the hybrid nature of the mesoporous 3-dimensional structure.

  14. Lattice dynamics of α-AlH3 and α-AlD3 by inelastic neutron scattering: High-energy band of optical bond-stretching vibrations

    NASA Astrophysics Data System (ADS)

    Kolesnikov, A. I.; Antonov, V. E.; Markushkin, Yu. E.; Natkaniec, I.; Sakharov, M. K.

    2007-08-01

    Inelastic neutron scattering (INS) spectra of trigonal α-AlH3 and α-AlD3 have been measured in a wide range (5-150meV) of energy transfers with a much better statistical accuracy than previously using the inverted-geometry NERA-PR spectrometer at JINR, Dubna. The studied energy interval covers the range of low-frequency lattice vibrations and a broad band of optical H vibrations. By using a direct-geometry HRMECS spectrometer at ANL, Argonne, the AlH3 hydride was also examined by INS at energy transfers up to 315meV in the regime of small momentum transfers. This significantly enhanced the contribution from the one-phonon neutron scattering and allowed an observation and accurate examination of one more, high-energy band of optical H vibrations predicted theoretically [C. Wolverton , Phys. Rev. B 69, 144109 (2004)]. Combining the obtained experimental data, the entire spectrum of phonon density of states was reconstructed for both α-AlH3 and α-AlD3 .

  15. Correlated atomic motions in liquid deuterium fluoride studied by coherent quasielastic neutron scattering.

    PubMed

    Fernandez-Alonso, F; McLain, S E; Taylor, J W; Bermejo, F J; Bustinduy, I; Ruiz-Martín, M D; Turner, J F C

    2007-06-21

    The collective dynamics of liquid deuterium fluoride are studied by means of high-resolution quasielastic and inelastic neutron scattering over a range of four decades in energy transfer. The spectra show a low-energy coherent quasielastic component which arises from correlated stochastic motions as well as a broad inelastic feature originating from overdamped density oscillations. While these results are at variance with previous works which report on the presence of propagating collective modes, they are fully consistent with neutron diffraction, nuclear magnetic resonance, and infrared/Raman experiments on this prototypical hydrogen-bonded fluid.

  16. Low energy supersymmetry phenomenology

    SciTech Connect

    Baer, H.; Chen, C.H.; Bartl, A.

    1995-03-01

    The authors summarize the current status and future prospects for low energy (weak scale) supersymmetry. In particular, they evaluate the capabilities of various e{sup +}e{sup {minus}}, p{anti p} and pp colliders to discover evidence for supersymmetric particles. Furthermore, assuming supersymmetry is discovered, they discuss capabilities of future facilities to disentangle the anticipated spectrum of superparticles, and, via precision measurements, to test mass and coupling parameters for comparison with various theoretical expectations. They comment upon the complementarity of proposed hadron and e{sup +}e{sup {minus}} machines for a comprehensive study of low energy supersymmetry.

  17. Low energy supersymmetry phenomenology

    SciTech Connect

    Baer, H.; Chen, C.H.; Bartl, A.; Feng, J.; Fujii, K.; Gunion, J.; Kamon, T.; Lopez, J.L.; Kao, C.

    1995-04-01

    The authors summarize the current status and future prospects for low energy (weak scale) supersymmetry. In particular, they evaluate the capabilities of various e{sup +}e{sup {minus}}, p{bar p} and pp colliders to discover evidence for supersymmetric particles. Furthermore, assuming supersymmetry is discovered, they discuss capabilities of future facilities to disentangle the anticipated spectrum of super-particles, and, via precision measurements, to test mass and coupling parameters for comparison with various theoretical expectations. The authors then comment upon the complementarity of proposed hadron and e{sup +}e{sup {minus}} machines for a comprehensive study of low energy supersymmetry.

  18. LOW ENERGY COUNTING CHAMBERS

    DOEpatents

    Hayes, P.M.

    1960-02-16

    A beta particle counter adapted to use an end window made of polyethylene terephthalate was designed. The extreme thinness of the film results in a correspondingly high transmission of incident low-energy beta particles by the window. As a consequence, the counting efficiency of the present counter is over 40% greater than counters using conventional mica end windows.

  19. Magnetic excitations in an exchange-coupled tetramer cluster of cobalt (II): a study by inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Gómez-García, C. J.; Coronado, E.; Borrás-Almenar, J. J.; Aebersold, M.; Güdel, H. U.; Mutka, H.

    1992-06-01

    The polyoxometalate K 10[Co 4(H 2O) 2(PW 9O 34) 2].20H 2O contains a ferromagnetically exchange-coupled tetramer of Co 11 encapsulated in between two diamagnetic molecules (PW 9O 34-9. At 2.5K several inelastic peaks are observed in the energy range 1.5-7 meV, which are assigned to magnetic excitations in the cluster. A tentative interpretation of these data from an anisotropic exchange model yields a cobalt-cobalt interaction of 3meV (24cm -1) and an amount of anisotropy Jxy/ Jz≌0.6. These values are consistent with the magnetic susceptibility measurements.

  20. Vibrational properties and phonon anharmonicity in ZnS1-xSex: Inelastic neutron scattering, Raman scattering, X-ray diffraction measurements and lattice dynamical studies

    NASA Astrophysics Data System (ADS)

    Basak, Tista; Rao, Mala N.; Chaplot, S. L.; Salke, Nilesh; Rao, Rekha; Dhanasekaran, R.; Rajarajan, A. K.; Rols, S.; Mittal, R.; Jayakrishnan, V. B.; Sastry, P. U.

    2014-01-01

    Inelastic neutron scattering, Raman and X-ray diffraction measurements coupled with lattice dynamical calculations (employing a semi-empirical transferable potential model) have been carried out to gain a detailed understanding of the peculiar vibrational spectrum exhibited by the mixed crystal ZnS1-xSex. Raman scattering measurements performed over a varying range of temperature (100-800 K) and pressure (up to 13 GPa) have confirmed that the additional mode observed in the spectra are visible over the entire range of temperature and pressure. Correlation of the individual motions of atoms (obtained from computed total and partial phonon density of states) with the inelastic neutron scattering measurements (carried out over the entire Brillouin zone) have then indicated that the existence of the additional mode in ZnS1-xSex is due to the vibrations of the Se atom being in resonance with that of the S atom. Further, it has been shown that the presence of this additional mode can be tuned by varying the mass of the atom at the Se site. In addition, an analysis of bond-length distribution with increasing Se concentration have elucidated that bond-length spread is not responsible for the presence of the additional mode. An analysis of the peak shifts of the Raman modes with temperature and pressure indicate that the anharmonicity of the vibrational modes increases with increasing compositional disorder. This is attributed to the fact that increasing Se concentration gives rise to a distribution of bond-lengths in ZnS1-xSex, which is responsible for this compositional disorder induced anharmonicity. Our computations have thus revealed that mass of the anion is responsible for the presence of additional mode while bond-length distribution gives rise to the existence of compositional disorder induced anharmonicity in ZnS1-xSex. Further, it is observed that the contribution of explicit anharmonicity to the total anharmonicity becomes dominant at higher temperatures. This

  1. Low energy antiproton beams

    NASA Astrophysics Data System (ADS)

    Klapisch, R.

    1992-04-01

    It was the invention of stochastic cooling by S. Van Meer that has allowed antiproton beams to become a powerful tool for the physicist. As a byproduct of the high energy proton-antiproton collider, a versatile low-energy facility, LEAR has been operating at CERN since 1984. The facility and its characteristics will be described as well as examples of its use for studying fundamental properties of the antiproton and for topics in atomic, nuclear and particle Physics.

  2. Inelastic Neutron Scattering Studies of High-Energy Spin Excitations in Superconducting BaFe1.9Ni0.1As2

    NASA Astrophysics Data System (ADS)

    Liu, Mengshu; Abernathy, Douglas; Zhao, Jun; Wang, Meng; Zhang, Chenglin; Wang, Miaoyin; Dai, Pengcheng

    2010-03-01

    Understanding how the spin fluctuations evolve with doping in iron pnictide superconductors is important because spin fluctuations may mediate electron pairing for superconductivity in these materials. Upon doping, the spin fluctuation persists long after the long-range antiferromagnetism is destroyed. More importantly, spin excitations are coupled to superconductivity in the appearance of a neutron magnetic resonance and a superconductivity-induced spin gap. However, all current neutron scattering results in iron based superconductors are confined to low energy excitations except for the ``11'' FeTe1-xSex system, which shows incommensurate excitations that are not found in other iron pnictide systems. Therefore, how the spin waves in parent compounds of the ``122'' (AFe2As2, A = Ca, Sr, Ba) system will evolve when the system becomes an optimal superconductor is still an open question. We use time-of-flight spectroscopy to determine S (Q,φ) at energy regions not accessed before. We compare spin fluctuations of iron arsenide superconductors with those of high-Tc copper oxides and discuss their role in the superconductivity of these materials.

  3. Inelastic neutron scattering (INS) observations of rotational tunneling within partially deuterated methane monolayers adsorbed on MgO(1 0 0) surfaces

    NASA Astrophysics Data System (ADS)

    Hicks, Andy S.; Larese, J. Z.

    2013-12-01

    High resolution inelastic neutron scattering (INS) measurements of the low temperature (T ∼ 2.0 K) rotational dynamics of isotopically substituted methane monolayers adsorbed on MgO(1 0 0) are presented. These spectra, obtained using BASIS at SNS, represent the most detailed measurements available for surface-adsorbed monolayer films of methane. Distinct excitations are readily observed at 15, 31, 45 and 127 μeV for the CH2D2 on MgO monolayer and at 40, 51, 95 and 138 μeV for CH3D/MgO. These features are attributed to tunneling transitions between sublevels within the ground librational state and are interpreted using the pocket state (PS) formalism first proposed by Hüller. This theoretical analysis employs the findings of earlier studies of CH4 on MgO(1 0 0) which suggest that molecules adsorb with their C2v axes normal to the surface plane. The comparison between theory and experiment provides direct insight into the impact of molecular versus surface symmetry on the observed tunneling spectra.

  4. Influence of pressure on the low-frequency vibrational modes of lysozyme and water: a complementary inelastic neutron scattering and molecular dynamics simulation study.

    PubMed

    Lerbret, Adrien; Hédoux, Alain; Annighöfer, Burkhard; Bellissent-Funel, Marie-Claire

    2013-02-01

    We performed complementary inelastic neutron scattering (INS) experiments and molecular dynamics (MD) simulations to study the influence of pressure on the low-frequency vibrational modes of lysozyme in aqueous solution in the 1 atm-6 kbar range. Increasing pressure induces a high-frequency shift of the low-frequency part (<10 meV = 80 cm(-1)) of the vibrational density of states (VDOS), g(ω), of both lysozyme and water that reveals a stiffening of the interactions ascribed to the reduction of the protein and water volumes. Accordingly, high pressures increase the curvature of the free energy profiles of the protein quasiharmonic vibrational modes. Furthermore, the nonlinear influence of pressure on the g(ω) of lysozyme indicates a change of protein dynamics that reflects the nonlinear pressure dependence of the protein compressibility. An analogous dynamical change is observed for water and stems from the distortion of its tetrahedral structure under pressure. Moreover, our study reveals that the structural, dynamical, and vibrational properties of the hydration water of lysozyme are less sensitive to pressure than those of bulk water, thereby evidencing the strong influence of the protein surface on hydration water.

  5. Orientational and translational correlations of liquid methane over the nanometer-picosecond scales by molecular dynamics simulation and inelastic neutron scattering

    NASA Astrophysics Data System (ADS)

    Sampoli, M.; Guarini, E.; Bafile, U.; Barocchi, F.

    2011-10-01

    Five models for the site-site intermolecular pair interactions of methane are compared in some detail and used to investigate both structural and dynamical properties of the dense liquid deuteromethane by means of molecular dynamics (MD) simulations. The orientational distribution probabilities of molecular pairs are carefully analyzed for each anisotropic potential model. We propose a revision of existing classification methods used to group the innumerable relative orientations of methane-methane pairs into six basic geometries. With this new approach, our results for the probability of the six basic categories as a function of the intermolecular distance are different from the ones present in the literature, where the role of the angular spread on the anisotropic interaction energy is not taken in full consideration and certain configurations with no significant change in the pair-potential are assigned to different categories. The analysis of the static orientational correlations in liquid methane and the prevalence of certain configurations in different ranges guide the subsequent discussion of the MD model-dependent results for the dynamic structure factor. Comparison with our inelastic neutron scattering results for liquid CD4 at the nanometer and picosecond space and time scales allows us to confirm the full adequacy of the Tsuzuki, Uchimaru and Tanabe model of 1998 with respect to more recent potentials.

  6. Anomalous lattice behavior of vanadium pentaoxide (V2O5): X-ray diffraction, inelastic neutron scattering and ab initio lattice dynamics.

    PubMed

    Singh, Baltej; Gupta, Mayanak Kumar; Mishra, Sanjay Kumar; Mittal, Ranjan; Sastry, P U; Rols, Stephane; Chaplot, Samrath Lal

    2017-07-21

    We present structural and dynamical studies of layered vanadium pentaoxide (V2O5). The temperature dependent X-ray diffraction measurements reveal highly anisotropic and anomalous thermal expansion from 12 K to 853 K. The results do not show any evidence of structural phase transition or decomposition of α-V2O5, contrary to the previous transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) experiments. The inelastic neutron scattering measurements performed up to 673 K corroborate the result of our X-ray diffraction measurements. The analysis of the experimental data is carried out using ab initio lattice dynamics calculations. The important role of van der Waals dispersion and Hubbard interactions in the structure and dynamics is revealed through ab initio calculations. The calculated anisotropic thermal expansion behavior agrees well with temperature dependent X-ray diffraction. The mechanism of anisotropic thermal expansion and anisotropic linear compressibility is discussed in terms of calculated anisotropy in the Grüneisen parameters and elastic coefficients. The calculated Gibbs free energy in various phases of V2O5 is used to understand the high pressure and temperature phase diagram of the compound.

  7. Muon spin relaxation and inelastic neutron scattering investigations of the all-in/all-out antiferromagnet Nd2Hf2O7

    NASA Astrophysics Data System (ADS)

    Anand, V. K.; Abernathy, D. L.; Adroja, D. T.; Hillier, A. D.; Biswas, P. K.; Lake, B.

    2017-06-01

    Nd2Hf2O7 , belonging to the family of geometrically frustrated cubic rare-earth pyrochlore oxides, was recently identified to order antiferromagnetically below TN≈0.55 K with an all-in/all-out arrangement of Nd3 + moments, however, with a much reduced ordered state moment. Herein, we investigate the spin dynamics and crystal-field states of Nd2Hf2O7 using muon spin relaxation (μ SR ) and inelastic neutron scattering (INS) measurements. Our μ SR study confirms the long-range magnetic ordering and shows evidence for coexisting persistent dynamic spin fluctuations deep inside the ordered state down to 42 mK. The INS data show the crystal electric field (CEF) excitations due to the transitions both within the ground-state multiplet and to the first excited state multiplet. The INS data are analyzed by a model based on CEF and crystal-field states are determined. Strong Ising-type anisotropy is inferred from the ground-state wave function. The CEF parameters indicate the CEF-split Kramers doublet ground state of Nd3 + to be consistent with the dipolar-octupolar character.

  8. Spin fluctuations in Sr1.6Ba0.4RuO4 : An inelastic neutron scattering study with polarization analysis

    NASA Astrophysics Data System (ADS)

    Li, Z. W.; Guo, H.; Liu, C.-F.; Bourdarot, F.; Schmidt, W.; Skoulatos, M.; Komarek, A. C.

    2017-01-01

    We present inelastic neutron scattering measurements on the ruthenate Sr1.6Ba0.4RuO4 which is on the hitherto almost unknown Ba-substituted side of the doping phase diagram of Sr2 -xAexRuO4 (Ae = Ca, Ba). Unlike the Ca-substituted side of the phase diagram no (quasi)static magnetic peaks can be observed in Sr1.6Ba0.4RuO4 . Instead, incommensurate spin fluctuations can be observed around q0=(±0.3 ,±0.3 ,0 ) . Both the absolute intensity of χ''(Q ,ω ) and its energy and temperature dependence as well as the anisotropy ratio χc''/χa,b '' resemble the ones in Sr2RuO4 . Hence, a random potential implied by the substitution of huge Ba ions as well as the induced increase of interatomic distances has less impact on the magnetic properties than octahedral tilts implied by Ca substitution. Moreover, any ferromagnetic spin fluctuations are either absent in Sr1.6Ba0.4RuO4 or below the detection limit.

  9. Studies of a Large Odd‐Numbered Odd‐Electron Metal Ring: Inelastic Neutron Scattering and Muon Spin Relaxation Spectroscopy of Cr8Mn

    PubMed Central

    Lancaster, Tom; Chiesa, Alessandro; Amoretti, Giuseppe; Baker, Peter J.; Barker, Claire; Carretta, Stefano; Collison, David; Güdel, Hans U.; Guidi, Tatiana; McInnes, Eric J. L.; Möller, Johannes S.; Mutka, Hannu; Ollivier, Jacques; Pratt, Francis L.; Santini, Paolo; Tuna, Floriana; Tregenna‐Piggott, Philip L. W.; Vitorica‐Yrezabal, Iñigo J.; Timco, Grigore A.

    2016-01-01

    Abstract The spin dynamics of Cr8Mn, a nine‐membered antiferromagnetic (AF) molecular nanomagnet, are investigated. Cr8Mn is a rare example of a large odd‐membered AF ring, and has an odd‐number of 3d‐electrons present. Odd‐membered AF rings are unusual and of interest due to the presence of competing exchange interactions that result in frustrated‐spin ground states. The chemical synthesis and structures of two Cr8Mn variants that differ only in their crystal packing are reported. Evidence of spin frustration is investigated by inelastic neutron scattering (INS) and muon spin relaxation spectroscopy (μSR). From INS studies we accurately determine an appropriate microscopic spin Hamiltonian and we show that μSR is sensitive to the ground‐spin‐state crossing from S=1/2 to S=3/2 in Cr8Mn. The estimated width of the muon asymmetry resonance is consistent with the presence of an avoided crossing. The investigation of the internal spin structure of the ground state, through the analysis of spin‐pair correlations and scalar‐spin chirality, shows a non‐collinear spin structure that fluctuates between non‐planar states of opposite chiralities. PMID:26748964

  10. Heisenberg Model Analysis on Inelastic Powder Neutron Scattering Data Using Pure and K doped BaMn2 As2 samples

    NASA Astrophysics Data System (ADS)

    Ramazanoglu, Mehmet; Sapkota, A.; Pandey, A.; Johnston, D.; Goldman, Alan; Kreyssig, A.; Abernathy, D.; Niedziela, J.; Stone, M.; McQueeney, R. J.

    Low temperature powder inelastic neutron scattering measurements (INS) were performed on powders of Ba(1-x)KxMn2As2 with x=0(BMA),0.125 and 0.25. BMA is a G type antiferromagnet (AFM) which has local magnetic modulations bridging between the pnictide and cuprate superconductors. Hole doping (K) introduces more metallic behavior. The magnetic contribution to the intensities were retrieved by subtracting the estimated phonon background obtained at high momentum transfers from the raw. The resultant estimated magnetic intensities were analyzed by using damped harmonic oscillator model. The K doping effects create a broadening in the magnetic peak profiles consistent with expected weak FM fluctuations. We also analyzed the INS data using a powder integration routine which is based on J1-J2-Jz Heisenberg Model. The Monte Carlo integration technique is used to obtain the powder-averaged S(Q,E) for a series of Js. The representative values (with lowest chi-squared) obtained for BMA are in agreement with previous results. The values obtained for K doped samples were found in the close proximity to the parent ones. Overall we conclude that the original AFM structure seen in BMA retained its character even in the K doped samples with minimal differences. Work at Ames Laboratory is supported by USDOE under Contract No. DE-AC02-07CH11358 and Work at ITU is supported by TUBITAK 2232.

  11. Lattice dynamics of the model percolation-type (Zn,Be)Se alloy: Inelastic neutron scattering, ab initio study, and shell-model calculations

    NASA Astrophysics Data System (ADS)

    Rao, Mala N.; Lamago, D.; Ivanov, A.; d'Astuto, M.; Postnikov, A. V.; Hussein, R. Hajj; Basak, Tista; Chaplot, S. L.; Firszt, F.; Paszkowicz, W.; Deb, S. K.; Pagès, O.

    2014-04-01

    The random Zn1-xBexSe zincblende alloy is known to exhibit a peculiar three-mode [1×(Zn-Se),2×(Be-Se)] vibration pattern near the Brillouin zone (BZ) center, of the so-called percolation type, apparent in its Raman spectra. This is due to an unusually large contrast between the physical properties (length, ionicity) of the constituting bonds. In the present work, the inelastic neutron scattering is applied to study the dispersion of modes away from the BZ center, with special attention to the q⃗ dependence of the BeSe-like transverse optic doublet. The discussion is supported by calculations of lattice dynamics done both ab initio (using the siesta code) and within the shell model. The BeSe-like doublet is found to survive nearly unchanged throughout the BZ up to the zone edge, indicating that its origin is at the ultimate bond scale. The microscopic mechanism of splitting is clarified by ab initio calculations. Namely, the local lattice relaxation needed to accommodate the contrast in physical properties of the Zn-Se and Be-Se bonds splits the stretching and bending modes of connected, i.e., percolativelike, (Be-Se) bonds.

  12. Evidence of Spin Resonance Signal in Oxygen Free Superconducting CaFe0.88Co0.12AsF: An Inelastic Neutron Scattering Study

    NASA Astrophysics Data System (ADS)

    Price, Stephen; Su, Yixi; Xiao, Yinguo; Adroja, Devashibhai T.; Guidi, Tatiana; Mittal, Ranjan; Nandi, Shibabrata; Matsuishi, Satoru; Hosono, Hideo; Brückel, Thomas

    2013-10-01

    The spin excitation spectrum of optimally doped superconducting CaFe0.88Co0.12AsF (Tc˜ 22 K) was studied by means of time-of-flight (ToF) inelastic neutron scattering experiments on a powder sample for temperatures above and below Tc and energies up to 15 meV. In the superconducting state, the spin resonance signal is observed as an enhancement of spectral weight of particle hole excitations of approximately 1.5 times relative to normal state excitations. The resonance energy ER˜ 7 meV scales to Tc via 3.7 kBTc which is in reasonable agreement to the scaling relation reported for other Fe-based compositions. For energies below 5 meV the spectrum of spin flip particle hole excitations in the superconducting state exhibits a strong reduction in spectral weight, indicating the opening of the spin gap. Nonetheless, a complete suppression of magnetic response cannot be observed. In contrast, the normal state spin excitations are not gapped and strongly two dimensional spin fluctuations persist up to temperatures at least as high as 150 K.

  13. Studies of a Large Odd-Numbered Odd-Electron Metal Ring: Inelastic Neutron Scattering and Muon Spin Relaxation Spectroscopy of Cr8 Mn.

    PubMed

    Baker, Michael L; Lancaster, Tom; Chiesa, Alessandro; Amoretti, Giuseppe; Baker, Peter J; Barker, Claire; Blundell, Stephen J; Carretta, Stefano; Collison, David; Güdel, Hans U; Guidi, Tatiana; McInnes, Eric J L; Möller, Johannes S; Mutka, Hannu; Ollivier, Jacques; Pratt, Francis L; Santini, Paolo; Tuna, Floriana; Tregenna-Piggott, Philip L W; Vitorica-Yrezabal, Iñigo J; Timco, Grigore A; Winpenny, Richard E P

    2016-01-26

    The spin dynamics of Cr8 Mn, a nine-membered antiferromagnetic (AF) molecular nanomagnet, are investigated. Cr8 Mn is a rare example of a large odd-membered AF ring, and has an odd-number of 3d-electrons present. Odd-membered AF rings are unusual and of interest due to the presence of competing exchange interactions that result in frustrated-spin ground states. The chemical synthesis and structures of two Cr8 Mn variants that differ only in their crystal packing are reported. Evidence of spin frustration is investigated by inelastic neutron scattering (INS) and muon spin relaxation spectroscopy (μSR). From INS studies we accurately determine an appropriate microscopic spin Hamiltonian and we show that μSR is sensitive to the ground-spin-state crossing from S=1/2 to S=3/2 in Cr8 Mn. The estimated width of the muon asymmetry resonance is consistent with the presence of an avoided crossing. The investigation of the internal spin structure of the ground state, through the analysis of spin-pair correlations and scalar-spin chirality, shows a non-collinear spin structure that fluctuates between non-planar states of opposite chiralities.

  14. Inelastic Neutron Scattering Study of Stripe and Overdoped Checkerboard Ordering in Layered Nickel Oxide Nd2-xSrxNiO4

    NASA Astrophysics Data System (ADS)

    Ikeda, Yoichi; Suzuki, Shota; Nakabayashi, Takuya; Yoshizawa, Hideki; Yokoo, Tetsuya; Itoh, Shinichi

    2016-02-01

    We have investigated magnetic excitations in both the stripe (x < 0.5) and overdoped checkerboard (CB) (x ≥ 0.5) regions in Nd2-xSrxNiO4 (x = 0.33, 0.60, and 0.70) samples by inelastic neutron scattering. The magnetic excitations of Nd1.67Sr0.33NiO4 in the stripe region can be described by the linear spin wave theory with the same exchange constants as estimated for La5/3Sr1/3NiO4. In strong contrast to the well-defined spin wave excitations in the stripe region, the CB-ordered x = 0.60 and 0.70 samples show nondispersive broad magnetic excitation spectra. The broad feature of the excitation spectra in the CB region appears to be independent of the hole concentration up to x = 0.7. We discuss the origin of the broad excitation spectra and the robustness of the CB order above x > 0.5.

  15. Low-energy neutrinos

    NASA Astrophysics Data System (ADS)

    Ludhova, Livia

    2016-05-01

    There exist several kinds of sources emitting neutrinos in the MeV energy range. These low-energy neutrinos from different sources can be often detected by the same multipurpose detectors. The status-of-art of the field of solar neutrinos, geoneutrinos, and the search for sterile neutrino with artificial neutrino sources is provided here; other neutrino sources, as for example reactor or high-energy neutrinos, are described elsewhere. For each of these three fields, the present-day motivation and open questions, as well as the latest experimental results and future perspectives are discussed.

  16. Measurement of coherent Debye-Waller factor in in vivo deuterated C-phycocyanin by inelastic neutron scattering.

    PubMed

    Bellissent-Funel, M C; Filabozzi, A; Chen, S H

    1997-04-01

    Quasielastic neutron scattering measurements of dry and 35% D2O hydrated amorphous protein powder of C-phycocyanin were made as a function of temperature ranging from 313K down to 100K. The protein is grown from blue-green algae cultured in D2O and is deuterated up to 99%. The scattering is thus dominated by coherent scattering. Within the best energy resolution of the time-of-flight instrument, which is 28 mueV FWHM, the scattering appears entirely elastic. For this reason we are able to extract a coherent Debye-Waller factor by making an independent measurement of the static structure factor. We observe a considerable difference in the q dependence of the Debye-Waller factor between the dry and hydrated proteins; furthermore, there is an interesting temperature dependence of the Debye-Waller factor that is quite different from that predicted for dense hard-sphere liquids.

  17. Slow Magnetic Relaxations in Cobalt(II) Tetranitrate Complexes. Studies of Magnetic Anisotropy by Inelastic Neutron Scattering and High-Frequency and High-Field EPR Spectroscopy

    DOE PAGES

    Chen, Lei; Cui, Hui-Hui; Stavretis, Shelby E.; ...

    2016-12-07

    We synthesized and studied three mononuclear cobalt(II) tetranitrate complexes (A)2[Co(NO3)4] with different countercations, Ph4P+ (1), MePh3P+ (2), and Ph4As+ (3), using X-ray single-crystal diffraction, magnetic measurements, inelastic neutron scattering (INS), high-frequency and high-field EPR (HF-EPR) spectroscopy, and theoretical calculations. Furthermore, the X-ray diffraction studies reveal that the structure of the tetranitrate cobalt anion varies with the countercation. 1 and 2 exhibit highly irregular seven-coordinate geometries, while the central Co(II) ion of 3 is in a distorted-dodecahedral configuration. The sole magnetic transition observed in the INS spectroscopy of 1–3 corresponds to the zero-field splitting (2(D2 + 3E2)1/2) from 22.5(2) cm–1 inmore » 1 to 26.6(3) cm–1 in 2 and 11.1(5) cm–1 in 3. The positive sign of the D value, and hence the easy-plane magnetic anisotropy, was demonstrated for 1 by INS studies under magnetic fields and HF-EPR spectroscopy. The combined analyses of INS and HF-EPR data yield the D values as +10.90(3), +12.74(3), and +4.50(3) cm–1 for 1–3, respectively. Frequency- and temperature-dependent alternating-current magnetic susceptibility measurements reveal the slow magnetization relaxation in 1 and 2 at an applied dc field of 600 Oe, which is a characteristic of field-induced single-molecule magnets (SMMs). Finally, the electronic structures and the origin of magnetic anisotropy of 1–3 were revealed by calculations at the CASPT2/NEVPT2 level.« less

  18. Temperature-dependent vibrational and conformational dynamics of photosystem II membrane fragments from spinach investigated by elastic and inelastic neutron scattering.

    PubMed

    Pieper, Jörg; Trapp, Marcus; Skomorokhov, Andrei; Natkaniec, Ireneusz; Peters, Judith; Renger, Gernot

    2012-08-01

    Vibrational and conformational protein dynamics of photosystem II (PS II) membrane fragments from spinach were investigated by elastic and inelastic incoherent neutron scattering (EINS and IINS). As to the EINS experiments, the average atomic mean square displacement values of PS II membrane fragments hydrated at a relative humidity of 57% exhibit a dynamical transition at ~230K. In contrast, the dynamical transition was absent at a relative humidity of 44%. These findings are in agreement with previous studies which reported a "freezing" of protein mobility due to dehydration (Pieper et al. (2008) Eur. Biophys. J. 37: 657-663) and its correlation with an inhibition of electron transfer from Q(A)(-) to Q(B) (Kaminskaya et al. (2003) Biochemistry 42, 8119-8132). IINS spectra of a sample hydrated at a relative humidity of 57% show a distinct Boson peak at ~7.5meV at 20K, which shifts towards lower energy values upon temperature increase to 250K. This unexpected effect is interpreted in terms of a "softening" of the protein matrix along with the onset of conformational protein dynamics as revealed by the EINS experiments. Information on the density of vibrational states of pigment-protein complexes is important for a realistic calculation of excitation energy transfer kinetics and spectral lineshapes and is often routinely obtained by optical line-narrowing spectroscopy at liquid helium temperature. The data presented here demonstrate that IINS is a valuable experimental tool in determining the density of vibrational states not only at cryogenic, but also at nearly physiological temperatures up to 250K. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.

  19. Inelastic neutron scattering spectra of a hydrogen molecule in a nanocavity: Methodology for quantum calculations incorporating the coupled five-dimensional translation-rotation eigenstates

    NASA Astrophysics Data System (ADS)

    Xu, Minzhong; Bačić, Zlatko

    2011-11-01

    We present an in-depth description of the methodology for accurate quantum calculation of the inelastic neutron scattering (INS) spectra of an H2 molecule confined inside a nanosize cavity of an arbitrary shape. This methodology was introduced in a recent work [M. Xu, L. Ulivi, M. Celli, D. Colognesi, and Z. Bačić, Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.83.241403 83, 241403(R) (2011)], where the INS spectra of para- and ortho-H2 in the small cage of the structure II clathrate hydrate were simulated and compared with the measured spectra. The key distinctive feature of our approach, and its main strength and advantage, is the use of the coupled quantum 5D translation-rotation (TR) energy levels and wave functions of the entrapped H2 molecule, rigorously calculated on the 5D intermolecular potential energy surface (PES), as the initial and the final states of the INS transitions. In this work, we describe the implementation of the 5D TR wave functions within the quantum INS formalism, and obtain the working expressions for the matrix elements required to compute the INS spectra of the nanoconfined H2 molecule. The computational approach devised for efficient calculation of the 5D TR eigenstates in the compact contracted basis, indispensable for our quantum simulation of the INS spectra, is presented as well. Since the TR coupling is fully taken into account, the computed INS spectra exhibit a uniquely high degree of realism and faithfully reflect the quantum dynamics of H2 on the PES of the host environment.

  20. Vibrational properties of CaAlH5 and α-AlH3 with different AlH6 networks studied by inelastic neutron scattering.

    PubMed

    Sato, Toyoto; Ramirez-Cuesta, A J; Ikeda, Kazutaka; Orimo, Shin-ichi; Yamada, Kazuyoshi

    2011-09-05

    We performed a combined study using inelastic neutron scattering (INS) and first-principles calculations of the vibrational properties of CaAlH(5) and α-AlH(3) with different AlH(6) networks, a zigzag one-dimensional AlH(6) network for CaAlH(5), and a three-dimensional AlH(6) network for α-AlH(3). Both materials showed qualitatively similar INS spectra, in which CaAlH(5)/α-AlH(3) was mainly divided into three regions: (i) the translational modes (318/316 cm(-1)), (ii) the librational modes of the octahedral AlH(6) units (external molecular motion) in the lower frequency range and H-Al-H bond-bending modes (intra molecular motion) at a higher frequency (420-1157/513-1038 cm(-1)), and (iii) the Al-H bond-stretching modes (1238-1750/1486-1942 cm(-1)). In region ii, the appearance of both librational and bond-bending modes was determined by the networked nature of the octahedral AlH(6) units. In addition, the librational modes of AlH(6) on α-AlH(3) exhibit higher frequencies than CaAlH(5) due to the tighter bonding between the octahedral AlH(6) units. With regard to average frequencies for the Al-H, ω(S), bond-stretching modes, and average Al-H bond distances on the aluminum-based hydrides including CaAlH(5) and α-AlH(3), ω(S) showed lower frequencies that correlate with lengthening of the Al-H bond distances.

  1. Inelastic and elastic neutron scattering studies of the vibrational and reorientational dynamics, crystal structure and solid-solid phase transition in [Mn(OS(CH3)2)6](ClO4)2 supported by theoretical (DFT) calculations

    NASA Astrophysics Data System (ADS)

    Szostak, Elżbieta; Hetmańczyk, Joanna; Migdał-Mikuli, Anna

    2015-06-01

    The vibrational and reorientational dynamics of CH3 groups from (CH3)2SO ligands in the high- and low-temperature phases of [Mn(OS(CH3)2)6](ClO4)2 were investigated by quasielastic and inelastic incoherent neutron scattering (QENS and IINS) methods. The results show that above the phase transition temperature (detected earlier by differential scanning calorimetry (DSC) at TC5c = 222.9 K on cooling and at TC5h = 225.4 K on heating) the CH3 groups perform fast (τR ≈ 10-12-10-13 s) reorientational motions. These motions start to slow down below TC5c Neutron powder diffraction (NPD) measurements, performed simultaneously with QENS and IINS, indicated that this phase transition is associated with a change of the crystal structure, too. Theoretical infrared absorption, Raman and inelastic incoherent neutron scattering spectra were calculated using DFT method (B3LYP functional, LANL2DZ ECP basis set (on Mn atom) and 6-311+G(d,p) basis set (on C, H, S, O atoms) for the isolated equilibrium model (isolated [Mn(DMSO)6]2+ cation and ClO4- anion). Calculated spectra show a good agreement with the experimental spectra (FT-IR, RS and IINS). The comparison of the results obtained by these complementary methods was made.

  2. Low energy ballasted flotation.

    PubMed

    Jarvis, P; Buckingham, P; Holden, B; Jefferson, B

    2009-08-01

    A novel process which involves the replacement or supplementation of bubbles in the dissolved air flotation process with low density beads is presented. The work comprised a series of bench-scale flotation trials treating three commonly encountered algal species (Microcystis, Melosira and Chlorella) that were removed in a flotation cell configured as either: conventional dissolved air flotation (DAF); ballasted flotation using low density 70 microm glass beads with a density of 100 kg m(-3); or a hybrid process of ballasted flotation combined with conventional DAF. Results indicated that the bead only system was capable of achieving better residual turbidity than standard DAF at bead concentrations of 500 mg L(-1). Addition of beads in combination with standard DAF reduced turbidity further to even lower residual turbidity levels. Algae removal was improved when glass beads were dosed, but removal was dependent on algal species. Microcystis was removed by 97% for bead only systems and this removal did not change significantly with the addition of air bubbles. Melosira was the next best removed algae with bead only dosed systems giving similar removals to that achieved by standard DAF using a 10% air recycle ratio (81 and 76% removal respectively). Chlorella was the least well removed algae by bead only systems (63% removal). However, removal was rapidly improved to 86% by the addition of air bubbles using only a 2% recycle ratio. Energy estimations suggested that at least a 50% energy reduction could be achieved using the process offering a potential route for future development of low energy separation processes for algae removal.

  3. Effect of Nematic Order on the Low-Energy Spin Fluctuations in Detwinned BaFe_{1.935}Ni_{0.065}As_{2}.

    PubMed

    Zhang, Wenliang; Park, J T; Lu, Xingye; Wei, Yuan; Ma, Xiaoyan; Hao, Lijie; Dai, Pengcheng; Meng, Zi Yang; Yang, Yi-Feng; Luo, Huiqian; Li, Shiliang

    2016-11-25

    The origin of nematic order remains one of the major debates in iron-based superconductors. In theories based on spin nematicity, one major prediction is that the spin-spin correlation length at (0,π) should decrease with decreasing temperature below the structural transition temperature T_{s}. Here, we report inelastic neutron scattering studies on the low-energy spin fluctuations in BaFe_{1.935}Ni_{0.065}As_{2} under uniaxial pressure. Both intensity and spin-spin correlation start to show anisotropic behavior at high temperature, while the reduction of the spin-spin correlation length at (0,π) happens just below T_{s}, suggesting the strong effect of nematic order on low-energy spin fluctuations. Our results favor the idea that treats the spin degree of freedom as the driving force of the electronic nematic order.

  4. Photon Strength and the Low-Energy Enhancement

    SciTech Connect

    Wiedeking, M; Bernstein, L A; Krticka, M; Bleuel, D L; Allmond, J M; Basunia, M S; Burke, J T; Fallon, P; Firestone, R B; Goldblum, B L; Hatarik, R; Lake, P T; Lee, I Y; Lesher, S R; Paschalis, S; Petri, M; Phair, L; Scielzo, N D

    2012-02-22

    The ability of atomic nuclei to emit and absorb photons with energy E{sub {gamma}} is known as the photon strength function f(E{sub {gamma}}). It has direct relevance to astrophysical element formation via neutron capture processes due to its central role in nuclear reactions. Studies of f(E{sub {gamma}}) have benefited from a wealth of data collected in neutron capture and direct reactions but also from newly commissioned inelastic photon scattering facilities. The majority of these experimental methods, however, rely on the use of models because measured {gamma}-ray spectra are simultaneously sensitive to both the nuclear level density and f(E{sub {gamma}}). As excitation energy increases towards the particle separation energies, the level density increases rapidly, creating the quasi-continuum. Nuclear properties in this excitation energy region are best characterized using statistical quantities, such as f(E{sub {gamma}}). A point of contention in studies of the quasi-continuum has been an unexpected and unexplained increase in f(E{sub {gamma}}) at low {gamma}-ray energies (i.e. below E{sub {gamma}} {approx}3 MeV) in a subset of light-to-medium mass nuclei. Ideally, a new model-independent experimental technique is required to address questions regarding the existence and origin of this low-energy enhancement in f(E{sub {gamma}}). Here such a model-independent approach is presented for determining the shape of f(E{sub {gamma}}) over a wide range of energies. The method involves the use of coupled high-resolution particle and {gamma}-ray spectroscopy to determine the emission of {gamma} rays from the quasi-continuum in a nucleus with defined excitation energy to individual discrete levels of known spins and parities. This method shares characteristics of two neutron capture-based techniques: the Average Resonance Capture (ARC) and the Two-Step Cascade analysis (TSC). The power of the new technique lies in the additional ability to positively identify primary

  5. Scattering of low-energy neutrinos on atomic shells

    NASA Astrophysics Data System (ADS)

    Babič, Andrej; Šimkovic, Fedor

    2015-10-01

    We present a derivation of the total cross section for inelastic scattering of low-energy solar neutrinos and reactor antineutrinos on bound electrons, resulting in a transition of the electron to an excited state. The atomic-shell structure of various chemical elements is treated in terms of a nonrelativistic approximation. We estimate the interaction rates for modern neutrino detectors, in particular the Borexino and GEMMA experiments. We establish that in these experiments the effect can be safely neglected, but it could be accessible to future large-volume neutrino detectors with low energy threshold.

  6. Scattering of low-energy neutrinos on atomic shells

    SciTech Connect

    Babič, Andrej; Šimkovic, Fedor

    2015-10-28

    We present a derivation of the total cross section for inelastic scattering of low-energy solar neutrinos and reactor antineutrinos on bound electrons, resulting in a transition of the electron to an excited state. The atomic-shell structure of various chemical elements is treated in terms of a nonrelativistic approximation. We estimate the interaction rates for modern neutrino detectors, in particular the Borexino and GEMMA experiments. We establish that in these experiments the effect can be safely neglected, but it could be accessible to future large-volume neutrino detectors with low energy threshold.

  7. Phase Shifts of p-3He Scattering at Low Energies

    NASA Astrophysics Data System (ADS)

    Yoshino, Y.; Limkaisang, V.; Nagata, J.; Yoshino, H.; Matsuda, M.

    2000-01-01

    A method employing single-energy phase-shift analysis of p-3He scattering is developed by using the S matrix in the Matsuda-Watari representation. This method can be applied for analyses in the low-energy region and also in the inelastic region. Phase-shift solutions of p-3He scattering are given at TL = 4.0, 5.5, 6.8, 8.5, 9.5 and 19.48 MeV.

  8. Slow Magnetic Relaxations in Cobalt(II) Tetranitrate Complexes. Studies of Magnetic Anisotropy by Inelastic Neutron Scattering and High-Frequency and High-Field EPR Spectroscopy

    SciTech Connect

    Chen, Lei; Cui, Hui-Hui; Stavretis, Shelby E.; Hunter, Seth C.; Zhang, Yi-Quan; Chen, Xue-Tai; Sun, Yi-Chen; Wang, Zhenxing; Song, You; Podlesnyak, Andrey A.; Ouyang, Zhong-Wen; Xue, Zi-Ling

    2016-12-07

    We synthesized and studied three mononuclear cobalt(II) tetranitrate complexes (A)2[Co(NO3)4] with different countercations, Ph4P+ (1), MePh3P+ (2), and Ph4As+ (3), using X-ray single-crystal diffraction, magnetic measurements, inelastic neutron scattering (INS), high-frequency and high-field EPR (HF-EPR) spectroscopy, and theoretical calculations. Furthermore, the X-ray diffraction studies reveal that the structure of the tetranitrate cobalt anion varies with the countercation. 1 and 2 exhibit highly irregular seven-coordinate geometries, while the central Co(II) ion of 3 is in a distorted-dodecahedral configuration. The sole magnetic transition observed in the INS spectroscopy of 1–3 corresponds to the zero-field splitting (2(D2 + 3E2)1/2) from 22.5(2) cm–1 in 1 to 26.6(3) cm–1 in 2 and 11.1(5) cm–1 in 3. The positive sign of the D value, and hence the easy-plane magnetic anisotropy, was demonstrated for 1 by INS studies under magnetic fields and HF-EPR spectroscopy. The combined analyses of INS and HF-EPR data yield the D values as +10.90(3), +12.74(3), and +4.50(3) cm–1 for 1–3, respectively. Frequency- and temperature-dependent alternating-current magnetic susceptibility measurements reveal the slow magnetization relaxation in 1 and 2 at an applied dc field of 600 Oe, which is a characteristic of field-induced single-molecule magnets (SMMs). Finally, the electronic structures and the origin of magnetic anisotropy of 1–3 were revealed by calculations at the CASPT2/NEVPT2 level.

  9. The application of inelastic neutron scattering to explore the significance of a magnetic transition in an iron based Fischer-Tropsch catalyst that is active for the hydrogenation of CO

    NASA Astrophysics Data System (ADS)

    Warringham, Robbie; McFarlane, Andrew R.; MacLaren, Donald A.; Webb, Paul B.; Tooze, Robert P.; Taylor, Jon; Ewings, Russell A.; Parker, Stewart F.; Lennon, David

    2015-11-01

    An iron based Fischer-Tropsch synthesis catalyst is evaluated using CO hydrogenation at ambient pressure as a test reaction and is characterised by a combination of inelastic neutron scattering (INS), powder X-ray diffraction, temperature-programmed oxidation, Raman scattering, and transmission electron microscopy. The INS spectrum of the as-prepared bulk iron oxide pre-catalyst (hematite, α-Fe2O3) is distinguished by a relatively intense band at 810 cm-1, which has previously been tentatively assigned as a magnon (spinon) feature. An analysis of the neutron scattering intensity of this band as a function of momentum transfer unambiguously confirms this assignment. Post-reaction, the spinon feature disappears and the INS spectrum is characterised by the presence of a hydrocarbonaceous overlayer. A role for the application of INS in magnetic characterisation of iron based FTS catalysts is briefly considered.

  10. The application of inelastic neutron scattering to explore the significance of a magnetic transition in an iron based Fischer-Tropsch catalyst that is active for the hydrogenation of CO

    SciTech Connect

    Warringham, Robbie; McFarlane, Andrew R.; Lennon, David; MacLaren, Donald A.; Webb, Paul B.; Tooze, Robert P.; Taylor, Jon; Ewings, Russell A.; Parker, Stewart F.

    2015-11-07

    An iron based Fischer-Tropsch synthesis catalyst is evaluated using CO hydrogenation at ambient pressure as a test reaction and is characterised by a combination of inelastic neutron scattering (INS), powder X-ray diffraction, temperature-programmed oxidation, Raman scattering, and transmission electron microscopy. The INS spectrum of the as-prepared bulk iron oxide pre-catalyst (hematite, α-Fe{sub 2}O{sub 3}) is distinguished by a relatively intense band at 810 cm{sup −1}, which has previously been tentatively assigned as a magnon (spinon) feature. An analysis of the neutron scattering intensity of this band as a function of momentum transfer unambiguously confirms this assignment. Post-reaction, the spinon feature disappears and the INS spectrum is characterised by the presence of a hydrocarbonaceous overlayer. A role for the application of INS in magnetic characterisation of iron based FTS catalysts is briefly considered.

  11. The application of inelastic neutron scattering to explore the significance of a magnetic transition in an iron based Fischer-Tropsch catalyst that is active for the hydrogenation of CO.

    PubMed

    Warringham, Robbie; McFarlane, Andrew R; MacLaren, Donald A; Webb, Paul B; Tooze, Robert P; Taylor, Jon; Ewings, Russell A; Parker, Stewart F; Lennon, David

    2015-11-07

    An iron based Fischer-Tropsch synthesis catalyst is evaluated using CO hydrogenation at ambient pressure as a test reaction and is characterised by a combination of inelastic neutron scattering (INS), powder X-ray diffraction, temperature-programmed oxidation, Raman scattering, and transmission electron microscopy. The INS spectrum of the as-prepared bulk iron oxide pre-catalyst (hematite, α-Fe2O3) is distinguished by a relatively intense band at 810 cm(-1), which has previously been tentatively assigned as a magnon (spinon) feature. An analysis of the neutron scattering intensity of this band as a function of momentum transfer unambiguously confirms this assignment. Post-reaction, the spinon feature disappears and the INS spectrum is characterised by the presence of a hydrocarbonaceous overlayer. A role for the application of INS in magnetic characterisation of iron based FTS catalysts is briefly considered.

  12. Magnetic interactions in the multiferroic phase of CuFe1 xGaxO2 (x = 0.035) refined by inelastic neutron scattering with uniaxial-pressure control of domain structure

    SciTech Connect

    Nakajima, Taro; Mitsuda, Setsuo; Haraldsen, Jason T.; Fishman, Randy Scott; Hong, Tao; Terada, Noriki; Uwatoko, Yoshiya

    2012-01-01

    We have performed inelastic neutron scattering measurements in the ferroelectric noncollinear- magnetic phase of CuFe1 xGaxO2 (CFGO) with x = 0.035 under applied uniaxial pressure. This system has three types of magnetic domains with three different orientations reflecting the trigonal symmetry of the crystal structure. To identify the magnetic excitation spectrum corresponding to a magnetic domain, we have produced a nearly single-domain multiferroic phase by applying a uniaxial pressure of 10 MPa onto the [1 10] surfaces of a single crystal CFGO sample. As a result, we have successfully observed the single-domain spectrum in the multiferroic phase. Using the Hamiltonian employed in the previous inelastic neutron scattering study on the multi-domain multiferroic phase of CFGO (x = 0.035) [Haraldsen et al. Phys. Rev. B 82 020404R (2010)], we have refined the Hamiltonian parameters so as to simultaneously reproduce both of the observed single-domain and multi-domaim spectra. Comparing between the Hamiltonian parameters in the multiferroic phase of CFGO and in the collinear four-sublattice magnetic ground state of undoped CuFeO2 [Nakajima et al, Phys. Rev. B 84 184401 (2011)], we suggest that the nonmagnetic substitution weakens the spin-lattice coupling, which often favors a collinear magnetic ordering, as a consequence of the partial release of the spin frustration.

  13. High-energy magnetic excitations in overdoped La2-xSrxCuO4 studied by neutron and resonant inelastic X-ray scattering

    SciTech Connect

    Wakimoto, S.; Ishii, K.; Kimura, H.; Fujita, M.; Dellea, G.; Kummer, K.; Braicovich, L.; Ghiringhelli, G.; Debeer-Schmitt, Lisa M.; Granroth, Garrett E.

    2015-05-21

    We have performed neutron inelastic scattering and resonant inelastic x-ray scattering (RIXS) at the Cu-L3 edge to study high-energy magnetic excitations at energy transfers of more than 100 meV for overdoped La2₋xSrxCuO4 with x=0.25 (Tc=15 K) and x=0.30 (nonsuperconducting) using identical single-crystal samples for the two techniques. From constant-energy slices of neutron-scattering cross sections, we have identified magnetic excitations up to ~250 meV for x=0.25. Although the width in the momentum direction is large, the peak positions along the (π,π) direction agree with the dispersion relation of the spin wave in the nondoped La2CuO4 (LCO), which is consistent with the previous RIXS results of cuprate superconductors. Using RIXS at the Cu-L3 edge, we have measured the dispersion relations of the so-called paramagnon mode along both (π,π) and (π,0) directions. Although in both directions the neutron and RIXS data connect with each other and the paramagnon along (π,0) agrees well with the LCO spin-wave dispersion, the paramagnon in the (π,π) direction probed by RIXS appears to be less dispersive and the excitation energy is lower than the spin wave of LCO near (π/2,π/2). Thus, our results indicate consistency between neutron inelastic scattering and RIXS, and elucidate the entire magnetic excitation in the (π,π) direction by the complementary use of two probes. The polarization dependence of the RIXS profiles indicates that appreciable charge excitations exist in the same energy range of magnetic excitations, reflecting the itinerant character of the overdoped sample. Lastly, we find a possible anisotropy in the charge excitation intensity might explain the apparent differences in the paramagnon dispersion in the (π,π) direction as detected by the x-ray scattering.

  14. C7LYC Scintillators and Fast Neutron Spectroscopy

    NASA Astrophysics Data System (ADS)

    Chowdhury, P.; Brown, T.; Doucet, E.; Lister, C. J.; Wilson, G. L.; D'Olympia, N.; Devlin, M.; Mosby, S.

    2016-09-01

    Cs2 LiYCl6 (CLYC) scintillators detect both gammas and neutrons with excellent pulse shape discrimination. At UML, fast neutron measurements with a 16-element 1''x1'' CLYC array show promise for low energy nuclear science. CLYC detects fast neutrons via the 35Cl (n,p) reaction (resolution < 10 % at < 8 MeV). In our 7Li-enriched C7LYC, the thermal neutron response from the 6Li(n, α)t reaction is virtually eliminated. The low intrinsic efficiency of CLYC for fast neutrons (< 1 %) is offset by increased solid angle with the array placed near the target, since TOF is not needed for energy resolution. The array was tested at LANL for measuring elastic and inelastic neutron scattering on 56Fe. The incident energy from the white neutron source was measured via TOF, and the scattered neutron energy via the pulse height in CLYC. The array was also tested at CARIBU for measuring beta-delayed neutrons. Larger CLYC crystals are now a reality. Measurements with the first 3'' x 3'' C7LYC crystal are in progress at UML. Results will be discussed in the context of constructing a C7LYC array at FRIB for reaction and decay spectroscopy of neutron-rich fragments. Supported by the NNSA Stewardship Science Academic Alliance Program under Grant DE-NA00013008.

  15. Microdosimetry of low-energy electrons.

    PubMed

    Liamsuwan, Thiansin; Emfietzoglou, Dimitris; Uehara, Shuzo; Nikjoo, Hooshang

    2012-12-01

    To investigate differences in energy depositions and microdosimetric parameters of low-energy electrons in liquid and gaseous water using Monte Carlo track structure simulations. KURBUC-liq (Kyushu University and Radiobiology Unit Code for liquid water) was used for simulating electron tracks in liquid water. The inelastic scattering cross sections of liquid water were obtained from the dielectric response model of Emfietzoglou et al. (Radiation Research 2005;164:202-211). Frequencies of energy deposited in nanometre-size cylindrical targets per unit absorbed dose and associated lineal energies were calculated for 100-5000 eV monoenergetic electrons and the electron spectrum of carbon K edge X-rays. The results for liquid water were compared with those for water vapour. Regardless of electron energy, there is a limit how much energy electron tracks can deposit in a target. Phase effects on the frequencies of energy depositions are largely visible for the targets with diameters and heights smaller than 30 nm. For the target of 2.3 nm by 2.3 nm (similar to dimension of DNA segments), the calculated frequency- and dose-mean lineal energies for liquid water are up to 40% smaller than those for water vapour. The corresponding difference is less than 12% for the targets with diameters ≥ 30 nm. Condensed-phase effects are non-negligible for microdosimetry of low-energy electrons for targets with sizes smaller than a few tens of nanometres, similar to dimensions of DNA molecular structures and nucleosomes.

  16. Deep Inelastic Scattering and Related Phenomena

    NASA Astrophysics Data System (ADS)

    D'Agostini, G.; Nigro, A.

    1997-03-01

    The Table of Contents for the book is as follows: * Organization * Foreword * Welcome Address * PLENARY SESSION: "From Paris to Rome" * Deep Inelastic Physics with H1 * Recent Results from ZEUS * Overview of the Status of Polarised Structure Functions * Quarks and Gluons at Hadron Colliders * Deep Inelastic Scattering - Theory and Phenomenology * WORKING GROUP 1: Structure Functions * Inclusive Jet Cross Section Measurement at CDF * Measurement of Direct Photons by the DØ Experiment * MRS Parton Distributions * Global QCD Analysis, the Gluon Distribution, and High Et Inclusive Jet Data * F2 Measurement and QCD Analysis on 94 H1 Data * The ZEUS 1994 F2 Measurement * Measurement of the Total γ*p Cross Section at very Low x and Q2 at HERA * New Results on F2 Structure Functions * Proton Structure Function and Gluon Distribution Functions from Fermilab Experiment E665 * The Transition from the Photoproduction to the DIS Region * The BFKL Pomeron: Can It Be Detected? * BFKL/CCFM Phenomenology * Physics and Mathematics of Dynamical Partons * k⊥-Factorization and Perturbative Invariants at Small x * Double Scaling Violations * On the Asymptotic Behaviour of F2(x, Q2) * Double Logarithmic Scaling of F2 * Differential Charged Current Cross-Sections at HERA * Neutral Current ep Deep Inelastic Scattering at High Q2 and Limits on New Physics * Charm Production in Charged-Current DIS and Extraction of the Strange Sea Density * Extraction of the Gluon Density * On Problems in Extracting the Gluon Density from the Nucleon Structure Function Measurements * Inclusive Measurement of the Strong Coupling at HERA * A Measurement of R = σL/σT in Deep Inelastic Neutrino-Nucleon Scattering at the Tevatron * A Measurement of R = σL/σT in Deep Inelastic μ - p and μ - d Scattering * A Determination of the Longitudinal Proton Structure Function FL(x, Q2) at Low x at HERA * Prospects for Measuring R = σL/σT at HERA in 1966 Low-Energy Running * A Leading Order, in ln(1/x) as well as

  17. Electromagnon excitation in the field-induced nonlinear ferrimagnetic phase of Ba2Mg2Fe12O22 studied by polarized inelastic neutron and terahertz time-domain optical spectroscopy

    DOE PAGES

    Nakajima, Taro; Takahashi, Youtarou; Kibayashi, Shunsuke; ...

    2016-01-19

    We have studied magnetic excitations in a field-induced noncollinear commensurate ferrimagnetic phase of Ba2Mg2Fe12O22 by means of polarized inelastic neutron scattering (PINS) and terahertz (THz) time-domain optical spectroscopy under magnetic field. A previous THz spectroscopy study reported that the field-induced phase exhibits electric-dipole-active excitations with energies of around 5 meV [Kida et al., Phys. Rev. B 83, 064422 (2011)]. In the present PINS measurements, we observed inelastic scattering signals around 5 meV at the zone center in the spin-flip channel. This directly shows that the electric-dipole-active excitations are indeed of magnetic origin, that is, electromagnons. In addition, the present THzmore » spectroscopy confirms that the excitations have oscillating electric polarization parallel to the c axis. In terms of the spin-current model (Katsura-Nagaosa-Balatsky model), the noncollinear magnetic order in the field-induced phase can induce static electric polarization perpendicular to the c axis, but not dynamic electric polarization along the c axis. Furthermore, we suggest that the electromagnon excitations can be explained by applying the magnetostriction model to the out-of-phase oscillations of the magnetic moments, which is deduced from the present experimental results.« less

  18. A low energy electron magnetometer

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Wood, G. M., Jr.; Rayborn, G. H.; White, F. A.

    1979-01-01

    The concept of a highly sensitive magnetometer based on the deflection of low energy electron beams in magnetic fields is analyzed. Because of its extremely low mass and consequently high e/m ratio, a low energy electron is easily deflected in a magnetic field, thus providing a basis for very low field measurement. Calculations for a specific instrument design indicate that a low energy electron magnetometer (LEEM) can measure magnetic fields as low as 1000 nT. The anticipated performance of LEEM is compared with that of the existing high resolution magnetometers in selected applications. The fast response time of LEEM makes it especially attractive as a potential instrument for magnetic signature analysis in large engineering systems.

  19. Inelastic neutron scattering study of a nonmagnetic collapsed tetragonal phase in nonsuperconducting CaFe2As2: evidence of the impact of spin fluctuations on superconductivity in the iron-arsenide compounds.

    PubMed

    Soh, J H; Tucker, G S; Pratt, D K; Abernathy, D L; Stone, M B; Ran, S; Bud'ko, S L; Canfield, P C; Kreyssig, A; McQueeney, R J; Goldman, A I

    2013-11-27

    The relationship between antiferromagnetic spin fluctuations and superconductivity has become a central topic of research in studies of superconductivity in the iron pnictides. We present unambiguous evidence of the absence of magnetic fluctuations in the nonsuperconducting collapsed tetragonal phase of CaFe2As2 via inelastic neutron scattering time-of-flight data, which is consistent with the view that spin fluctuations are a necessary ingredient for unconventional superconductivity in the iron pnictides. We demonstrate that the collapsed tetragonal phase of CaFe2As2 is nonmagnetic, and discuss this result in light of recent reports of high-temperature superconductivity in the collapsed tetragonal phase of closely related compounds.

  20. Inelastic Neutron Scattering Study of a Nonmagnetic Collapsed Tetragonal Phase in Nonsuperconducting CaFe2As2: Evidence of the Impact of Spin Fluctuations on Superconductivity in the Iron-Arsenide Compounds

    SciTech Connect

    Soh, Jing-Han; Tucker, Ggregory S.; Pratt, Daniel K.; Abernathy, D. L.; Stone, M. B.; Ran, Sheng; Budko, Sergey L.; Canfield, Paul C.; Kreyssig, Andreas; McQueeney, Robert J.; Goldman, Alan I.

    2013-11-27

    The relationship between antiferromagnetic spin fluctuations and superconductivity has become a central topic of research in studies of superconductivity in the iron pnictides. We present unambiguous evidence of the absence of magnetic fluctuations in the nonsuperconducting collapsed tetragonal phase of CaFe2As2 via inelastic neutron scattering time-of-flight data, which is consistent with the view that spin fluctuations are a necessary ingredient for unconventional superconductivity in the iron pnictides. We demonstrate that the collapsed tetragonal phase of CaFe2As2 is nonmagnetic, and discuss this result in light of recent reports of high-temperature superconductivity in the collapsed tetragonal phase of closely related compounds.

  1. Neutron inelastic scattering investigation of the magnetic excitations in Cu{sub 2}Te{sub 2}O{sub 5}X{sub 2} (X=Br,Cl)

    SciTech Connect

    Crowe, S.J.; Majumdar, S.; Lees, M.R.; Paul, D. McK.; Bewley, R.I.; Levett, S.J.; Ritter, C.

    2005-06-01

    Neutron inelastic scattering investigations have been performed on the spin tetrahedral system Cu{sub 2}Te{sub 2}O{sub 5}X{sub 2} (X=Cl,Br). We report the observation of magnetic excitations with a dispersive component in both compounds, associated with the three-dimensional incommensurate magnetic order that develops below T{sub N}{sup Cl}=18.2 K and T{sub N}{sup Br}=11.4 K. The excitation in Cu{sub 2}Te{sub 2}O{sub 5}Cl{sub 2} softens as the temperature approaches T{sub N}{sup Cl}, leaving diffuse quasi-elastic scattering above the transition temperature. In the bromide, the excitations are present well above T{sub N}{sup Br}, which might be attributed to the presence of a degree of low dimensional correlations above T{sub N}{sup Br} in this compound.

  2. Inelastic Neutron Scattering Study of a Nonmagnetic Collapsed Tetragonal Phase in Nonsuperconducting CaFe2As2: Evidence of the Impact of Spin Fluctuations on Superconductivity in the Iron-Arsenide Compounds

    NASA Astrophysics Data System (ADS)

    Soh, J. H.; Tucker, G. S.; Pratt, D. K.; Abernathy, D. L.; Stone, M. B.; Ran, S.; Bud'ko, S. L.; Canfield, P. C.; Kreyssig, A.; McQueeney, R. J.; Goldman, A. I.

    2013-11-01

    The relationship between antiferromagnetic spin fluctuations and superconductivity has become a central topic of research in studies of superconductivity in the iron pnictides. We present unambiguous evidence of the absence of magnetic fluctuations in the nonsuperconducting collapsed tetragonal phase of CaFe2As2 via inelastic neutron scattering time-of-flight data, which is consistent with the view that spin fluctuations are a necessary ingredient for unconventional superconductivity in the iron pnictides. We demonstrate that the collapsed tetragonal phase of CaFe2As2 is nonmagnetic, and discuss this result in light of recent reports of high-temperature superconductivity in the collapsed tetragonal phase of closely related compounds.

  3. HYSPEC : A CRYSTAL TIME OF FLIGHT HYBRID SPECTROMETER FOR THE SPALLATION NEUTRON SOURCE.

    SciTech Connect

    SHAPIRO,S.M.; ZALIZNYAK,I.A.

    2002-12-30

    This document lays out a proposal by the Instrument Development Team (IDT) composed of scientists from leading Universities and National Laboratories to design and build a conceptually new high-flux inelastic neutron spectrometer at the pulsed Spallation Neutron Source (SNS) at Oak Ridge. This instrument is intended to supply users of the SNS and scientific community, of which the IDT is an integral part, with a platform for ground-breaking investigations of the low-energy atomic-scale dynamical properties of crystalline solids. It is also planned that the proposed instrument will be equipped with a polarization analysis capability, therefore becoming the first polarized beam inelastic spectrometer in the SNS instrument suite, and the first successful polarized beam inelastic instrument at a pulsed spallation source worldwide. The proposed instrument is designed primarily for inelastic and elastic neutron spectroscopy of single crystals. In fact, the most informative neutron scattering studies of the dynamical properties of solids nearly always require single crystal samples, and they are almost invariably flux-limited. In addition, in measurements with polarization analysis the available flux is reduced through selection of the particular neutron polarization, which puts even more stringent limits on the feasibility of a particular experiment. To date, these investigations have mostly been carried out on crystal spectrometers at high-flux reactors, which usually employ focusing Bragg optics to concentrate the neutron beam on a typically small sample. Construction at Oak Ridge of the high-luminosity spallation neutron source, which will provide intense pulsed neutron beams with time-averaged fluxes equal to those at medium-flux reactors, opens entirely new opportunities for single crystal neutron spectroscopy. Drawing upon experience acquired during decades of studies with both crystal and time-of-flight (TOF) spectrometers, the IDT has developed a conceptual

  4. Low Energy Schools in Ireland

    ERIC Educational Resources Information Center

    Heffernan, Martin

    2004-01-01

    Out of a commitment to reducing carbon dioxide emissions, Ireland's Department of Education and Science has designed and constructed two low energy schools, in Tullamore, County Offaly, and Raheen, County Laois. With energy use in buildings responsible for approximately 55% of the CO[subscript 2] released into the atmosphere and a major…

  5. Low Energy Schools in Ireland

    ERIC Educational Resources Information Center

    Heffernan, Martin

    2004-01-01

    Out of a commitment to reducing carbon dioxide emissions, Ireland's Department of Education and Science has designed and constructed two low energy schools, in Tullamore, County Offaly, and Raheen, County Laois. With energy use in buildings responsible for approximately 55% of the CO[subscript 2] released into the atmosphere and a major…

  6. Measurement of the structure function of the nearly free neutron using spectator tagging in inelastic H2 ( e, e'ps ) X scattering with CLAS

    DOE PAGES

    Tkachenko, S.; Baillie, N.; Kuhn, S. E.; ...

    2014-04-24

    In this study, much less is known about neutron structure than that of the proton due to the absence of free neutron targets. Neutron information is usually extracted from data on nuclear targets such as deuterium, requiring corrections for nuclear binding and nucleon off-shell effects. These corrections are model dependent and have significant uncertainties, especially for large values of the Bjorken scaling variable x. As a consequence, the same data can lead to different conclusions, for example, about the behavior of the d quark distribution in the proton at large x.

  7. Low energy phonons in the NTE compounds Zn(CN)2 and ZnPt(CN)6

    NASA Astrophysics Data System (ADS)

    Chapman, Karena W.; Hagen, Mark; Kepert, Cameron J.; Manuel, Pascal

    2006-11-01

    The compounds Zn(CN)2 and ZnPt(CN)6 both display negative thermal expansion (NTE) properties, that is to say they undergo a volume contraction with increasing temperature. In the case of Zn(CN)2 this volume contraction occurs over a temperature range from 25 to 375 K with a coefficient of thermal expansion α=-16.9(2)×10-6 K [A.L. Goodwin, C.J. Kepert, Phys. Rev. B 71 (2005) 14030]. This phenomenon is believed to be related to the presence of low energy rigid unit modes (RUMS) in the phonon dispersion relations of Zn(CN)2 [A.L. Goodwin, C.J. Kepert, Phys. Rev. B 71 (2005) 14030]. We have examined the low energy part of the phonon density of states in Zn(CN)2 and ZnPt(CN)6 using time of flight inelastic neutron scattering from powder samples. In Zn(CN)2 there is a strong peak in the density of states at 2 meV whose temperature dependence can be correlated with that of α. There is a similar peak in the density of states of ZnPt(CN)6 at 7.5 meV, which correlates with the smaller NTE effect in this compound.

  8. Evaluation of proton inelastic reaction models in Geant4 for prompt gamma production during proton radiotherapy

    NASA Astrophysics Data System (ADS)

    Jeyasugiththan, Jeyasingam; Peterson, Stephen W.

    2015-10-01

    During proton beam radiotherapy, discrete secondary prompt gamma rays are induced by inelastic nuclear reactions between protons and nuclei in the human body. In recent years, the Geant4 Monte Carlo toolkit has played an important role in the development of a device for real time dose range verification purposes using prompt gamma radiation. Unfortunately the default physics models in Geant4 do not reliably replicate the measured prompt gamma emission. Determining a suitable physics model for low energy proton inelastic interactions will boost the accuracy of prompt gamma simulations. Among the built-in physics models, we found that the precompound model with a modified initial exciton state of 2 (1 particle, 1 hole) produced more accurate discrete gamma lines from the most important elements found within the body such as 16O, 12C and 14N when comparing them with the available gamma production cross section data. Using the modified physics model, we investigated the prompt gamma spectra produced in a water phantom by a 200 MeV pencil beam of protons. The spectra were attained using a LaBr3 detector with a time-of-flight (TOF) window and BGO active shield to reduce the secondary neutron and gamma background. The simulations show that a 2 ns TOF window could reduce 99% of the secondary neutron flux hitting the detector. The results show that using both timing and active shielding can remove up to 85% of the background radiation which includes a 33% reduction by BGO subtraction.

  9. Evaluation of proton inelastic reaction models in Geant4 for prompt gamma production during proton radiotherapy.

    PubMed

    Jeyasugiththan, Jeyasingam; Peterson, Stephen W

    2015-10-07

    During proton beam radiotherapy, discrete secondary prompt gamma rays are induced by inelastic nuclear reactions between protons and nuclei in the human body. In recent years, the Geant4 Monte Carlo toolkit has played an important role in the development of a device for real time dose range verification purposes using prompt gamma radiation. Unfortunately the default physics models in Geant4 do not reliably replicate the measured prompt gamma emission. Determining a suitable physics model for low energy proton inelastic interactions will boost the accuracy of prompt gamma simulations. Among the built-in physics models, we found that the precompound model with a modified initial exciton state of 2 (1 particle, 1 hole) produced more accurate discrete gamma lines from the most important elements found within the body such as 16O, 12C and 14N when comparing them with the available gamma production cross section data. Using the modified physics model, we investigated the prompt gamma spectra produced in a water phantom by a 200 MeV pencil beam of protons. The spectra were attained using a LaBr3 detector with a time-of-flight (TOF) window and BGO active shield to reduce the secondary neutron and gamma background. The simulations show that a 2 ns TOF window could reduce 99% of the secondary neutron flux hitting the detector. The results show that using both timing and active shielding can remove up to 85% of the background radiation which includes a 33% reduction by BGO subtraction.

  10. Inelastic neutron scattering cross sections for Ge76 relevant to background in neutrinoless double- β decay experiments

    SciTech Connect

    Crider, B. P.; Peters, E. E.; Allmond, J. M.; McEllistrem, M. T.; Prados-Estévez, F. M.; Ross, T. J.; Vanhoy, J. R.; Yates, S. W.

    2015-09-11

    The experimental signature in searches for the neutrinoless double- decay of 76Ge is a peak near 2039 keV in the spectrum. Given the low probability of the process, it is important that the background in this region be well understood. Moreover, inelastic scattering reactions with neutrons from muon-induced interactions and ( ,n) reactions in the surrounding materials or in the detector can provide contributions to the background. We also measured the production cross sections for rays from the 76Ge(n,n ) reaction in the 2039-keV region at incident neutron energies up to 4.9 MeV. In addition to determining that the cross sections of a previously known 2040.7-keV ray from the 3952-keV level in 76 Ge are rather small, we find that a larger contribution arises from a 2037.5-keV ray which is attributed to a newly identified level at 3147 keV in 76Ge. Finally, a third contribution is also possible from another new level at 3577 keV. These results indicate that the 2039-keV region in 76Ge neutrinoless double- decay searches is more complex than was previously thought.

  11. The low energy signaling network

    PubMed Central

    Tomé, Filipa; Nägele, Thomas; Adamo, Mattia; Garg, Abhroop; Marco-llorca, Carles; Nukarinen, Ella; Pedrotti, Lorenzo; Peviani, Alessia; Simeunovic, Andrea; Tatkiewicz, Anna; Tomar, Monika; Gamm, Magdalena

    2014-01-01

    Stress impacts negatively on plant growth and crop productivity, caicultural production worldwide. Throughout their life, plants are often confronted with multiple types of stress that affect overall cellular energy status and activate energy-saving responses. The resulting low energy syndrome (LES) includes transcriptional, translational, and metabolic reprogramming and is essential for stress adaptation. The conserved kinases sucrose-non-fermenting-1-related protein kinase-1 (SnRK1) and target of rapamycin (TOR) play central roles in the regulation of LES in response to stress conditions, affecting cellular processes and leading to growth arrest and metabolic reprogramming. We review the current understanding of how TOR and SnRK1 are involved in regulating the response of plants to low energy conditions. The central role in the regulation of cellular processes, the reprogramming of metabolism, and the phenotypic consequences of these two kinases will be discussed in light of current knowledge and potential future developments. PMID:25101105

  12. The Low Energy Neutrino Factory

    SciTech Connect

    Bross, Alan; Geer, Steve; Ellis, Malcolm; Fernandez Martinez, Enrique; Li, Tracey; Pascoli, Silvia; Mena, Olga

    2010-03-30

    We show that a low energy neutrino factory with a baseline of 1300 km and muon energy of 4.5 GeV has an excellent physics reach. The results of our optimisation studies demonstrate that such a setup can have remarkable sensitivity to theta{sub 13} and delta for sin{sup 2}(2theta{sub 13})>10{sup -4}, and to the mass hierarchy for sin{sup 2}(2theta{sub 13})>10{sup -3}. We also illustrate the power of the unique combination of golden and platinum channels accessible to the low energy neutrino factory. We have considered both a 20 kton totally active scintillating detector and a 100 kton liquid argon detector as possible detector technologies, finding that a liquid argon detector with very good background rejection can produce sensitivity to theta{sub 13} and delta with that of the International Design Study neutrino factory.

  13. Review of Low Energy Neutrinos

    NASA Astrophysics Data System (ADS)

    Vergados, J. D.

    2007-04-01

    Some issues regarding low energy neutrinos are reviewed. We focus on three aspects i)We show that by employing very low energy (a few keV) electron neutrinos, neutrino disappearance oscillations can be investigated by detecting recoiling electrons with low threshold spherical gaseous TPC's. In such an experiment, which is sensitive to the small mixing angle θ13, the novel feature is that the oscillation length is so small that the full oscillation takes place inside the detector. Thus one can determine accurately all the oscillation parameters and, in particular, measure or set a good limit on θ13. ii) Low threshold gaseous TPC detectors can also be used in detecting nuclear recoils by exploiting the neutral current interaction. Thus these robust and stable detectors can be employed in supernova neutrino detection. iii) The lepton violating neutrinoless double decay is investigated focusing on how the absolute neutrino mass can be extracted from the data.

  14. Spin-phonon coupling and high-pressure phase transitions of RMnO3 (R=Ca and Pr): An inelastic neutron scattering and first-principles study

    SciTech Connect

    Mishra, S. K.; Gupta, M. K.; Mittal, R.; Kolesnikov, Alexander I.; Chaplot, S. L.

    2016-06-22

    Here, we report inelastic neutron scattering measurements over 7–1251 K in CaMnO3 covering various phase transitions, and over 6–150 K in PrMnO3 covering the magnetic transition. The excitations around 20 meV in CaMnO3 and at 17 meV in PrMnO3 at low temperatures are found to be associated with magnetic origin. We observe coherent magnetic neutron scattering in localized regions in reciprocal space and show it to arise from long-range correlated magnetic spin-waves below the magnetic transition temperature (TN) and short-range stochastic spin-spin fluctuations above TN. In spite of the similarity of the structure of the two compounds, the neutron inelastic spectrum of PrMnO3 exhibits broad features at 150 K unlike well-defined peaks in the spectrum of CaMnO3. This might result from the difference in the nature of interactions in the two compounds (magnetic and Jahn-Teller distortion). Ab initio phonon calculations have been used to interpret the observed phonon spectra. The ab initio calculations at high pressures show that the variations of Mn-O distances are isotropic for CaMnO3 and highly anisotropic for PrMnO3. The calculation in PrMnO3 shows the suppression of Jahn-Teller distortion and simultaneous insulator-to-metal transition. It appears that this transition may not be associated with the occurrence of the tetragonal phase above 20 GPa as reported in the literature, since the tetragonal phase is found to be dynamically unstable, although it is found to be energetically favored over the orthorhombic phase above 20 GPa. CaMnO3 does not show any phase transition up to 60 GPa.

  15. Spin-phonon coupling and high-pressure phase transitions of RMnO3 (R=Ca and Pr): An inelastic neutron scattering and first-principles study

    SciTech Connect

    Mishra, S. K.; Gupta, M. K.; Mittal, R.; Kolesnikov, Alexander I.; Chaplot, S. L.

    2016-06-22

    Here, we report inelastic neutron scattering measurements over 7–1251 K in CaMnO3 covering various phase transitions, and over 6–150 K in PrMnO3 covering the magnetic transition. The excitations around 20 meV in CaMnO3 and at 17 meV in PrMnO3 at low temperatures are found to be associated with magnetic origin. We observe coherent magnetic neutron scattering in localized regions in reciprocal space and show it to arise from long-range correlated magnetic spin-waves below the magnetic transition temperature (TN) and short-range stochastic spin-spin fluctuations above TN. In spite of the similarity of the structure of the two compounds, the neutron inelastic spectrum of PrMnO3 exhibits broad features at 150 K unlike well-defined peaks in the spectrum of CaMnO3. This might result from the difference in the nature of interactions in the two compounds (magnetic and Jahn-Teller distortion). Ab initio phonon calculations have been used to interpret the observed phonon spectra. The ab initio calculations at high pressures show that the variations of Mn-O distances are isotropic for CaMnO3 and highly anisotropic for PrMnO3. The calculation in PrMnO3 shows the suppression of Jahn-Teller distortion and simultaneous insulator-to-metal transition. It appears that this transition may not be associated with the occurrence of the tetragonal phase above 20 GPa as reported in the literature, since the tetragonal phase is found to be dynamically unstable, although it is found to be energetically favored over the orthorhombic phase above 20 GPa. CaMnO3 does not show any phase transition up to 60 GPa.

  16. Vibrations and reorientations of H2O molecules in [Sr(H2O)6]Cl2 studied by Raman light scattering, incoherent inelastic neutron scattering and proton magnetic resonance.

    PubMed

    Hetmańczyk, Joanna; Hetmańczyk, Lukasz; Migdał-Mikuli, Anna; Mikuli, Edward; Florek-Wojciechowska, Małgorzata; Harańczyk, Hubert

    2014-04-24

    Vibrational-reorientational dynamics of H2O ligands in the high- and low-temperature phases of [Sr(H2O)6]Cl2 was investigated by Raman Spectroscopy (RS), proton magnetic resonance ((1)H NMR), quasielastic and inelastic incoherent Neutron Scattering (QENS and IINS) methods. Neutron powder diffraction (NPD) measurements, performed simultaneously with QENS, did not indicated a change of the crystal structure at the phase transition (detected earlier by differential scanning calorimetry (DSC) at TC(h)=252.9 K (on heating) and at TC(c)=226.5K (on cooling)). Temperature dependence of the full-width at half-maximum (FWHM) of νs(OH) band at ca. 3248 cm(-1) in the RS spectra indicated small discontinuity in the vicinity of phase transition temperature, what suggests that the observed phase transition may be associated with a change of the H2O reorientational dynamics. However, an activation energy value (Ea) for the reorientational motions of H2O ligands in both phases is nearly the same and equals to ca. 8 kJ mol(-1). The QENS peaks, registered for low temperature phase do not show any broadening. However, in the high temperature phase a small QENS broadening is clearly visible, what implies that the reorientational dynamics of H2O ligands undergoes a change at the phase transition. (1)H NMR line is a superposition of two powder Pake doublets, differentiated by a dipolar broadening, suggesting that there are two types of the water molecules in the crystal lattice of [Sr(H2O)6]Cl2 which are structurally not equivalent average distances between the interacting protons are: 1.39 and 1.18 Å. However, their reorientational dynamics is very similar (τc=3.3⋅10(-10) s). Activation energies for the reorientational motion of these both kinds of H2O ligands have nearly the same values in an experimental error limit: and equal to ca. 40 kJ mole(-1). The phase transition is not seen in the (1)H NMR spectra temperature dependencies. Infrared (IR), Raman (RS) and inelastic

  17. Enhanced low-energy magnetic excitations via suppression of the itinerancy in Fe0.98-zCuzTe0.5Se0.5

    NASA Astrophysics Data System (ADS)

    Wen, Jinsheng; Li, Shichao; Xu, Zhijun; Zhang, Cheng; Matsuda, M.; Sobolev, O.; Park, J. T.; Christianson, A. D.; Bourret-Courchesne, E.; Li, Qiang; Gu, Genda; Lee, Dung-Hai; Tranquada, J. M.; Xu, Guangyong; Birgeneau, R. J.

    2013-10-01

    We have performed resistivity and inelastic neutron scattering measurements on three samples of Fe0.98-zCuzTe0.5Se0.5 with z=0, 0.02, and 0.1. It is found that with increasing Cu doping the sample's resistivity deviates progressively from that of a metal. However, in contrast to expectations that replacing Fe with Cu would suppress the magnetic correlations, the low-energy (≤12 meV) magnetic scattering is enhanced in strength, with greater spectral weight and longer dynamical spin-spin correlation lengths. Such enhancements can be a consequence of either enlarged local moments or a slowing down of the spin fluctuations. In either case, the localization of the conduction states induced by the Cu doping should play a critical role. Our results are not applicable to models that treat 3d transition metal dopants simply as effective electron donors.

  18. Spin-phonon coupling and high-pressure phase transitions of RMnO3 (R=Ca and Pr): An inelastic neutron scattering and first-principles study

    DOE PAGES

    Mishra, S. K.; Gupta, M. K.; Mittal, R.; ...

    2016-06-22

    Here, we report inelastic neutron scattering measurements over 7–1251 K in CaMnO3 covering various phase transitions, and over 6–150 K in PrMnO3 covering the magnetic transition. The excitations around 20 meV in CaMnO3 and at 17 meV in PrMnO3 at low temperatures are found to be associated with magnetic origin. We observe coherent magnetic neutron scattering in localized regions in reciprocal space and show it to arise from long-range correlated magnetic spin-waves below the magnetic transition temperature (TN) and short-range stochastic spin-spin fluctuations above TN. In spite of the similarity of the structure of the two compounds, the neutron inelasticmore » spectrum of PrMnO3 exhibits broad features at 150 K unlike well-defined peaks in the spectrum of CaMnO3. This might result from the difference in the nature of interactions in the two compounds (magnetic and Jahn-Teller distortion). Ab initio phonon calculations have been used to interpret the observed phonon spectra. The ab initio calculations at high pressures show that the variations of Mn-O distances are isotropic for CaMnO3 and highly anisotropic for PrMnO3. The calculation in PrMnO3 shows the suppression of Jahn-Teller distortion and simultaneous insulator-to-metal transition. It appears that this transition may not be associated with the occurrence of the tetragonal phase above 20 GPa as reported in the literature, since the tetragonal phase is found to be dynamically unstable, although it is found to be energetically favored over the orthorhombic phase above 20 GPa. CaMnO3 does not show any phase transition up to 60 GPa.« less

  19. Intense low-energy ferromagnetic fluctuations in the antiferromagnetic heavy-fermion metal CeB6.

    PubMed

    Jang, Hoyoung; Friemel, G; Ollivier, J; Dukhnenko, A V; Shitsevalova, N Yu; Filipov, V B; Keimer, B; Inosov, D S

    2014-07-01

    Heavy-fermion metals exhibit a plethora of low-temperature ordering phenomena . Among these are the so-called hidden-order phases that, in contrast to conventional magnetic order, are invisible to standard neutron diffraction experiments. One of the structurally most simple hidden-order compounds, CeB6, has been intensively studied for an elusive phase that was attributed to the antiferroquadrupolar ordering of cerium-4f moments . As the ground state of CeB6 is characterized by a more conventional antiferromagnetic (AFM) order , the low-temperature physics of this system has generally been assumed to be governed solely by AFM interactions between the dipolar and multipolar Ce moments . Here we overturn this established picture by observing an intense ferromagnetic (FM) low-energy collective mode that dominates the magnetic excitation spectrum of CeB6. Inelastic neutron-scattering data reveal that the intensity of this FM excitation significantly exceeds that of conventional spin-wave magnons emanating from the AFM wavevectors, thus placing CeB6 much closer to a FM instability than previously anticipated. This propensity for ferromagnetism may account for much of the unexplained behaviour of CeB6, and should lead to a re-examination of existing theories that have so far largely neglected the role of FM interactions.

  20. Is there a low energy enhancement in the photon strength function in molybdenum?

    SciTech Connect

    Sheets, S A

    2008-01-30

    Recent claims of a low energy enhancement in the photon strength function of {sup 96}Mo are investigated. Using the DANCE detector the gamma-ray spectra following resonance neutron capture was measured. The spectrum fitting method was used to indirectly extract a photon strength function from the gamma-ray spectra. No strong low energy enhancement in the photon strength function was found.

  1. Electric and Magnetic Dipole Strength at Low Energy

    NASA Astrophysics Data System (ADS)

    Sieja, K.

    2017-08-01

    A low-energy enhancement of radiative strength functions was deduced from recent experiments in several mass regions of nuclei, which is believed to impact considerably the calculated neutron capture rates. In this Letter we investigate the behavior of the low-energy γ -ray strength of the Sc 44 isotope, for the first time taking into account both electric and magnetic dipole contributions obtained coherently in the same theoretical approach. The calculations are performed using the large-scale shell-model framework in a full 1 ℏω s d -p f -g d s model space. Our results corroborate previous theoretical findings for the low-energy enhancement of the M 1 strength but show quite different behavior for the E 1 strength.

  2. Calculation of astrophysical S factor at low energy levels

    NASA Astrophysics Data System (ADS)

    Andic, Halil Ibrahim; Ozer, Okan

    2017-02-01

    Nuclear reactions are very important for the structure, evolution, nucleosynthesis and various observational manifestations of main-sequence stars, white dwarfs and neutron stars. For astrophysical applications, one needs to know value of S-factor for many reactions at low energies. The experimental measurements of cross-sections at such low energies are essentially not easily available since the Coulomb barrier. Theoretical calculations are model dependent, so that nuclear physics uncertainties of calculated S-factor can be substantial. Using the supersymmetric quantum mechanics one can obtain the supersymmetric partner potential that can vary by several orders of magnitude in the energy range of a given reaction in the calculation of S factor. Since the determination of reaction rates requires accurate values of cross sections at very low energies, then in order to eliminate the main part of the energy dependence of these cross sections one makes use of the astrophysical S-factor in Taylor Expansion series about zero-energy.

  3. Elastic/Inelastic Measurement Project

    SciTech Connect

    Yates, Steven; Hicks, Sally; Vanhoy, Jeffrey; McEllistrem, Marcus

    2016-03-01

    The work scope involves the measurement of neutron scattering from natural sodium (23Na) and two isotopes of iron, 56Fe and 54Fe. Angular distributions, i.e., differential cross sections, of the scattered neutrons will be measured for 5 to 10 incident neutron energies per year. The work of the first year concentrates on 23Na, while the enriched iron samples are procured. Differential neutron scattering cross sections provide information to guide nuclear reaction model calculations in the low-­energy (few MeV) fast-­neutron region. This region lies just above the isolated resonance region, which in general is well studied; however, model calculations are difficult in this region because overlapping resonance structure is evident and direct nuclear reactions are becoming important. The standard optical model treatment exhibits good predictive ability for the wide-­region average cross sections but cannot treat the overlapping resonance features. In addition, models that do predict the direct reaction component must be guided by measurements to describe correctly the strength of the direct component, e.g., β2 must be known to describe the direct component of the scattering to the first excited state. Measurements of the elastic scattering differential cross sections guide the optical model calculations, while inelastic differential cross sections provide the crucial information for correctly describing the direct component. Activities occurring during the performance period are described.

  4. Method and apparatus for generating low energy nuclear particles

    DOEpatents

    Powell, J.R.; Reich, M.; Ludewig, H.; Todosow, M.

    1999-02-09

    A particle accelerator generates an input particle beam having an initial energy level above a threshold for generating secondary nuclear particles. A thin target is rotated in the path of the input beam for undergoing nuclear reactions to generate the secondary particles and correspondingly decrease energy of the input beam to about the threshold. The target produces low energy secondary particles and is effectively cooled by radiation and conduction. A neutron scatterer and a neutron filter are also used for preferentially degrading the secondary particles into a lower energy range if desired. 18 figs.

  5. Method and apparatus for generating low energy nuclear particles

    DOEpatents

    Powell, James R.; Reich, Morris; Ludewig, Hans; Todosow, Michael

    1999-02-09

    A particle accelerator (12) generates an input particle beam having an initial energy level above a threshold for generating secondary nuclear particles. A thin target (14) is rotated in the path of the input beam for undergoing nuclear reactions to generate the secondary particles and correspondingly decrease energy of the input beam to about the threshold. The target (14) produces low energy secondary particles and is effectively cooled by radiation and conduction. A neutron scatterer (44) and a neutron filter (42) are also used for preferentially degrading the secondary particles into a lower energy range if desired.

  6. Vibrational spectra of light and heavy water with application to neutron cross section calculations

    SciTech Connect

    Damian, J. I. Marquez; Granada, J. R.; Malaspina, D. C.

    2013-07-14

    The design of nuclear reactors and neutron moderators require a good representation of the interaction of low energy (E < 1 eV) neutrons with hydrogen and deuterium containing materials. These models are based on the dynamics of the material, represented by its vibrational spectrum. In this paper, we show calculations of the frequency spectrum for light and heavy water at room temperature using two flexible point charge potentials: SPC-MPG and TIP4P/2005f. The results are compared with experimental measurements, with emphasis on inelastic neutron scattering data. Finally, the resulting spectra are applied to calculation of neutron scattering cross sections for these materials, which were found to be a significant improvement over library data.

  7. Fusion reactions at low energy

    SciTech Connect

    Beckerman, M.

    1985-01-01

    Fusion measurement methods at low energies are briefly described, and experimental and theoretical fusion cross sections for /sup 58/Ni + /sup 58/Ni, /sup 58/Ni + /sup 64/Ni and /sup 64/Ni + /sup 64/Ni reactions are discussed. It is shown that quantal tunneling calculations do not describe the near- and sub-barrier behavior of the fusion data. Instead, the WKB predictions fall progressively further blow the experimental results as the energy is lowered. At far subbarrier energies the measured cross sections exceed the WKB predictions by more than three orders of magnitude. The unexpectedly strong dependence of the fusion probability upon the nuclear valence structure is illustrated and discussed. The relationship of channel coupling and quantal tunneling is discussed. In conclusion, it was established that atomic nuclei fuse far more readily at low energies that would be expected from quantal tunneling considerations alone. It was found that the behavior of the cross sections for fusion depends strongly upon the valence structure of the collision partners. This structural dependence extends from light 1p-shell systems to systems involving nearly 200 nucleons. These new phenomena may be viewed as characterizing the tunneling of a quantal system with many degrees of freedom. The failure of standard tunneling models may be understood as resulting from the ability of the dinuclear system to tunnel into the classically forbidden region by means of couplings to intrinsic degrees of freedom. 38 refs. (WHK)

  8. Low energy p p physics

    SciTech Connect

    Amsler, C.; Crowe, K. . Inst. fuer Physik; Lawrence Berkeley Lab., CA )

    1989-02-01

    A detailed investigation of proton-antiproton interactions at low energy has become feasible with the commissioning of the LEAR facility in 1983. We shall shortly review the status of {bar p}p annihilation at rest and the physics motivations for second generation experiments with the Crystal Barrel detector. This type of detector would be adequate for the study of both Kp and {bar p}p interactions on an extracted beam of the KAON Factory. We shall conclude with a few remarks on the physics opportunities with {bar p}'s at the KAON Factory which, in our opinion, will not be covered by the present LEAR facility. 11 refs., 10 figs., 2 tabs.

  9. Low-energy electron potentiometry.

    PubMed

    Jobst, Johannes; Kautz, Jaap; Mytiliniou, Maria; Tromp, Rudolf M; van der Molen, Sense Jan

    2017-10-01

    In a lot of systems, charge transport is governed by local features rather than being a global property as suggested by extracting a single resistance value. Consequently, techniques that resolve local structure in the electronic potential are crucial for a detailed understanding of electronic transport in realistic devices. Recently, we have introduced a new potentiometry method based on low-energy electron microscopy (LEEM) that utilizes characteristic features in the reflectivity spectra of layered materials [1]. Performing potentiometry experiments in LEEM has the advantage of being fast, offering a large field of view and the option to zoom in and out easily, and of being non-invasive compared to scanning-probe methods. However, not all materials show clear features in their reflectivity spectra. Here we, therefore, focus on a different version of low-energy electron potentiometry (LEEP) that uses the mirror mode transition, i.e. the drop in electron reflectivity around zero electron landing energy when they start to interact with the sample rather than being reflected in front of it. This transition is universal and sensitive to the local electrostatic surface potential (either workfunction or applied potential). It can consequently be used to perform LEEP experiments on a broader range of material compared to the method described in Ref[1]. We provide a detailed description of the experimental setup and demonstrate LEEP on workfunction-related intrinsic potential variations on the Si(111) surface and for a metal-semiconductor-metal junction with external bias applied. In the latter, we visualize the Schottky effect at the metal-semiconductor interface. Finally, we compare how robust the two LEEP techniques discussed above are against image distortions due to sample inhomogeneities or contamination. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Neutron-emission measurements at a white neutron source

    SciTech Connect

    Haight, Robert C

    2010-01-01

    Data on the spectrum of neutrons emittcd from neutron-induced reactions are important in basic nuclear physics and in applications. Our program studies neutron emission from inelastic scattering as well as fission neutron spectra. A ''white'' neutron source (continuous in energy) allows measurements over a wide range of neutron energies all in one experiment. We use the tast neutron source at the Los Alamos Neutron Science Center for incident neutron energies from 0.5 MeV to 200 MeV These experiments are based on double time-of-flight techniques to determine the energies of the incident and emitted neutrons. For the fission neutron measurements, parallel-plate ionization or avalanche detectors identify fission in actinide samples and give the required fast timing pulse. For inelastic scattering, gamma-ray detectors provide the timing and energy spectroscopy. A large neutron-detector array detects the emitted neutrons. Time-of-flight techniques are used to measure the energies of both the incident and emitted neutrons. Design considerations for the array include neutron-gamma discrimination, neutron energy resolution, angular coverage, segmentation, detector efficiency calibration and data acquisition. We have made preliminary measurements of the fission neutron spectra from {sup 235}U, {sup 238}U, {sup 237}Np and {sup 239}Pu. Neutron emission spectra from inelastic scattering on iron and nickel have also been investigated. The results obtained will be compared with evaluated data.

  11. Exchange and crystal field in Sm-based magnets. I. Inelastic neutron scattering and high-field magnetization study of Sm2Fe17 and Sm2Fe17N3

    NASA Astrophysics Data System (ADS)

    Sippel, A.; Jahn, L.; Loewenhaupt, M.; Eckert, D.; Kerschl, P.; Handstein, A.; Müller, K.-H.; Wolf, M.; Kuz'Min, M. D.; Steinbeck, L.; Richter, M.; Teresiak, A.; Bewley, R.

    2002-02-01

    A peak is detected in the high-energy inelastic neutron scattering spectra of Sm2Fe17 and Sm2Fe17N3, which is associated with the intermultiplet transition in the 4f shell of samarium. The peak in the nitride Sm2Fe17N3 is situated at a lower energy (163 meV) as compared with the parent compound Sm2Fe17 (177 meV). The peak position provides direct information on the strength of the exchange field on Sm in both compounds: Bex=380 and 270 T in Sm2Fe17 and Sm2Fe17N3, respectively. The 30% reduction in Bex as a result of nitrogenating Sm2Fe17 is consistent with the earlier discovered similar effect in Gd2Fe17. High-field (B<=50 T) magnetization curves have been measured on an oriented powder sample of Sm2Fe17N3 and analyzed using the newly determined Bex. The leading crystal field parameter is thus found to be A02=-28 meV.

  12. Low-Energy Proton Testing Methodology

    NASA Technical Reports Server (NTRS)

    Pellish, Jonathan A.; Marshall, Paul W.; Heidel, David F.; Schwank, James R.; Shaneyfelt, Marty R.; Xapsos, M.A.; Ladbury, Raymond L.; LaBel, Kenneth A.; Berg, Melanie; Kim, Hak S.; Phan, Anthony; Friendlich, M.R.; Rodbell, Kenneth P.; Hakey, Mark C.; Dodd, Paul E.; Reed, Robert A.; Weller, Robert A.; Mendenhall, Marcus H.; Sierawski, B.D.

    2009-01-01

    Use of low-energy protons and high-energy light ions is becoming necessary to investigate current-generation SEU thresholds. Systematic errors can dominate measurements made with low-energy protons. Range and energy straggling contribute to systematic error. Low-energy proton testing is not a step-and-repeat process. Low-energy protons and high-energy light ions can be used to measure SEU cross section of single sensitive features; important for simulation.

  13. Neutron scattering studies in the actinide region. Progress report, August 1, 1992--July 31, 1993

    SciTech Connect

    Kegel, G.H.R.; Egan, J.J.

    1993-09-01

    This report discusses the following topics: Prompt fission neutron energy spectra for {sup 235}U and {sup 239}Pu; Two-parameter measurement of nuclear lifetimes; ``Black`` neutron detector; Data reduction techniques for neutron scattering experiments; Inelastic neutron scattering studies in {sup 197}Au; Elastic and inelastic scattering studies in {sup 239}Pu; and neutron induced defects in silicon dioxide MOS structures.

  14. Intense low energy positron beams

    SciTech Connect

    Lynn, K.G.; Jacobsen, F.M.

    1993-12-31

    Intense positron beams are under development or being considered at several laboratories. Already today a few accelerator based high intensity, low brightness e{sup +} beams exist producing of the order of 10{sup 8} {minus} 10{sup 9} e{sup +}/sec. Several laboratories are aiming at high intensity, high brightness e{sup +} beams with intensities greater than 10{sup 9} e{sup +}/sec and current densities of the order of 10{sup 13} {minus} 10{sup 14} e{sup +} sec{sup {minus}} {sup 1}cm{sup {minus}2}. Intense e{sup +} beams can be realized in two ways (or in a combination thereof) either through a development of more efficient B{sup +} moderators or by increasing the available activity of B{sup +} particles. In this review we shall mainly concentrate on the latter approach. In atomic physics the main trust for these developments is to be able to measure differential and high energy cross-sections in e{sup +} collisions with atoms and molecules. Within solid state physics high intensity, high brightness e{sup +} beams are in demand in areas such as the re-emission e{sup +} microscope, two dimensional angular correlation of annihilation radiation, low energy e{sup +} diffraction and other fields. Intense e{sup +} beams are also important for the development of positronium beams, as well as exotic experiments such as Bose condensation and Ps liquid studies.

  15. Low energy neutral atom imaging

    SciTech Connect

    McComas, D.J.; Funsten, H.O.; Gosling, J.T.; Moore, K.R.; Thomsen, M.F.

    1992-01-01

    Energetic neutral atom (ENA) and low energy neutral atom (LENA) imaging of space plasmas are emerging new technology which promises to revolutionize the way we view and understand large scale space plasma phenomena and dynamics. ENAs and LENAs are produced in the magnetosphere by charge exchange between energetic and plasma ions and cold geocoronal neutrals. While imaging techniques have been previously developed for observing ENAs, with energies above several tens of keV, most of the ions found in the terrestrial magnetosphere have lower energies. We recently suggested that LENAs could be imaged by first converting the neutrals to ions and then electrostatically analyzing them to reject the UV background. In this paper we extend this work to examine in detail the sensor elements needed to make an LENA imager. These elements are (1) a biased collimator to remove the ambient plasma ions and electrons and set the azimuthal field-of-view; (2) a charge modifier to convert a portion of the incident LENAs to ions; (3) an electrostatic analyzer to reject UV light and set the energy passband; and (4) a coincidence detector to measure converted LENAs while rejecting noise and penetrating radiation. We also examine the issue of LENA imager sensitivity and describe ways of optimizing sensitivity in the various sensor components. Finally, we demonstrate in detail how these general considerations are implemented by describing one relatively straightforward design based on a hemispherical electrostatic analyzer.

  16. Low-energy enhancement of nuclear γ strength and its impact on astrophysical reaction rates

    NASA Astrophysics Data System (ADS)

    Larsen, A. C.; Blasi, N.; Bracco, A.; Bürger, A.; Camera, F.; Eriksen, T. K.; Giacoppo, F.; Goriely, S.; Guttormsen, M.; Görgen, A.; Hagen, T. W.; Harissopulos, S.; Koehler, P. E.; Leoni, S.; Million, B.; Nyhus, H. T.; Renstrøm, T. T.; Rose, S.; Ruud, I. E.; Schiller, A.; Siem, S.; Tornyi, T.; Tveten, G. M.; Voinov, A. V.; Wiedeking, M.

    2014-03-01

    An unexpected enhancement in the low-energy part of the γ-strength function for light and medium-mass nuclei has been discovered at the Oslo Cyclotron Laboratory. This enhancement could lead to an increase in the neutron-capture rates up to two orders of magnitude for very exotic, neutron-rich nuclei. However, it is still an open question whether this structure persists when approaching the neutron drip line.

  17. Low-Energy Sputtering Research

    NASA Technical Reports Server (NTRS)

    Ray, P. K.; Shutthanandan, V.

    1999-01-01

    An experimental study is described to measure low-energy (less than 600 eV) sputtering yields of molybdenum with xenon ions using Rutherford backscattering spectroscopy (RBS) and secondary neutral mass spectroscopy (SNMS). An ion gun was used to generate the ion beam. The ion current density at the target surface was approximately 30 (micro)A/sq cm. For RBS measurements, the sputtered material was collected on a thin aluminum strip which was mounted on a semi-circular collector plate. The target was bombarded with 200 and 500 eV xenon ions at normal incidence. The differential sputtering yields were measured using the RBS method with 1 MeV helium ions. The differential yields were fitted with a cosine fitting function and integrated with respect to the solid angle to provide the total sputtering yields. The sputtering yields obtained using the RBS method are in reasonable agreement with those measured by other researchers using different techniques. For the SNMS measurements, 150 to 600 eV xenon ions were used at 50deg angle of incidence. The SNMS spectra were converted to sputtering yields for perpendicular incidence by normalizing SNMS spectral data at 500 eV with the yield measured by Rutherford backscattering spectrometry. Sputtering yields as well as the shape of the yield-energy curve obtained in this manner are in reasonable agreement with those measured by other researchers using different techniques. Sputtering yields calculated by using two semi-spherical formulations agree reasonably well with measured data. The isotopic composition of secondary ions were measured by bombarding copper with xenon ions at energies ranging from 100 eV to 1.5 keV. The secondary ion flux was found to be enriched in heavy isotopes at low incident ion energies. The heavy isotope enrichment was observed to decrease with increasing impact energy. Beyond 700 eV, light isotopes were sputtered preferentially with the enrichment remaining nearly constant.

  18. Study of the soft dipole modes in 140Ce via inelastic scattering of 17O

    NASA Astrophysics Data System (ADS)

    Krzysiek, M.; Kmiecik, M.; Maj, A.; Bednarczyk, P.; Ciemała, M.; Fornal, B.; Grȩbosz, J.; Mazurek, K.; Mȩczyński, W.; Ziȩbliński, M.; Crespi, F. C. L.; Bracco, A.; Benzoni, G.; Blasi, N.; Boiano, C.; Bottoni, S.; Brambilla, S.; Camera, F.; Giaz, A.; Leoni, S.; Million, B.; Morales, A. I.; Nicolini, R.; Pellegri, L.; Riboldi, S.; Vandone, V.; Wieland, O.; De Angelis, G.; Napoli, D. R.; Valiente-Dobon, J. J.; Bazzacco, D.; Farnea, E.; Gottardo, A.; Lenzi, S.; Lunardi, S.; Mengoni, D.; Michelagnoli, C.; Recchia, F.; Ur, C.; Gadea, A.; Huyuk, T.; Barrientos, D.; Birkenbach, B.; Geibel, K.; Hess, H.; Reiter, P.; Steinbach, T.; Wiens, A.; Bürger, A.; Görgen, A.; Guttormsen, M.; Larsen, A. C.; Siem, S.

    2014-05-01

    The main aim of this study was a deeper understanding of the nuclear structure properties of the soft dipole modes in 140Ce, excited via inelastic scattering of weakly bound 17O projectiles. An important aim was to investigate the ‘splitting’ of the PDR into two parts: a low-energy isoscalar component dominated by neutron-skin oscillations and a higher-energy component lying on the tail of the giant dipole resonance of a rather isovector character. This was already observed for this nucleus, investigated in (α, α‧) and (γ, γ‧) experiments. The experiment was performed at Laboratori Nazionali di Legnaro, Italy. Inelastic scattering of 17O ion beam at 20 MeV A-1 was used to excite the resonance modes in the 140Ce target. Gamma-rays were registered by five triple clusters of AGATA-Demonstrator and nine large volume scintillators (LaBr3). The scattered 17O ions were identified by two ΔE - E Si telescopes of the TRACE array mounted inside the scattering chamber. The telescopes consisted of two segmented Si-pad detectors, each of 60 pixels. Very preliminary data have shown a strong domination of the E1 transitions in the ‘pygmy’ region with a character more similar to the one obtained in alpha scattering experiment.

  19. Global Map of Thermal Neutrons

    NASA Image and Video Library

    2002-05-28

    Observations by NASA Mars Odyssey spacecraft show a global view of Mars in low energy, or thermal, neutrons. Thermal neutrons are sensitive to the presence of hydrogen and the presence of carbon dioxide, in this case dry ice frost.

  20. Lindblad equation for the inelastic loss of ultracold atoms

    NASA Astrophysics Data System (ADS)

    Braaten, Eric; Hammer, H.-W.; Lepage, G. Peter

    2017-01-01

    The loss of ultracold trapped atoms due to highly inelastic reactions has previously been taken into account in effective theories for low-energy atoms by adding local anti-Hermitian terms to the effective Hamiltonian. We show that an additional modification is required in the equation governing the density matrix for multiatom systems. The effective density matrix obtained by tracing over states containing high-momentum atoms produced by the highly inelastic reactions satisfies the Lindblad equation, with local Lindblad operators that are determined by the anti-Hermitian terms in the effective Hamiltonian. We use the Lindblad equation to derive the universal relation for the two-atom inelastic loss rate for fermions with two spin states and the universal relation for the three-atom inelastic loss rate for identical bosons.

  1. Towards Low Energy Atrial Defibrillation

    PubMed Central

    Walsh, Philip; Kodoth, Vivek; McEneaney, David; Rodrigues, Paola; Velasquez, Jose; Waterman, Niall; Escalona, Omar

    2015-01-01

    transcutaneous power transfer and sensing of ICI during cardioversion are evidenced as key to the advancement of low-energy atrial defibrillation. PMID:26404298

  2. Towards Low Energy Atrial Defibrillation.

    PubMed

    Walsh, Philip; Kodoth, Vivek; McEneaney, David; Rodrigues, Paola; Velasquez, Jose; Waterman, Niall; Escalona, Omar

    2015-09-03

    transcutaneous power transfer and sensing of ICI during cardioversion are evidenced as key to the advancement of low-energy atrial defibrillation.

  3. Fast-neutron interaction with the fission product {sup 103}Rh

    SciTech Connect

    Smith, A.B. |; Guenther, P.T.

    1993-09-01

    Neutron total and differential elastic- and inelastic-scattering cross sections of {sup 103}Rh are measured from {approximately} 0.7 to 4.5 MeV (totals) and from {approximately} 1.5 to 10 MeV (scattering) with sufficient detail to define the energy-averaged behavior of the neutron processes. Neutrons corresponding to excitations of groups of levels at 334 {plus_minus} 13, 536 {plus_minus} 10, 648 {plus_minus} 25, 796 {plus_minus} 20, 864 {plus_minus} 22, 1120 {plus_minus} 22, 1279 {plus_minus} 60, 1481 {plus_minus} 27 and 1683 {plus_minus} 39 keV were observed. Additional groups at 1840 {plus_minus} 79 and 1991 {plus_minus} 71 key were tentatively identified. Assuming the target is a collective nucleus reasonably approximated by a simple one-phonon vibrator, spherical-optical, dispersive-optical, and coupled-channels models were developed from the data base with attention to the parameterization of the large inelastic-scattering cross sections. The physical properties of these models are compared with theoretical predictions and the systematics of similar model parameterizations in this mass region. In particular, it is shown that the inelastic-scattering cross section of the {sup 103}Rh fission product is large at the relatively low energies of applied interest.

  4. Rotational excitation of physisorbed H2 by low-energy electron scattering

    NASA Astrophysics Data System (ADS)

    Berlinsky, A. J.

    1982-07-01

    The inelastic-scattering spectrum for pure rotational transitions (J, m)=(0, 0)-->(2, m) by low-energy electrons (2

  5. Ionization cooling in a low-energy proton storage ring

    SciTech Connect

    Neuffer, David V.; /Fermilab

    2006-03-01

    At the FFAG05 meeting, Mori and Okabe presented a scenario in which the lifetime of protons in a low-energy storage ring ({approx}10 MeV) is extended by energy-loss in a wedge foil, and this enables greater neutron production from the foil. The lifetime extension is due to the cooling effect of this energy loss. We have previously analyzed ionization cooling for muons at optimal cooling energies. The same equations, with appropriate adaptations, can be used to analyze the dynamic situation for proton-material interactions at low energies. In this note we discuss this extension and calculate cooling and heating effects at these very different parameters. The ring could provide a practical application of ionization cooling methods.

  6. Low-energy dipole modes in unstable nuclei

    NASA Astrophysics Data System (ADS)

    Suzuki, T.; Sagawa, H.

    2001-01-01

    Enhancement of electric dipole (E1) strength at low energy is investigated in light neutron and proton drip-line nuclei with halo or skin by large scale shell model calculations. Large E1 strength are found in low excitation energy region below 5 MeV in 11Li, 12Be and 13O. Both the effects of extended halo or skin wave functions and the coherence in the transition amplitudes are important to enhance the E1 strength. The particle (hole)- vibration coupling model is shown to explain the splitting of the low energy E1 strength in 11Li and 13O. Melting of the shell magicity at N=8 and Z=8 is pointed out. Pigmy resonances in oxygen isotopes are also studied. The pigmy strength below E x = 15 MeV are shown to have about 10 % of the Thomas- Reiche-Kuhn (TRK) sum rule and more than 40 % of the cluster sum rule.

  7. Neutron scattering and models: Iron. Nuclear data and measurements series

    SciTech Connect

    Smith, A.B.

    1995-08-01

    Differential elastic and inelastic neutron-scattering cross sections of elemental iron are measured from 4.5 to 10 MeV in increments of {approx} 0.5 MeV. At each incident energy the measurements are made at forty or more scattering angles distributed between {approx} 17{degrees} and 160{degrees}, with emphasis on elastic scattering and inelastic scattering due to the excitation of the yrast 2{sup +} state. The measured data is combined with earlier lower-energy results from this laboratory, with recent high-precision {approx} 9.5 {yields} 15 MeV results from the Physilalisch Technische Bundesanstalt and with selected values from the literature to provide a detailed neutron-scattering data base extending from {approx} 1.5 to 26 MeV. This data is interpreted in the context of phenomenological spherical-optical and coupled-channels (vibrational and rotational) models, and physical implications discussed. Deformation, coupling, asymmetry and dispersive effects are explored. It is shown that, particularly in a collective context, a good description of the interaction of neutrons with iron is achieved over the energy range {approx} 0 {yields} 26 MeV, avoiding the dichotomy between high and low-energy interpretations found in previous work.

  8. Cross section measurements for neutron inelastic scattering and the (n, 2nγ) reaction on Pb206

    SciTech Connect

    Negret, A.; Mihailescu, L. C.; Borcea, C.; Dessagne, Ph.; Guber, K. H.; Kerveno, M.; Koning, A. J.; Olacel, A.; Plompen, A. J. M.; Rouki, C.; Rudolf, G.

    2015-06-30

    We measured excitation functions for γ production associated with the neutron inelastic scattering and the (n, 2n) reactions on 206Pb from threshold up to 18 MeV for about 40 transitions. Two independent measurements were performed using different samples and acquisition systems to check consistency of the results. Moreover, the neutron flux was determined with a 235U fission chamber and a procedure that were validated against a fluence standard. For incident energy higher than the threshold for the first excited level and up to 3.5 MeV, estimates are provided for the total inelastic and level cross sections by combining the present γ production cross sections with the level and decay data of 206Pb reported in the literature. The uncertainty common to all incident energies is 3.0% allowing overall uncertainties from 3.3% to 30% depending on transition and neutron energy. Finally, the present data agree well with earlier work, but significantly expand the experimental database while comparisons with model calculations using the talys reaction code show good agreement over the full energy range.

  9. Is there a low-energy enhancement in the photon strength function in molybdenum?

    SciTech Connect

    Sheets, S. A.

    2008-04-17

    Recent claims of a low-energy enhancement in the photon strength function of {sup 96}Mo are investigated. Using the DANCE detector the gamma-ray spectra following resonance neutron capture was measured. The spectrum fitting method was used to indirectly extract a photon strength function from the gamma-ray spectra. No strong low energy enhancement in the photon strength function was found.

  10. Understanding Low Energy Gamma Emission from Fission and Capture with DANCE

    NASA Astrophysics Data System (ADS)

    Wilburn, Grey; Couture, Aaron; Mosby, Shea

    2012-10-01

    Los Alamos National Laboratory's Detector for Advanced Neutron Capture Experiments (DANCE) consists of 160 barium fluoride (BaF2) detectors in a 4π array used to study cross-section measurements from neutron capture reactions. Further, recent studies have taken advantage of DANCE to study the gamma emission from fission, which is not well characterized. Neutron capture is studied because of its relevance to nuclear astrophysics (almost all elements heavier than iron are formed via neutron capture) and nuclear energy, where neutron capture is a poison in the reactor. Gamma ray cascades following neutron capture and fission include photons with energies between 100 keV and 10 MeV. DANCE uses a ^6LiH sphere to attenuate scattered neutrons, the primary background in DANCE. Unfortunately, it also attenuates low energy gamma rays. In order to quantify this effect and validate simulations, direct measurements of low energy gammas were made with a high purity germanium (HPGe) crystal. HPGe's allow for high resolution measurements of low energy gamma rays that are not possible using the BaF2 crystals. The results and their agreement with simulations will be discussed.

  11. Low energy prompt gamma-ray tests of a large volume BGO detector.

    PubMed

    Naqvi, A A; Kalakada, Zameer; Al-Anezi, M S; Raashid, M; Khateeb-ur-Rehman; Maslehuddin, M; Garwan, M A

    2012-01-01

    Tests of a large volume Bismuth Germinate (BGO) detector were carried out to detect low energy prompt gamma-rays from boron and cadmium-contaminated water samples using a portable neutron generator-based Prompt Gamma Neutron Activation Analysis (PGNAA) setup. Inspite of strong interference between the sample- and the detector-associated prompt gamma-rays, an excellent agreement has been observed between the experimental and calculated yields of the prompt gamma-rays, indicating successful application of the large volume BGO detector in the PGNAA analysis of bulk samples using low energy prompt gamma-rays. Copyright © 2011 Elsevier Ltd. All rights reserved.

  12. Low energy neutron deuteron scattering to N3LO

    NASA Astrophysics Data System (ADS)

    Margaryan, Arman; Vanasse, Jared; Springer, Roxanne

    2015-10-01

    We calculate the next-to-next-to-next-to-leading order (N3LO) nd scattering amplitude in the framework of nonrelativistic pionless effective field theory (EFTπ/). This theory is only valid when the typical momentum exchange in the scattering is smaller then the mass of the pion. The power counting parameter for EFTπ/ is the ratio Q/Λπ /, where Q is the typical momentum exchange in the scattering and Λπ / is the EFTπ/ breakdown scale, Λπ /

  13. Magnetic ordering in double perovskites R2CoMnO6 (R = Y , Tb) investigated by high resolution neutron spectroscopy

    NASA Astrophysics Data System (ADS)

    Chatterji, Tapan; Frick, Bernhard; Nair, Harikrishnan S.

    2012-07-01

    We have investigated low energy nuclear spin excitations in double perovskite compounds R2CoMnO6 (R=Y, Tb) by inelastic neutron scattering with a high resolution back-scattering spectrometer. We observed inelastic signals at about 2.1 μeV for Y2CoMnO6 and also for Tb2CoMnO6 at T = 2 K in both energy-loss and energy-gain sides. We interpret these inelastic peaks to be due to the transitions between the hyperfine split nuclear levels of the 59Co nucleus. The inelastic peaks move towards the central elastic peak and finally merge with it at the magnetic ordering temperature TC. The energy of the low energy excitations decreases continuously and becomes zero at TC ≈ 75 K for Y2CoMnO6 and TC ≈ 100 K for Tb2CoMnO6. For Tb2CoMnO6, which contains magnetic rare earth ions, additional quasielastic scattering due presumably to the fluctuations of large Tb magnetic moments was observed. The present study reveals the magnetic ordering of the Co sublattice. The results of this investigation along with that obtained by us for other compounds indicate the presence of unquenched orbital moments in some of the Co compounds.

  14. Solar-assisted low energy dwellings

    SciTech Connect

    Esbensen, T V

    1980-02-01

    The Zero Energy House Group was formed as a subproject of the CCMS Solar Energy Pilot Study in 1974 by seven participating countries experimenting with solar-assisted low-energy dwellings for temperate and northern European climatic conditions. A Zero Energy House is one in which solar energy is used to meet the reduced energy needs of buildings incorporating various thermal energy conservation features. This final report of the Zero Energy House Group includes brief descriptions of 13 major low-energy dwellings in the participating CCMS countries. An overall assessment of the state-of-the-art in solar-assisted low-energy dwellings is also included.

  15. Single track nanodosimetry of low energy electrons

    NASA Astrophysics Data System (ADS)

    Bantsar, A.; Grosswendt, B.; Pszona, S.; Kula, J.

    2009-02-01

    Auger-electron-emitting radionuclides (for instance, 125I) with a predominant energy spectrum below 3 keV are an active area of research towards the clinical application of radiopharmaceuticals. Hence, the necessity for an adequate description of the effects of radiation by low-energy electrons on nanometric biological targets seems to be unquestionable. Experimental nanodosimetry for low-energy electrons has been accomplished with a device named JET COUNTER. The present paper describes, for the first time, nanodosimetric experiments in nanometer-sized cavities of nitrogen using low energy electrons ranging from 100 eV to 2 keV.

  16. Low energy ghosts and the Jeans' instability

    NASA Astrophysics Data System (ADS)

    Gümrükçüoǧlu, A. Emir; Mukohyama, Shinji; Sotiriou, Thomas P.

    2016-09-01

    We show that a massless canonical scalar field minimally coupled to general relativity can become a tachyonic ghost at low energies around a background in which the scalar's gradient is spacelike. By performing a canonical transformation we demonstrate that this low energy ghost can be recast, at the level of the action, in a form of a fluid that undergoes a Jeans-like instability affecting only modes with large wavelength. This illustrates that low energy tachyonic ghosts do not lead to a catastrophic quantum vacuum instability, unlike the usual high-energy ghost degrees of freedom.

  17. Toroidal, compressive, and E 1 properties of low-energy dipole modes in 10Be

    NASA Astrophysics Data System (ADS)

    Kanada-En'yo, Yoshiko; Shikata, Yuki

    2017-06-01

    We studied dipole excitations in 10Be based on an extended version of the antisymmetrized molecular dynamics, which can describe 1p-1h excitations and large amplitude cluster modes. Toroidal and compressive dipole operators are found to be good proves to separate the low-energy and high-energy parts of the isoscalar dipole excitations, respectively. Two low-energy 1- states, the toroidal dominant 11- state at E ˜8 MeV and the E 1 dominant 12- state at E ˜16 MeV, were obtained. By analysis of transition current densities, the 11- state is understood as a toroidal dipole mode with exotic toroidal neutron flow caused by rotation of a deformed 6He cluster, whereas the 12- state is regarded as a neutron-skin oscillation mode, which are characterized by surface neutron flow with inner isoscalar flow caused by the surface neutron oscillation against the 2 α core.

  18. Interatomic inelastic current

    NASA Astrophysics Data System (ADS)

    Hansen, Tim; Solomon, Gemma C.; Hansen, Thorsten

    2017-03-01

    In order to identify the location of an inelastic event and to distinguish between situations that are before or after this event, we derive equations for the interatomic inelastic transmission as a perturbation series in the electron-phonon interaction. This series contains both even and odd ordered corrections, and while the even ordered corrections can be thought as a Dyson's expansion of the interatomic elastic transmission in the electron-phonon self-energy, the odd ordered corrections represent something new. We explicitly derive expressions for the interatomic inelastic transmission up to second order and the 1st order correction represents the lowest order term of this new family of terms. We apply this to three model systems and are able to distinguish between situations before and after the inelastic event as steps in the 2nd order transmission. We also see that when the transmission is evaluated between atoms that are coupled by the electron-phonon interaction, the 1st and 2nd order terms must be added together to form a meaningful transmission. Within the limited scope of the models considered here, the 1st order term appears to be the signature of the inelastic event.

  19. Low-Energy Charged Particle Instrument Assembly

    NASA Image and Video Library

    2012-12-03

    This image shows the low-energy charged particle instrument before it was installed on one of NASA Voyager spacecraft in 1977. The instrument includes a stepper motor that turns the platform on which the sensors are mounted.

  20. Inelastic electron scattering from a moving nucleon

    SciTech Connect

    Kuhn, S.E.; Griffioen, K.

    1994-04-01

    The authors propose to measure inelastically scattered electrons in coincidence with spectator protons emitted backwards relative to the virtual photon direction in the reaction d(e, e{prime}p{sub s})X. In a simple spectator model, the backward proton has equal and opposite momentum to the neutron before it is struck, allowing the authors to study the dependence on kinematics and off-shell behaviour of the electron-nucleon inelastic cross section. If the photon couples to a quark in a 6-quark bag, a different dependence of the cross section on the kinematic variables (x, Q{sup 2}, and p{sub s}) can be observed. This proposed experiment requires large acceptance and beam energies above 6 GeV. It is ideally suited for the CEBAF Large Acceptance Spectrometer (CLAS).

  1. Measurement of the isoscalar monopole response in the neutron-rich nucleus 68Ni.

    PubMed

    Vandebrouck, M; Gibelin, J; Khan, E; Achouri, N L; Baba, H; Beaumel, D; Blumenfeld, Y; Caamaño, M; Càceres, L; Colò, G; Delaunay, F; Fernandez-Dominguez, B; Garg, U; Grinyer, G F; Harakeh, M N; Kalantar-Nayestanaki, N; Keeley, N; Mittig, W; Pancin, J; Raabe, R; Roger, T; Roussel-Chomaz, P; Savajols, H; Sorlin, O; Stodel, C; Suzuki, D; Thomas, J C

    2014-07-18

    The isoscalar monopole response has been measured in the unstable nucleus (68)Ni using inelastic alpha scattering at 50A  MeV in inverse kinematics with the active target MAYA at GANIL. The isoscalar giant monopole resonance (ISGMR) centroid was determined to be 21.1 ± 1.9 MeV and indications for a soft monopole mode are provided for the first time at 12.9 ± 1.0 MeV. Analysis of the corresponding angular distributions using distorted-wave-born approximation with random-phase approximation transition densities indicates that the L = 0 multipolarity dominates the cross section for the ISGMR and significantly contributes to the low-energy mode. The L=0 part of this low-energy mode, the soft monopole mode, is dominated by neutron excitations. This demonstrates the relevance of inelastic alpha scattering in inverse kinematics in order to probe both the ISGMR and isoscalar soft modes in neutron-rich nuclei.

  2. Measurement of the Isoscalar Monopole Response in the Neutron-Rich Nucleus Ni68

    NASA Astrophysics Data System (ADS)

    Vandebrouck, M.; Gibelin, J.; Khan, E.; Achouri, N. L.; Baba, H.; Beaumel, D.; Blumenfeld, Y.; Caamaño, M.; Càceres, L.; Colò, G.; Delaunay, F.; Fernandez-Dominguez, B.; Garg, U.; Grinyer, G. F.; Harakeh, M. N.; Kalantar-Nayestanaki, N.; Keeley, N.; Mittig, W.; Pancin, J.; Raabe, R.; Roger, T.; Roussel-Chomaz, P.; Savajols, H.; Sorlin, O.; Stodel, C.; Suzuki, D.; Thomas, J. C.

    2014-07-01

    The isoscalar monopole response has been measured in the unstable nucleus Ni68 using inelastic alpha scattering at 50A MeV in inverse kinematics with the active target MAYA at GANIL. The isoscalar giant monopole resonance (ISGMR) centroid was determined to be 21.1±1.9 MeV and indications for a soft monopole mode are provided for the first time at 12.9±1.0 MeV. Analysis of the corresponding angular distributions using distorted-wave-born approximation with random-phase approximation transition densities indicates that the L =0 multipolarity dominates the cross section for the ISGMR and significantly contributes to the low-energy mode. The L=0 part of this low-energy mode, the soft monopole mode, is dominated by neutron excitations. This demonstrates the relevance of inelastic alpha scattering in inverse kinematics in order to probe both the ISGMR and isoscalar soft modes in neutron-rich nuclei.

  3. A study of low-energy type II supernovae

    NASA Astrophysics Data System (ADS)

    Lisakov, Sergey M.; Dessart, Luc; Hillier, D. John; Waldman, Roni; Livne, Eli

    2015-08-01

    All stars with an initial mass greater than 8Msun, but not massive enough to encounter the pair-production instability, eventually form a degenerate core and collapse to form a compact object, either a neutron star or a black hole.At the lower mass end, these massive stars die as red-supergiant stars and give rise to Type II supernovae (SNe). The diversity of observed properties of SNe II suggests a range of progenitor mass, radii, but also explosion energy.We have performed a large grid simulations designed to cover this range of progenitor and explosion properties. Using MESA STAR, we compute a set of massive star models (12-30Msun) from the main sequence until core collapse. We then generate explosions with V1D to produce ejecta with a range of explosion energies and yields. Finally, all ejecta are evolved with CMFGEN to generate multi-band light curves and spectra.In this poster, we focus our attention on the properties of low-energy explosions that give rise to low-luminosity Type II Plateau (II-P) SNe. In particular, we present a detailed study of SN 2008bk, but also include other notorious low-energy SNe II-P like 2005cs, emphasising their non-standard properties by comparing to models that match well events like SN 1999em. Such low-energy explosions, characterised by low ejecta expansion rates, are more suitable for reliable spectral line identifications.Based on our models, we discuss the distinct signatures of low-energy explosions in lower and higher mass models. One important goal is to identify whether there is a progenitor-mass bias leading to such events.

  4. The Neutron Structure Function

    NASA Astrophysics Data System (ADS)

    Holt, Roy

    2013-10-01

    Knowledge of the neutron structure function is important for testing models of the nucleon, for a complete understanding of deep inelastic scattering (DIS) from nuclei, and for high energy experiments. As there exist no free neutron targets, neutron structure functions have been determined from deep inelastic scattering from the deuteron. Unfortunately, the short-range part of the deuteron wave function becomes important in extracting the neutron structure function at very high Bjorken x. New methods have been devised for Jefferson Lab experiments to mitigate this problem. The BONUS experiment involves tagging spectator neutrons in the deuteron, while the MARATHON experiment minimizes nuclear structure effects by a comparison of DIS from 3H and 3He. A summary of the status and future plans will be presented. This work supported by the U. S. Department of Energy, Office of Nuclear Physics, under contract DE-AC02-06CH11357.

  5. Neutron streak camera

    DOEpatents

    Wang, Ching L.

    1983-09-13

    Apparatus for improved sensitivity and time resolution of a neutron measurement. The detector is provided with an electrode assembly having a neutron sensitive cathode which emits relatively low energy secondary electrons. The neutron sensitive cathode has a large surface area which provides increased sensitivity by intercepting a greater number of neutrons. The cathode is also curved to compensate for differences in transit time of the neutrons emanating from the point source. The slower speeds of the secondary electrons emitted from a certain portion of the cathode are matched to the transit times of the neutrons impinging thereupon.

  6. Neutron streak camera

    DOEpatents

    Wang, C.L.

    1981-05-14

    Apparatus for improved sensitivity and time resolution of a neutron measurement. The detector is provided with an electrode assembly having a neutron sensitive cathode which emits relatively low energy secondary electrons. The neutron sensitive cathode has a large surface area which provides increased sensitivity by intercepting a greater number of neutrons. The cathode is also curved to compensate for differences in transit time of the neutrons emanating from the point source. The slower speeds of the secondary electrons emitted from a certain portion of the cathode are matched to the transit times of the neutrons impinging thereupon.

  7. Neutron streak camera

    DOEpatents

    Wang, C.L.

    1983-09-13

    Disclosed is an apparatus for improved sensitivity and time resolution of a neutron measurement. The detector is provided with an electrode assembly having a neutron sensitive cathode which emits relatively low energy secondary electrons. The neutron sensitive cathode has a large surface area which provides increased sensitivity by intercepting a greater number of neutrons. The cathode is also curved to compensate for differences in transit time of the neutrons emanating from the point source. The slower speeds of the secondary electrons emitted from a certain portion of the cathode are matched to the transit times of the neutrons impinging thereupon. 4 figs.

  8. Inelastic electron tunneling spectroscopy in molecular junctions showing quantum interference

    NASA Astrophysics Data System (ADS)

    Salhani, C.; Della Rocca, M. L.; Bessis, C.; Bonnet, R.; Barraud, C.; Lafarge, P.; Chevillot, A.; Martin, P.; Lacroix, J.-C.

    2017-04-01

    Destructive quantum interference effect is implemented in large area molecular junctions to improve signatures of electron-phonon interaction. Vertical molecular junctions based on a cross-conjugated anthraquinone layer were fabricated and low-noise transport measurements were performed by acquiring simultaneously the current-voltage characteristics, its second derivative, and the differential conductance. Signatures of vibrational modes excited by inelastic events are present in the whole measured voltage range and superpose to the conductance suppression induced by destructive quantum interference. As a consequence vibrational modes have improved visibility in the low energy window (<80 meV ). Inelastic electron transport spectroscopy data are compared to infrared attenuated total reflection spectroscopy on Au/anthraquinone thin films. Common vibrational modes can be clearly identified, but inelastic electron tunneling spectroscopy reveals the existence of vibrational modes in a wider energy range (0 -400 meV ) where infrared spectroscopy is lacking.

  9. Constraints on inelastic dark matter from XENON10

    SciTech Connect

    Angle, J; Aprile, E; Arneodo, F; Baudis, L; Bernstein, A; Bolozdynya, A; Coelho, L C; Dahl, C E; DeViveiros, L; Ferella, A D; Fernandes, L P; Fiorucci, S; Gaitskell, R J; Giboni, K L; Gomez, R; Hasty, R; Kastens, L; Kwong, J; Lopes, J M; Madden, N; Manalaysay, A; Manzur, A; McKinsey, D N; Monzani, M E; Ni, K; Oberlack, U; Orboeck, J; Plante, G; Santorelli, R; dos Santos, J; Shagin, P; Shutt, T; Sorensen, P; Schulte, S; Winant, C; Yamashita, M

    2009-11-23

    It has been suggested that dark matter particles which scatter inelastically from detector target nuclei could explain the apparent incompatibility of the DAMA modulation signal (interpreted as evidence for particle dark matter) with the null results from CDMS-II and XENON10. Among the predictions of inelastically interacting dark matter are a suppression of low-energy events, and a population of nuclear recoil events at higher nuclear recoil equivalent energies. This is in stark contrast to the well-known expectation of a falling exponential spectrum for the case of elastic interactions. We present a new analysis of XENON10 dark matter search data extending to E{sub nr} = 75 keV nuclear recoil equivalent energy. Our results exclude a significant region of previously allowed parameter space in the model of inelastically interacting dark matter. In particular, it is found that dark matter particle masses m{sub x} {approx}> 150 GeV are disfavored.

  10. Elastic and Inelastic Collisions

    ERIC Educational Resources Information Center

    Gluck, Paul

    2010-01-01

    There have been two articles in this journal that described a pair of collision carts used to demonstrate vividly the difference between elastic and inelastic collisions. One cart had a series of washers that were mounted rigidly on a rigid wooden framework, the other had washers mounted on rubber bands stretched across a framework. The rigidly…

  11. Deep inelastic phenomena

    SciTech Connect

    Prescott, C.Y.

    1980-10-01

    Nucleon structure as seen in the context of deep inelastic scattering is discussed. The lectures begin with consideration of the quark-parton model. The model forms the basis of understanding lepton-nucleon inelastic scattering. As improved data in lepton-nucleon scattering at high energies became available, the quark-parton model failed to explain some crucial features of these data. At approximately the same time a candidate theory of strong interactions based on a SU(3) gauge theory of color was being discussed in the literature, and new ideas on the explanation of inelastic scattering data became popular. A new theory of strong interactions, now called quantum chromodynamics provides a new framework for understanding the data, with a much stronger theoretical foundation, and seems to explain well the features of the data. The lectures conclude with a look at some recent experiments which provide new data at very high energies. These lectures are concerned primarily with charged lepton inelastic scattering and to a lesser extent with neutrino results. Furthermore, due to time and space limitations, topics such as final state hadron studies, and multi-muon production are omitted here. The lectures concentrate on the more central issues: the quark-parton model and concepts of scaling, scale breaking and the ideas of quantum chromodynamics, the Q/sup 2/ dependence of structure function, moments, and the important parameter R.

  12. Elastic and Inelastic Collisions

    ERIC Educational Resources Information Center

    Gluck, Paul

    2010-01-01

    There have been two articles in this journal that described a pair of collision carts used to demonstrate vividly the difference between elastic and inelastic collisions. One cart had a series of washers that were mounted rigidly on a rigid wooden framework, the other had washers mounted on rubber bands stretched across a framework. The rigidly…

  13. Neutron-scattering evidence for a periodically modulated superconducting phase in the underdoped cuprate La1.905Ba0.095CuO4

    DOE PAGES

    Xu, Zhijun; Stock, C.; Chi, Songxue; ...

    2014-10-01

    The role of antiferromagnetic spin correlations in high-temperature superconductors remains a matter of debate. We present inelastic neutron-scattering evidence that gapless spin fluctuations coexist with superconductivity in La1.905Ba0.095CuO4. Furthermore, we observe that both the low-energy magnetic spectral weight and the spin incommensurability are enhanced with the onset of superconducting correlations. We propose that the coexistence occurs through intertwining of spatial modulations of the pair wave function and the antiferromagnetic correlations. This proposal is also directly relevant to sufficiently underdoped La2-xSrxCuO4 and YBa2Cu3O6+x.

  14. Neutron-Scattering Evidence for a Periodically Modulated Superconducting Phase in the Underdoped Cuprate La1.905Ba0.095CuO4

    NASA Astrophysics Data System (ADS)

    Xu, Zhijun; Stock, C.; Chi, Songxue; Kolesnikov, A. I.; Xu, Guangyong; Gu, Genda; Tranquada, J. M.

    2014-10-01

    The role of antiferromagnetic spin correlations in high-temperature superconductors remains a matter of debate. We present inelastic neutron-scattering evidence that gapless spin fluctuations coexist with superconductivity in La1.905Ba0.095CuO4. Furthermore, we observe that both the low-energy magnetic spectral weight and the spin incommensurability are enhanced with the onset of superconducting correlations. We propose that the coexistence occurs through intertwining of spatial modulations of the pair wave function and the antiferromagnetic correlations. This proposal is also directly relevant to sufficiently underdoped La2-xSrxCuO4 and YBa2Cu3O6+x.

  15. Neutron-scattering evidence for a periodically modulated superconducting phase in the underdoped cuprate La1.905Ba0.095CuO4.

    PubMed

    Xu, Zhijun; Stock, C; Chi, Songxue; Kolesnikov, A I; Xu, Guangyong; Gu, Genda; Tranquada, J M

    2014-10-24

    The role of antiferromagnetic spin correlations in high-temperature superconductors remains a matter of debate. We present inelastic neutron-scattering evidence that gapless spin fluctuations coexist with superconductivity in La1.905Ba0.095CuO4. Furthermore, we observe that both the low-energy magnetic spectral weight and the spin incommensurability are enhanced with the onset of superconducting correlations. We propose that the coexistence occurs through intertwining of spatial modulations of the pair wave function and the antiferromagnetic correlations. This proposal is also directly relevant to sufficiently underdoped La(2-x)Sr(x)CuO(4) and YBa(2)Cu(3)O(6+x).

  16. Deep inelastic scattering on asymmetric nuclei

    NASA Astrophysics Data System (ADS)

    Saito, K.; Boros, C.; Tsushima, K.; Bissey, F.; Afnan, I. R.; Thomas, A. W.

    2000-11-01

    We study deep inelastic scattering on isospin asymmetric nuclei. In particular, the difference of the nuclear structure functions and the Gottfried sum rule for the lightest mirror nuclei, 3He and 3H, are investigated. It is found that such systems can provide significant information on charge symmetry breaking and flavor asymmetry in the nuclear medium. Furthermore, we propose a new method to extract the neutron structure function from radioactive isotopes far from the line of stability. We also discuss the flavor asymmetry in the Drell-Yan process with isospin asymmetric nuclei.

  17. Neutron reflectivity

    NASA Astrophysics Data System (ADS)

    Cousin, Fabrice; Menelle, Alain

    2015-10-01

    The specular neutron reflectivity is a technique enabling the measurement of neutron scattering length density profile perpendicular to the plane of a surface or an interface, and thereby the profile of chemical composition. The characteristic sizes that are probed range from around 5 Å up 5000 Å. It is a scattering technique that averages information on the entire surface and it is therefore not possible to obtain information within the plane of the interface. The specific properties of neutrons (possibility of tuning the contrast by isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons) makes it particularly interesting in the fields of soft matter, biophysics and magnetic thin films. This course is a basic introduction to the technique and does not address the magnetic reflectivity. It is composed of three parts describing respectively its principle and its formalism, the experimental aspects of the method (spectrometers, samples) and two examples related to the materials for energy.

  18. Deep Inelastic Transfer Reactions - A New Way to Exotic Nuclei?

    NASA Astrophysics Data System (ADS)

    Heinz, Sophie; Beliuskina, Olga

    2014-05-01

    We studied deep inelastic multinucleon transfer reactions in collisions of 64Ni+207Pb and 48Ca+238U at energies around the Coulomb barrier. The experiments were performed at the velocity filter SHIP at GSI Darmstadt. One of the goals was to investigate if deep inelastic transfer is superior to fragmentation reactions for producing neutron-rich isotopes in the astrophysically interesting region of nuclei along the magic neutron number N = 126. With both collision systems, rather neutron-rich transfer products were populated, some of them reaching out to the limits of the present chart of nuclides. New isotopes could not be identified. A comparison of the measured transfer cross-sections and yields with those from fragmentation reactions allowed for interesting conclusions.

  19. Magnetic inelastic scattering: Present results and future trends

    SciTech Connect

    Osborn, R.

    1996-04-01

    Experience over the last 15 years has shsown that pulsed neutron spectrometers are able to contribute to the field of magnetic inelastic scattering. Such spectrometers have high resolution and wide dynamic range, both of which are necessary in order to characterize the magnetic response of the complex systems of current interest, ranging from rare earth-transition metal permanent magnets to quantum critical scatterers. Howevera, all these studies have been constrained by current flux limitations. The development of more powerful spallation neutron sources, such as the JHP, is likely to transform these interesting demonstrations of the potential of pulsed neutron scattering into routine tools for the study of magnetic correlations.

  20. Symmetry Energy Effects on Low Energy Dissipative Heavy Ion Collisions

    NASA Astrophysics Data System (ADS)

    Rizzo, C.; Baran, V.; Colonna, M.; Di Toro, M.; Odsuren, M.

    2011-02-01

    We investigate the reaction path followed by Heavy Ion Collisions with exotic nuclear beams at low energies. We focus on the interplay between reaction mechanisms, fusion vs. break-up (fast-fission, deep-inelastic), that in exotic systems is expected to be influenced by the symmetry energy term at densities around the normal value. The method described here, based on the event by event evolution of phase space quadrupole collective modes, will nicely allow to extract the fusion probability at relatively early times, when the transport results are reliable. Fusion probabilities for reactions induced by 132Sn on 64,58Ni targets at 10 AMeV are evaluated. We obtain larger fusion cross sections for the more n-rich composite system, and, for a given reaction, with a soft symmetry term above saturation. A collective charge equilibration mechanism (the Dynamical Dipole Resonance, DDR) is revealed in both fusion and break-up events, depending on the stiffness of the symmetry term just below saturation. Finally we investigate the effect of the mass asymmetry in the entrance channel for systems with the same overall isospin content and similar initial charge asymmetry. As expected we find reduced fusion probabilities for the more mass symmetric case, while the DDR strength appears not much affected. This is a nice confirmation of the prompt nature of such collective isovector mode.

  1. Very Low Energy Electron Scattering from Ozone and Chlorine Dioxide

    NASA Astrophysics Data System (ADS)

    Gulley, R. J.; Field, T. A.; Steer, W. A.; Mason, N. J.; Ziesel, J. P.; Lunt, S. L.; Field, D.

    1998-10-01

    Total cross-sections are reported for the scattering of electrons from ozone (O_3) and chlorine dioxide (OClO) for energies in the range of 9 meV to 10 eV. The measurements were made in transmission experiments using a synchrotron photoionization apparatus with an energy resolution in the incident electron beam of ~ 3.5 meV (FWHM). The cross section for O3 shows strong rotational scattering at low energy, through the presence of the permanent dipole moment of O_3. Superposed on this strong scattering signal, there is evidence of a weak structure around 50 meV associated with dissociative attachment. A shape resonance, known from earlier work at ~ 4 meV, is also observed. Electron scattering from OClO is dominated by rotationally inelastic scattering decreasing from a peak at essentially zero eV to an energy of 40 meV, where p-wave attachment becomes more important, peaking at 50--60 meV and extending to several hundred meV.

  2. First evidence of low energy enhancement in Ge isotopes

    NASA Astrophysics Data System (ADS)

    Renstrøm, T.; Nyhus, H.-T.; Utsunomiya, H.; Larsen, A. C.; Siem, S.; Guttormsen, M.; Filipescu, D. M.; Gheorghe, I.; Goriely, S.; Bernstein, L. A.; Bleuel, D. L.; Glodariu, T.; Görgen, A.; Hagen, T. W.; Lui, Y.-W.; Negi, D.; Ruud, I. E.; Şahin, E.; Schwengner, R.; Shima, T.; Takahisa, K.; Tesileanu, O.; Tornyi, T. G.; Tveten, G. M.; Wiedeking, M.

    2015-05-01

    The γ-strength functions and level densities of 73,74Ge have been extracted from particle-γ coincidence data using the Oslo method. In addition the γ-strength function of 74Ge above the neutron separation threshold, Sn = 10.196 MeV has been extracted from photoneutron measurements. When combined, these two experiments give a γ-strength function covering the energy range of ˜1-13 MeV for 74Ge. This thorough investigation of 74Ge is a part of an international campaign to study the previously reported low energy enhancement in this mass region in the γ-strength function from ˜3MeV towards lower γ energies. The obtained data show that both 73,74Ge display an increase in strength at low γ energies.

  3. Low-energy Coulomb excitation of Sr,9896 beams

    NASA Astrophysics Data System (ADS)

    Clément, E.; Zielińska, M.; Péru, S.; Goutte, H.; Hilaire, S.; Görgen, A.; Korten, W.; Doherty, D. T.; Bastin, B.; Bauer, C.; Blazhev, A.; Bree, N.; Bruyneel, B.; Butler, P. A.; Butterworth, J.; Cederkäll, J.; Delahaye, P.; Dijon, A.; Ekström, A.; Fitzpatrick, C.; Fransen, C.; Georgiev, G.; Gernhäuser, R.; Hess, H.; Iwanicki, J.; Jenkins, D. G.; Larsen, A. C.; Ljungvall, J.; Lutter, R.; Marley, P.; Moschner, K.; Napiorkowski, P. J.; Pakarinen, J.; Petts, A.; Reiter, P.; Renstrøm, T.; Seidlitz, M.; Siebeck, B.; Siem, S.; Sotty, C.; Srebrny, J.; Stefanescu, I.; Tveten, G. M.; Van de Walle, J.; Vermeulen, M.; Voulot, D.; Warr, N.; Wenander, F.; Wiens, A.; De Witte, H.; Wrzosek-Lipska, K.

    2016-11-01

    The structure of neutron-rich Sr,9896 nuclei was investigated by low-energy safe Coulomb excitation of radioactive beams at the REX-ISOLDE facility, CERN, with the MINIBALL spectrometer. A rich set of transitional and diagonal E 2 matrix elements, including those for non-yrast structures, has been extracted from the differential Coulomb-excitation cross sections. The results support the scenario of a shape transition at N =60 , giving rise to the coexistence of a highly deformed prolate and a spherical configuration in 98Sr, and are compared to predictions from several theoretical calculations. The experimental data suggest a significant contribution of the triaxal degree of freedom in the ground state of both isotopes. In addition, experimental information on low-lying states in 98Rb has been obtained.

  4. Low-energy nuclear reactions in crystal structures

    NASA Astrophysics Data System (ADS)

    Bagulya, A. V.; Dalkarov, O. D.; Negodaev, M. A.; Rusetskii, A. S.

    2017-09-01

    Results of studying low-energy nuclear reactions at the HELIS facility (LPI) are presented. Investigations of yields from DD reactions in deuterated crystal structures at deuteron energies of 10 to 25 keV show a considerable enhancement effect. It is shown that exposure of the deuterated targets to the H+ (proton) and Ne+ beams with energies from 10 to 25 keV and an X-ray beam with the energy of 20 to 30 keV stimulates DD reaction yields. For the CVD diamond target, it is shown that its orientation with respect to the deuteron beam affects the neutron yield. The D+ beam is shown to cause much higher heat release in the TiDx target than the H+ and Ne+ beams, and this heat release depends on the deuterium concentration in the target and the current density of the deuteron beam.

  5. Theoretical Study of Low Energy Scattering from Metal Nuclei.

    NASA Astrophysics Data System (ADS)

    Gomez, Bernadette; Hira, Ajit; Duran, Joe; Jaramillo, Danelle

    2015-04-01

    We continue our interest in the interactions between different nuclear species with a computational study of the scattering of the low-energy nuclei of H through F atoms (Z <= 9 ) from Silver, Palladium and other metals. Recent work has shown that neutron scattering can be used to record holographic images of materials. We have developed a FORTRAN computer program to compute stopping cross sections and scattering angles in Ag and other metals for the small nuclear projectiles, using Monte Carlo calculation. This code allows for different angles of incidence. Next, simulations were done in the energy interval from 50 to 210 keV. The computational results thus obtained are compared with relevant experimental data. The data are further analyzed to identify periodic trends in terms of the atomic number of the projectile. Such studies have potential applications in nuclear physics and in nuclear medicine.

  6. Low energy strong electroweak sector with decoupling

    SciTech Connect

    Casalbuoni, R.; Dominici, D. |; Deandrea, A.; Gatto, R.; De Curtis, S.; Grazzini, M. |

    1996-05-01

    We discuss possible symmetries of effective theories describing spinless and spin-1 bosons, mainly to concentrate on an intriguing phenomenological possibility: that of a hardly noticeable strong electroweak sector at relatively low energies. Specifically, a model with both vector and axial vector strong interacting bosons may possess a discrete symmetry imposing degeneracy of the two sets of bosons (degenerate BESS model). In such a case its effects at low energies become almost invisible and the model easily passes all low energy precision tests. The reason lies essentially in the fact that the model automatically satisfies decoupling, contrary to models with only vectors. For large mass of the degenerate spin-one bosons the model becomes identical at the classical level to the standard model taken in the limit of infinite Higgs boson mass. For these reasons we have thought it worthwhile to fully develop the model, together with its possible generalizations, and to study the expected phenomenology. For instance, just because of its invisibility at low energy, it is conceivable that degenerate BESS has low mass spin-one states and gives quite visible signals at existing or forthcoming accelerators. {copyright} {ital 1996 The American Physical Society.}

  7. What is a low-energy house?

    SciTech Connect

    Litt, B.R.; Meier, A.K.

    1994-08-01

    Traditionally, a ``low-energy`` house has been one that used little energy for space heating. But space heating typically accounts for less than half of the energy used by new US homes, and for low heating energy homes, space heating is often the third largest end use, behind water heating and appliances, and sometimes behind cooling. Low space heat alone cannot identify a low-energy house. To better understand the determinants of a low-energy house, we collected data on housing characteristics, incremental costs, and energy measurements from energy-efficient houses around the world and in a range of climates. We compare the energy required to provide thermal comfort as well as water heating, and other appliances. We do not have a single definition of a low-energy house, but through comparisons of actual buildings, we show how different definitions and quantitative indicators fail. In comparing the energy use of whole houses, weather normalization can be important, but for cases in which heating or cooling energy is surpassed by other end uses, other normalization methods must be used.

  8. The Simbol-X Low Energy Detector

    SciTech Connect

    Lechner, Peter

    2009-05-11

    For the Low Energy Detector of Simbol-X a new type of active pixel sensor based on the integrated amplifier DEPFET has been developed. This concept combines large area, scalable pixel size, low noise, and ultra-fast readout. Flight representative prototypes have been processed with a performance matching the Simbol-X specifications and demonstrating the technology readiness.

  9. The Simbol-X Low Energy Detector

    NASA Astrophysics Data System (ADS)

    Lechner, Peter

    2009-05-01

    For the Low Energy Detector of Simbol-X a new type of active pixel sensor based on the integrated amplifier DEPFET has been developed. This concept combines large area, scalable pixel size, low noise, and ultra-fast readout. Flight representative prototypes have been processed with a performance matching the Simbol-X specifications and demonstrating the technology readiness.

  10. Parity violation in low-energy

    SciTech Connect

    Martin Savage

    2001-12-01

    Parity violation in low-energy nuclear observables is included in the pionless effective field theory. The model-independent relation between the parity-violating asymmetry in polarized np -> d gamma and the non-nucleon part of the deuteron anapole moment is discussed. The asymmetry in np -> d gamma computed with KSW power-counting, and recently criticized by Desplanques, is discussed.

  11. Studies in Low-Energy Nuclear Science

    SciTech Connect

    Carl R. Brune; Steven M. Grimes

    2010-01-13

    This report presents a summary of research projects in the area of low energy nuclear reactions and structure, carried out between March 1, 2006 and October 31, 2009 which were supported by U.S. DOE grant number DE-FG52-06NA26187.

  12. Superspace duality in low-energy superstrings

    SciTech Connect

    Siegel, W. )

    1993-09-15

    We extend spacetime duality to superspace, including fermions in the low-energy limits of superstrings. The tangent space is a curved, extended superspace. The geometry is based on an enlarged coordinate space where the vanishing of the d'Alembertian is as fundamental as the vanishing of the curl of a gradient.

  13. Nonlinear, inelastic fast reactor subassembly interaction analyses

    SciTech Connect

    Sutherland, W.H.; Bard, F.E.

    1983-01-01

    Liquid Metal Fast Breeder Reactor (LMFBR) core structural design is complicated by the trade-offs associated with keeping the subassemblies closely packed for the neutronic considerations and accommodating the volumetric changes associated with irradiation swelling. The environmental variation across the reactor core results in temperature and neutron flux gradients across the subassemblies which in turn cause the subassemblies to bow as well as dilate and grow volumetrically. These deformations in a tightly packed reactor core cause the subassemblies to interact and can potentially result in excessive withdrawal loads during the refueling operations. ABADAN, a general purpose, nonlinear, inelastic, multi-dimensional finite element structural analysis computer code, was developed for the express purpose of solving large nonlinear problems as typified by the above interaction problems. For the subassembly interaction problem ABADAN has been applied to the solution of an interacting radial row of Fast Flux Test Facility (FFTF) fuel assemblies.

  14. Neutron scattering study on CuV 2S 4 and CuTi 2S 4

    NASA Astrophysics Data System (ADS)

    Mücksch, M.; Krimmel, A.; Koza, M. M.; Mutka, H.; Horn, S.

    2006-05-01

    The metallic thiospinel CuV 2S 4 shows an enhanced value of the low-temperature specific heat with γ=C/T≈60 mJ/mol K, suggesting magnetic or electronic correlations. To elucidate the nature of this low-temperature phase with respect to possible magnetic fluctuations, inelastic neutron scattering measurements were performed on polycrystalline CuV 2S 4 and CuTi 2S 4. Both compounds show an inelastic response dominated by phonons. The low-energy phonon response of CuTi 2S 4 is centered around 13 meV and depends only weakly on temperature. The corresponding phonon intensity in the low energy transfer region of CuV 2S 4 is centered at around 6 meV ( T=120 K). The center of gravity of this intensity shifts to about 10 meV ( T=1.8 K) below the structural phase transition at T≈90 K .The significant difference in the low-energy phonon response between both compounds, which display the same lattice symmetry at 120 K, and the strong renormalization of the phonon energies below the structural transition might reflect the influence of strong electron-phonon coupling in CuV 2S 4.

  15. Low energy probes of PeV scale sfermions

    SciTech Connect

    Altmannshofer, Wolfgang; Harnik, Roni; Zupan, Jure

    2013-11-27

    We derive bounds on squark and slepton masses in mini-split supersymmetry scenario using low energy experiments. In this setup gauginos are at the TeV scale, while sfermions are heavier by a loop factor. We cover the most sensitive low energy probes including electric dipole moments (EDMs), meson oscillations and charged lepton flavor violation (LFV) transitions. A leading log resummation of the large logs of gluino to sfermion mass ratio is performed. A sensitivity to PeV squark masses is obtained at present from kaon mixing measurements. A number of observables, including neutron EDMs, mu->e transitions and charmed meson mixing, will start probing sfermion masses in the 100 TeV-1000 TeV range with the projected improvements in the experimental sensitivities. We also discuss the implications of our results for a variety of models that address the flavor hierarchy of quarks and leptons. We find that EDM searches will be a robust probe of models in which fermion masses are generated radiatively, while LFV searches remain sensitive to simple-texture based flavor models.

  16. Ranges and profiles of distribution of low-energy ions channeling in metal and semiconductor single crystals

    NASA Astrophysics Data System (ADS)

    Umarov, F. F.; Rasulov, A. M.; Khaidarov, A. K.

    2003-07-01

    In the present work peculiarities of trajectories and energy losses, ranges and profiles of distribution of low-energy different-mass ions channeling in thin single crystals of metals and semiconductors have been thoroughly studied by computer simulation in binary collision approximation. The character of oscillations of channeled-ion trajectories depending on their energies, aiming points from the axis of a channel, kind of interaction potential, crystal lattice type and temperature has been determined. It has been found that, in the case of light ions even at low energy, the main contribution to energy loss is made by inelastic energy losses, whereas for heavy ions, already at E < 10 keV elastic energy losses exceed inelastic ones. Profiles of the distribution of channeled ions have been calculated depending on crystal lattice type, kind of ions and their energy.

  17. Inelastic electron tunneling spectroscopy

    NASA Technical Reports Server (NTRS)

    Khanna, S. K.; Lambe, J.

    1983-01-01

    Inelastic electron tunneling spectroscopy is a useful technique for the study of vibrational modes of molecules adsorbed on the surface of oxide layers in a metal-insulator-metal tunnel junction. The technique involves studying the effects of adsorbed molecules on the tunneling spectrum of such junctions. The data give useful information about the structure, bonding, and orientation of adsorbed molecules. One of the major advantages of inelastic electron tunneling spectroscopy is its sensitivity. It is capable of detecting on the order of 10 to the 10th molecules (a fraction of a monolayer) on a 1 sq mm junction. It has been successfully used in studies of catalysis, biology, trace impurity detection, and electronic excitations. Because of its high sensitivity, this technique shows great promise in the area of solid-state electronic chemical sensing.

  18. Inelastic electron injection in a water chain

    PubMed Central

    Rizzi, Valerio; Todorov, Tchavdar N.; Kohanoff, Jorge J.

    2017-01-01

    Irradiation of biological matter triggers a cascade of secondary particles that interact with their surroundings, resulting in damage. Low-energy electrons are one of the main secondary species and electron-phonon interaction plays a fundamental role in their dynamics. We have developed a method to capture the electron-phonon inelastic energy exchange in real time and have used it to inject electrons into a simple system that models a biological environment, a water chain. We simulated both an incoming electron pulse and a steady stream of electrons and found that electrons with energies just outside bands of excited molecular states can enter the chain through phonon emission or absorption. Furthermore, this phonon-assisted dynamical behaviour shows great sensitivity to the vibrational temperature, highlighting a crucial controlling factor for the injection and propagation of electrons in water. PMID:28350013

  19. Inelastic electron injection in a water chain

    NASA Astrophysics Data System (ADS)

    Rizzi, Valerio; Todorov, Tchavdar N.; Kohanoff, Jorge J.

    2017-03-01

    Irradiation of biological matter triggers a cascade of secondary particles that interact with their surroundings, resulting in damage. Low-energy electrons are one of the main secondary species and electron-phonon interaction plays a fundamental role in their dynamics. We have developed a method to capture the electron-phonon inelastic energy exchange in real time and have used it to inject electrons into a simple system that models a biological environment, a water chain. We simulated both an incoming electron pulse and a steady stream of electrons and found that electrons with energies just outside bands of excited molecular states can enter the chain through phonon emission or absorption. Furthermore, this phonon-assisted dynamical behaviour shows great sensitivity to the vibrational temperature, highlighting a crucial controlling factor for the injection and propagation of electrons in water.

  20. Electromagnon excitation in the field-induced nonlinear ferrimagnetic phase of Ba2Mg2Fe12O22 studied by polarized inelastic neutron and terahertz time-domain optical spectroscopy

    SciTech Connect

    Nakajima, Taro; Takahashi, Youtarou; Kibayashi, Shunsuke; Matsuda, Masaaki; Kakurai, Kazuhisa; Ishiwata, Shintaro; Taguchi, Yasujiro; Tokura, Yoshinori; Arima, Taka-hisa

    2016-01-19

    We have studied magnetic excitations in a field-induced noncollinear commensurate ferrimagnetic phase of Ba2Mg2Fe12O22 by means of polarized inelastic neutron scattering (PINS) and terahertz (THz) time-domain optical spectroscopy under magnetic field. A previous THz spectroscopy study reported that the field-induced phase exhibits electric-dipole-active excitations with energies of around 5 meV [Kida et al., Phys. Rev. B 83, 064422 (2011)]. In the present PINS measurements, we observed inelastic scattering signals around 5 meV at the zone center in the spin-flip channel. This directly shows that the electric-dipole-active excitations are indeed of magnetic origin, that is, electromagnons. In addition, the present THz spectroscopy confirms that the excitations have oscillating electric polarization parallel to the c axis. In terms of the spin-current model (Katsura-Nagaosa-Balatsky model), the noncollinear magnetic order in the field-induced phase can induce static electric polarization perpendicular to the c axis, but not dynamic electric polarization along the c axis. Furthermore, we suggest that the electromagnon excitations can be explained by applying the magnetostriction model to the out-of-phase oscillations of the magnetic moments, which is deduced from the present experimental results.