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Sample records for low-energy coulomb excitation

  1. 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.

  2. TOPICAL REVIEW: Shapes and collectivity of exotic nuclei via low-energy Coulomb excitation

    NASA Astrophysics Data System (ADS)

    Görgen, Andreas

    2010-10-01

    The way in which an atomic nucleus responds to excitations, whether by promoting individual nucleons into higher shells or by collective rotation or vibration, reveals many details of the underlying nuclear structure. The response of the nucleus is closely related to its macroscopic shape. Low-energy Coulomb excitation provides a well-understood means of exciting atomic nuclei, allowing the measurement of static and dynamic electromagnetic moments as a probe of the nuclear wavefunctions. Owing to the availability of radioactive heavy-ion beams with energies near the Coulomb barrier, it is now possible to study the shape and collectivity of short-lived nuclei far from β stability (the so-called exotic nuclei), providing a particularly stringent test of modern theoretical nuclear structure models. This review gives an introduction to the experimental techniques related to low-energy Coulomb excitation with radioactive ion beams and summarizes the results that were obtained over the last 10 years for a wide variety of exotic nuclei at various laboratories employing the isotope separation on-line technique.

  3. 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.

  4. First measurement with a new setup for low-energy Coulomb excitation studies at INFN LNL

    NASA Astrophysics Data System (ADS)

    Rocchini, M.; Hadyńska-Klȩk, K.; Nannini, A.; Valiente-Dobón, J. J.; Goasduff, A.; Testov, D.; John, P. R.; Mengoni, D.; Zielińska, M.; Bazzacco, D.; Benzoni, G.; Boso, A.; Cocconi, P.; Chiari, M.; Doherty, D. T.; Galtarossa, F.; Jaworski, G.; Komorowska, M.; Matejska-Minda, M.; Melon, B.; Menegazzo, R.; Napiorkowski, P.; Napoli, D. R.; Ottanelli, M.; Perego, A.; Ramina, L.; Rampazzo, M.; Recchia, F.; Riccetto, S.; Rosso, D.; Siciliano, M.; Sona, P.

    2017-07-01

    A new segmented particle detector, SPIDER, has been designed to be used as an ancillary device with the GALILEO γ-ray spectrometer, as well as with other multi-detector γ-ray arrays that will be available at LNL in the future (e.g. AGATA). To commission the SPIDER-GALILEO experimental setup, a multi-step Coulomb excitation experiment was carried out with a 240 MeV beam of 66Zn produced by the Tandem-XTU accelerator at INFN Laboratori Nazionali di Legnaro. The measured particle and γ-ray spectra are compared with the results of detailed GEANT4 simulations which used the Coulomb excitation cross sections, estimated with the computer code GOSIA, as an input. The preliminary results indicate that precise transition probabilities will be obtained which are essential for solving discrepancies reported in the literature for this nucleus.

  5. /B(E2) values from low-energy Coulomb excitation at an ISOL facility: the /N=80,82 Te isotopes

    NASA Astrophysics Data System (ADS)

    Barton, C. J.; Caprio, M. A.; Shapira, D.; Zamfir, N. V.; Brenner, D. S.; Gill, R. L.; Lewis, T. A.; Cooper, J. R.; Casten, R. F.; Beausang, C. W.; Krücken, R.; Novak, J. R.

    2003-01-01

    B(E2;0+1→2+1) values for the unstable, neutron-rich nuclei 132,134Te were determined through Coulomb excitation, in inverse kinematics, of accelerated beams of these nuclei. The systematics of measured B(E2) values from the ground state to the first excited state have been extended to the N=82 shell closure in the Te nuclei and have been compared with the predictions of different theories. The measurements were performed at the Holifield Radioactive Ion Beam Facility (HRIBF) using the GRAFIK detector. The success of this approach, which couples a 5.7% efficient through-well NaI(Tl) γ-ray detector with thin foil microchannel plate beam detectors, also demonstrates the feasibility for Coulomb excitation studies of neutron-rich nuclei even further from the valley of beta stability, both at present-generation ISOL facilities and at the proposed Rare Isotope Accelerator.

  6. Coulomb effects in low-energy nuclear fragmentation

    NASA Technical Reports Server (NTRS)

    Wilson, John W.; Chun, Sang Y.; Badavi, Francis F.; John, Sarah

    1993-01-01

    Early versions of the Langley nuclear fragmentation code NUCFRAG (and a publicly released version called HZEFRG1) assumed straight-line trajectories throughout the interaction. As a consequence, NUCFRAG and HZEFRG1 give unrealistic cross sections for large mass removal from the projectile and target at low energies. A correction for the distortion of the trajectory by the nuclear Coulomb fields is used to derive fragmentation cross sections. A simple energy-loss term is applied to estimate the energy downshifts that greatly alter the Coulomb trajectory at low energy. The results, which are far more realistic than prior versions of the code, should provide the data base for future transport calculations. The systematic behavior of charge-removal cross sections compares favorably with results from low-energy experiments.

  7. Coulomb path'' interference in low energy He sup + + He collisions

    SciTech Connect

    Swenson, J.K. ); Burgdoerfer, J. ); Meyer, F.W.; Havener, C.C.; Gregory, D.C.; Stolterfoht, N. )

    1990-01-01

    A new interference mechanism, analogous to classic'' double-slit electron scattering, has been identified in low energy ion-atom collisions. This Coulomb path'' interference results from the existence of two trajectories, indistinguishable with respect to laboratory energy and emission angle, along which ejected autoionizing electrons may be scattered by the attractive Coulomb potential of the slowly receding spectator ion. We present a simple semi-classical model for this effect in which we account for the path dependence of the amplitude of the ejected electron following decay of the autoionizing state. Calculated model lineshapes are found to be in excellent agreement with strong angular dependence of the interference structure observed in the He target 2s{sup 2} {sup 1}S autoionizing lineshape measured near 0{degree} following 10 keV He{sup +} + He collisions.

  8. Low Energy Electron Impact Excitation of Water

    NASA Astrophysics Data System (ADS)

    Ralphs, Kevin; Serna, Gabriela; Hargreaves, Leigh R.; Khakoo, Murtadha A.; Winstead, Carl; McKoy, B. Vincent

    2011-10-01

    We present normalized absolute differential and integral cross-section measurements for the low energy electron impact excitation of the lowest dissociative 3B1, 1B1,3A1 and 1A1 states of H2O. The DCS were taken at incident energies of 9 eV, 10 eV, 12 eV, 15 eV and 20 eV and scattering angles of 15° to 130° and normalized to the elastic electron scattering measurements of. The DCS were obtained after a sophisticated unfolding of the electron energy loss spectrum of water using photoabsorption data in the literature as investigated by Thorn et al.. Our measurements extend those of to near-threshold energies. We find both important agreements and differences between our DCS and those of. Comparison to our theory (multi-channel Schwinger) and that of earlier work will also be presented. Funded by an NSF grant # RUI-PHY 0968874.

  9. Coulomb-dominated low-energy deuteron stripping

    SciTech Connect

    Austern, N. )

    1991-02-01

    Analysis of a three-body model shows that Coulomb polarization of the deuteron has very little influence on the branching ratio {ital A}({ital d},{ital p})/{ital A}({ital d},{ital n}) for transfer reactions on target nucleus {ital A} at very low deuteron energies (the Oppenheimer-Phillips effect). We see that polarization effects in transfer reactions are not related to the long range of the Coulomb field, but are caused by the more intense fields near the target nucleus. However, even in that region the induced dipole moment is limited by the deuteron binding, and it is small for low {ital Z} targets. We see in addition that the transfer amplitudes tend to be {ital insensitive} to any polarization admixtures in the entrance channel. On the other hand, the branching ratio can be affected by the Coulomb barrier for the bound final-state wave function of the proton, especially for very weakly bound final states. Brief remarks about the relation of stripping theory to special properties of the {ital d}+{ital d} system are included.

  10. 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.

  11. Coulomb excitations of monolayer germanene

    NASA Astrophysics Data System (ADS)

    Shih, Po-Hsin; Chiu, Yu-Huang; Wu, Jhao-Ying; Shyu, Feng-Lin; Lin, Ming-Fa

    2017-01-01

    The feature-rich electronic excitations of monolayer germanene lie in the significant spin-orbit coupling and the buckled structure. The collective and single-particle excitations are diversified by the magnitude and direction of transferred momentum, the Fermi energy and the gate voltage. There are four kinds of plasmon modes, according to the unique frequency- and momentum-dependent phase diagrams. They behave as two-dimensional acoustic modes at long wavelength. However, for the larger momenta, they might change into another kind of undamped plasmons, become the seriously suppressed modes in the heavy intraband e–h excitations, keep the same undamped plasmons, or decline and then vanish in the strong interband e–h excitations. Germanene, silicene and graphene are quite different from one another in the main features of the diverse plasmon modes.

  12. Coulomb excitations of monolayer germanene

    PubMed Central

    Shih, Po-Hsin; Chiu, Yu-Huang; Wu, Jhao-Ying; Shyu, Feng-Lin; Lin, Ming-Fa

    2017-01-01

    The feature-rich electronic excitations of monolayer germanene lie in the significant spin-orbit coupling and the buckled structure. The collective and single-particle excitations are diversified by the magnitude and direction of transferred momentum, the Fermi energy and the gate voltage. There are four kinds of plasmon modes, according to the unique frequency- and momentum-dependent phase diagrams. They behave as two-dimensional acoustic modes at long wavelength. However, for the larger momenta, they might change into another kind of undamped plasmons, become the seriously suppressed modes in the heavy intraband e–h excitations, keep the same undamped plasmons, or decline and then vanish in the strong interband e–h excitations. Germanene, silicene and graphene are quite different from one another in the main features of the diverse plasmon modes. PMID:28091555

  13. Coulomb excitation of radioactive {sup 79}Pb

    SciTech Connect

    Lister, C.J.; Blumenthal, D.; Davids, C.N.

    1995-08-01

    The technical challenges expected in experiments with radioactive beams can already be explored by using ions produced in primary reactions. In addition, the re-excitation of these ions by Coulomb excitation allows a sensitive search for collective states that are well above the yrast line. We are building an experiment to study Coulomb excitation of radioactive ions which are separated from beam particles by the Fragment Mass Analyzer. An array of gamma detectors will be mounted at the focal plane to measure the gamma radiation following re-excitation. Five Compton-suppressed Ge detectors and five planar LEPS detectors will be used. The optimum experiment of this type appears to be the study of {sup 79}Rb following the {sup 24}Mg ({sup 58}Ni,3p) reaction. We calculate that about 5 x 10{sup 5} {sup 79}Rb nuclei/second will reach the excitation foil. This rubidium isotope was selected for study as it is strongly produced and is highly deformed, so easily re-excited. The use of a {sup 58}Ni re-excitation foil offers the best yields. After re-excitation the ions will be subsequently transported into a shielded beamdump to prevent the accumulation of activity.

  14. Coulomb Excitation of the N = 50 nucleus 80Zn

    NASA Astrophysics Data System (ADS)

    van de Walle, J.; Aksouh, F.; Ames, 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.; Nilsson, T.; Pantea, M.; Perru, O.; 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.; van Duppen, P.; Verney, D.; Voulot, D.; Warr, N.; Weisshaar, D.; Wenander, F.; Wolf, B. H.; Zielińska, M.

    2008-05-01

    Neutron rich Zinc isotopes, including the N = 50 nucleus 80Zn, were produced and post-accelerated at the Radioactive Ion Beam (RIB) facility REX-ISOLDE (CERN). Low-energy Coulomb excitation was induced on these isotopes after post-acceleration, yielding B(E2) strengths to the first excited 2+ states. For the first time, an excited state in 80Zn was observed and the 21+ state in 78Zn was established. The measured B(E2,21+-->01+) values are compared to two sets of large scale shell model calculations. Both calculations reproduce the observed B(E2) systematics for the full Zinc isotopic chain. The results for N = 50 isotones indicate a good N = 50 shell closure and a strong Z = 28 proton core polarization. The new results serve as benchmarks to establish theoretical models, predicting the nuclear properties of the doubly magic nucleus 78Ni.

  15. Effect of Coulomb attraction on low-energy structure of ATI spectra

    NASA Astrophysics Data System (ADS)

    Telnov, Dmitry; Chu, Shih-I.

    2011-05-01

    Recent experimental observations of above-threshold ionization (ATI) of rare gas atoms and diatomic molecules by mid-infrared laser fields revealed a prominent maximum in the electron energy spectrum very close to the ionization threshold. This low-energy structure (LES) cannot be reproduced by the widely used Keldysh- Faisal-Reiss theories. We have performed a theoretical analysis and fully ab initio precision calculations for the hydrogen atom. Our results show that LES is related to the effect of Coulomb attraction in the final state of the electron. The probability density of slow electrons is condensed in the vicinity of the nucleus favoring the ionization process. As a result, the ATI electron energy spectrum increases when approaching the threshold. Our numerical data on the hydrogen atom show a maximum in the energy distribution close to the threshold, similar to the low-energy structure revealed by the experiments. This work was partially supported by DOE and NSF.

  16. Relativistic Coulomb excitation of 88Kr

    NASA Astrophysics Data System (ADS)

    Moschner, K.; Blazhev, A.; Jolie, J.; Warr, N.; Boutachkov, P.; Bednarczyk, P.; Sieja, K.; Algora, A.; Ameil, F.; Bentley, M. A.; Brambilla, S.; Braun, N.; Camera, F.; Cederkäll, J.; Corsi, A.; Danchev, M.; DiJulio, D.; Fahlander, C.; Gerl, J.; Giaz, A.; Golubev, P.; Górska, M.; Grebosz, J.; Habermann, T.; Hackstein, M.; Hoischen, R.; Kojouharov, I.; Kurz, N.; Mǎrginean, N.; Merchán, E.; Möller, T.; Naqvi, F.; Nara Singh, B. S.; Nociforo, C.; Pietralla, N.; Pietri, S.; Podolyák, Zs.; Prochazka, A.; Reese, M.; Reiter, P.; Rudigier, M.; Rudolph, D.; Sava, T.; Schaffner, H.; Scruton, L.; Taprogge, J.; Thomas, T.; Weick, H.; Wendt, A.; Wieland, O.; Wollersheim, H.-J.

    2016-11-01

    To investigate the systematics of mixed-symmetry states in N =52 isotones, a relativistic Coulomb excitation experiment was performed during the PreSPEC campaign at the GSI Helmholtzzentrum für Schwerionenforschung to determine E 2 transition strengths to 2+ states of the radioactive nucleus 88Kr. Absolute transition rates could be measured towards the first and third 2+ states. For the latter a mixed-symmetry character is suggested on the basis of the indication for a strong M 1 transition to the fully symmetric 21+ state, extending the knowledge of the N =52 isotones below Z =40 . A comparison with the proton-neutron interacting boson model and shell-model predictions is made and supports the assignment.

  17. Coulomb excitation of states in 238U

    NASA Astrophysics Data System (ADS)

    McGowan, F. K.; Milner, W. T.

    1994-05-01

    Twenty-two states in 238U have been observed with 18 MeV 4He ions on a thick target. Eight 2 + states between 966 and 1782 keV and three 3 - states are populated by direct E2 and E3, respectively. The remaining states are either weakly excited by multiple Coulomb excitation and /or populated by the γ-ray decay of the directly excited states. Spin assignments are based on γ-ray angular distributions. Reduced transition probabilities have been deduced from the γ-ray yields. The B(E2) values for excitation of the 2 + states range from 0.10 to 3.0 W.u. (281 W.u. for the first 2 + state). For the 3 states, the B(E3, 0 → 3 -) values are 7.1, 7.8, and 24.2 W.u. Several of the 2 + states have decay branches to the one-phonon states with B(E2) values between 27 and 56 W.u. which are an order of magnitude larger than the B(E2) values between the one- and zero-phonon states. This disagrees with our present understanding of collectivity in nuclei if these 2 + states are considered to be collective two-phonon excitations. However, the excitation energies of these 2 + states with respect to the one-phonon states are only 1.3 to 1.6. The B(E1) values for 17 transitions between the positive- and negative-parity states range between 10 -3 and 10 -7 W.u. The B(E1) branching ratios for many of these transitions have large deviations from the Alaga-rule predictions. These deviations can be understood by the strong Coriolis coupling between the states of the one-phonon octupole quadruplet in deformed nuclei. The general features of the experimental results for the B(E3) values are reproduced by the microscopic calculations of Neergård and Vogel when the Coriolis coupling between the states of the octupole quadruplet is included.

  18. Coulomb excitation of states in 232Th

    NASA Astrophysics Data System (ADS)

    McGowan, F. K.; Milner, W. T.

    1993-09-01

    Twenty-five states in 232Th have been observed with 18 MeV 4He ions on a thick target. Eleven 2 + states between 774 and 1554 keV and three 3 - states are populated by direct E2 and E3, respectively. The remaining states are either weakly excited by multiple Coulomb excitation and/or populated by the decay of the directly excited states. Spin assignments are based on γ-ray angular distributions. Reduced transition probabilities have been deduced from the γ-ray yields. The B(E2) values for excitation of the 2 + states range from 0.024 to 3.5 W.u. (222 W.u. for the first 2 + state). For the 3 - states, the B(E3,0 → 3 -) values are 1.7, 11, and 24 W.u. A possible two-phonon state at 1554 keV, which is nearly harmonic, decays to four members of the one-phonon states, to the ground-state band, and to the K = 0 - octupole band. The B(E2) value for excitation of this state is 0.66 ± 0.05 W.u. and the B(E1) values for decay of this state are (2 and 6)×10 -4 W.u. The B(E2) values between two- and one-phonon vibrational states range between 16 and 53 W.u. which are an order of magnitude larger than the B(E2) values between the one- and zero-phonon states. This disagrees with our present understanding of collectivity in nuclei if this 2 + state is considered to be a collective two-phonon excitation. The 2 + states at 1477 and 1387 keV, which are also nearly harmonic, are possible candidates with two-phonon structure. The agreement between the experimental results and the microscopic calculations by Neergård and Vogel of the B(E3,0 → 3) for the 3 - members of the one-phonon octupole quadruplet is satisfactory when the Coriolis coupling between the states with K and K ± 1 is included. The B(E1) branching ratios for transitions from the 3 - and 1 - states to the ground-state band have large deviations from the Alaga-rule predictions. These deviations can be understood by the strong Coriolis coupling between the states of the octupole quadruplet in deformed nuclei.

  19. Coulomb excitation of radioactive nuclear beams in inverse kinematics

    SciTech Connect

    Zamfir, N.V. |||; Barton, C.J.; Brenner, D.S.; Casten, R.F. |; Gill, R.L.; Zilges, A. |

    1996-12-31

    Techniques for the measurement of B (E2:0{sub 1}{sup +} {r_arrow} 2{sub 1}{sup +}) values by Coulomb excitation of Radioactive Nuclear Beams in inverse kinematics are described. Using a thin, low Z target, the Coulomb excited beam nuclei will decay in flight downstream of the target. For long lifetimes (nanosecond range) these nuclei decay centimeters downstream of the target and for shorter lifetimes (picoseconds or less) they decay near the target. Corresponding to these two lifetime regimes two methods have been developed to measure {gamma} rays from the Coulomb excited nuclei: the lifetime method in which the lifetime of the excited state is deduced from the decay curve and the integral method in which the B(E2) value is extracted from the measured total Coulomb excitation cross section.

  20. Electronic excitation of molecular hydrogen by low-energy electrons

    NASA Astrophysics Data System (ADS)

    Hargreaves, Leigh

    2016-09-01

    Molecular hydrogen is the most abundant element in the universe, particularly in interstellar plasmas such as atmospheres of gas giant planets and stars. Electron collision data for hydrogen is critical to interpreting the spectroscopy of interstellar objects, as well as being of applied value for modelling technological plasmas. Hydrogen is also fundamentally interesting, as while highly accurate wave functions for this simple molecule are available, providing an accurate, ab initio, treatment the collision dynamics has proven challenging, on account of the need to have a complete description of channel coupling and polarization effects. To date, no single theoretical approach has been able to replicate experimental results across all transitions and incident energies, while the experimental database that is available is far from complete and not all available measurements are in satisfactory agreement. In this talk, we present differential and integral cross section measurements for electronic excitation cross sections for molecular hydrogen by low-energy electron impact. The data were measured at incident energies below 20eV, using a well-tested crossed beam apparatus and employing a moveable gas source approach to ensure that background contributions to the scattering are accurately accounted for. These measurements are compared with new theoretical results employing the convergent close coupling approach.

  1. Generalized oscillator strength and Coulomb excitation

    NASA Astrophysics Data System (ADS)

    Chidichimo, Marita C.; Thorsley, Michael D.

    2003-02-01

    Coulomb interaction is characterized by two nondimensional fundamental quantities: the Sommerfeld parameter η and the adiabaticity parameter ξ=ηf-ηi. In this different approach, we choose these variables to describe the behavior of the generalized oscillator strength (GOS). The expression we obtain is valid for scattering of electrons, positrons, and nuclei by arbitrary targets. We present asymptotic expansions, in the quantal and semiclassical approximation, of the electric dipole GOS.

  2. Characterizing intra-exciton Coulomb scattering in terahertz excitations

    SciTech Connect

    Zybell, S.; Eßer, F.; Helm, M.; Bhattacharyya, J.; Winnerl, S.; Schneider, H.; Schneebeli, L.; Böttge, C. N.; Kira, M.; Koch, S. W.; Andrews, A. M.; Strasser, G.

    2014-11-17

    An intense terahertz field is applied to excite semiconductor quantum wells yielding strong non-equilibrium exciton distributions. Even though the relaxation channels involve a complicated quantum kinetics of Coulomb and phonon effects, distinct relaxation signatures of Coulomb scattering are identified within time-resolved photoluminescence by comparing the experiment with a reduced model that contains all relevant microscopic processes. The analysis uncovers a unique time scale for the Coulomb scattering directly from experiments and reveals the influence of phonon relaxation as well as radiative decay.

  3. Analytic model for low energy excitation states and phase transitions in spin-ice systems

    NASA Astrophysics Data System (ADS)

    López-Bara, F. I.; López-Aguilar, F.

    2017-04-01

    Low energy excitation states in magnetic structures of the so-called spin-ices are produced via spin flips among contiguous tetrahedra of their crystal structure. These spin flips generate entities which mimic magnetic dipoles in every two tetrahedra according to the dumbbell model. When the temperature increases, the spin-flip processes are transmitted in the lattice, generating so-called Dirac strings, which constitute structural entities that can present mimetic behavior similar to that of magnetic monopoles. In recent studies of both specific heat and ac magnetic susceptibility, two (even possibly three) phases have been shown to vary the temperature. The first of these phases presents a sharp peak in the specific heat and another phase transition occurs for increasing temperature whose peak is broader than that of the former phase. The sharp peak occurs when there are no free individual magnetic charges and temperature of the second phase transition coincides with the maximum proliferation of free deconfined magnetic charges. In the present paper, we propose a model for analyzing the low energy excitation many-body states of these spin-ice systems. We give analytical formulas for the internal energy, specific heat, entropy and their temperature evolution. We study the description of the possible global states via the nature and structure of their one-body components by means of the thermodynamic functions. Below 0.37 K, the Coulomb-like magnetic charge interaction can generate a phase transition to a condensation of pole–antipole pairs, possibly having Bose–Einstein structure which is responsible for the sharp peak of the first phase transition. When there are sufficient free positive and negative charges, the system tends to behave as a magnetic plasma, which implies the broader peak in the specific heat appearing at higher temperature than the sharper experimental peak.

  4. Analytic model for low energy excitation states and phase transitions in spin-ice systems.

    PubMed

    López-Bara, F I; López-Aguilar, F

    2017-04-20

    Low energy excitation states in magnetic structures of the so-called spin-ices are produced via spin flips among contiguous tetrahedra of their crystal structure. These spin flips generate entities which mimic magnetic dipoles in every two tetrahedra according to the dumbbell model. When the temperature increases, the spin-flip processes are transmitted in the lattice, generating so-called Dirac strings, which constitute structural entities that can present mimetic behavior similar to that of magnetic monopoles. In recent studies of both specific heat and ac magnetic susceptibility, two (even possibly three) phases have been shown to vary the temperature. The first of these phases presents a sharp peak in the specific heat and another phase transition occurs for increasing temperature whose peak is broader than that of the former phase. The sharp peak occurs when there are no free individual magnetic charges and temperature of the second phase transition coincides with the maximum proliferation of free deconfined magnetic charges. In the present paper, we propose a model for analyzing the low energy excitation many-body states of these spin-ice systems. We give analytical formulas for the internal energy, specific heat, entropy and their temperature evolution. We study the description of the possible global states via the nature and structure of their one-body components by means of the thermodynamic functions. Below 0.37 K, the Coulomb-like magnetic charge interaction can generate a phase transition to a condensation of pole-antipole pairs, possibly having Bose-Einstein structure which is responsible for the sharp peak of the first phase transition. When there are sufficient free positive and negative charges, the system tends to behave as a magnetic plasma, which implies the broader peak in the specific heat appearing at higher temperature than the sharper experimental peak.

  5. Coulomb excitation of C{sub 60} molecules

    SciTech Connect

    Esbensen, H.; Berry, H.G.; Cheng, S.

    1995-08-01

    The ionization and dissociation of C{sub 60} molecules in the Coulomb field from fast, highly-charged xenon ions was measured recently at ATLAS. The Coulomb excitation was modeled as a coherent excitation of the giant plasmon resonance. Guided by photo-absorption measurements, single-plasmon excitations were identified with the production of single-charged C{sub 60}{sup +} molecular ions. The calculated cross sections do indeed reproduce the beam energy-dependence of the measured C{sub 60}{sup +} yield. The calculations show that single-plasmon excitations are responsible for about half of the total reaction cross section. The other half, i.e., multiplasmon excitations, leads to multiple ionization and dissociation of the molecule.

  6. Low-energy structure of above-threshold-ionization electron spectra: Role of the Coulomb threshold effect

    NASA Astrophysics Data System (ADS)

    Telnov, Dmitry A.; Chu, Shih-I.

    2011-06-01

    Recent experimental observations of above-threshold ionization of rare gas atoms and diatomic molecules by midinfrared laser fields [C. I. Blaga , Nat. Phys.PRLTAO1745-247310.1038/nphys1228 5, 335 (2009); W. Quan , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.103.093001 103, 093001 (2009)] revealed a prominent maximum in the electron energy spectrum very close to the ionization threshold which is not reproduced by widely used Keldysh-Faisal-Reiss theories. We have performed fully ab initio theoretical analysis and precision calculations to explore the quantum origin of the low-energy structure (LES) observed in the experiments. Our study shows that an important role in shaping of LES is played by the effect of Coulomb attraction in the final electron state and the Coulomb threshold effect.

  7. Resonant vibrational excitation of CO by low-energy electrons

    SciTech Connect

    Poparic, G. B.; Belic, D. S.; Vicic, M. D.

    2006-06-15

    Electron impact vibrational excitation of the CO molecule, via the {sup 2}{pi} resonance, in the 0-4 eV energy region has been investigated. The energy dependence of the resonant excitation of the first ten vibrational levels, v=1 to v=10, has been measured by use of a crossed-beams double trochoidal electron spectrometer. Obtained relative differential cross sections are normalized to the absolute values. Integral cross sections are determined by using our recent results on scattered electrons angular distributions, which demonstrate clear p-partial wave character of this resonance. Substructures appear in the {sup 2}{pi} resonant excitation of the CO molecule which have not been previously observed.

  8. Slow Interatomic Coulombic Decay of Multiply Excited Neon Clusters

    NASA Astrophysics Data System (ADS)

    Iablonskyi, D.; Nagaya, K.; Fukuzawa, H.; Motomura, K.; Kumagai, Y.; Mondal, S.; Tachibana, T.; Takanashi, T.; Nishiyama, T.; Matsunami, K.; Johnsson, P.; Piseri, P.; Sansone, G.; Dubrouil, A.; Reduzzi, M.; Carpeggiani, P.; Vozzi, C.; Devetta, M.; Negro, M.; Calegari, F.; Trabattoni, A.; Castrovilli, M. C.; Faccialà, D.; Ovcharenko, Y.; Möller, T.; Mudrich, M.; Stienkemeier, F.; Coreno, M.; Alagia, M.; Schütte, B.; Berrah, N.; Kuleff, A. I.; Jabbari, G.; Callegari, C.; Plekan, O.; Finetti, P.; Spezzani, C.; Ferrari, E.; Allaria, E.; Penco, G.; Serpico, C.; De Ninno, G.; Nikolov, I.; Diviacco, B.; Di Mitri, S.; Giannessi, L.; Prince, K. C.; Ueda, K.

    2016-12-01

    Ne clusters (˜5000 atoms ) were resonantly excited (2 p →3 s ) by intense free electron laser (FEL) radiation at FERMI. Such multiply excited clusters can decay nonradiatively via energy exchange between at least two neighboring excited atoms. Benefiting from the precise tunability and narrow bandwidth of seeded FEL radiation, specific sites of the Ne clusters were probed. We found that the relaxation of cluster surface atoms proceeds via a sequence of interatomic or intermolecular Coulombic decay (ICD) processes while ICD of bulk atoms is additionally affected by the surrounding excited medium via inelastic electron scattering. For both cases, cluster excitations relax to atomic states prior to ICD, showing that this kind of ICD is rather slow (picosecond range). Controlling the average number of excitations per cluster via the FEL intensity allows a coarse tuning of the ICD rate.

  9. Slow Interatomic Coulombic Decay of Multiply Excited Neon Clusters.

    PubMed

    Iablonskyi, D; Nagaya, K; Fukuzawa, H; Motomura, K; Kumagai, Y; Mondal, S; Tachibana, T; Takanashi, T; Nishiyama, T; Matsunami, K; Johnsson, P; Piseri, P; Sansone, G; Dubrouil, A; Reduzzi, M; Carpeggiani, P; Vozzi, C; Devetta, M; Negro, M; Calegari, F; Trabattoni, A; Castrovilli, M C; Faccialà, D; Ovcharenko, Y; Möller, T; Mudrich, M; Stienkemeier, F; Coreno, M; Alagia, M; Schütte, B; Berrah, N; Kuleff, A I; Jabbari, G; Callegari, C; Plekan, O; Finetti, P; Spezzani, C; Ferrari, E; Allaria, E; Penco, G; Serpico, C; De Ninno, G; Nikolov, I; Diviacco, B; Di Mitri, S; Giannessi, L; Prince, K C; Ueda, K

    2016-12-30

    Ne clusters (∼5000  atoms) were resonantly excited (2p→3s) by intense free electron laser (FEL) radiation at FERMI. Such multiply excited clusters can decay nonradiatively via energy exchange between at least two neighboring excited atoms. Benefiting from the precise tunability and narrow bandwidth of seeded FEL radiation, specific sites of the Ne clusters were probed. We found that the relaxation of cluster surface atoms proceeds via a sequence of interatomic or intermolecular Coulombic decay (ICD) processes while ICD of bulk atoms is additionally affected by the surrounding excited medium via inelastic electron scattering. For both cases, cluster excitations relax to atomic states prior to ICD, showing that this kind of ICD is rather slow (picosecond range). Controlling the average number of excitations per cluster via the FEL intensity allows a coarse tuning of the ICD rate.

  10. Coulomb three-body effects in low-energy impact ionization of H(1{ital s})

    SciTech Connect

    Roeder, J.; Rasch, J.; Jung, K.; Whelan, C.T.; Ehrhardt, H.; Allan, R.J.; Walters, H.R. |||

    1996-01-01

    The different kinematical and geometrical arrangements that may be used in ({ital e},2{ital e}) studies are briefly reviewed. The ionization of H(1{ital s}) is considered, and within the confines of a relatively simple theoretical model, it is shown how to define experimental setups where one may extract information on the role of Coulomb three-body effects in the incident and final channels. Theoretical and experimental results are presented for coplanar constant geometry where the focus is primarily on incident channel effects. {copyright} {ital 1996 The American Physical Society.}

  11. Ultrafast dynamics of low energy elementary excitations in semiconductors

    NASA Astrophysics Data System (ADS)

    Stevens, Troy Eugene

    2000-10-01

    The theory of impulsive stimulated Raman scattering (ISRS) is extended to include the generation and detection of coherent phonons in the opaque régime. A quantum mechanical calculation yields an expression for the frequency-dependent Raman susceptibility appropriate for impulsive excitation. Expressions for the time-dependent phonon amplitude and relative change in transmissivity ΔT/T and reflectivity Δ R/R are derived for two-band processes and important differences between stimulated and spontaneous Raman scattering are discussed. Experiments in which impulsively-stimulated coherent phonons were resonantly excited are presented. Continuously tunable pulses produced by an optical parametric amplifier were used in a pump-probe geometry. Changes in the reflectivity induced by the A1g phonon in the vicinity of the E'2 gap at 1.95 eV in the semimetal Sb and changes in the transmissivity induced by the A'1 phonon in the vicinity of the fundamental gap at 2.1 eV in the semiconductor GaSe were measured. Calculations of Δ R/R and ΔT/T based on the theory of ISRS compare well with the experimental results. An investigation of coherent polaritons in the optically isotropic semiconductor ZnSe at 10 K is presented. The polaritons were generated with a single ultrafast pulse and their dispersion was measured for wave vectors in the range 1370 cm-1 to 2780 cm- 1 by varying the central pulse energy in the range 1.97 eV to 2.3 eV. Phase matching was achieved due to the large dispersion in the index of refraction. The observed monotonic increase in decay rate as the wave vector decreases is attributed to inhomogeneous broadening and propagation effects. Observations of several inverted peaks and plateaus in the transmissivity as a function of delay in the semiconductor AS2Se3 are discussed. Interactions between the incident probe pulse and co- and counter-propagating internally-reflected pump pulses account for the inverted peaks and plateaus, respectively. Based on phase

  12. Interatomic Coulombic decay cascades in multiply excited neon clusters

    PubMed Central

    Nagaya, K.; Iablonskyi, D.; Golubev, N. V.; Matsunami, K.; Fukuzawa, H.; Motomura, K.; Nishiyama, T.; Sakai, T.; Tachibana, T.; Mondal, S.; Wada, S.; Prince, K. C.; Callegari, C.; Miron, C.; Saito, N.; Yabashi, M.; Demekhin, Ph. V.; Cederbaum, L. S.; Kuleff, A. I.; Yao, M.; Ueda, K.

    2016-01-01

    In high-intensity laser light, matter can be ionized by direct multiphoton absorption even at photon energies below the ionization threshold. However on tuning the laser to the lowest resonant transition, the system becomes multiply excited, and more efficient, indirect ionization pathways become operative. These mechanisms are known as interatomic Coulombic decay (ICD), where one of the species de-excites to its ground state, transferring its energy to ionize another excited species. Here we show that on tuning to a higher resonant transition, a previously unknown type of interatomic Coulombic decay, intra-Rydberg ICD occurs. In it, de-excitation of an atom to a close-lying Rydberg state leads to electron emission from another neighbouring Rydberg atom. Moreover, systems multiply excited to higher Rydberg states will decay by a cascade of such processes, producing even more ions. The intra-Rydberg ICD and cascades are expected to be ubiquitous in weakly-bound systems exposed to high-intensity resonant radiation. PMID:27917867

  13. Interatomic Coulombic decay cascades in multiply excited neon clusters.

    PubMed

    Nagaya, K; Iablonskyi, D; Golubev, N V; Matsunami, K; Fukuzawa, H; Motomura, K; Nishiyama, T; Sakai, T; Tachibana, T; Mondal, S; Wada, S; Prince, K C; Callegari, C; Miron, C; Saito, N; Yabashi, M; Demekhin, Ph V; Cederbaum, L S; Kuleff, A I; Yao, M; Ueda, K

    2016-12-05

    In high-intensity laser light, matter can be ionized by direct multiphoton absorption even at photon energies below the ionization threshold. However on tuning the laser to the lowest resonant transition, the system becomes multiply excited, and more efficient, indirect ionization pathways become operative. These mechanisms are known as interatomic Coulombic decay (ICD), where one of the species de-excites to its ground state, transferring its energy to ionize another excited species. Here we show that on tuning to a higher resonant transition, a previously unknown type of interatomic Coulombic decay, intra-Rydberg ICD occurs. In it, de-excitation of an atom to a close-lying Rydberg state leads to electron emission from another neighbouring Rydberg atom. Moreover, systems multiply excited to higher Rydberg states will decay by a cascade of such processes, producing even more ions. The intra-Rydberg ICD and cascades are expected to be ubiquitous in weakly-bound systems exposed to high-intensity resonant radiation.

  14. Interatomic Coulombic decay cascades in multiply excited neon clusters

    NASA Astrophysics Data System (ADS)

    Nagaya, K.; Iablonskyi, D.; Golubev, N. V.; Matsunami, K.; Fukuzawa, H.; Motomura, K.; Nishiyama, T.; Sakai, T.; Tachibana, T.; Mondal, S.; Wada, S.; Prince, K. C.; Callegari, C.; Miron, C.; Saito, N.; Yabashi, M.; Demekhin, Ph. V.; Cederbaum, L. S.; Kuleff, A. I.; Yao, M.; Ueda, K.

    2016-12-01

    In high-intensity laser light, matter can be ionized by direct multiphoton absorption even at photon energies below the ionization threshold. However on tuning the laser to the lowest resonant transition, the system becomes multiply excited, and more efficient, indirect ionization pathways become operative. These mechanisms are known as interatomic Coulombic decay (ICD), where one of the species de-excites to its ground state, transferring its energy to ionize another excited species. Here we show that on tuning to a higher resonant transition, a previously unknown type of interatomic Coulombic decay, intra-Rydberg ICD occurs. In it, de-excitation of an atom to a close-lying Rydberg state leads to electron emission from another neighbouring Rydberg atom. Moreover, systems multiply excited to higher Rydberg states will decay by a cascade of such processes, producing even more ions. The intra-Rydberg ICD and cascades are expected to be ubiquitous in weakly-bound systems exposed to high-intensity resonant radiation.

  15. Coulomb excitations for a short linear chain of metallic shells

    SciTech Connect

    Zhemchuzhna, Liubov; Gumbs, Godfrey; Iurov, Andrii; Huang, Danhong; Gao, Bo

    2015-03-15

    A self-consistent-field theory is given for the electronic collective modes of a chain containing a finite number, N, of Coulomb-coupled spherical two-dimensional electron gases arranged with their centers along a straight line, for simulating electromagnetic response of a narrow-ribbon of metallic shells. The separation between nearest-neighbor shells is arbitrary and because of the quantization of the electron energy levels due to their confinement to the spherical surface, all angular momenta L of the Coulomb excitations, as well as their projections M on the quantization axis, are coupled. However, for incoming light with a given polarization, only one angular momentum quantum number is usually required. Therefore, the electromagnetic response of the narrow-ribbon of metallic shells is expected to be controlled externally by selecting different polarizations for incident light. We show that, when N = 3, the next-nearest-neighbor Coulomb coupling is larger than its value if they are located at opposite ends of a right-angle triangle forming the triad. Additionally, the frequencies of the plasma excitations are found to depend on the orientation of the line joining them with respect to the axis of quantization since the magnetic field generated from the induced oscillating electric dipole moment on one sphere can couple to the induced magnetic dipole moment on another. Although the transverse inter-shell electromagnetic coupling can be modeled by an effective dynamic medium, the longitudinal inter-shell Coulomb coupling, on the other hand, can still significantly modify the electromagnetic property of this effective medium between shells.

  16. Coulomb excitation of the proton-dripline nucleus {sup 20}Na

    SciTech Connect

    Schumaker, M. A.; Svensson, C. E.; Bandyopadhyay, D.; Demand, G. A.; Finlay, P.; Garrett, P. E.; Green, K. L.; Grinyer, G. F.; Leach, K. G.; Phillips, A. A.; Wong, J.; Cline, D.; Hayes, A. B.; Whitbeck, A.; Hackman, G.; Pearson, C. J.; Andreyev, A.; Ball, G. C.; Buchmann, L.; Churchman, R.

    2009-10-15

    The low-energy structure of the proton dripline nucleus {sup 20}Na has been studied using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. A 1.7-MeV/nucleon {sup 20}Na beam of {approx}5x10{sup 6} ions/s was Coulomb excited by a 0.5-mg/cm{sup 2nat}Ti target. Scattered beam and target particles were detected by the BAMBINO segmented Si detector while {gamma} rays were detected by two TIGRESS HPGe clover detectors set perpendicular to the beam axis. Coulomb excitation from the 2{sup +} ground state to the first excited 3{sup +} and 4{sup +} states was observed, and B({lambda}L) values were determined using the 2{sup +}{yields}0{sup +} de-excitation in {sup 48}Ti as a reference. The resulting B({lambda}L){down_arrow} values are B(E2;3{sup +}{yields}2{sup +})=55{+-}6 e{sup 2} fm{sup 4} (17.0{+-}1.9 W.u.), B(E2;4{sup +}{yields}2{sup +})=35.7{+-}5.7 e{sup 2} fm{sup 4} (11.1{+-}1.8 W.u.), and B(M1;4{sup +}{yields}3{sup +})=0.154{+-}0.030 {mu}{sub N}{sup 2} (0.086{+-}0.017 W.u.). These measurements provide the first experimental determination of B({lambda}L) values for this proton dripline nucleus of astrophysical interest.

  17. 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.

  18. Triaxiality near the 110Ru ground state from Coulomb excitation

    NASA Astrophysics Data System (ADS)

    Doherty, D. T.; Allmond, J. M.; Janssens, R. V. F.; Korten, W.; Zhu, S.; Zielińska, M.; Radford, D. C.; Ayangeakaa, A. D.; Bucher, B.; Batchelder, J. C.; Beausang, C. W.; Campbell, C.; Carpenter, M. P.; Cline, D.; Crawford, H. L.; David, H. M.; Delaroche, J. P.; Dickerson, C.; Fallon, P.; Galindo-Uribarri, A.; Kondev, F. G.; Harker, J. L.; Hayes, A. B.; Hendricks, M.; Humby, P.; Girod, M.; Gross, C. J.; Klintefjord, M.; Kolos, K.; Lane, G. J.; Lauritsen, T.; Libert, J.; Macchiavelli, A. O.; Napiorkowski, P. J.; Padilla-Rodal, E.; Pardo, R. C.; Reviol, W.; Sarantites, D. G.; Savard, G.; Seweryniak, D.; Srebrny, J.; Varner, R.; Vondrasek, R.; Wiens, A.; Wilson, E.; Wood, J. L.; Wu, C. Y.

    2017-03-01

    A multi-step Coulomb excitation measurement with the GRETINA and CHICO2 detector arrays was carried out with a 430-MeV beam of the neutron-rich 110Ru (t1/2 = 12 s) isotope produced at the CARIBU facility. This represents the first successful measurement following the post-acceleration of an unstable isotope of a refractory element. The reduced transition probabilities obtained for levels near the ground state provide strong evidence for a triaxial shape; a conclusion confirmed by comparisons with the results of beyond-mean-field and triaxial rotor model calculations.

  19. Triaxiality near the 110Ru ground state from Coulomb excitation

    DOE PAGES

    Doherty, D. T.; Allmond, James M.; Janssens, R. V. F.; ...

    2017-01-20

    A multi-step Coulomb excitation measurement with the GRETINA and CHICO2 detector arrays was carried out with a 430-MeV beam of the neutron-rich 110Ru (t1/2 = 12 s) isotope produced at the CARIBU facility. This represents the first successful measurement following the post-acceleration of an unstable isotope of a refractory element. The reduced transition probabilities obtained for levels near the ground state provide strong evidence for a triaxial shape; a conclusion confirmed by comparisons with the results of beyond-mean-field and triaxial rotor model calculations.

  20. Coulomb excitation of levels in 143Nd and 145Nd

    NASA Astrophysics Data System (ADS)

    Drǎgulescu, E.; Ivaşcu, M.; Mihu, R.; Popescu, D.; Semenescu, G.; Paar, V.; Vretenar, D.

    1984-04-01

    The low-lying states of 143Nd and 154Nd have been studied by means of Coulomb excitation with 16O and α-particles. Angular distribution measurements were carried out for some transitions in 145Nd with 11.2 MeV α-particles. Level energy decay schemes and B(E2)↑ values were measured for two states in 143Nd and for six states in 145Nd. Some spin assignments have been established for the 145Nd nucleus. 143Nd and 145Nd have been theoretically described by coupling one and three particles, respectively, to quadrupole vibrations, and rather good agreement with experiment was achieved.

  1. Plunger lifetime measurements after Coulomb excitation at intermediate beam energies

    SciTech Connect

    Dewald, A.; Hackstein, M.; Rother, W.; Jolie, J.; Melon, B.; Pissulla, T.; Shimbara, Y.; Starosta, K.; Adrich, P.; Amthor, A. M.; Baumann, T.; Bazin, D.; Bowen, M.; Chester, A.; Dunomes, A.; Gade, A.; Galaviz, D.; Glasmacher, T.; Ginter, T.; Hausmann, M.

    2009-01-28

    Absolute transition probabilities of the first 2{sup +} state in {sup 110,114}Pd were remeasured using the recoil distance Doppler shift technique following projectile Coulomb excitation at intermediate beam energies for the first time. The {sup 110}Pd experiment served to check the novel technique as well as the method used for the data analysis which is based on the examination of {gamma}-ray lineshapes. Whereas the measured B(E2) value for {sup 110}Pd agrees very well with the literature, the value obtained for {sup 114}Pd differs considerably. The data is also used to test a novel concept, called the valence proton symmetry, which allows one to extrapolate nuclear properties to very neutron rich nuclei.

  2. Low-energy electron excitation effect on formation of graphene nanocrystallites during carbon film growth process

    NASA Astrophysics Data System (ADS)

    Chen, Wencong; Zhang, Xi; Diao, Dongfeng

    2017-09-01

    We report a low-energy electron excitation effect on the formation of graphene nanocrystallites embedded in carbon films in an electron cyclotron resonance plasma. In this work, carbon films were deposited at different irradiation electron energies and fluxes monitored using a retarding field energy analyzer, while the deposition temperature was measured using an infrared thermometer. We found that the size and concentration of graphene nanocrystallites strongly depend on the irradiation electron energy and the electron flux but not the temperature, which indicates that the electron excitation effect of the covalent bonds dominates the formation process of these nanocrystallites. This finding shed light on the new fabrication method of 2D materials.

  3. 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.

  4. Synthesis of silver nanorods by low energy excitation of spherical plasmonic seeds.

    PubMed

    Zhang, Jian; Langille, Mark R; Mirkin, Chad A

    2011-06-08

    Plasmon excitation of Ag seed particles with 600-750 nm light in the presence of Ag(+) and trisodium citrate was used to synthesize penta-twinned nanorods. Importantly, the excitation wavelength can be used to control the reaction rate and, consequently, the aspect ratio of the nanorods. When the excitation wavelength is red-shifted from the surface plasmon resonance of the spherical seed particles, the rate of Ag(+) reduction becomes slower and more kinetically controlled. Such conditions favor the deposition of silver onto the tips of the growing nanorods as compared to their sides, resulting in the generation of higher aspect ratio rods. However, control experiments reveal that there is only a range of low energy excitation wavelengths (between 600 and 750 nm) that yields monodisperse nanorods. This study further highlights the utility of using wavelength to control the size and shape of growing nanoparticles using plasmon-mediated methods.

  5. Coulomb excitation of radioactive {sup 21}Na and its stable mirror {sup 21}Ne

    SciTech Connect

    Schumaker, M. A.; Svensson, C. E.; Demand, G. A.; Finlay, P.; Garrett, P. E.; Green, K. L.; Grinyer, G. F.; Leach, K. G.; Phillips, A. A.; Wong, J.; Cline, D.; Hayes, A. B.; Whitbeck, A.; Hackman, G.; Morton, A. C.; Pearson, C. J.; Andreyev, A.; Ball, G. C.; Buchmann, L.; Churchman, R.

    2008-10-15

    The low-energy structures of the mirror nuclei {sup 21}Ne and radioactive {sup 21}Na have been examined by using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. Beams of {approx}5x10{sup 6} ions/s were accelerated to 1.7 MeV/A and Coulomb excited in a 0.5 mg/cm{sup 2} {sup nat}Ti target. Scattered beam and target particles were detected by the segmented Si detector BAMBINO, while {gamma} rays were observed by using two TIGRESS HPGe clover detectors perpendicular to the beam axis. For each isobar, Coulomb excitation from the (3/2){sup +} ground state to the first excited (5/2){sup +} state was observed and B(E2) values were determined by using the 2{sup +}{yields}0{sup +} de-excitation in {sup 48}Ti as a reference. The {phi} segmentation of BAMBINO was used to deduce tentative assignments for the signs of the mixing ratios between the E2 and M1 components of the transitions. The resulting B(E2){up_arrow} values are 131{+-}9 e{sup 2} fm{sup 4} (25.4{+-}1.7 W.u.) for {sup 21}Ne and 205{+-}14 e{sup 2} fm{sup 4} (39.7{+-}2.7 W.u.) for {sup 21}Na. The fit to the present data and the known lifetimes determined E2/M1 mixing ratios and B(M1){down_arrow} values of {delta}=(-)0.0767{+-}0.0027 and 0.1274{+-}0.0025 {mu}{sub N}{sup 2} and {delta}=(+)0.0832{+-}0.0028 and 0.1513{+-}0.0017 {mu}{sub N}{sup 2} for {sup 21}Ne and {sup 21}Na, respectively (with Krane and Steffen sign convention). By using the effective charges e{sub p}=1.5e and e{sub n}=0.5e, the B(E2) values produced by the p-sd shell model are 30.7 and 36.4 W.u. for {sup 21}Ne and {sup 21}Na, respectively. This analysis resolves a significant discrepancy between a previous experimental result for {sup 21}Na and shell-model calculations.

  6. Coulomb excitation of radioactive Na21 and its stable mirror Ne21

    NASA Astrophysics Data System (ADS)

    Schumaker, M. A.; Cline, D.; Hackman, G.; Morton, A. C.; Pearson, C. J.; Svensson, C. E.; Wu, C. Y.; Andreyev, A.; Austin, R. A. E.; Ball, G. C.; Bandyopadhyay, D.; Becker, J. A.; Boston, A. J.; Boston, H. C.; Buchmann, L.; Churchman, R.; Cifarelli, F.; Cooper, R. J.; Cross, D. S.; Dashdorj, D.; Demand, G. A.; Dimmock, M. R.; Drake, T. E.; Finlay, P.; Gallant, A. T.; Garrett, P. E.; Green, K. L.; Grint, A. N.; Grinyer, G. F.; Harkness, L. J.; Hayes, A. B.; Kanungo, R.; Leach, K. G.; Lee, G.; Maharaj, R.; Martin, J.-P.; Moisan, F.; Mythili, S.; Nelson, L.; Newman, O.; Nolan, P. J.; Orce, J. N.; Padilla-Rodal, E.; Phillips, A. A.; Porter-Peden, M.; Ressler, J. J.; Roy, R.; Ruiz, C.; Sarazin, F.; Scraggs, D. P.; Waddington, J. C.; Wan, J. M.; Whitbeck, A.; Williams, S. J.; Wong, J.

    2008-10-01

    The low-energy structures of the mirror nuclei Ne21 and radioactive Na21 have been examined by using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. Beams of ~5×106 ions/s were accelerated to 1.7 MeV/A and Coulomb excited in a 0.5 mg/cm2 natTi target. Scattered beam and target particles were detected by the segmented Si detector BAMBINO, while γ rays were observed by using two TIGRESS HPGe clover detectors perpendicular to the beam axis. For each isobar, Coulomb excitation from the (3)/(2)+ ground state to the first excited (5)/(2)+ state was observed and B(E2) values were determined by using the 2+→0+ de-excitation in Ti48 as a reference. The ϕ segmentation of BAMBINO was used to deduce tentative assignments for the signs of the mixing ratios between the E2 and M1 components of the transitions. The resulting B(E2)↑ values are 131±9e2 fm4 (25.4±1.7 W.u.) for Ne21 and 205±14e2 fm4 (39.7±2.7 W.u.) for Na21. The fit to the present data and the known lifetimes determined E2/M1 mixing ratios and B(M1)↓ values of δ=(-)0.0767±0.0027 and 0.1274±0.0025μN2 and δ=(+)0.0832±0.0028 and 0.1513±0.0017μN2 for Ne21 and Na21, respectively (with Krane and Steffen sign convention). By using the effective charges ep=1.5e and en=0.5e, the B(E2) values produced by the p-sd shell model are 30.7 and 36.4 W.u. for Ne21 and Na21, respectively. This analysis resolves a significant discrepancy between a previous experimental result for Na21 and shell-model calculations.

  7. Cold chemistry with electronically excited Ca{sup +} Coulomb crystals

    SciTech Connect

    Gingell, Alexander D.; Bell, Martin T.; Oldham, James M.; Softley, Timothy P.; Harvey, Jeremy N.

    2010-11-21

    Rate constants for chemical reactions of laser-cooled Ca{sup +} ions and neutral polar molecules (CH{sub 3}F, CH{sub 2}F{sub 2}, or CH{sub 3}Cl) have been measured at low collision energies (/k{sub B}=5-243 K). Low kinetic energy ensembles of {sup 40}Ca{sup +} ions are prepared through Doppler laser cooling to form ''Coulomb crystals'' in which the ions form a latticelike arrangement in the trapping potential. The trapped ions react with translationally cold beams of polar molecules produced by a quadrupole guide velocity selector or with room-temperature gas admitted into the vacuum chamber. Imaging of the Ca{sup +} ion fluorescence allows the progress of the reaction to be monitored. Product ions are sympathetically cooled into the crystal structure and are unambiguously identified through resonance-excitation mass spectrometry using just two trapped ions. Variations of the laser-cooling parameters are shown to result in different steady-state populations of the electronic states of {sup 40}Ca{sup +} involved in the laser-cooling cycle, and these are modeled by solving the optical Bloch equations for the eight-level system. Systematic variation of the steady-state populations over a series of reaction experiments allows the extraction of bimolecular rate constants for reactions of the ground state ({sup 2}S{sub 1/2}) and the combined excited states ({sup 2}D{sub 3/2} and {sup 2}P{sub 1/2}) of {sup 40}Ca{sup +}. These results are analyzed in the context of capture theories and ab initio electronic structure calculations of the reaction profiles. In each case, suppression of the ground state rate constant is explained by the presence of a submerged or real barrier on the ground state potential surface. Rate constants for the excited states are generally found to be in line with capture theories.

  8. Low-energy electron attachment and detachment in vibrationally excited oxygen

    NASA Astrophysics Data System (ADS)

    Aleksandrov, N. L.; Anokhin, E. M.

    2009-11-01

    Three-body electron attachment to O2 molecules and electron detachment from O_{2}^{-} ions have been theoretically studied in vibrationally excited oxygen and O2-containing mixtures. Assuming that electron attachment and detachment proceed via the formation of vibrationally excited temporary O_{2}^{-} ions, the rates of these processes were determined on the basis of the statistical approach for the vibrational transfer and relaxation in collisions between O_{2}^{-} ions and O2 molecules. The calculated attachment and detachment rate constants turned out to agree well with available measurements in unexcited oxygen. This method was extended to calculate attachment and detachment rates in vibrationally excited oxygen. It was shown that the effect of vibrational excitation on electron detachment is profound, whereas attachment of low-energy electrons to vibrationally excited O2 is inefficient. The calculated vibrational distribution of stable O_{2}^{-} ions turned out to be non-equilibrium in an excited gas and the effective vibrational temperature of the ions was much lower than the vibrational temperature of molecules. An analytical method was suggested to determine this distribution and the effective vibrational temperature. The calculated rate constants were used to simulate the formation and decay of an electron-beam-generated plasma in N2 : O2 mixtures at elevated vibrational temperatures. The calculations showed that vibrational excitation of molecules leads to orders of magnitude increase in the plasma density and in the plasma lifetime, in agreement with available observations.

  9. Low-Energy Excitation Spectra in the Excitonic Phase of Cobalt Oxides

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Tomoki; Sugimoto, Koudai; Ohta, Yukinori

    2017-04-01

    We study the excitonic phase and low-energy excitation spectra of perovskite cobalt oxides. Constructing the five-orbital Hubbard model defined on the three-dimensional cubic lattice for the 3d bands of Pr0.5Ca0.5CoO3, we calculate the excitonic susceptibility in the normal state in the random-phase approximation (RPA) to show the presence of the instability toward excitonic condensation. On the basis of the excitonic ground state with a magnetic multipole obtained in the mean-field approximation, we calculate the dynamical susceptibility of the excitonic phase in the RPA and find that there appear a gapless collective excitation in the spin-transverse mode (Goldstone mode) and a gapful collective excitation in the spin-longitudinal mode (Higgs mode). The experimental relevance of our results is discussed.

  10. Low-energy electronic excitations and band-gap renormalization in CuO

    NASA Astrophysics Data System (ADS)

    Rödl, Claudia; Ruotsalainen, Kari O.; Sottile, Francesco; Honkanen, Ari-Pekka; Ablett, James M.; Rueff, Jean-Pascal; Sirotti, Fausto; Verbeni, Roberto; Al-Zein, Ali; Reining, Lucia; Huotari, Simo

    2017-05-01

    Combining nonresonant inelastic x-ray scattering experiments with state-of-the-art ab initio many-body calculations, we investigate the electronic screening mechanisms in strongly correlated CuO in a large range of energy and momentum transfers. The excellent agreement between theory and experiment, including the low-energy charge excitations, allows us to use the calculated dynamical screening as a safe building block for many-body perturbation theory and to elucidate the crucial role played by d -d excitations in renormalizing the band gap of CuO. In this way we can dissect the contributions of different excitations to the electronic self-energy which is illuminating concerning both the general theory and this prototypical material.

  11. Effects of Coulomb quadrupole excitation in heavy-ion reactions

    NASA Astrophysics Data System (ADS)

    Cheoun, Myung-Ki; Choi, K. S.; Kim, K. S.; Kim, T. H.; So, W. Y.

    2016-09-01

    For 12C + 184W, 18O + 184W, and 20Ne + 208Pb systems, we investigate the suppression of the ratios P E = σ el/ σ RU by using the Coulomb quadrupole excitation (CQE) potentials. In order to explain the effect of the CQE potentials, we first use a well-known Love's CQE potential, and reproduce the experimental P E data well by using this potential. We also introduce a simple CQE potential written as W CQE( r) = - W P / r n , which is much simpler than the conventional Love's potential, to investigate the suppression of the P E ratios. Using this potential, we perform a χ2 analysis to find the adjustable parameter n, then, we find that the best fit parameters n ≈ 5 is close to the lowest order term, 1/ r 5. Consequently, we find that using the simple CQE potential explains the experimental P E data and that the ratio P E depends on the n values sensitively.

  12. Coulomb Excitation of Radioactive Mo-Ru Isotopes

    NASA Astrophysics Data System (ADS)

    Allmond, J. M.; Gretina-Chico2 Collaboration

    2016-09-01

    The study of shapes in atomic nuclei has been a major focus of nuclear structure ever since the observation of large electric quadrupole moments in the first half of the 20th century. A leading challenge has been to experimentally establish regions of oblate deformation, which are very limited, and triaxial deformation. The neutron-rich Mo-Ru region is expected to exhibit triaxial deformation in the low-lying states, mediated by a relatively rare instance of prolate-to-oblate shape evolution. A survey of equipment, techniques, and preliminary results from recent Coulomb-excitation and beta-decay experiments in the neutron-rich Mo-Ru region will be presented. These experiments were conducted at the CARIBU-ANL facility using GRETINA-CHICO2. An emphasis will be placed on unique opportunities with 3-MeV/u beams. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics.

  13. 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.

  14. Mechanisms for production of doubly excited states in low energies Iq+-He collisions

    NASA Astrophysics Data System (ADS)

    Harel, C.; Jouin, H.; Pons, B.

    1993-06-01

    We present a theoretical study of the mechanisms leading to the formation of doubly excited states of the series 3l3l' (or 4l') and 2lnl' in N7+, O8+ and C6+-He low energy collisions. The importance of both direct transitions from the entry channel (involving electron-electron interaction couplings) and transitions through a single electron capture channel has been analyzed for a range of impact velocities between 0.2 and 0.6 a.u.

  15. Lifetime and g-factor measurements of excited states using Coulomb excitation and alpha transfer reactions

    SciTech Connect

    Guevara, Z. E. Torres, D. A.

    2016-07-07

    In this contribution the challenges in the use of a setup to simultaneously measure lifetimes and g-factor values will be presented. The simultaneous use of the transient field technique and the Doppler Shift Attenuation Method, to measure magnetic moments and lifetimes respectively, allows to obtain a complete characterization of the currents of nucleons and the deformation in excited states close to the ground state. The technique is at the moment limited to Coulomb excitation and alpha-transfer reactions, what opens an interesting perspective to consider this type of experiments with radioactive beams. The use of deep-inelastic and fusion-evaporation reactions will be discussed. An example of a setup that makes use of a beam of {sup 106}Cd to study excited states of {sup 110}Sn and the beam nuclei itself will be presented.

  16. Lifetime and g-factor measurements of excited states using Coulomb excitation and alpha transfer reactions

    NASA Astrophysics Data System (ADS)

    Guevara, Z. E.; Torres, D. A.

    2016-07-01

    In this contribution the challenges in the use of a setup to simultaneously measure lifetimes and g-factor values will be presented. The simultaneous use of the transient field technique and the Doppler Shift Attenuation Method, to measure magnetic moments and lifetimes respectively, allows to obtain a complete characterization of the currents of nucleons and the deformation in excited states close to the ground state. The technique is at the moment limited to Coulomb excitation and alpha-transfer reactions, what opens an interesting perspective to consider this type of experiments with radioactive beams. The use of deep-inelastic and fusion-evaporation reactions will be discussed. An example of a setup that makes use of a beam of 106Cd to study excited states of 110Sn and the beam nuclei itself will be presented.

  17. Role of the low-energy excited states in the radiolysis of aromatic liquids.

    PubMed

    Baidak, Aliaksandr; Badali, Matthew; LaVerne, Jay A

    2011-07-07

    The contribution of the low-energy excited states to the overall product formation in the radiolysis of simple aromatic liquids--benzene, pyridine, toluene, and aniline--has been examined by comparison of product yields obtained in UV-photolysis and in γ-radiolysis. In photolysis, these electronic excited states were selectively populated using UV-light excitation sources with various energies. Yields of molecular hydrogen and of "dimers" (biphenyl, bibenzyl, dipyridyl for benzene, toluene, pyridine, respectively, and of ammonia and diphenylamine for aniline) have been determined, since they are the most abundant radiolytic products. Negligibly small production of molecular hydrogen in the UV-photolysis of aromatic liquids with excitation to energies of 4.88, 5.41, 5.79, and 6.70 eV and the lack of a scavenger effect suggest that this product originates from short-lived high-energy singlet states. A significant reduction in "dimer" radiation-chemical yields in the presence of scavengers such as anthracene or naphthalene indicates that the triplet excited states are important precursors to these products. The results for toluene and aniline suggest that efficient dissociation from the lowest-energy excited triplet state leads to noticeable "dimer" production. For benzene and pyridine, the lowest-energy triplet excited states are not likely to fragment into radicals because of the relatively large energy gap between the excited state level and corresponding bond dissociation energy. The "dimer" formation in the radiolysis of benzene and pyridine is likely to involve short-lived high-energy triplet states.

  18. Vibrational excitation of adsorbed molecules by low-energy photon-emitted electrons: A dynamical model

    NASA Astrophysics Data System (ADS)

    González Ureña, A.; Telle, H. H.; Tornero, J.

    2013-01-01

    A simple, inelastic electron-scattering dynamical model is presented to account for vibrational excitation in molecular adsorbates. The basic two ingredients of the theoretical model are: (i) the conservation of the total angular momentum, and (ii) the requirement of a critical time to allow for the intra-molecular energy re-arrangement of the transient negative-ion complex. The model is applied to the vibrational excitation dynamics of molecules chemisorbed at sub-monolayer conditions on ordered metal surfaces. This was exemplified for Acrylonitrile adsorbed on Cu(1 0 0), whose vibrational excitation was studied via energy loss spectra of low-energy two-photon photoemission (2PPE) electrons, and for ammonia (NH3 and ND3) adsorbed on Cu(1 0 0), being probed in a STM experiment. Fits of the model to the data allowed for deducing the energy threshold of the vibrational excitation of the Cdbnd C and Ctbnd N bonds of the ACN adsorbate molecules, and the threshold for the symmetric ν1-stretch mode excitation of adsorbed NH3/ND3. Also, information about the temporal dynamics underlying the inelastic electron scattering was gained.

  19. Coulomb suppression in the low-energy p-p elastic scattering via the Trojan Horse Method

    SciTech Connect

    Tumino, A.; Spitaleri, C.; Rapisarda, G. G.; Cherubini, S.; Crucilla, V.; Gulino, M.; La Cognata, M.; Lamia, L.; Pizzone, R. G.; Puglia, S. M. R.; Romano, S.; Sergi, M. L.; Mukhamedzhanov, A.; Campajola, L.; Elekes, Z.; Fueloep, Zs.; Gyuerky, G.; Kiss, G. G.; Somorjai, E.; Gialanella, L.

    2010-11-24

    We present here an important test of the main feature of the Trojan Horse Method (THM), namely the suppression of Coulomb effects in the entrance channel due to off-energy-shell effects. This is done by measuring the THM p-p elastic scattering via the p+d{yields}p+p+n reaction at 4.7 and 5 MeV, corresponding to a p-p relative energy ranging from 80 to 670 keV. In contrast to the on-energy-shell (OES) case, the extracted p-p cross section does not exhibit the Coulomb-nuclear interference minimum due to the suppression of the Coulomb amplitude. This is confirmed by the half-off-energy shell (HOES) calculations and strengthened by the agreement with the calculated OES nuclear cross sections.

  20. Excitation probability and effective temperature in the stationary regime of conductivity for Coulomb Glasses

    NASA Astrophysics Data System (ADS)

    Caravaca Garratón, Manuel; Fernández-Martínez, Manuel

    2017-07-01

    In this paper, we shall illustrate the numerical calculation of the effective temperature in Coulomb glasses by excitation probability provided that the system has been placed in a stationary state after applying a strong electric field. The excitation probability becomes a better alternative than the occupation probability, which has been classically employed to calculate the effective temperature and characterize the thermodynamics of Coulomb glasses out of equilibrium. This is due to the fact that the excitation probability shows better statistics than the occupation probability. In addition, our simulations show that the excitation probability does not depend on the choice of the chemical potential, which critically affects the occupation probability. Our results allow us to propose the excitation probability as a standard procedure to determine the effective temperature in Coulomb glasses as well as in other complex systems such as spin glasses.

  1. Coulomb Excitation of 78,80Se and the radioactive 84Se (N = 50) isotopes

    NASA Astrophysics Data System (ADS)

    Galindo-Uribarri, A.; Padilla-Rodal, E.; Garcia-Ruiz, R. F.; Allmond, J. M.; Batchelder, J. C.; Beene, J. R.; Lagergren, K. B.; Mueller, P. E.; Radford, D. C.; Stracener, D. W.; Urrego-Blanco, J. P.; Varner, R. L.; Yu, C.-H.

    2011-10-01

    Coulomb excitation is a purely electromagnetic excitation process of nuclear states due to the Coulomb field of two colliding nuclei. It is a very precise tool to measure excitation probabilities and provide insight on the collectivity of nuclear excitations and in particular on nuclear shapes. We have measured the B(E2) value of various nuclei in the mass A ~ 80 region using particle-gamma coincidences with the HyBall and Clarion arrays at HRIBF. The Coulomb excitation of various projectile-target combinations (ASe on 12C, 24Mg, 27Al and 50Ti) allow the use of consistency cross checks and the systematic study of isotopic and isotonic chains using both stable and radioactive nuclei under almost identical experimental conditions.We present new results for 78Se, 80Se and the radioactive nucleus 84Se (N = 50). Research sponsored by the Office of Nuclear Physics, U.S. Department of Energy and CONACyT Grant 103366.

  2. Statistics of low energy excitations for the directed polymer in a random medium.

    PubMed

    Monthus, Cécile; Garel, Thomas

    2006-05-01

    We consider a directed polymer of length L in a random medium of space dimension d = 1,2,3. The statistics of low energy excitations as a function of their size l is numerically evaluated. These excitations can be divided into bulk and boundary excitations, with respective densities rho(bulk)(L) (E = 0,l) and rho(boundary)(L)(E=0,l). We find that both densities follow the scaling behavior rho(bulk, boundary)(L)(E = 0,l)=L(-1-theta)(d)R(bulk,boundary)(x = l/L), where theta(d) is the exponent governing the energy fluctuations at zero temperature (with the well-known exact value theta(1)= 1/3 in one dimension). In the limit x = l/L --> 0, both scaling functions R(bulk)(x) and R(boundary)(x) behave as R(bulk,boundary)(x) approximately x(-1-theta)(d), leading to the droplet power law rho(bulk, boundary)(L) (E = 0,l) approximately l(-1-theta)(d) in the regime 1 < l < L. Beyond their common singularity near x --> 0, the two scaling functions R(bulk,boundary)(x) are very different: whereas R(bulk)(x) decays monotonically for 0 < x < 1, the function R(boundary)(x) first decays for 0 < x < x(min), then grows for x(min) < x < 1, and finally presents a power law singularity R(boundary)(x) approximately (1-x)(-sigma)(d) near x -->1. The density of excitations of length l = L accordingly decays as rho(boundary)(L)(E = 0,l = L) approximately L(-lambda)(d) where gamma(d) = 1+ theta(d) - lambda(d). We obtain lambda(1) approximately 10.67, lambda(2) = 0.53, and lambda(3) approximately 0.39, suggesting the possible relation lambda(d) = 2theta(d).

  3. Origin of low-energy excitations in charge-ordered manganites

    NASA Astrophysics Data System (ADS)

    Zhukova, E.; Gorshunov, B.; Zhang, T.; Wu, D.; Prokhorov, A. S.; Torgashev, V. I.; Maksimov, E. G.; Dressel, M.

    2010-04-01

    The low-energy excitations in the charge-ordered phase of polycrystalline La0.25Ca0.75MnO3 are explored by frequency-domain terahertz spectroscopy. In the frequency range from 4 cm-1 to 700 cm-1 (energies from 0.4 meV to 90 meV) and at temperatures down to 5 K, we do not detect any feature that can be associated with the collective response of the spatially modulated charge continuum. In the antiferromagnetically ordered phase, broad absorption bands appear in the conductivity and permittivity spectra around 30 cm-1 and 100 cm-1 which are assigned to former acoustic phonons optically activated due to a fourfold superstructure in the crystal lattice. Our results indicate that characteristic energies of collective excitations of the charge-ordered phase in La0.25Ca0.75MnO3, if any, lie below 1 meV. At our lowest frequencies of only few wave numbers a strong relaxation is observed above 100 K connected to the formation of the charge-ordered state.

  4. Challenging the nature of low-energy plasmon excitations in CaC6 using electron energy-loss spectroscopy

    NASA Astrophysics Data System (ADS)

    Roth, Friedrich; König, Andreas; Kramberger, Christian; Pichler, Thomas; Büchner, Bernd; Knupfer, Martin

    2013-04-01

    The nature of low-energy plasmon excitations plays an important role in understanding the low-energy electronic properties and coupling mechanism of different superconducting compounds such as CaC6. Recent ab initio studies predict a charge carrier intraband plasmon in keeping with a low-energy acoustic plasmon. Here, we have studied the low-energy electronic excitations of CaC6 using high-resolution electron energy-loss spectroscopy in transmission at low temperatures. The analysis of the core level excitations leads to the conclusion that hybridization between graphite and calcium states plays an essential role in this graphite-intercalated compound. Regarding the low-energy plasmon excitation, we observe the formation of an intraband (charge carrier) plasmon with a negative dispersion at about 3.5 eV in sound agreement with the theory. Finally, a weak excitation around 1.2 eV with an almost linear dispersion relation can be observed as predicted for an acoustic plasmon that may mediate the superconducting coupling in CaC6. However its optical limit at ~1 eV challenges the theoretical predictions and safely rules out an electronic superconducting coupling mechanism in CaC6

  5. Low-energy electron scattering by N2 molecules physisorbed on Ag: Study of the resonant vibrational excitation process

    NASA Astrophysics Data System (ADS)

    Djamo, V.; Teillet-Billy, D.; Gauyacq, J. P.

    1995-02-01

    Molecules adsorbed on a metal surface can be excited by low-energy electron impact. Resonant processes in which an intermediate negative ion is formed during the collision are very efficient. The resonant vibrational excitation of N2 molecules physisorbed on Ag by low-energy electrons is studied theoretically with the coupled-angular-mode method. The influence of the neighboring surface on the excitation process (including the excitation of overtones) is analyzed. The results are compared with the experimental results of Demuth, Schmeisser, and Avouris. It is found that in a scattering experiment, most of the vibrational excitation concerns electrons that are inelastically scattered into the metal and are thus not observed experimentally.

  6. Low-energy excitations of two-dimensional diluted Heisenberg quantum antiferromagnets

    NASA Astrophysics Data System (ADS)

    Wang, Ling; Sandvik, Anders W.

    2010-02-01

    We study the low-energy dynamics of S=1/2 antiferromagnetic Heisenberg clusters constructed by diluting a square lattice at vacancy concentration p at and below the percolation threshold p∗≈0.407 . The finite-size scaling behavior of the average excitation gap, ⟨Δ⟩˜L-z , where L is the cluster length, is obtained using quantum Monte Carlo results for an upper bound Δ∗ to Δ , derived from sum rules. At the percolation threshold, we obtain a dynamic exponent z=3.6±0.1≈2Df for clusters with singlet (S=0) ground state. Here Df=91/48 is the fractal dimensionality of the percolating cluster. We argue that this large dynamic exponent—roughly twice that expected for quantum-rotor excitations—is a consequence of weakly interacting localized effective magnetic moments, which form due to local sublattice imbalance. This picture is supported by an extremal-value analysis of local spectral gaps, which delivers an exponent relation (between z and two exponents characterizing the local-gap distribution) reproduced by our simulation data. However, the average ⟨Δ∗⟩ over all clusters, which have mostly ground-state spin S>0 , scales with a smaller exponent than for the S=0 clusters alone; z≈1.5Df . Lanczos exact diagonalization for small clusters show that typically, S→S-1 in the lowest-energy excitations while the dominant spectral weight originates from S→S+1 excitations. Thus, the scaling of ⟨Δ∗⟩ for clusters with ground state S>0 does not reflect the lowest-energy excitations but the higher S→S+1 excitations. This result can be understood within a valence bond picture. To further explore the scenario of localized moments, we introduce a classical dimer-monomer aggregation model to study the distribution of nearest-neighbor sites forming dimers (which are the objects used in mapping to the quantum-rotor model) and unpaired spins (monomers). The monomers are localized and, thus, effective magnetic moments should form in the spin system

  7. Z=50 Shell Gap near Sn100 from Intermediate-Energy Coulomb Excitations in Even-Mass Sn106-112 Isotopes

    NASA Astrophysics Data System (ADS)

    Vaman, C.; Andreoiu, C.; Bazin, D.; Becerril, A.; Brown, B. A.; Campbell, C. M.; Chester, A.; Cook, J. M.; Dinca, D. C.; Gade, A.; Galaviz, D.; Glasmacher, T.; Hjorth-Jensen, M.; Horoi, M.; Miller, D.; Moeller, V.; Mueller, W. F.; Schiller, A.; Starosta, K.; Stolz, A.; Terry, J. R.; Volya, A.; Zelevinsky, V.; Zwahlen, H.

    2007-10-01

    Rare isotope beams of neutron-deficient Sn106,108,110 from the fragmentation of Xe124 were employed in an intermediate-energy Coulomb excitation experiment. The measured B(E2,01+→21+) values for Sn108 and Sn110 and the results obtained for the Sn106 show that the transition strengths for these nuclei are larger than predicted by current state-of-the-art shell-model calculations. This discrepancy might be explained by contributions of the protons from within the Z=50 shell to the structure of low-energy excited states in this region.

  8. Optimum forward scattering zone for intermediate-energy Coulomb excitation experiments

    NASA Astrophysics Data System (ADS)

    Kumar, Rajiv; Singh, Pardeep; Kharab, Rajesh

    2015-08-01

    Here we present a comparative study of various schemes commonly used for the determination of the safe minimum value of the impact parameter, which decides the maximum value of forward laboratory scattering angle, in intermediate-energy Coulomb excitation experiments. We have found that these are special cases of the recently proposed parameterization scheme in Kumar Rajiv et al., Phys. Rev. C, 81 (2010) 037602. The scheme may be used to demarcate the absorption-free as well as no-flux loss zone for intermediate-energy Coulomb excitation experiments.

  9. Challenges facing an understanding of the nature of low-energy excited states in photosynthesis.

    PubMed

    Reimers, Jeffrey R; Biczysko, Malgorzata; Bruce, Douglas; Coker, David F; Frankcombe, Terry J; Hashimoto, Hideki; Hauer, Jürgen; Jankowiak, Ryszard; Kramer, Tobias; Linnanto, Juha; Mamedov, Fikret; Müh, Frank; Rätsep, Margus; Renger, Thomas; Styring, Stenbjörn; Wan, Jian; Wang, Zhuan; Wang-Otomo, Zheng-Yu; Weng, Yu-Xiang; Yang, Chunhong; Zhang, Jian-Ping; Freiberg, Arvi; Krausz, Elmars

    2016-09-01

    While the majority of the photochemical states and pathways related to the biological capture of solar energy are now well understood and provide paradigms for artificial device design, additional low-energy states have been discovered in many systems with obscure origins and significance. However, as low-energy states are naively expected to be critical to function, these observations pose important challenges. A review of known properties of low energy states covering eight photochemical systems, and options for their interpretation, are presented. A concerted experimental and theoretical research strategy is suggested and outlined, this being aimed at providing a fully comprehensive understanding. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Low-energy d-d excitations in MnO studied by resonant x-ray fluorescence spectroscopy

    SciTech Connect

    Butorin, S.M.; Guo, J.; Magnuson, M.

    1997-04-01

    Resonant soft X-ray emission spectroscopy has been demonstrated to possess interesting abilities for studies of electronic structure in various systems, such as symmetry probing, alignment and polarization dependence, sensitivity to channel interference, etc. In the present abstract the authors focus on the feasibility of resonant soft X-ray emission to probe low energy excitations by means of resonant electronic X-ray Raman scattering. Resonant X-ray emission can be regarded as an inelastic scattering process where a system in the ground state is transferred to a low excited state via a virtual core excitation. The energy closeness to a core excitation of the exciting radiation enhances the (generally) low probability for inelastic scattering at these wavelengths. Therefore soft X-ray emission spectroscopy (in resonant electronic Raman mode) can be used to study low energy d-d excitations in transition metal systems. The involvement of the intermediate core state allows one to use the selection rules of X-ray emission, and the appearance of the elastically scattered line in the spectra provides the reference to the ground state.

  11. The low-energy, charge-transfer excited states of 4-amino-4-prime-nitrodiphenyl sulfide

    NASA Technical Reports Server (NTRS)

    O'Connor, Donald B.; Scott, Gary W.; Tran, Kim; Coulter, Daniel R.; Miskowski, Vincent M.; Stiegman, Albert E.; Wnek, Gary E.

    1992-01-01

    Absorption and emission spectra of 4-amino-4-prime-nitrodiphenyl sulfide in polar and nonpolar solvents were used to characterize and assign the low-energy excited states of the molecule. Fluorescence-excitation anisotropy spectra and fluorescence quantum yields were also used to characterize the photophysics of these states. The lowest-energy fluorescent singlet state was determined to be an intramolecular charge transfer (ICT) state involving transfer of a full electron charge from the amino to the nitro group yielding a dipole moment of about 50 D. A low-energy, intense absorption band is assigned as a transition to a different ICT state involving a partial electron charge transfer from sulfur to the nitro group.

  12. Multiple low-energy excitation states in FeNi disks observed by broadband ferromagnetic resonance measurement

    NASA Astrophysics Data System (ADS)

    Huo, Y.; Zhou, C.; Sun, L.; Chui, S. T.; Wu, Y. Z.

    2016-11-01

    Magnetization excitation in micron sized FeNi disks with different diameters is studied by broadband ferromagnetic resonance (FMR) measurement. Except the main FMR peak, additional adsorption peaks with lower energies are observed. Both micromagnetic simulation and quantum spin wave calculation confirm that the low-energy excitation states are attributed to backward volume magnetostatic (BVM) spin waves. The size dependence of the low-energy states is systematically studied in 50-nm-thick Py disks with diameters larger than 500 nm, and the linewidth of the first BVM state is found to be obviously smaller than that of the FMR absorption peak. Through a quantitative comparison with experimental results, the quantum spin wave calculation is proven to be a reliable method to get the susceptibility and is much faster than the classical micromagnetic simulations.

  13. Interatomic Coulombic Decay of HeNe dimers after ionization and excitation of He and Ne

    NASA Astrophysics Data System (ADS)

    Sann, H.; Havermeier, T.; Kim, H.-K.; Sturm, F.; Trinter, F.; Waitz, M.; Zeller, S.; Ulrich, B.; Meckel, M.; Voss, S.; Bauer, T.; Schneider, D.; Schmidt-Böcking, H.; Wallauer, R.; Schöffler, M.; Williams, J. B.; Dörner, R.; Jahnke, T.

    2017-01-01

    We study the decay of a helium/neon dimer after ionization and simultaneous excitation of either the neon or the helium atom using Cold Target Recoil Ion Momentum Spectroscopy (COLTRIMS). We find that, depending on the decaying state, either direct Interatomic Coulombic Decay (ICD) (i.e. mediated by a virtual photon exchange), exchange ICD (mediated by electron exchange) or radiative charge transfer occurs. The corresponding channels are identified.

  14. 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

  15. Two-photon excitation into low-energy singlet states of anthracene in mixed crystals

    NASA Astrophysics Data System (ADS)

    Bree, A.; Leyderman, A.; Taliani, C.

    1985-08-01

    The two-photon excitation spectrum of the first excited state of anthracene in fluorene and biphenyl at 4.2 K has been measured. Intensity is induced into the origin by the static dipole moment of fluorene, and into b 1u vibrons through coupling to an A g state near 29400 cm -1; the nature of this A g state is discussed.

  16. Dynamical coupling of pygmy and giant resonances in relativistic Coulomb excitation

    DOE PAGES

    Brady, N. S.; Aumann, T.; Bertulani, C. A.; ...

    2016-04-20

    We study the Coulomb excitation of pygmy dipole resonances (PDR) in heavy ion reactions at 100 MeV/nucleon and above. The reactions Ni-68 + Au-197 and Ni-68 + Pb-208 are taken as practical examples. Our goal is to address the question of the influence of giant resonances on the PDR as the dynamics of the collision evolves. We show that the coupling to the giant resonances affects considerably the excitation probabilities of the PDR, a result that indicates the need of an improved theoretical treatment of the reaction dynamics at these bombarding energies. (C) 2016 The Authors. Published by Elsevier B.V.

  17. Coulomb excitation of highly charged projectile ions in relativistic collisions with diatomic molecules

    SciTech Connect

    Artemyev, A. N.; McConnell, S. R.; Surzhykov, A.; Najjari, B.; Voitkiv, A. B.

    2011-10-15

    We investigate the Coulomb excitation of highly charged ions colliding with diatomic molecules. In this process, the coherent interaction between the projectile electron and two molecular centers may cause clear interference patterns in the (collision) energy dependencies of the total cross sections and alignment parameters. We discuss such a Young-type interference for the particular case of the K{yields}L excitation of hydrogen- and helium-like projectile ions. Calculations, performed for the scattering of these ions on nitrogen molecules, indicate that the interference effects are extremely sensitive to the collisional geometry and are pronounced only if the molecular axis is aligned almost parallel to the incident beam trajectory.

  18. Odd-even effect dependence on the excitation energy in low energy fission

    NASA Astrophysics Data System (ADS)

    Mirea, M.

    2017-09-01

    An inversion of the odd-even effect was observed experimentally in cold fission: the odd-odd fragmentation yields are favored over the even-even ones for excitations energies of the fragments smaller than 4 MeV. This effect is linked to the important problem of quasiparticle excitations during the dynamical evolution of the nuclear system from its ground-state configuration up to scission. An explanation based on the Landau-Zener promotion mechanism generalized for superfluid systems is offered for the inversion of the odd-even effect. In principle, the even-even fission products cannot be produced at very low excitation energies due dynamical quasiparticle excitations produced in the avoided- level-crossing regions. These excitations are produced with a large probability when the nuclear system deforms slowly.

  19. Excitation function measurements and integral yields estimation for natZnp,x reactions at low energies.

    PubMed

    Al-Saleh, F S; Al Mugren, K S; Azzam, A

    2007-10-01

    Excitation functions have been measured for a number of proton-induced nuclear reactions on natural zinc in the energy range from 27.5 MeV down to their threshold energy, using the activation method on stacked foils. Excitation functions and thick target yield for the reactions leading to the formation of (67)Ga,(66)Ga,(68)Ga,(62)Zn and (65)Zn are presented and compared with earlier reported experimental data. The experimental cross-sections and the production yields are tabulated; the excitation functions and the thick target yield curves are plotted in graphs.

  20. Intermediate-energy Coulomb excitation of 104Sn: Moderate E 2 strength decrease approaching 100Sn

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    The reduced transition probability B (E 2 )↑ of the first excited 2+ state in the nucleus 104Sn was measured via Coulomb excitation in inverse kinematics at intermediate energies. A value of 0.173(28) e2b 2 was extracted from the absolute cross section on a Pb target. Feeding contributions in 104Sn from higher lying states were estimated by a reference measurement of the stable 112Sn. Corresponding only to a moderate decrease of excitation strength relative to the almost constant values observed in the proton-rich, even-A Sn-114106 isotopes, present state-of-the-art shell-model predictions, which include proton and neutron excitations across the N =Z =50 shell closures as well as standard polarization charges, underestimate the experimental findings.

  1. Excitation functions of {sup 6,7}Li+{sup 7}Li reactions at low energies

    SciTech Connect

    Prepolec, L.; Soic, N.; Blagus, S.; Miljanic, D.; Siketic, Z.; Skukan, N.; Uroic, M.; Milin, M.

    2009-08-26

    Differential cross sections of {sup 6,7}Li+{sup 7}Li nuclear reactions have been measured at forward angles (10 deg. and 20 deg.), using particle identification detector telescopes, over the energy range 2.75-10.00 MeV. Excitation functions have been obtained for low-lying residual-nucleus states. The well pronounced peak in the excitation function of {sup 7}Li({sup 7}Li,{sup 4}He){sup 10}Be(3.37 MeV,2{sup +}) at beam energy about 8 MeV, first observed by Wyborny and Carlson in 1971 at 0 deg., has been observed at 10 deg., but is less evident at 20 deg. The cross section obtained for the {sup 7}Li({sup 7}Li,{sup 4}He){sup 10}Be(g.s,0{sup +}) reaction is about ten times smaller. The well pronounced peak in the excitation function of {sup 7}Li({sup 7}Li,{sup 4}He){sup 10}Be(3.37 MeV,2{sup +}) reaction could correspond to excited states in {sup 14}C, at excitation energies around 30 MeV.

  2. B(E1) Strengths from Coulomb excitation of 11Be

    SciTech Connect

    Summers, N C; Pain, S D; Orr, N A; Catford, W N; Angelique, J C; Ashwood, N I; Bouchat, V; Clarke, N M; Curtis, N; Freer, M; Fulton, B R; Hanappe, F; Labiche, M; Loucey, J L; Lemmon, R C; Mahboub, D; Ninane, A; Normand, G; Nunes, F M; Soic, N; Stuttge, L; Timis, C N; Thompson, I; Winfield, J S; Ziman, V

    2007-03-06

    The B(E1;1/2{sup +}{yields} 1/2{sup -}) strength for {sup 11}Be has been extracted from intermediate energy Coulomb excitation measurements, over a range of beam energies using a new reaction model, the extended continuum discretized coupled channels (XCDCC) method. In addition, a measurement of the excitation cross section for {sup 11}Be+{sup 208}Pb at 38.6 MeV/nucleon is reported. The B(E1) strength of 0.105(12) e{sup 2}fm{sup 2} derived from this measurement is consistent with those made previously at 60 and 64 MeV/nucleon, in contrast to an anomalously low result obtained at 43 MeV/nucleon. By coupling a multi-configuration description of the projectile structure with realistic reaction theory, the XCDCC model provides for the first time a fully quantum mechanical description of Coulomb excitation. The XCDCC calculations reveal that the excitation process involves significant contributions from nuclear, continuum, and higher-order effects. An analysis of the present and two earlier intermediate energy measurements yields a combined B(E1) strength of 0.105(7) e{sup 2}fm{sup 2}. This value is in good agreement with the value deduced independently from the lifetime of the 1/2{sup -} state in {sup 11}Be, and has a comparable precision.

  3. Coulomb excitation of ground band rotational states in /sup 249/Bk

    SciTech Connect

    Bemis, C.E. Jr.; McGowan, F.K.; Ford, J.L.C. Jr.; Milner, W.T.; Robinson, R.L.; Stelson, P.H.

    1982-03-01

    Coulomb-excitation probabilities for the first few members of the 7/2/sup +/(633up-arrow) ground-state rotational band in /sup 249/Bk have been determined with 17.06-MeV /sup 4/He ions. These previously know excited states include the 9/2/sup +/ (41.8-keV), 11/2/sup +/ (93.7-keV), and 13/2/sup +/ (155.8-keV) members of the 7/2/sup +/(633up-arrow) band. Within experimental uncertainties, the Coulomb-excitation probabilities for these rotational states are reproduced by calculated values when only E2 excitations are considered with an intrinsic quadrupole moment, Q/sub 20/, of 12.70 +- 0.24 eb in the rigid rotor limit. The deduced ground-state spectroscopic quadrupole moment is 5.93 +- 0.11 eb. Intraband M1 transition rates have been deduced by combining the Q/sub 20/ result with other experimental data. Within the rotational model, a ground-state magnetic moment of +3.45 +- 0.10 ..mu../sub N/ is indicated.

  4. Low-energy electron elastic scattering cross sections for excited Au and Pt atoms

    NASA Astrophysics Data System (ADS)

    Felfli, Zineb; Eure, Amanda R.; Msezane, Alfred Z.; Sokolovski, Dmitri

    2010-05-01

    Electron elastic total cross sections (TCSs) and differential cross sections (DCSs) in both impact energy and scattering angle for the excited Au and Pt atoms are calculated in the electron impact energy range 0 ⩽ E ⩽ 4.0 eV. The cross sections are found to be characterized by very sharp long-lived resonances whose positions are identified with the binding energies of the excited anions formed during the collisions. The recent novel Regge-pole methodology wherein is embedded through the Mulholland formula the electron-electron correlations is used together with a Thomas-Fermi type potential incorporating the crucial core-polarization interaction for the calculations of the TCSs. The DCSs are evaluated using a partial wave expansion. The Ramsauer-Townsend minima, the shape resonances and the binding energies of the excited Au - and Pt - anions are extracted from the cross sections, while the critical minima are determined from the DCSs.

  5. Calculated low-energy electron-impact vibrational excitation cross sections for CO2 molecule

    NASA Astrophysics Data System (ADS)

    Laporta, V.; Tennyson, J.; Celiberto, R.

    2016-12-01

    Vibrational-excitation cross sections of ground electronic states of a carbon dioxide molecule by electron-impact through CO2-≤ft({{}2}{{\\Pi}u}\\right) shape resonance is considered in the separation of the normal modes approximation. Resonance curves and widths are computed for each vibrational mode. The calculations assume a decoupling between normal modes and employ the local complex potential model for the treatment of nuclear dynamics, usually adopted for electron-scattering involving diatomic molecules. Results are presented for excitation up to 10 vibrational levels in each mode and a comparison with data present in the literature is discussed.

  6. Electron Attachment in Low-Energy Electron Elastic Collisions with Au and Pt Atoms: Identification of Excited Anions

    NASA Astrophysics Data System (ADS)

    Msezane, A. Z.; Eure, A.; Felfli, Z.; Sokolovski, D.

    2009-11-01

    The recent Regge-pole methodology has been benchmarked [1] on the accurately measured binding energies of the excited Ge= and Sn= anions [2] through the binding energies (BEs) extracted from the Regge-pole calculated elastic total cross sections (TCSs). Here the methodology is applied together with a Thomas-Fermi type potential that incorporates the vital core polarization interaction to investigate the possibility of forming excited Au= and Pt= anions in low-energy electron elastic collisions with Au and Pt atoms. From the positions of the characteristic extremely narrow resonances in the total cross sections, we extract the binding energies of the excited Au= and Pt= anions formed as Regge resonances during the collisions. The angular life of the complexes thus formed is used to differentiate the stable excited bound states of the anions from the shape resonances [3]. The BEs for the excited Au= and Pt= anions are found to be 0.475eVand 0.543eV, respectively, challenging both theory and experiment to verify. [1] A. Msezane et al, Phys. Rev. A, Submitted (2009) [2] M. Scheer et al, Phys. Rev. A 58, 2844 (1998) [3] Z. Felfli et al, Phys. Rev. A 79, 012714 (2009)

  7. Z=50 Shell Gap near {sup 100}Sn from Intermediate-Energy Coulomb Excitations in Even-Mass {sup 106-112}Sn Isotopes

    SciTech Connect

    Vaman, C.; Bazin, D.; Galaviz, D.; Mueller, W. F.; Schiller, A.; Stolz, A.; Andreoiu, C.; Becerril, A.; Brown, B. A.; Campbell, C. M.; Chester, A.; Cook, J. M.; Dinca, D. C.; Gade, A.; Glasmacher, T.; Miller, D.; Moeller, V.; Starosta, K.; Terry, J. R.; Zelevinsky, V.

    2007-10-19

    Rare isotope beams of neutron-deficient {sup 106,108,110}Sn from the fragmentation of {sup 124}Xe were employed in an intermediate-energy Coulomb excitation experiment. The measured B(E2,0{sub 1}{sup +}{yields}2{sub 1}{sup +}) values for {sup 108}Sn and {sup 110}Sn and the results obtained for the {sup 106}Sn show that the transition strengths for these nuclei are larger than predicted by current state-of-the-art shell-model calculations. This discrepancy might be explained by contributions of the protons from within the Z=50 shell to the structure of low-energy excited states in this region.

  8. Coulomb Excitation of Neutron-Rich Zn Isotopes: First Observation of the 21+ State in Zn80

    NASA Astrophysics Data System (ADS)

    van de Walle, J.; Aksouh, F.; Ames, 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.; Nilsson, T.; Pantea, M.; Perru, O.; 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.; van Duppen, P.; Verney, D.; Voulot, D.; Warr, N.; Weisshaar, D.; Wenander, F.; Wolf, B. H.; Zielińska, M.

    2007-10-01

    Neutron-rich, radioactive Zn isotopes were investigated at the Radioactive Ion Beam facility REX-ISOLDE (CERN) using low-energy Coulomb excitation. The energy of the 21+ state in Zn78 could be firmly established and for the first time the 2+→01+ transition in Zn80 was observed at 1492(1) keV. B(E2,21+→01+) values were extracted for Zn74,76,78,80 and compared to large scale shell model calculations. With only two protons outside the Z=28 proton core, Zn80 is the lightest N=50 isotone for which spectroscopic information has been obtained to date. Two sets of advanced shell model calculations reproduce the observed B(E2) systematics. The results for N=50 isotones indicate a good N=50 shell closure and a strong Z=28 proton core polarization. The new results serve as benchmarks to establish theoretical models, predicting the nuclear properties of the doubly magic nucleus Ni78.

  9. Quadrupole Collectivity beyond N=28: Intermediate-Energy Coulomb Excitation of Ar47,48

    NASA Astrophysics Data System (ADS)

    Winkler, R.; Gade, A.; Baugher, T.; Bazin, D.; Brown, B. A.; Glasmacher, T.; Grinyer, G. F.; Meharchand, R.; McDaniel, S.; Ratkiewicz, A.; Weisshaar, D.

    2012-05-01

    We report on the first experimental study of quadrupole collectivity in the very neutron-rich nuclei Ar47,48 using intermediate-energy Coulomb excitation. These nuclei are located along the path from doubly magic Ca to collective S and Si isotopes, a critical region of shell evolution and structural change. The deduced B(E2) transition strengths are confronted with large-scale shell-model calculations in the sdpf shell using the state-of-the-art SDPF-Uand EPQQM effective interactions. The comparison between experiment and theory indicates that a shell-model description of Ar isotopes around N=28 remains a challenge.

  10. Quadrupole collectivity beyond N = 28: intermediate-energy Coulomb excitation of (47,48)Ar.

    PubMed

    Winkler, R; Gade, A; Baugher, T; Bazin, D; Brown, B A; Glasmacher, T; Grinyer, G F; Meharchand, R; McDaniel, S; Ratkiewicz, A; Weisshaar, D

    2012-05-04

    We report on the first experimental study of quadrupole collectivity in the very neutron-rich nuclei (47,48)Ar using intermediate-energy Coulomb excitation. These nuclei are located along the path from doubly magic Ca to collective S and Si isotopes, a critical region of shell evolution and structural change. The deduced B(E2) transition strengths are confronted with large-scale shell-model calculations in the sdpf shell using the state-of-the-art SDPF-Uand EPQQM effective interactions. The comparison between experiment and theory indicates that a shell-model description of Ar isotopes around N=28 remains a challenge.

  11. Absolute cross sections for electronic excitations of cytosine by low energy electron impact

    PubMed Central

    Bazin, M.; Michaud, M.; Sanche, L.

    2013-01-01

    The absolute cross sections (CS) for electronic excitations of cytosine by electron impact between 5 and 18 eV were measured by electron-energy loss (EEL) spectroscopy of the molecule deposited at low coverage on an inert Ar substrate. The lowest EEL features found at 3.55 and 4.02 eV are ascribed to transitions from the ground state to the two lowest triplet 1 3A′(π→π*) and 2 3A′(π→π*) valence states of the molecule. Their energy dependent CS exhibit essentially a common maximum at about 6 eV with a value of 1.84 × 10−17 cm2 for the former and 4.94 × 10−17 cm2 for the latter. In contrast, the CS for the next EEL feature at 4.65 eV, which is ascribed to the optically allowed transition to the 2 1A′(π→π*) valence state, shows only a steep rise to about 1.04 × 10−16 cm2 followed by a monotonous decrease with the incident electron energy. The higher EEL features at 5.39, 6.18, 6.83, and 7.55 eV are assigned to the excitations of the 3 3, 1A′(π→π*), 4 1A′(π→π*), 5 1A′(π→π*), and 6 1A′(π→π*) valence states, respectively. The CS for the 3 3, 1A′ and 4 1A′ states exhibit a common enhancement at about 10 eV superimposed on a more or less a steep rise, reaching respectively a maximum of 1.27 and 1.79 × 10−16 cm2, followed by a monotonous decrease. This latter enhancement and the maximum seen at about 6 eV in the lowest triplet states correspond to the core-excited electron resonances that have been found by dissociative electron attachment experiments with cytosine in the gas phase. The weak EEL feature found at 5.01 eV with a maximum CS of 3.8 × 10−18 cm2 near its excitation threshold is attributed to transitions from the ground state to the 1 3, 1A″(n→π*) states. The monotonous rise of the EEL signal above 8 eV is attributed to the ionization of the molecule. It is partitioned into four excitation energy regions at about 8.55, 9.21, 9.83, and 11.53 eV, which correspond closely to the ionization energies of

  12. Nonlinear saturation of wave packets excited by low-energy electron horseshoe distributions.

    PubMed

    Krafft, C; Volokitin, A

    2013-05-01

    Horseshoe distributions are shell-like particle distributions that can arise in space and laboratory plasmas when particle beams propagate into increasing magnetic fields. The present paper studies the stability and the dynamics of wave packets interacting resonantly with electrons presenting low-energy horseshoe or shell-type velocity distributions in a magnetized plasma. The linear instability growth rates are determined as a function of the ratio of the plasma to the cyclotron frequencies, of the velocity and the opening angle of the horseshoe, and of the relative thickness of the shell. The nonlinear stage of the instability is investigated numerically using a symplectic code based on a three-dimensional Hamiltonian model. Simulation results show that the dynamics of the system is mainly governed by wave-particle interactions at Landau and normal cyclotron resonances and that the high-order normal cyclotron resonances play an essential role. Specific features of the dynamics of particles interacting simultaneously with two or more waves at resonances of different natures and orders are discussed, showing that such complex processes determine the main characteristics of the wave spectrum's evolution. Simulations with wave packets presenting quasicontinuous spectra provide a full picture of the relaxation of the horseshoe distribution, revealing two main phases of the evolution: an initial stage of wave energy growth, characterized by a fast filling of the shell, and a second phase of slow damping of the wave energy, accompanied by final adjustments of the electron distribution. The influence of the density inhomogeneity along the horseshoe on the wave-particle dynamics is also discussed.

  13. Theorectical Studies of Excitation in Low-Energy Electron-Polyatomic Molecule Collisions

    SciTech Connect

    Rescigno, T N; McCurdy, C W; Isaacs, W A; Orel, A E; Meyer, H D

    2001-08-13

    This paper focuses on the channeling of energy from electronic to nuclear degrees of freedom in electron-polyatomic molecule collisions. We examine the feasibility of attacking the full scattering problem, both the fixed-nuclei electronic problem and the post-collision nuclear dynamics, entirely from first principles. The electron-CO{sub 2} system is presented as an example. We study resonant vibrational excitation, showing how a6 initio, fixed-nuclei electronic cross sections can provide the necessary input for a multi-dimensional treatment of the nuclear vibrational dynamics.

  14. Low Energy Excitations of a Bose-Einstein Condensate: A Time-Dependent Variational Analysis

    SciTech Connect

    Perez-Garcia, V.M.; Michinel, H.; Cirac, J.; Lewenstein, M.; Zoller, P. ||||

    1996-12-01

    We solve the time-dependent Gross-Pitaevskii equation by a variational ansatz to calculate the excitation spectrum of a Bose-Einstein condensate in a trap. The trial wave function is a Gaussian which allows an essentially analytical treatment of the problem. Our results reproduce numerical calculations over the whole range from small to large particle numbers, and agree exactly with the Stringari results in the strong interaction limit. Excellent agreement is obtained with the recent JILA experiment and predictions for the negative scattering length case are also made. {copyright} {ital 1996 The American Physical Society.}

  15. Optimal load resistance of a randomly excited nonlinear electromagnetic energy harvester with Coulomb friction

    NASA Astrophysics Data System (ADS)

    Tian, Y. P.; Wang, Y.; Jin, X. L.; Huang, Z. L.

    2014-09-01

    A nonlinear electromagnetic energy harvester directly powering a load resistance is considered in this manuscript. The nonlinearity includes the cubic stiffness and the unavoidable Coulomb friction, and the base excitation is confined to Gaussian white noise. Directly starting from the coupled equations, a novel procedure to evaluate the random responses and the mean output power is developed through the generalized harmonic transformation and the equivalent non-linearization technique. The dependence of the optimal ratio of the load resistance to the internal resistance and the associated optimal mean output power on the internal resistance of the coil is established. The principle of impedance matching is correct only when the internal resistance is infinity, and the optimal mean output power approaches an upper limit as the internal resistance is close to zero. The influence of the Coulomb friction on the optimal resistance ratio and the optimal mean output power is also investigated. It is proved that the Coulomb friction almost does not change the optimal resistance ratio although it prominently reduces the optimal mean output power.

  16. Low-energy l-mixing collisions of excited positronium with protons and antiprotons

    NASA Astrophysics Data System (ADS)

    Fabrikant, I. I.; Kadyrov, A. S.; Bray, I.; Charlton, M.

    2017-07-01

    We investigate l-mixing processes in collisions of excited positronium (Ps) atoms with protons in the range of the principal quantum number n of the Ps atom between 4 and 8. We show first that results of the threshold theory agree very well with convergent close-coupling calculations. We then compare quantum cross sections with results of semiclassical and classical theories. In the semiclassical theory, the Ps atom is treated quantum-mechanically, whereas the relative Ps-p motion is described classically. For l-mixing processes there is a good agreement between quantum and semiclassical results, whereas classical theory strongly underestimates the l-mixing cross sections. The conclusions are important for the interpretation of Classical Trajectory Monte Carlo simulations and the use of their data in the design of experiments.

  17. Doping dependence of low-energy quasiparticle excitations in superconducting Bi2212

    PubMed Central

    2013-01-01

    The doping-dependent evolution of the d-wave superconducting state is studied from the perspective of the angle-resolved photoemission spectra of a high-Tc cuprate, Bi2Sr2CaCu2 O8+δ (Bi2212). The anisotropic evolution of the energy gap for Bogoliubov quasiparticles is parametrized by critical temperature and superfluid density. The renormalization of nodal quasiparticles is evaluated in terms of mass enhancement spectra. These quantities shed light on the strong coupling nature of electron pairing and the impact of forward elastic or inelastic scatterings. We suggest that the quasiparticle excitations in the superconducting cuprates are profoundly affected by doping-dependent screening. PMID:24314035

  18. Do nuclei go pear-shaped? Coulomb excitation of 220Rn and 224Ra at REX-ISOLDE (CERN)

    NASA Astrophysics Data System (ADS)

    Scheck, M.; Gaffney, L. P.; Butler, P. A.; Hayes, A. B.; Wenander, F.; Albers, M.; Bastin, B.; Bauer, C.; Blazhev, A.; Boenig, S.; Bree, N.; Cederkall, J.; Chupp, T.; Cline, D.; Cocolios, T. E.; Davinson, T.; De Witte, H.; Diriken, J.; Grahn, T.; Herzan, A.; Huyse, M.; Jenkins, D. G.; Joss, D. T.; Kesteloot, N.; Konki, J.; Kowalczyk, M.; Kroell, Th.; Kwan, E.; Lutter, R.; Moschner, K.; Napiorkowski, P.; Pakarinen, J.; Pfeiffer, M.; Radeck, D.; Reiter, P.; Reynders, K.; Rigby, S. V.; Robledo, L. M.; Rudigier, M.; Sambi, S.; Seidlitz, M.; Siebeck, B.; Stora, T.; Thoele, P.; Van Duppen, P.; Vermeulen, M. J.; von Schmid, M.; Voulot, D.; Warr, N.; Wimmer, K.; Wrzosek-Lipska, K.; Wu, C. Y.; Zielinska, M.

    2015-05-01

    The IS475 collaboration conducted Coulomb-excitation experiments with post-accelerated radioactive 220Rn and 224Ra beams at the REX-ISOLDE facility. The beam particles (Ebeam: 2.83 MeV/u) were Coulomb excited using 60Ni, 114Cd, and 120Sn scattering targets. De-excitation γ-rays were detected employing the Miniball array and scattered particles were detected in a silicon detector. Exploiting the Coulomb-excitation code GOSIA for each nucleus several matrix elements could be obtained from the measured γ-ray yields. The extracted ‹3-||E3||0+› matrix element allows for the conclusion that, while 220Rn represents an octupole vibrational system, 224Ra has already substantial octupole correlations in its ground state. This finding has implications for the search of CP-violating Schiff moments in the atomic systems of the adjacent odd-mass nuclei.

  19. Relativistic Coulomb excitation within the time dependent superfluid local density approximation

    SciTech Connect

    Stetcu, I.; Bertulani, C. A.; Bulgac, A.; Magierski, P.; Roche, K. J.

    2015-01-06

    Within the framework of the unrestricted time-dependent density functional theory, we present for the first time an analysis of the relativistic Coulomb excitation of the heavy deformed open shell nucleus 238U. The approach is based on the superfluid local density approximation formulated on a spatial lattice that can take into account coupling to the continuum, enabling self-consistent studies of superfluid dynamics of any nuclear shape. We compute the energy deposited in the target nucleus as a function of the impact parameter, finding it to be significantly larger than the estimate using the Goldhaber-Teller model. The isovector giant dipole resonance, the dipole pygmy resonance, and giant quadrupole modes are excited during the process. As a result, the one-body dissipation of collective dipole modes is shown to lead a damping width Γ↓≈0.4 MeV and the number of preequilibrium neutrons emitted has been quantified.

  20. Development of a new Recoil Distance Technique using Coulomb Excitation in Inverse Kinematics

    SciTech Connect

    Rother, Wolfram; Dewald, Alfred; Ilie, Gabriela; Pissulla, Thomas; Melon, Barbara; Jolie, Jan; Pascovici, Gheorghe; Iwasaki, Hironori; Hackstein, Matthias; Zell, Karl-Oskar; Julin, Rauno; Jones, Peter; Greenlees, Paul; Rahkila, Panu; Uusitalo, Juha; Scholey, Cath; Harissopulos, Sotirios; Lagoyannis, Anastasios; Konstantinopoulos, Theodore; Grahn, Tuomas

    2009-01-28

    We report on an experiment using Coulomb excitation in inverse kinematics in combination with the plunger technique for measuring lifetimes of excited states of the projectiles. Aside from the investigation of E(5) features in {sup 128}Xe, the aim was to explore the special features of such experiments which are also suited to be used with radioactive beams. The measurement was performed at the JYFL with the Koeln coincidence plunger device and the JUROGAM spectrometer using a {sup 128}Xe beam impinging on a {sup nat}Fe target at a beam energy of 525 MeV. Recoils were detected by means of 32 solar cells placed at extreme forward angles. Particle-gated {gamma}-singles and {gamma}{gamma}-coincidences were measured at different target-degrader distances. Details of the experiment and first results are presented.

  1. Analysis methods of safe Coulomb-excitation experiments with radioactive ion beams using the GOSIA code

    NASA Astrophysics Data System (ADS)

    Zielińska, M.; Gaffney, L. P.; Wrzosek-Lipska, K.; Clément, E.; Grahn, T.; Kesteloot, N.; Napiorkowski, P.; Pakarinen, J.; Van Duppen, P.; Warr, N.

    2016-04-01

    With the recent advances in radioactive ion beam technology, Coulomb excitation at safe energies becomes an important experimental tool in nuclear-structure physics. The usefulness of the technique to extract key information on the electromagnetic properties of nuclei has been demonstrated since the 1960s with stable beam and target combinations. New challenges present themselves when studying exotic nuclei with this technique, including dealing with low statistics or number of data points, absolute and relative normalisation of the measured cross-sections and a lack of complementary experimental data, such as excited-state lifetimes and branching ratios. This paper addresses some of these common issues and presents analysis techniques to extract transition strengths and quadrupole moments utilising the least-squares fit code, GOSIA.

  2. Spin clusters and low-energy excitations in rare earth kagome systems

    NASA Astrophysics Data System (ADS)

    Hoch, M. J. R.

    2017-01-01

    The rare earth kagome systems R3Ga5SiO14 (R = Nd or Pr), which are weakly frustrated antiferromagnets, do not exhibit long-range order at temperatures down to 40 mK as revealed by neutron scattering. The neutron experiments provide evidence for the emergence at low temperatures of correlated spins in nanoscale cluster regions with magnetic field-dependent correlation lengths. A variety of techniques have been used to determine the magnetic and thermal properties of these systems. In particular, high-field electron spin resonance (ESR), nuclear magnetic resonance (NMR) and muon spin resonance (μSR) experiments have established that dynamic correlation of spins remains significant at temperatures well above 1 K. ESR provides evidence for spin wave excitations in spin clusters and the spectra have been interpreted using a Heisenberg model approach. While Nd3+ (J = 9/2) is a Kramers ion Pr3+ (J = 4) is not. This difference leads to contrasts in the magnetic properties of the two systems. This review surveys the information that has been obtained on the properties of these kagome materials over the past decade.

  3. Organic surfaces excited by low-energy ions: atomic collisions, molecular desorption and buckminsterfullerenes.

    PubMed

    Delcorte, Arnaud

    2005-10-07

    This article reviews the recent progress in the understanding of kiloelectronvolt particle interactions with organic solids, including atomic displacements in a light organic medium, vibrational excitation and desorption of fragments and entire molecules. This new insight is the result of a combination of theoretical and experimental approaches, essentially molecular dynamics (MD) simulations and secondary ion mass spectrometry (SIMS). Classical MD simulations provide us with a detailed microscopic view of the processes occurring in the bombarded target, from the collision cascade specifics to the scenarios of molecular emission. Time-of-flight SIMS measures the mass and energy distributions of sputtered ionized fragments and molecular species, a precious source of information concerning their formation, desorption, ionization and delayed unimolecular dissociation in the gas phase. The mechanisms of energy transfer and sputtering are compared for bulk molecular solids, organic overlayers on metal and large molecules embedded in a low-molecular weight matrix. These comparisons help understand some of the beneficial effects of metal substrates and matrices for the analysis of molecules by SIMS. In parallel, I briefly describe the distinct ionization channels of molecules sputtered from organic solids and overlayers. The specific processes induced by polyatomic projectile bombardment, especially fullerenes, are discussed on the basis of new measurements and calculations. Finally, the perspective addresses the state-of-the-art and potential developments in the fields of surface modification and analysis of organic materials by kiloelectronvolt ion beams.

  4. Absolute cross sections for vibrational excitations of cytosine by low energy electron impact

    PubMed Central

    Michaud, M.; Bazin, M.; Sanche, L.

    2013-01-01

    The absolute cross sections (CSs) for vibrational excitations of cytosine by electron impact between 0.5 and 18 eV were measured by electron-energy loss (EEL) spectroscopy of the molecule deposited at monolayer coverage on an inert Ar substrate. The vibrational energies compare to those that have been reported from IR spectroscopy of cytosine isolated in Ar matrix, IR and Raman spectra of poly-crystalline cytosine, and ab initio calculation. The CSs for the various H bending modes at 142 and 160 meV are both rising from their energy threshold up to 1.7 and 2.1 × 10−17 cm2 at about 4 eV, respectively, and then decrease moderately while maintaining some intensity at 18 eV. The latter trend is displayed as well for the CS assigned to the NH2 scissor along with bending of all H at 179 meV. This overall behavior in electron-molecule collision is attributed to direct processes such as the dipole, quadrupole, and polarization contributions, etc. of the interaction of the incident electron with a molecule. The CSs for the ring deformation at 61 meV, the ring deformation with N-H symmetric wag at 77 meV, and the ring deformations with symmetric bending of all H at 119 meV exhibit common enhancement maxima at 1.5, 3.5, and 5.5 eV followed by a broad hump at about 12 eV, which are superimposed on the contribution due to the direct processes. At 3.5 eV, the CS values for the 61-, 77-, and 119-meV modes reach 4.0, 3.0, and 4.5 × 10−17 cm2, respectively. The CS for the C-C and C-O stretches at 202 meV, which dominates in the intermediate EEL region, rises sharply until 1.5 eV, reaches its maximum of 5.7 × 10−17 cm2 at 3.5 eV and then decreases toward 18 eV. The present vibrational enhancements, correspond to the features found around 1.5 and 4.5 eV in electron transmission spectroscopy (ETS) and those lying within 1.5–2.1 eV, 5.2–6.8 eV, and 9.5–10.9 eV range in dissociative electron attachment (DEA) experiments with cytosine in gas phase. While the ETS features

  5. Field-orientation dependence of low-energy quasiparticle excitations in the heavy-electron superconductor UBe(13).

    PubMed

    Shimizu, Yusei; Kittaka, Shunichiro; Sakakibara, Toshiro; Haga, Yoshinori; Yamamoto, Etsuji; Amitsuka, Hiroshi; Tsutsumi, Yasumasa; Machida, Kazushige

    2015-04-10

    Low-energy quasiparticle excitations in the superconducting (SC) state of UBe_{13} were studied by means of specific-heat (C) measurements in a rotating field. Quite unexpectedly, the magnetic-field dependence of C(H) is linear in H with no angular dependence at low fields in the SC state, implying that the gap is fully open over the Fermi surfaces, in stark contrast to previous expectations. In addition, a characteristic cubic anisotropy of C(H) was observed above 2 T with a maximum (minimum) for H∥[001] ([111]) within the (11[over ¯]0) plane, in the normal as well as in the SC states. This oscillation possibly originates from the anisotropic response of the heavy quasiparticle bands, and might be a key to understand the unusual properties of UBe_{13}.

  6. Low-energy magnetic excitations from the Fe1+y-z(Ni/Cu)zTe1-xSex system

    NASA Astrophysics Data System (ADS)

    Xu, Zhijun; Wen, Jinsheng; Schneeloch, J.; Christianson, A. D.; Birgeneau, R. J.; Gu, Genda; Tranquada, J. M.; Xu, Guangyong

    2014-05-01

    We report neutron scattering measurements on low-energy (ℏω ˜5 meV) magnetic excitations from a series of Fe1+y-z(Ni/Cu)zTe1-xSex samples which belong to the "11" Fe-chalcogenide family. Our results suggest a strong correlation between the magnetic excitations near (0.5,0.5,0) and the superconducting properties of the system. The low-energy magnetic excitations are found to gradually move away from (0.5,0.5,0) to incommensurate positions when superconductivity is suppressed, either by heating or chemical doping, confirming previous observations.

  7. 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.

  8. In-depth analysis of Coulomb Volkov approaches to ionization and excitation by laser pulses

    NASA Astrophysics Data System (ADS)

    R, Guichard; H, Bachau; E, Cormier; R, Gayet; D, Rodriguez V.

    2007-10-01

    In perturbation conditions, above-threshold ionization spectra produced in the interaction of atoms with femtosecond short-wavelength laser pulses are well predicted by a theoretical approach called CV2-, which is based on Coulomb-Volkov-type states. However, when resonant intermediate states play a significant role in a multiphoton transition, the CV2- transition amplitude does not take their influence into account. In a previous paper, this influence has been introduced separately as a series of additional sequential processes interfering with the direct process. To give more credit to this procedure, called modified CV2- (MCV2-), a perturbation expansion of the standard CV2- transition amplitude is compared here to the standard time-dependent perturbation series and the strong field approximation. It is shown that the CV2- transition amplitude consists merely in a simultaneous absorption of all photons involved in the transition, thus avoiding all intermediate resonant state influence. The present analysis supports the MCV2- procedure that consists in introducing explicitly the other quantum paths, which contribute significantly to ionization, such as passing through intermediate resonances. Further, this analysis permits to show that multiphoton excitation may be addressed by a Coulomb-Volkov approach akin to MCV2-.

  9. Coulomb Enhancement of Superfluorescence Bursts from the Fermi Edge in Highly-Excited Quantum Wells

    NASA Astrophysics Data System (ADS)

    Kim, Ji-Hee; Noe, Tim; McGill, Stephen A.; Wang, Yongrui; Wójcik, Aleksander K.; Belyanin, Alexey A.; Kono, Junichiro

    2013-03-01

    Superfluorescence (SF) is a many-body process in which an ensemble of excited dipoles spontaneously develops macroscopic coherence and abruptly decays by producing a burst of coherent radiation. We have recently reported the first observation of SF from semiconductor quantum wells in the presence of a strong perpendicular magnetic field. Here, we report on results of our systematic magnetic field dependent studies of light emission from high-density electron-hole systems with gain. We observed SF pulses even at 0 Tesla when the excitation power is high and the temperature is low. The SF radiation at 0 Tesla shows a continuous band of emission in time-resolved photoluminescence images, i.e., the photon energy of the emitted light changes continuously with time. We interpret this phenomenon in terms of Coulomb enhancement of gain near the Fermi energy in a high-density electron-hole system. In addition, we demonstrate that the delay between the pump pulse and the SF pulses is tunable through the magnetic field and excitation pump power. Finally, the delay is longer for a lower-energy Landau level at a given magnetic field, i.e., the SF bursts proceed in a sequential manner from higher to lower Landau levels.

  10. Investigating shape evolution and the emergence of collectivity through the synergy of Coulomb excitation and beta decay

    SciTech Connect

    Allmond, James M

    2016-01-01

    The synthesis of Coulomb excitation and decay offers very practical advantages in the study of nuclear shapes and collectivity. For instance, Coulomb excitation is unique in its ability to measure the electric quadrupole moments, i.e., I2 ||M(E2)||I1 matrix elements, of excited, non-isomeric states in atomic nuclei, providing information on the intrinsic shape. However, the Coulomb excitation analysis and structural inter- pretation can be strongly dependent upon weak transitions or decay branches, which are often obscured by the Compton background. Transitions of particular interest are those low in energy and weak in intensity due to the E 5 attenuation factor. These weak decay branches can often be determined with high precision from -decay studies. Recently, 106Mo and 110Cd were studied by both Coulomb excitation and decay. Preliminary results of new weak decay branches following decay of 110mAg to 110Cd are presented; these results will challenge competing interpretations based on vibrations and configuration mixing.

  11. Investigating shape evolution and the emergence of collectivity through the synergy of Coulomb excitation and β decay

    NASA Astrophysics Data System (ADS)

    Allmond, J. M.

    2016-09-01

    The synthesis of Coulomb excitation and β decay offers very practical advantages in the study of nuclear shapes and collectivity. For instance, Coulomb excitation is unique in its ability to measure the electric quadrupole moments, i.e., < I_2^π allel M(E2)allel I_1^π > matrix elements, of excited, non-isomeric states in atomic nuclei, providing information on the intrinsic shape. However, the Coulomb excitation analysis and structural interpretation can be strongly dependent upon weak transitions or decay branches, which are often obscured by the Compton background. Transitions of particular interest are those low in energy and weak in intensity due to the Eγ5 attenuation factor. These weak decay branches can often be determined with high precision from β-decay studies. Recently, 106Mo and 110Cd were studied by both Coulomb excitation and β decay. Preliminary results of new weak decay branches following β decay of 110mAg to 110Cd are presented; these results will challenge competing interpretations based on vibrations and configuration mixing.

  12. Circularly polarized luminescence spectroscopy reveals low-energy excited states and dynamic localization of vibronic transitions in CP43.

    PubMed

    Hall, Jeremy; Renger, Thomas; Picorel, Rafael; Krausz, Elmars

    2016-01-01

    Circularly polarized luminescence (CPL) spectroscopy is an established but relatively little-used technique that monitors the chirality of an emission. When applied to photosynthetic pigment assemblies, we find that CPL provides sensitive and detailed information on low-energy exciton states, reflecting the interactions, site energies and geometries of interacting pigments. CPL is the emission analog of circular dichroism (CD) and thus spectra explore the optical activity only of fluorescent states of the pigment-protein complex and consequently the nature of the lowest-energy excited states (trap states), whose study is a critical area of photosynthesis research. In this work, we develop the new approach of temperature-dependent CPL spectroscopy, over the 2-120 K temperature range, and apply it to the CP43 proximal antenna protein of photosystem II. Our results confirm strong excitonic interactions for at least one of the two well-established emitting states of CP43 named "A" and "B". Previous structure-based models of CP43 spectra are evaluated in the light of the new CPL data. Our analysis supports the assignments of Shibata et al. [Shibata et al. J. Am. Chem. Soc. 135 (2013) 6903-6914], particularly for the highly-delocalized B-state. This state dominates CPL spectra and is attributed predominantly to chlorophyll a's labeled Chl 634 and Chl 636 (alternatively labeled Chl 43 and 45 by Shibata et al.). The absence of any CPL intensity in intramolecular vibrational sidebands associated with the delocalized "B" excited state is attributed to the dynamic localization of intramolecular vibronic transitions.

  13. Nonlinear SU(2,1) Model of Multiple Giant Dipole Resonance Coulomb Excitation

    NASA Astrophysics Data System (ADS)

    Hussein, Mahir; de Toledo Piza, Antonio; Vorov, Oleg

    2000-10-01

    We construct a three-dimensional analytically soluble model of the nonlinear effects in Coulomb excitation of multiphonon Giant Dipole Resonances (GDR) based on the SU(2,1) algebra^1. Analytical expressions for the multi-phonon transition probabilities are derived. For reasonably small magnitude of nonlinearity x~= 0.15-0.3, the enhancement factor for the Double Giant Resonance excitation probabilities and the cross sections reaches values 1.3-2 compatible^1,2 with experimental data from relativistic ion collision experiments^3. The full 3-dimensional model predicts enhancement of the multiple GDR cross sections at low and high bombarding energies (with the minimum at ~= 1.3 GeV for the Pb+Pb colliding system). Enhancement factors for Double GDR measured in thirteen different processes with various projectiles and targets at different bombarding energies are well reproduced with the same value of the nonlinearity parameter with the exception of the anomalous case of ^136Xe which requires a larger value. The work has been supported by the FAPESP and by the CNPq. References ^1 M. S. Hussein, A. F. R. de Toledo Piza and O. K.Vorov, Ann. Phys. (N.Y.), 2000, to appear. ^2 M. S. Hussein, A. F. R. de Toledo Piza and O. K.Vorov, Phys. Rev. C59,R1242 (1999). ^3 T. Aumann, P.F. Bortignon, and H. Emling, Annu. Rev. Nucl. Part. Sci. 48, 351 (1998).

  14. Relativistic Coulomb excitation within the time dependent superfluid local density approximation

    DOE PAGES

    Stetcu, I.; Bertulani, C. A.; Bulgac, A.; ...

    2015-01-06

    Within the framework of the unrestricted time-dependent density functional theory, we present for the first time an analysis of the relativistic Coulomb excitation of the heavy deformed open shell nucleus 238U. The approach is based on the superfluid local density approximation formulated on a spatial lattice that can take into account coupling to the continuum, enabling self-consistent studies of superfluid dynamics of any nuclear shape. We compute the energy deposited in the target nucleus as a function of the impact parameter, finding it to be significantly larger than the estimate using the Goldhaber-Teller model. The isovector giant dipole resonance, themore » dipole pygmy resonance, and giant quadrupole modes are excited during the process. As a result, the one-body dissipation of collective dipole modes is shown to lead a damping width Γ↓≈0.4 MeV and the number of preequilibrium neutrons emitted has been quantified.« less

  15. Magnetic moment and lifetime measurements of Coulomb-excited states in Cd106

    DOE PAGES

    Benczer-Koller, N.; Kumbartzki, G. J.; Speidel, K. -H.; ...

    2016-09-06

    The Cd isotopes are well studied, but experimental data for the rare isotopes are sparse. At energies above the Coulomb barrier, higher states become accessible. Remeasure and supplement existing lifetimes and magnetic moments of low-lying states in 106Cd. Methods: In an inverse kinematics reaction, a 106Cd beam impinging on a 12C target was used to Coulomb excite the projectiles. The high recoil velocities provide a unique opportunity to measure g factors with the transient-field technique and to determine lifetimes from lineshapes by using the Doppler-shift-attenuation method. Large-scale shell-model calculations were carried out for 106Cd. As a result, the g factorsmore » of the 2+1 and 4+1 states in 106Cd were measured to be g(2+1) = +0.398(22) and g(4+1) = +0.23(5). A lineshape analysis yielded lifetimes in disagreement with published values. The new results are τ(106Cd; 2+1) = 7.0(3) ps and τ(106Cd; 4+1) = 2.5(2) ps. The mean life τ(106Cd; 2+2) = 0.28(2) ps was determined from the fully-Doppler-shifted γ line. Mean lives of τ(106Cd; 4+3) = 1.1(1) ps and τ(106Cd; 3–1) = 0.16(1) ps were determined for the first time. In conclusion, the newly measured g(4+1) of 106Cd is found to be only 59% of the g(2+1). This difference cannot be explained by either shell-model or collective-model calculations.« less

  16. Magnetic moment and lifetime measurements of Coulomb-excited states in 106Cd

    NASA Astrophysics Data System (ADS)

    Benczer-Koller, N.; Kumbartzki, G. J.; Speidel, K.-H.; Torres, D. A.; Robinson, S. J. Q.; Sharon, Y. Y.; Allmond, J. M.; Fallon, P.; Abramovic, I.; Bernstein, L. A.; Bevins, J. E.; Crawford, H. L.; Guevara, Z. E.; Hurst, A. M.; Kirsch, L.; Laplace, T. A.; Lo, A.; Matthews, E. F.; Mayers, I.; Phair, L. W.; Ramirez, F.; Wiens, A.

    2016-09-01

    Background: The Cd isotopes are well studied, but experimental data for the rare isotopes are sparse. At energies above the Coulomb barrier, higher states become accessible. Purpose: Remeasure and supplement existing lifetimes and magnetic moments of low-lying states in 106Cd. Methods: In an inverse kinematics reaction, a 106Cd beam impinging on a 12C target was used to Coulomb excite the projectiles. The high recoil velocities provide a unique opportunity to measure g factors with the transient-field technique and to determine lifetimes from lineshapes by using the Doppler-shift-attenuation method. Large-scale shell-model calculations were carried out for 106Cd. Results: The g factors of the 21+ and 41+ states in 106Cd were measured to be g (21+)=+0.398 (22 ) and g (41+)=+0.23 (5 ) . A lineshape analysis yielded lifetimes in disagreement with published values. The new results are τ (106Cd;21+)=7.0 (3 )ps and τ (106Cd;41+)=2.5 (2 )ps . The mean life τ (106Cd;22+)=0.28 (2 )ps was determined from the fully-Doppler-shifted γ line. Mean lives of τ (106Cd;43+)=1.1 (1 )ps and τ (106Cd;31-)=0.16 (1 )ps were determined for the first time. Conclusions: The newly measured g (41+) of 106Cd is found to be only 59% of the g (21+) . This difference cannot be explained by either shell-model or collective-model calculations.

  17. Yrast and non-yrast 2 + states of 134Ce and 136Nd populated in relativistic Coulomb excitation

    NASA Astrophysics Data System (ADS)

    Saito, T. R.; Saito, N.; Starosta, K.; Beller, J.; Pietralla, N.; Wollersheim, H. J.; Balabanski, D. L.; Banu, A.; Bark, R. A.; Beck, T.; Becker, F.; Bednarczyk, P.; Behr, K.-H.; Benzoni, G.; Bizzeti, P. G.; Boiano, C.; Bracco, A.; Brambilla, S.; Brünle, A.; Bürger, A.; Caceres, L.; Camera, F.; Crespi, F. C. L.; Doornenbal, P.; Garnsworthy, A. B.; Geissel, H.; Gerl, J.; Górska, M.; Grebosz, J.; Hagemann, G.; Jolie, J.; Kavatsyuk, M.; Kavatsyuk, O.; Koike, T.; Kojouharov, I.; Kurz, N.; Leske, J.; Lo Bianco, G.; Maj, A.; Mallion, S.; Mandal, S.; Maliage, M.; Otsuka, T.; Petrache, C. M.; Podolyak, Zs.; Prokopowicz, W.; Rainovski, G.; Reiter, P.; Richard, A.; Schaffner, H.; Schielke, S.; Sletten, G.; Thompson, N. J.; Tonev, D.; Walker, J.; Warr, N.; Wieland, O.; Zhong, Q.

    2008-10-01

    The first 2+ states in 134Ce and 136Nd and the second 2+ state in 136Nd were populated by Coulomb excitation at relativistic energies, and γ-rays were measured using the RISING setup at GSI. For 134Ce an indication of the excitation to the second 2+ state was observed. This experiment performed for the first time Coulomb excitation to second 2+ states with rare isotope beams at relativistic energies. For 136Nd the B (E 2 ;21+ →0+), B (E 2 ;22+ →0+), and B (E 2 ;22+ →21+) values relative to the previously known B (E 2 ;21+ →0+) value for 134Ce are determined as 81(10), 11(3) and 180(92) W.u., respectively. The results are discussed in the framework of geometrical models that indicate pronounced γ-softness in these nuclei.

  18. Coulomb dissociation of 8B and the low-energy cross section of the 7Be(p,gamma)8B solar fusion reaction.

    PubMed

    Schümann, F; Hammache, F; Typel, S; Uhlig, F; Sümmerer, K; Böttcher, I; Cortina, D; Förster, A; Gai, M; Geissel, H; Greife, U; Iwasa, N; Koczoń, P; Kohlmeyer, B; Kulessa, R; Kumagai, H; Kurz, N; Menzel, M; Motobayashi, T; Oeschler, H; Ozawa, A; Płoskoń, M; Prokopowicz, W; Schwab, E; Senger, P; Strieder, F; Sturm, C; Sun, Zhi-Yu; Surówka, G; Wagner, A; Waluś, W

    2003-06-13

    An exclusive measurement of the Coulomb breakup of 8B into 7Be+p at 254A MeV allowed the study of the angular correlations of the breakup particles. These correlations demonstrate clearly that E1 multipolarity dominates and that E2 multipolarity can be neglected. By using a simple single-particle model for 8B and treating the breakup in first-order perturbation theory, we extract a zero-energy S factor of S17(0)=18.6+/-1.2+/-1.0 eV b, where the first error is experimental and the second one reflects the theoretical uncertainty in the extrapolation.

  19. Coulomb Excitation of n-rich nuclei along the N = 50 shell closure

    NASA Astrophysics Data System (ADS)

    Padilla-Rodal, E.; Galindo-Uribarri, A.; Batchelder, J. C.; Beene, J. R.; Bingham, C.; Brown, B. A.; Lagergren, K. B.; Mueller, P. E.; Radford, D. C.; Stracener, D. W.; Urrego-Blanco, J. P.; Varner, R. L.; Yu, C.-H.

    2008-04-01

    Recently, we have been investigating characteristics of nuclear states around the neutron-rich mass A=80 region [1]. Using the Radioactive Ion Beams (RIBs) produced at HRIBF, we have successfully measured the B(E2) values for ^78,80,82Ge , using Coulomb excitation in inverse kinematics. For the germanium isotopes, these data allow a study of the systematic trend between the subshell N= 40 and the N=50 shell. Using the same technique, we have measured the B(E2) value of various nuclei along the N=50 shell including the radioactive nucleus ^84Se. This value together with our previously measured ^82Ge, and the recent result on ^80Zn from ISOLDE [2] are providing basic experimental information needed for a better understanding of the neutron-rich nuclei around A˜80. We report the new results and compare with shell model calculations. [1] E. Padilla-Rodal et al., Phys. Rev. Lett. 94 (2005) 122501. [2] J. Van de Walle et al., Phys. Rev. Lett. 99 (2007) 142501.

  20. Preparation of actinide targets by molecular plating for Coulomb excitation studies at ATLAS.

    SciTech Connect

    Greene, J. P.

    1998-11-18

    Molecular plating is now routinely used to prepare sources and targets of actinide elements. Although the technique is simple and fairly reproducible, because of the radioactive nature of the target it is very useful to record various parameters in the preparation of such targets. At Argonne, {approximately}200 {micro}g/cm{sup 2} thick targets of Pu and Cm were required for Coulomb Excitation (COULEX) Studies with the Argonne-Notre Dame BGO gamma ray facility and later with the GAMMASPHERE. These targets were plated on 50 mg/cm{sup 2} Au backing and were covered with 150 {micro}g/cm{sup 2} Au foil. Targets of {sup 239}Pu, {sup 240}Pu, {sup 242}Pu, {sup 244}Pu and {sup 248}Cm were prepared by dissolving the material in isopropyl alcohol and electroplating the actinide ions by applying 600 volts. The amount of these materials on the target was determined by alpha particle counting and gamma ray counting. Details of the molecular plating and counting will be discussed.

  1. Octupole deformation in 144,146Ba measured by Coulomb excitation of radioactive beams

    NASA Astrophysics Data System (ADS)

    Bucher, Brian; Zhu, Shaofei; ANL, LBNL, LLNL, Rochester, Florida State, Liverpool, Maryland, Notre Dame, Ohio, W. Scotland Collaboration

    2015-10-01

    The exotic, neutron-rich 144Ba (t1 / 2 = 11.5 s) and 146Ba (t1 / 2 = 2.2 s) nuclei are expected to exhibit some of the strongest octupole correlations in A < 200 systems. Up to now, evidence for such strong octupole correlations has been inferred from observations of low-lying negative-parity states and from the interleaving of positive- and negative-parity levels in the ground-state band. However, the E1 transition strengths are very different in these two nuclei, with two orders of magnitude reduction in 146Ba. In this experiment, we measure the octupole strength directly by Coulomb excitation of post-accelerated 144,146Ba beams produced at CARIBU using CHICO2 and GRETINA. In 144Ba, we found B(E3;3 -->0) = 48(-34+ 25) W.u., a value considerably larger than theoretical predictions, while preliminary results for 146Ba are also indicative of strong octupole collectivity. The experimental conditions, the analysis, and the results from these challenging new measurements will be presented. This work is supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357 (ANL), DE-AC02-05CH11231 (LBNL, GRETINA), DOE DE-AC52-07NA27344 (LLNL), and NSF.

  2. Effects of low-energy excitations on spectral properties at higher binding energy: the metal-insulator transition of VO(2).

    PubMed

    Gatti, Matteo; Panaccione, Giancarlo; Reining, Lucia

    2015-03-20

    The effects of electron interaction on spectral properties can be understood in terms of coupling between excitations. In transition-metal oxides, the spectral function close to the Fermi level and low-energy excitations between d states have attracted particular attention. In this work we focus on photoemission spectra of vanadium dioxide over a wide (10 eV) range of binding energies. We show that there are clear signatures of the metal-insulator transition over the whole range due to a cross coupling of the delocalized s and p states with low-energy excitations between the localized d states. This coupling can be understood by advanced calculations based on many-body perturbation theory in the GW approximation. We also advocate the fact that tuning the photon energy up to the hard-x-ray range can help to distinguish fingerprints of correlation from pure band-structure effects.

  3. Crossover of Feshbach Resonances to Shape-Type Resonances in Electron-Hydrogen Atom Excitation with a Screened Coulomb Interaction

    SciTech Connect

    Zhang Songbin; Wang Jianguo; Janev, R. K.

    2010-01-15

    The effects of Coulomb interaction screening on electron-hydrogen atom excitation in the n=2 threshold region are investigated by using the R-matrix method with pseudostates. The interaction screening lifts the l degeneracy of n=2 Coulomb energy level, producing two distinct thresholds for 2s and 2p states. The phenomenon of transformation of {sup 1,3}P and {sup 1}D Feshbach resonances into shape-type resonances is observed when they pass across the 2s and 2p threshold, respectively, as the interaction screening increases. It is shown that this resonance transformation leads to dramatic effects in the 1s->2s and 1s->2p excitation collision strengths in the n=2 threshold collision energy region.

  4. Coulomb excitation of a Am242 isomeric target: E2 and E3 strengths, rotational alignment, and collective enhancement

    NASA Astrophysics Data System (ADS)

    Hayes, A. B.; Cline, D.; Moody, K. J.; Ragnarsson, I.; Wu, C. Y.; Becker, J. A.; Carpenter, M. P.; Carroll, J. J.; Gohlke, D.; Greene, J. P.; Hecht, A. A.; Janssens, R. V. F.; Karamian, S. A.; Lauritsen, T.; Lister, C. J.; Macri, R. A.; Propri, R.; Seweryniak, D.; Wang, X.; Wheeler, R.; Zhu, S.

    2010-10-01

    A 98% pure 242mAm (K=5-, t1/2=141 years) isomeric target was Coulomb excited with a 170.5-MeV Ar40 beam. The selectivity of Coulomb excitation, coupled with the sensitivity of Gammasphere plus CHICO, was sufficient to identify 46 new states up to spin 18ℏ in at least four rotational bands; 11 of these new states lie in the isomer band, 13 in a previously unknown yrast Kπ=6- rotational band, and 13 in a band tentatively identified as the predicted yrast Kπ=5+ band. The rotational bands based on the Kπ=5- isomer and the 6- bandhead were populated by Coulomb excitation with unexpectedly equal cross sections. The γ-ray yields are reproduced by Coulomb excitation calculations using a two-particle plus rotor model (PRM), implying nearly complete ΔK=1 mixing of the two almost-degenerate rotational bands, but recovering the Alaga rule for the unperturbed states. The degeneracy of the 5- and 6- bands allows for precise determination of the mixing interaction strength V, which approaches the strong-mixing limit; this agrees with the 50% attenuation of the Coriolis matrix element assumed in the model calculations. The fractional admixture of the IKπ=66- state in the nominal 65- isomer band state is measured within the PRM as 45.6-1.1+0.3%. The E2 and M1 strengths coupling the 5- and 6- bands are enhanced significantly by the mixing, while E1 and E2 couplings to other low-K bands are not measurably enhanced. The yields of the 5+ band are reproduced by an E3 strength of ≈15 W.u., competitive with the interband E2 strength. Alignments of the identified two-particle Nilsson states in Am242 are compared with the single-particle alignments in Am241.

  5. Coulomb-nuclear interference with {alpha} particles in the excitation of the 2{sup +}{sub 1} states in {sup 100,102,104}Ru

    SciTech Connect

    Gomes, L.C.; Horodynski-Matsushigue, L.B.; Borello-Lewin, T.; Duarte, J.L.; Hirata, J.H.; Salem-Vasconcelos, S.; Dietzsch, O.

    1996-11-01

    Coulomb-nuclear interference data for incident energies between 9 and 17 MeV were obtained in the form of elastic and inelastic (to the 2{sup +}{sub 1} states) excitation functions of backscattered ({theta}{approx_equal}172.8{degree}) alpha particles on {sup 100,102,104}Ru. The analysis was done in a distorted-wave Born approximation within a deformed optical model approach. {ital B}({ital E}2) values, obtained from the charge deformation lengths {delta}{sup {ital C}} extracted from the low energy data, are compatible for the three isotopes within {approximately} 2{sigma} with published values. The nuclear quadrupolar deformation lengths {delta}{sup {ital N}}, obtained from the analysis of the interference region of the excitation functions, and also of one angular distribution at 22 MeV measured for {sup 100}Ru are generally lower than the corresponding charge deformation lengths, the difference increasing with increasing {ital A} of the isotope, {delta}{sup {ital N}} being 18{percent} lower than {delta}{sup {ital C}} for {sup 104}Ru (2{sup +}{sub 1}). Nuclear deformation lengths associated with the 3{sub 1}{sup {minus}} states of {sup 100,102,104}Ru and with the 4{sup +}{sub 2} state of {sup 100}Ru at 2.367 MeV were also obtained as a by-product of the present work. {copyright} {ital 1996 The American Physical Society.}

  6. Time-Resolved Measurement of Interatomic Coulombic Decay Induced by Two-Photon Double Excitation of Ne2

    NASA Astrophysics Data System (ADS)

    Takanashi, T.; Golubev, N. V.; Callegari, C.; Fukuzawa, H.; Motomura, K.; Iablonskyi, D.; Kumagai, Y.; Mondal, S.; Tachibana, T.; Nagaya, K.; Nishiyama, T.; Matsunami, K.; Johnsson, P.; Piseri, P.; Sansone, G.; Dubrouil, A.; Reduzzi, M.; Carpeggiani, P.; Vozzi, C.; Devetta, M.; Negro, M.; Faccialà, D.; Calegari, F.; Trabattoni, A.; Castrovilli, M. C.; Ovcharenko, Y.; Mudrich, M.; Stienkemeier, F.; Coreno, M.; Alagia, M.; Schütte, B.; Berrah, N.; Plekan, O.; Finetti, P.; Spezzani, C.; Ferrari, E.; Allaria, E.; Penco, G.; Serpico, C.; De Ninno, G.; Diviacco, B.; Di Mitri, S.; Giannessi, L.; Jabbari, G.; Prince, K. C.; Cederbaum, L. S.; Demekhin, Ph. V.; Kuleff, A. I.; Ueda, K.

    2017-01-01

    The hitherto unexplored two-photon doubly excited states [Ne*(2 p-13 s )]2 were experimentally identified using the seeded, fully coherent, intense extreme ultraviolet free-electron laser FERMI. These states undergo ultrafast interatomic Coulombic decay (ICD), which predominantly produces singly ionized dimers. In order to obtain the rate of ICD, the resulting yield of Ne2+ ions was recorded as a function of delay between the extreme ultraviolet pump and UV probe laser pulses. The extracted lifetimes of the long-lived doubly excited states, 390 (-130 /+450 ) fs , and of the short-lived ones, less than 150 fs, are in good agreement with ab initio quantum mechanical calculations.

  7. Coulomb Excitation and One-Neutron Transfer Studies of Stable and Radioactive Nuclei at HRIBF-ORNL

    SciTech Connect

    Allmond, James M

    2015-01-01

    Several stable and radioactive nuclei ranging from $A=58$ to 208 were recently studied in inverse kinematics by Coulomb excitation and heavy-ion induced one-neutron transfer at the Holifield Radioactive Ion Beam Facility of Oak Ridge National Laboratory. These studies used a CsI-HPGe detector array to detect scattered charged particles and emitted $\\gamma$ rays from the in-beam reactions. A Bragg-curve detector was used to measure the energy loss of the various beams through the targets and to measure the radioactive beam compositions. Stable nickel, strontium, zirconium, molybdenum, tin, tellurium, and lead isotopes and neutron-rich radioactive tin and tellurium isotopes were among the nuclei recently studied. Coulomb excitation was used to measure the electromagnetic moments of the first excited states and heavy-ion induced one-neutron transfer was used to measure the absolute cross sections and lifetimes of the excited single-particle states. A sample of these results are presented here with an emphasis on the tin isotopes. In particular, a survey of the Bragg-curve measurements, Doppler corrections, and inconclusive $i_{13/2}$ candidate in $^{133}$\\textrm{Sn} are presented.

  8. Impact of low-energy nuclear excitations on neutrino-nucleus scattering at MiniBooNE and T2K kinematics

    NASA Astrophysics Data System (ADS)

    Pandey, V.; Jachowicz, N.; Martini, M.; González-Jiménez, R.; Ryckebusch, J.; Van Cuyck, T.; Van Dessel, N.

    2016-11-01

    Background: Meticulous modeling of neutrino-nucleus interactions is essential to achieve the unprecedented precision goals of present and future accelerator-based neutrino-oscillation experiments. Purpose: Confront our calculations of charged-current quasielastic cross sections with the measurements of MiniBooNE and T2K, and to quantitatively investigate the role of nuclear-structure effects, in particular, low-energy nuclear excitations in forward muon scattering. Method: The model takes the mean-field approach as the starting point, and solves Hartree-Fock (HF) equations using a Skyrme (SkE2) nucleon-nucleon interaction. Long-range nuclear correlations are taken into account by means of the continuum random-phase approximation (CRPA) framework. Results: We present our calculations on flux-folded double differential, and flux-unfolded total cross sections off 12C and compare them with MiniBooNE and (off-axis) T2K measurements. We discuss the importance of low-energy nuclear excitations for the forward bins. Conclusions: The HF and CRPA predictions describe the gross features of the measured cross sections. They underpredict the data (more in the neutrino than in the antineutrino case) because of the absence of processes beyond pure quasielastic scattering in our model. At very forward muon scattering, low-energy HF-CRPA nuclear excitations (ω <50 MeV) account for nearly 50% of the flux-folded cross section. This extra low-energy strength is a feature of the detailed microscopic nuclear model used here, that is not accessed in a Fermi-gas based approach.

  9. Excitation of the \\tilde{a}\\,^3B_1 and \\tilde{A}\\,^1B_1 states of H2O by low-energy electron impact

    NASA Astrophysics Data System (ADS)

    Hargreaves, L.; Ralphs, K.; Serna, G.; Khakoo, M. A.; Winstead, C.; McKoy, V.

    2012-10-01

    We report measured and calculated differential cross-sections for inelastic scattering of low-energy electrons by water leading to excitation of the dissociative (1b1 → 4a1) 1, 3B1 states. The measurements were taken using conventional energy-loss spectroscopy at incident energies of 9, 10, 12, 15, and 20 eV for scattering angles from 10° to 130°. The calculations were carried out using the Schwinger multichannel method, with a Born-dipole correction applied in the singlet excitation channel. Integral excitation cross sections for the \\tilde{a}\\,^3B_1 and \\tilde{A}\\,^1B_1 states are also derived from the differential cross section results.

  10. Low-energy electrodynamics of novel spin excitations in the quantum spin ice Yb₂Ti₂O₇.

    PubMed

    Pan, LiDong; Kim, Se Kwon; Ghosh, A; Morris, Christopher M; Ross, Kate A; Kermarrec, Edwin; Gaulin, Bruce D; Koohpayeh, S M; Tchernyshyov, Oleg; Armitage, N P

    2014-09-18

    In condensed matter systems, formation of long-range order (LRO) is often accompanied by new excitations. However, in many geometrically frustrated magnetic systems, conventional LRO is suppressed, while non-trivial spin correlations are still observed. A natural question to ask is then what is the nature of the excitations in this highly correlated state without broken symmetry? Frequently, applying a symmetry breaking field stabilizes excitations whose properties reflect certain aspects of the anomalous state without LRO. Here we report a THz spectroscopy study of novel excitations in quantum spin ice Yb2Ti2O7 under a <001> directed magnetic field. At large positive fields, both right- and left-handed magnon and two-magnon-like excitations are observed. The g-factors of these excitations are dramatically enhanced in the low-field limit, showing a crossover of these states into features consistent with the quantum string-like excitations proposed to exist in quantum spin ice in small <001> fields.

  11. Vibrational excitation in low-energy electron scattering by H 2 molecules physisorbed on a metal surface

    NASA Astrophysics Data System (ADS)

    Teillet-Billy, D.; Stibbe, D. T.; Tennyson, J.; Gauyacq, J. P.

    1999-12-01

    The electron impact vibrational excitation of H 2 molecules physisorbed on a free-electron metal surface is studied theoretically at collision energies of a few eV. The role of the short-lived low-lying 2Σ u resonance is investigated. The electron scattering by a free H 2 molecule is described by the R-matrix method and the corresponding results are used to model the electron scattering by the physisorbed molecule with the coupled angular mode (CAM) method. The strength of the vibrational excitation and, in particular, the overtone vibrational excitation ratio are found to be smaller for the physisorbed molecule than for the free molecule. However, the energy dependence of the vibrational excitation process is found to be weakly influenced by the physisorption, as observed experimentally by Demuth et al. [Phys. Rev. Lett. 47 (1981) 1166].

  12. Complex-Scaling Treatment for Doubly Excited Inter-Shell Resonances in H- Interacting with Screened Coulomb (Yukawa) Potentials

    NASA Astrophysics Data System (ADS)

    Ho, Y. K.; Kar, S.

    2012-10-01

    The doubly-excited inter-shell resonance states of the hydrogen negative ion with screened Coulomb potentials are investigated in the framework of complex-scaling method. Highly correlated wave functions with terms up to 1078 in Hylleraas coordinates are used. The resonance parameters for the 2 s3 s 1 S e associated with the H ( N = 2) threshold and the 3 s4 s 1 S e state associated with the H ( N = 3) threshold for various screening strengths are reported. Comparisons are made with other available data in the literature.

  13. First Results with TIGRESS and Accelerated Radioactive Ion Beams from ISAC: Coulomb Excitation of {sup 20,21,29}Na

    SciTech Connect

    Schumaker, M. A.; Svensson, C. E.; Demand, G. A.; Finlay, P.; Green, K. L.; Grinyer, G. F.; Leach, K. G.; Millar, B. A.; Phillips, A. A.; Sumithrarachchi, C. S.; Triambak, S.; Wong, J.; Hurst, A. M.; Wu, C. Y.; Becker, J. A.; Stoyer, M. A.; Cline, D.; Hayes, A. B.; Whitbeck, A.; Hackman, G.

    2009-03-10

    The TRIUMF-ISAC Gamma-Ray Escape Suppressed Spectrometer (TIGRESS) is a state-of-the-art {gamma}-ray spectrometer being constructed at the ISAC-II radioactive ion beam facility at TRIUMF. TIGRESS will be comprised of twelve 32-fold segmented high-purity germanium (HPGe) clover-type {gamma}-ray detectors, with BGO/CsI(Tl) Compton-suppression shields, and is currently operational at ISAC-II in an early-implementation configuration of six detectors. Results have been obtained for the first experiments performed using TIGRESS, which examined the A = 20, 21, and 29 isotopes of Na by Coulomb excitation.

  14. Excited State Investigation of a New Ru(II) Complex for Dual Reactivity with Low Energy Light

    PubMed Central

    Knoll, J. D.; Albani, B. A.; Turro, C.

    2015-01-01

    The new complex [Ru(tpy)(Me2dppn)(py)]2+ efficiently photodissociates py in CH3CN with Φ500 = 0.053(1) induced by steric bulk from methyl substituents and produces 1O2 with ΦΔ = 0.69(9) from its long-lived 3ππ* excited state. The unique excited state processes that result in dual reactivity were investigated using ultrafast transient absorption spectroscopy. PMID:25912170

  15. Observation of sputtering of yttrium from Y2O3 ceramics by low-energy Ar, Kr, and Xe ion bombardment in microwave-excited plasma

    NASA Astrophysics Data System (ADS)

    Goto, Tetsuya; Sugawa, Shigetoshi

    2015-12-01

    Y2O3 ceramics were immersed in microwave-excited Ar, Kr, and Xe plasmas, and the sputtering of yttrium atoms from Y2O3 ceramics as a result of low-energy (range of approximately 10 eV) Ar, Kr, and Xe ion bombardment was observed. The amount of sputtered yttrium atoms well correlated with the ion bombardment energy estimated by Langmuir probe measurement. The estimated sputtering yield was 10-5 or less for such a low ion bombardment condition.

  16. 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.

  17. Collectivity in {}^{{196,198}}Pb isotopes probed in Coulomb-excitation experiments at REX-ISOLDE

    NASA Astrophysics Data System (ADS)

    Pakarinen, J.; Grahn, T.; Gaffney, L. P.; Algora, A.; Bauer, C.; Blazhev, A.; Bree, N.; Cocolios, T. E.; De Witte, H.; Diriken, J.; Fernier, P.; Hadyńska-Klȩk, K.; Herzáň, A.; Huyse, M.; Iwanicki, J.; Jakobsson, U.; Jenkins, D.; Kesteloot, N.; Konki, J.; Lannoo, B.; Papadakis, P.; Peura, P.; Rahkila, P.; Rainovski, G.; Rapisarda, E.; Reiter, P.; Sambi, S.; Scheck, M.; Seibeck, B.; Seidlitz, M.; Stora, T.; Van Duppen, P.; Warr, N.; Wenander, F.; Vermeulen, M. J.; Voulot, D.; Wrzosek-Lipska, K.; Zielińska, M.

    2017-06-01

    The neutron-deficient {}{196,198}Pb isotopes have been studied in Coulomb-excitation experiments employing the Miniball γ-ray spectrometer and radioactive ion beams from the REX-ISOLDE post-accelerator at CERN. The reduced transition probabilities of the first excited 2+ states in 196Pb and 198Pb nuclei have been measured for the first time. Values of B(E2)={18.2}-4.1+4.8 W.u. and B(E2)={13.1}-3.5+4.9 W.u., were obtained, respectively. The experiment sheds light on the development of collectivity when moving from the regime governed by the generalised seniority scheme to a region, where intruding structures, associated with different deformed shapes, start to come down in energy and approach the spherical ground state.

  18. Shape coexistence in the neutron-deficient even-even (182-188)Hg isotopes studied via coulomb excitation.

    PubMed

    Bree, N; Wrzosek-Lipska, K; Petts, A; Andreyev, A; Bastin, B; Bender, M; Blazhev, A; Bruyneel, B; Butler, P A; Butterworth, J; Carpenter, M P; Cederkäll, J; Clément, E; Cocolios, T E; Deacon, A; Diriken, J; Ekström, A; Fitzpatrick, C; Fraile, L M; Fransen, Ch; Freeman, S J; Gaffney, L P; García-Ramos, J E; Geibel, K; Gernhäuser, R; Grahn, T; Guttormsen, M; Hadinia, B; Hadyńska-Kle K, K; Hass, M; Heenen, P-H; Herzberg, R-D; Hess, H; Heyde, K; Huyse, M; Ivanov, O; Jenkins, D G; Julin, R; Kesteloot, N; Kröll, Th; Krücken, R; Larsen, A C; Lutter, R; Marley, P; Napiorkowski, P J; Orlandi, R; Page, R D; Pakarinen, J; Patronis, N; Peura, P J; Piselli, E; Rahkila, P; Rapisarda, E; Reiter, P; Robinson, A P; Scheck, M; Siem, S; Singh Chakkal, K; Smith, J F; Srebrny, J; Stefanescu, I; Tveten, G M; Van Duppen, P; Van de Walle, J; Voulot, D; Warr, N; Wenander, F; Wiens, A; Wood, J L; Zielińska, M

    2014-04-25

    Coulomb-excitation experiments to study electromagnetic properties of radioactive even-even Hg isotopes were performed with 2.85  MeV/nucleon mercury beams from REX-ISOLDE. Magnitudes and relative signs of the reduced E2 matrix elements that couple the ground state and low-lying excited states in Hg182-188 were extracted. Information on the deformation of the ground and the first excited 0+ states was deduced using the quadrupole sum rules approach. Results show that the ground state is slightly deformed and of oblate nature, while a larger deformation for the excited 0+ state was noted in Hg182,184. The results are compared to beyond mean field and interacting-boson based models and interpreted within a two-state mixing model. Partial agreement with the model calculations was obtained. The presence of two different structures in the light even-mass mercury isotopes that coexist at low excitation energy is firmly established.

  19. 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.

  20. Low-energy excitations of the semimetallic one-dimensional S=1/2 antiferromagnet Yb 4As 3

    NASA Astrophysics Data System (ADS)

    Schmidt, B.; Aoki, H.; Cichorek, T.; Custers, J.; Gegenwart, P.; Kohgi, M.; Lang, M.; Langhammer, C.; Ochiai, A.; Paschen, S.; Steglich, F.; Suzuki, T.; Thalmeier, P.; Wand, B.; Yaresko, A.

    2001-07-01

    We investigate a new route to quasi-one-dimensional spin-chain systems which originates from the charge-ordering transition out of a homogeneous mixed-valence state. We present evidence that Yb 4As 3 and P, Sb doped mixed crystals are well described by this mechanism. Many thermodynamic and low-temperature transport heavy-fermion-like properties can be explained by the existence of low-lying quasi-one-dimensional spin excitations in the Yb 3+-chains. The observation of soliton excitations in a transverse external field gives further support to the existence of spin chains in Yb 4As 3. We also present recent results on spin-glass behavior at very low temperature caused by the interchain coupling and disorder. In addition, the yet unexplained magnetotransport effects are discussed.

  1. Electron-hydrogen-atom elastic and inelastic scattering with screened Coulomb interaction around the n=2 excitation threshold

    SciTech Connect

    Zhang Songbin; Wang Jianguo; Janev, R. K.

    2010-03-15

    The effects of Coulomb interaction screening on electron-hydrogen-atom elastic and excitation scattering around the n=2 threshold have been investigated by using the R-matrix method with pseudostates. The elastic and excitation collision strengths show dramatic changes when the interaction screening length D varies from {infinity} to 3.8 a.u., as a result of the convergence of {sup 1,3}S Feshbach resonances to the varying 2s threshold and of the transformation of {sup 1,3}P and {sup 1}D Feshbach resonances into shape-type resonances when they pass across the 2s and 2p threshold at certain critical value of D, respectively [S. B. Zhang et al., Phys. Rev. Lett. 104, 023203 (2010)]. The resonance parameters for a large number of D in the range D={infinity}-3.8 a.u. are presented. It is observed that the {sup 1,3}P and {sup 1}D resonance contributions to the elastic and excitation collision strengths decrease rapidly with decreasing D after the resonance passes the critical D value. The contribution of a {sup 1}S{sup e} Feshbach resonance to the elastic or excitation collision strength changes into a cusp after the resonance merges into its parent 2s state and immerses into the background with the further decrease of D.

  2. Low-energy dipole excitations in neon isotopes and N=16 isotones within the quasiparticle random-phase approximation and the Gogny force

    SciTech Connect

    Martini, M.; Peru, S.; Dupuis, M.

    2011-03-15

    Low-energy dipole excitations in neon isotopes and N=16 isotones are calculated with a fully consistent axially-symmetric-deformed quasiparticle random phase approximation (QRPA) approach based on Hartree-Fock-Bogolyubov (HFB) states. The same Gogny D1S effective force has been used both in HFB and QRPA calculations. The microscopical structure of these low-lying resonances, as well as the behavior of proton and neutron transition densities, are investigated in order to determine the isoscalar or isovector nature of the excitations. It is found that the N=16 isotones {sup 24}O, {sup 26}Ne, {sup 28}Mg, and {sup 30}Si are characterized by a similar behavior. The occupation of the 2s{sub 1/2} neutron orbit turns out to be crucial, leading to nontrivial transition densities and to small but finite collectivity. Some low-lying dipole excitations of {sup 28}Ne and {sup 30}Ne, characterized by transitions involving the {nu}1d{sub 3/2} state, present a more collective behavior and isoscalar transition densities. A collective proton low-lying excitation is identified in the {sup 18}Ne nucleus.

  3. Coulomb Excitation and Few Nucleon Transfer Reactions with ^209Bi Beams on ^237Np and ^241Am Targets

    NASA Astrophysics Data System (ADS)

    Abu Saleem, K.; Janssens, R. V. F.; Carpenter, M. P.; Kondev, F. G.; Ahmad, I.; Greene, J. P.; Caggiano, J.; Heinz, A.; Khoo, T. L.; Lauritsen, T.; Lister, C. J.; Seweryniak, D.; Sonzogni, A.; Wiedenhoever, I.; Hackman, G.; Chowdhury, P.; Cline, D.; Wu, C.; Machiavelli, A. O.; Devlin, M.; Fotiades, N.; Seabury, E. H.

    2002-10-01

    Two separate Coloumb excitation measurements have been performed at ATLAS using Pb beams, at bombarding energies ˜ 15% above the Coulomb barrier, incident upon ^237Np and ^241Am targets. Using these reactions, γ-ray coincidence data were collected with the Gammasphere array. In both measurements, rotational bands built on a πi_13/2 configuration were observed to high-spin in the target nuclei. From these new data and those available for even- and odd-A U and Pu isotopes, we have concluded that the i_13/2 quasiprotons dominate the observed alignments in this mass region and that there is little contribution from aligning j_15/2 neutron pairs. This is unexpected based on Cranked Shell Model predictions which indicate that both quasiparticle pairs should be involved in the observed alignment processes.

  4. Application of the Broad Energy Germanium detector: A technique for elucidating β-decay schemes which involve daughter nuclei with very low energy excited states

    NASA Astrophysics Data System (ADS)

    Venhart, M.; Wood, J. L.; Boston, A. J.; Cocolios, T. E.; Harkness-Brennan, L. J.; Herzberg, R.-D.; Joss, D. T.; Judson, D. S.; Kliman, J.; Matoušek, V.; Motyčák, Š.; Page, R. D.; Patel, A.; Petrík, K.; Sedlák, M.; Veselský, M.

    2017-03-01

    A technique for elucidating β-decay schemes of isotopes with a large density of states at low excitation energy has been developed, in which a Broad Energy Germanium (BEGe) detector is used in conjunction with coaxial hyper-pure germanium detectors. The power of this technique is demonstrated using the example of 183Hg decay. Mass-separated samples of 183Hg were produced by a deposition of the low-energy radioactive-ion beam delivered by the ISOLDE facility at CERN. The excellent energy resolution of the BEGe detector allowed γ-ray energies to be determined with a precision of a few tens of eV, which was sufficient for the analysis of the Rydberg-Ritz combinations (in conjunction with γ-γ coincidences) in the level scheme. The timestamped structure of the data was used for unambiguous separation of γ rays arising from the decay of 183Hg from those due to the daughter decays.

  5. Dipolon Theory of High Temperature Superconductors- Prediction of the Existence of New Very Low Energy Excitations to be Observed in Photoemission Experiments

    NASA Astrophysics Data System (ADS)

    Sharma, Ram R.

    The dipolon theory first discovered two high energy kinks in electron energy. It [1-2] has also predicted two superconducting states, symmetric (''s'') and anti-symmetric (''as''). Here we report the prediction of very low energy excitations due to transition from ''as'' state to ''s'' state (''ass'') (or vice versa) which creates (annihilates) the quantum (''asson'') of energy ℏωa (q-->a) =Es (k' -->) -Eas (k'' -->) ; ''a'' is for ''asson'' and Es (k' -->) and Eas (k'' -->) are electron energies in ''s'' and ''as'' states, respectively (Ei (k -->) =Eri (k -->) [1-4]). Our theory [1-4] finds in BISCCO at M point on Fermi level at T=13 K asson energy about 14 +/- 8 meV . We predict that these assons create a new kink in electron energy at this energy. Also, a single pair transitions are possible which involve two assons.

  6. 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.

  7. Systematic investigation of the low-energy dipole excitations in 176,178,180Hf within rotational, translational and Galilean invariant quasiparticle RPA

    NASA Astrophysics Data System (ADS)

    Guliyev, E.; Kuliev, A. A.; Ertugral, F.

    2013-10-01

    Low-energy magnetic and electric dipole excitations in the even-even isotopes 176-180Hf have been systematically studied within the rotational, translational and Galilean invariant Quasiparticle Random Phase Approximation (QRPA). The results of the calculations show that most of the states predicted to have magnetic character and the computed M1 strength in these nuclei is less strongly fragmented than in mid-shell isotopes. The results of the calculations are in good agreement with experimental data. The results of the calculations indicate the presence of a few prominent negative parity dipole K=1 states in the energy investigated region. The comparison of the calculations with the available experimental data makes possible the interpretation of the states where parity could not be assigned experimentally.

  8. 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.

  9. Controlling the coulomb explosion of silver clusters by femtosecond dual-pulse laser excitation.

    PubMed

    Döppner, T; Fennel, Th; Diederich, Th; Tiggesbäumker, J; Meiwes-Broer, K H

    2005-01-14

    Silver clusters grown in helium nanodroplets are excited by intense femtosecond laser pulses resulting in the formation of a hot electron plasma far from equilibrium. The ultrafast dynamics is studied by applying optically delayed dual pulses, which allows us to pursue and control the coupling of the laser field to the clusters on a femtosecond time scale. A distinct influence of the optical delay on the ionization efficiency gives strong evidence that a significant contribution of collective dipolar electron motion is present, which is verified by corresponding Vlasov dynamics simulations on a model system. The microscopic approach demonstrates the outstanding role of giant resonances in clusters also in intense laser fields.

  10. Level lifetimes and quadrupole moments from Coulomb excitation in the Ba chain and the N = 80 isotones

    NASA Astrophysics Data System (ADS)

    Bauer, C.; Guastalla, G.; Leske, J.; Möller, O.; Möller, T.; Pakarinen, J.; Pietralla, N.; Rainovski, G.; Rapisarda, E.; Seweryniak, D.; Stahl, C.; Stegmann, R.; Wiederhold, J.; Zhu, S.

    2012-12-01

    The chain of Barium isotopes enables us to study experimentally the evolution of nuclear quadrupole collectivity from the shell closure at N = 82 towards neutron-deficient or neutron-rich deformed nuclei. The TU Darmstadt group has investigated several nuclei from stable 130,132Ba up to radioactive 140,142Ba with the projectile-Coulomb excitation technique including the use of the Doppler-shift attenuation method (DSAM). Lifetimes of quadrupole-collective states of 132Ba and 140Ba were obtained for the first time as well as the static electric quadrupole moments Q(21+) for 130,132Ba and 140,142Ba. The results are compared to Monte Carlo shell model and Beyond-Mean-Field calculations. The phenomenon of shell stabilization in the N = 80 isotones is further investigated by measurements of the B(E2;21+ → 01+) values of 140Nd and 142Sm and comparison to the quasi-particle phonon model and shell-model calculations.

  11. Excitation and charge transfer in low-energy hydrogen-atom collisions with neutral atoms: Theory, comparisons, and application to Ca

    NASA Astrophysics Data System (ADS)

    Barklem, Paul S.

    2016-04-01

    A theoretical method is presented for the estimation of cross sections and rates for excitation and charge-transfer processes in low-energy hydrogen-atom collisions with neutral atoms, based on an asymptotic two-electron model of ionic-covalent interactions in the neutral atom-hydrogen-atom system. The calculation of potentials and nonadiabatic radial couplings using the method is demonstrated. The potentials are used together with the multichannel Landau-Zener model to calculate cross sections and rate coefficients. The main feature of the method is that it employs asymptotically exact atomic wave functions, which can be determined from known atomic parameters. The method is applied to Li+H , Na+H , and Mg+H collisions, and the results compare well with existing detailed full-quantum calculations. The method is applied to the astrophysically important problem of Ca+H collisions, and rate coefficients are calculated for temperatures in the range 1000-20 000 K.

  12. Enhanced production of low energy electrons by alpha particle impact

    PubMed Central

    Kim, Hong-Keun; Titze, Jasmin; Schöffler, Markus; Trinter, Florian; Waitz, Markus; Voigtsberger, Jörg; Sann, Hendrik; Meckel, Moritz; Stuck, Christian; Lenz, Ute; Odenweller, Matthias; Neumann, Nadine; Schössler, Sven; Ullmann-Pfleger, Klaus; Ulrich, Birte; Fraga, Rui Costa; Petridis, Nikos; Metz, Daniel; Jung, Annika; Grisenti, Robert; Czasch, Achim; Jagutzki, Ottmar; Schmidt, Lothar; Jahnke, Till; Schmidt-Böcking, Horst; Dörner, Reinhard

    2011-01-01

    Radiation damage to living tissue stems not only from primary ionizing particles but to a substantial fraction from the dissociative attachment of secondary electrons with energies below the ionization threshold. We show that the emission yield of those low energy electrons increases dramatically in ion–atom collisions depending on whether or not the target atoms are isolated or embedded in an environment. Only when the atom that has been ionized and excited by the primary particle impact is in immediate proximity of another atom is a fragmentation route known as interatomic Coulombic decay (ICD) enabled. This leads to the emission of a low energy electron. Over the past decade ICD was explored in several experiments following photoionization. Most recent results show its observation even in water clusters. Here we show the quantitative role of ICD for the production of low energy electrons by ion impact, thus approaching a scenario closer to that of radiation damage by alpha particles: We choose ion energies on the maximum of the Bragg peak where energy is most efficiently deposited in tissue. We compare the electron production after colliding He+ ions on isolated Ne atoms and on Ne dimers (Ne2). In the latter case the Ne atom impacted is surrounded by a most simple environment already opening ICD as a deexcitation channel. As a consequence, we find a dramatically enhanced low energy electron yield. The results suggest that ICD may have a significant influence on cell survival after exposure to ionizing radiation. PMID:21730184

  13. Enhanced production of low energy electrons by alpha particle impact.

    PubMed

    Kim, Hong-Keun; Titze, Jasmin; Schöffler, Markus; Trinter, Florian; Waitz, Markus; Voigtsberger, Jörg; Sann, Hendrik; Meckel, Moritz; Stuck, Christian; Lenz, Ute; Odenweller, Matthias; Neumann, Nadine; Schössler, Sven; Ullmann-Pfleger, Klaus; Ulrich, Birte; Fraga, Rui Costa; Petridis, Nikos; Metz, Daniel; Jung, Annika; Grisenti, Robert; Czasch, Achim; Jagutzki, Ottmar; Schmidt, Lothar; Jahnke, Till; Schmidt-Böcking, Horst; Dörner, Reinhard

    2011-07-19

    Radiation damage to living tissue stems not only from primary ionizing particles but to a substantial fraction from the dissociative attachment of secondary electrons with energies below the ionization threshold. We show that the emission yield of those low energy electrons increases dramatically in ion-atom collisions depending on whether or not the target atoms are isolated or embedded in an environment. Only when the atom that has been ionized and excited by the primary particle impact is in immediate proximity of another atom is a fragmentation route known as interatomic Coulombic decay (ICD) enabled. This leads to the emission of a low energy electron. Over the past decade ICD was explored in several experiments following photoionization. Most recent results show its observation even in water clusters. Here we show the quantitative role of ICD for the production of low energy electrons by ion impact, thus approaching a scenario closer to that of radiation damage by alpha particles: We choose ion energies on the maximum of the Bragg peak where energy is most efficiently deposited in tissue. We compare the electron production after colliding He(+) ions on isolated Ne atoms and on Ne dimers (Ne(2)). In the latter case the Ne atom impacted is surrounded by a most simple environment already opening ICD as a deexcitation channel. As a consequence, we find a dramatically enhanced low energy electron yield. The results suggest that ICD may have a significant influence on cell survival after exposure to ionizing radiation.

  14. Precise Coulomb excitation B(E2) measurements for first 2+states of projectile nuclei near the doubly magic nuclei 78Ni and 132Sn

    NASA Astrophysics Data System (ADS)

    Galindo-Uribarri, A.

    2012-09-01

    Coulomb excitation is a very precise tool to measure excitation probabilities and provide insight on the collectivity of nuclear excitations and in particular on nuclear shapes. In the last few years radioactive ion beam facilities such as HRIBF opened unique opportunities to explore the structure of nuclei in the regions near the doubly magic nuclei 78Ni (Z=28 and N=50) and 132Sn (Z=50 and N=82). For this purpose we have developed specialized methods and instrumentation to measure various observables. There is also the opportunity to perform precision experiments with stable beams using exactly the same state-of-the-art instrumentation and techniques as with their radioactive ion beam counterpart. I describe some of the recent efforts at HRIBF to do more precise measurements using particle-gamma techniques.

  15. 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.

  16. X-ray production with heavy post-accelerated radioactive-ion beams in the lead region of interest for Coulomb-excitation measurements

    NASA Astrophysics Data System (ADS)

    Bree, N.; Wrzosek-Lipska, K.; Butler, P. A.; Gaffney, L. P.; Grahn, T.; Huyse, M.; Kesteloot, N.; Pakarinen, J.; Petts, A.; Van Duppen, P.; Warr, N.

    2015-10-01

    Characteristic K X-rays have been observed in Coulomb-excitation experiments with heavy radioactive-ion beams in the lead region (Z = 82), produced at the REX-ISOLDE facility, and were used to identify the decay of strongly converted transitions as well as monopole 02+ → 01+ transitions. Different targets were used, and the X-rays were detected by the Miniball γ-ray spectrometer surrounding the target position. A stable mercury isotope, as well as neutron-deficient mercury, lead, polonium, and radon isotopes were studied, and a detailed description of the analysis using the radioactive 182,184,186,188Hg isotopes is presented. Apart from strongly converted transitions originating from the decay of excited states, the heavy-ion induced K-vacancy creation process has been identified as an extra source for K X-ray production. Isolating the atomic component of the observed K X-rays is essential for a correct analysis of the Coulomb-excitation experiment. Cross sections for the atomic reaction have been estimated and are compared to a theoretical approach.

  17. Phonon spectroscopy of the low-energy excitations in the solid solutions of yttrium–rare-earth metal–aluminum garnets

    SciTech Connect

    Khazanov, E. N. Taranov, A. V.; Shevchenko, E. V.; Charnaya, E. V.

    2015-07-15

    The transport characteristics of thermal-frequency phonons and the specific heat of a series of single crystals of yttrium–rare-earth metal–aluminum garnet solid solutions are studied at the helium temperatures. It is found that the existence of low-energy levels of various origins, which are responsible for an increase in the specific heat, retards phonon transport by one–three orders of magnitude. The temperature dependences of specific heat and the kinetic characteristics of phonons have a similar character.

  18. Phonon spectroscopy of the low-energy excitations in the solid solutions of yttrium-rare-earth metal-aluminum garnets

    NASA Astrophysics Data System (ADS)

    Khazanov, E. N.; Taranov, A. V.; Shevchenko, E. V.; Charnaya, E. V.

    2015-07-01

    The transport characteristics of thermal-frequency phonons and the specific heat of a series of single crystals of yttrium-rare-earth metal-aluminum garnet solid solutions are studied at the helium temperatures. It is found that the existence of low-energy levels of various origins, which are responsible for an increase in the specific heat, retards phonon transport by one-three orders of magnitude. The temperature dependences of specific heat and the kinetic characteristics of phonons have a similar character.

  19. Low energy excitations and Drude-Smith carrier dynamics in Sm0.5Sr0.5MnO3

    NASA Astrophysics Data System (ADS)

    Kumar, K. Santhosh; Das, Sarmistha; Prajapati, G. L.; Philip, Sharon S.; Rana, D. S.

    2017-05-01

    We have performed terahertz time-domain spectroscopic measurements on half-doped charge-ordered manganite Sm0.5Sr0.5MnO3 in the temperature range of 5-300 K to explore the possibilities of the charge density wave (CDW) ground state and understand the low energy charge carrier dynamics. While a resonance absorption peak at 0.275 meV suggests formation of a CDW condensate, the increase in background conductivity due to uncondensed carriers obey the Drude-Smith model of carrier dynamics. This study confirms that CDW is a generic feature of charge-ordered manganites.

  20. Spectrum of low-energy excitations in the vortex state: Comparison of the Doppler-shift method to a quasiclassical approach

    NASA Astrophysics Data System (ADS)

    Dahm, T.; Graser, S.; Iniotakis, C.; Schopohl, N.

    2002-10-01

    We present a detailed comparison of numerical solutions of the quasiclassical Eilenberger equations with several approximation schemes for the density of states of s- and d-wave superconductors in the vortex state, which have been used recently. In particular, we critically examine the use of the Doppler-shift method, which has been claimed to give good results for d-wave superconductors. Studying the single-vortex case we show that there are important contributions coming from core states, which extend far from the vortex cores into the nodal directions and are not present in the Doppler-shift method, but significantly affect the density of states at low energies. This leads to sizable corrections to Volovik's law, which we expect to be sensitive to impurity scattering. For a vortex lattice we also show comparisons with the method due to Brandt, Pesch, and Tewordt and an approximate analytical method, generalizing a method due to Pesch. These are high-field approximations strictly valid close to the upper critical field Bc2. At low energies the approximate analytical method turns out to give impressively good results over a broad field range and we recommend the use of this method for studies of the vortex state at not too low magnetic fields.

  1. 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.

  2. Effect of proton irradiation on the normal-state low-energy excitations of Ba (Fe1-xRhx) 2As2 superconductors

    NASA Astrophysics Data System (ADS)

    Moroni, M.; Gozzelino, L.; Ghigo, G.; Tanatar, M. A.; Prozorov, R.; Canfield, P. C.; Carretta, P.

    2017-09-01

    We present a 75As nuclear magnetic resonance (NMR) and resistivity study of the effect of 5.5 MeV proton irradiation on the optimal electron doped (x =0.068 ) and overdoped (x =0.107 ) Ba (Fe1-xRhx) 2As2 iron based superconductors. While the proton induced defects only mildly suppress the critical temperature and increase residual resistivity in both compositions, sizable broadening of the NMR spectra was observed in all the irradiated samples at low temperature. The effect is significantly stronger in the optimally doped sample where the Curie Weiss temperature dependence of the line width suggests the onset of ferromagnetic correlations coexisting with superconductivity at the nanoscale. 1 /T2 measurements revealed that the energy barrier characterizing the low energy spin fluctuations of these compounds is enhanced upon proton irradiation, suggesting that the defects are likely slowing down the fluctuations between (0 ,π ) and (π ,0) nematic ground states.

  3. Orientation and alignment of alkali p-states excited in low-energy collisions of alkali ions with noble gas atoms

    NASA Astrophysics Data System (ADS)

    Menner, B.; Ohlendorf, G.; Patorra, F.; Kempter, V.

    1990-12-01

    The orientation and alignment of Li(2 p) excited in 1 2.5 keV Li+ collisions with He and Ar, and of Na(3 p) excited in 2.5 keV Na+ collisions with He and Ne have been studied by the polarized photon-scattered particle coincidence technique. The covered range of scattering angles is between 1 and 18 degrees. The data are presented in terms of the alignment angle γ and the transferred angular momentum L ⊥. A qualitative analysis of the data is attempted on the basis of diabatic molecular orbital diagrams for the studied collisions systems.

  4. High-precision B(E2) measurements of semi-magic 58,60,62,64Ni by Coulomb excitation

    SciTech Connect

    Allmond, James M; Brown, Alex; Stuchbery, Andrew E; Galindo-Uribarri, Alfredo {nmn}; Padilla-Rodal, Elizabeth; Radford, David C; Batchelder, J. C.; Howard, Meredith E; Liang, J Felix; Manning, Brett M; Varner Jr, Robert L; Yu, Chang-Hong

    2014-01-01

    High-precision reduced electric-quadrupole transition probabilities B(E2) have been measured from single-step Coulomb excitation of semi-magic 58,60,62,64 Ni (Z = 28) beams at 1.8 MeV per nucleon on a natural carbon target. The energy loss of the nickel beams through the carbon target were directly measured with a zero-degree Bragg detector and the absolute B(E2) values were normalized by Rutherford scattering. The B(E2) values disagree with recent lifetime studies that employed the Doppler-shift attenuation method. The present high-precision B(E2) values reveal an asymmetry about 62 Ni, midshell between N = 28 and 40, with larger values towards 56 Ni (Z = N = 28). The experimental B(E2) values are compared with shell-model calculations in the full pf model space and the results indicate a soft 56 Ni core.

  5. The Raman scattering investigation of the features of low-energy electronic excitations of the terbium ion in the KTb(WO4)2 crystal

    NASA Astrophysics Data System (ADS)

    Peschanskii, A. V.; Fomin, V. I.; Yeremenko, A. V.

    2012-06-01

    Raman scattering of light in the KTb(WO4)2 single crystal is investigated in the frequency range of 3-950 cm-1 at 5 K. The ground multiplet 7F6 of Tb3+ ion is split by the crystal field with symmetry C2, and all the multiplet components are detected. It is found that the first excited electronic quasidoublet consists of two singlet levels of different symmetry and is separated from the ground quasidoublet by ~75 cm-1. Behavior of all the detected levels is investigated in external magnetic fields H ⊥ C2 and H || C2. Spectroscopic splitting factors are determined for the ground and excited levels of the Tb3+ ion in the KTb(WO4)2 crystal. Experimental data support the view that at low temperatures the case of Ising anisotropy is realized, and the crystal under study should be considered as a system of two-level magnetic ions.

  6. The Raman scattering investigation of the features of low-energy electronic excitations of the terbium ion in the KTb(WO4)2 crystal

    NASA Astrophysics Data System (ADS)

    Peschanskii, A. V.; Fomin, V. I.; Yeremenko, A. V.

    2012-06-01

    Raman scattering of light in the KTb(WO4)2 single crystal is investigated in the frequency range of 3-950 cm-1 at 5 K. The ground multiplet 7F6 of Tb3+ ion is split by the crystal field with symmetry C2, and all the multiplet components are detected. It is found that the first excited electronic quasidoublet consists of two singlet levels of different symmetry and is separated from the ground quasidoublet by ˜75 cm-1. Behavior of all the detected levels is investigated in external magnetic fields H ⊥ C2 and H || C2. Spectroscopic splitting factors are determined for the ground and excited levels of the Tb3+ ion in the KTb(WO4)2 crystal. Experimental data support the view that at low temperatures the case of Ising anisotropy is realized, and the crystal under study should be considered as a system of two-level magnetic ions.

  7. Effect of proton irradiation on the normal-state low-energy excitations of Ba(Fe1-xRhx)2As2 superconductors

    DOE PAGES

    Moroni, M.; Gozzelino, L.; Ghigo, G.; ...

    2017-09-19

    Here, we present a 75As nuclear magnetic resonance (NMR) and resistivity study of the effect of 5.5 MeV proton irradiation on the optimal electron doped (x = 0.068) and overdoped (x = 0.107) Ba(Fe1–xRhx)2As2 iron based superconductors. While the proton induced defects only mildly suppress the critical temperature and increase residual resistivity in both compositions, sizable broadening of the NMR spectra was observed in all the irradiated samples at low temperature. The effect is significantly stronger in the optimally doped sample where the Curie Weiss temperature dependence of the line width suggests the onset of ferromagnetic correlations coexisting with superconductivitymore » at the nanoscale. 1/T2 measurements revealed that the energy barrier characterizing the low energy spin fluctuations of these compounds is enhanced upon proton irradiation, suggesting that the defects are likely slowing down the fluctuations between (0,π) and (π,0) nematic ground states.« less

  8. Terahertz spectroscopy of low-energy excitations in charge-ordered La0.25Ca0.75MnO3

    NASA Astrophysics Data System (ADS)

    Zhang, T.; Zhukova, E.; Gorshunov, B.; Wu, D.; Prokhorov, A. S.; Torgashev, V. I.; Maksimov, E. G.; Dressel, M.

    2010-03-01

    The low-energy electrodynamic response of a series of La0.25Ca0.75MnO3 samples of different morphology is systematically studied in the frequency range from 4 to 700cm-1 (0.1-20 THz, quantum energies 0.4-90 meV) with particular attention focused at frequencies below 40cm-1 . In the antiferromagnetically ordered phase below 140 K, a resonancelike absorption band appears in the spectra around 20-40cm-1 that is assigned to acoustical phonons which acquire optical activity due to a fourfold superstructure appearance in the crystallographic a direction and correspondent Brillouin-zone folding. Nanosize effects in charge and magnetic subsystems are investigated by measuring the spectra of samples with grain diameters reduced from several micrometers down to 40 nm. A strong relaxation in the lowest-frequency spectra is observed above 100 K in all samples, indicating that the charge-order transition shows characteristics typical for order-disorder transitions.

  9. Decay of the excited compound system *56Ni formed through various channels using deformed Coulomb and deformed nuclear proximity potentials

    NASA Astrophysics Data System (ADS)

    Santhosh, K. P.; Subha, P. V.

    2017-06-01

    The total cross section, the intermediate mass fragment (IMF) production cross section, and the cross section for the formation of light particles (LPs) for the decay of compound system *56Ni formed through the entrance channel 32S+24Mg have been evaluated by taking the scattering potential as the sum of deformed Coulomb and deformed nuclear proximity potentials, for various Ec .m . values. The computed results have been compared with the available experimental data of total cross section corresponding to Ec .m .=60.5 and 51.6 MeV for the entrance channel 32S+24Mg , which were found to be in good agreement. The experimental values for the LP production cross section and IMF cross section for the channel 32S+24Mg were also found to agree with our calculations. Hence we have extended our studies and have thus computed the total cross section, IMF cross section, and LP cross section for the decay of *56Ni formed through the other three entrance channels 36Ar+20Ne,40Ca+16O , and 28Si+28Si with different Ec .m . values. Hence, we hope that our predictions on the evaluations of the IMF cross sections and the LP cross sections for the decay of *56Ni formed through these three channels can be used for further experimental studies.

  10. Search for intrinsic collective excitations in Sm152

    NASA Astrophysics Data System (ADS)

    Kulp, W. D.; Wood, J. L.; Garrett, P. E.; Wu, C. Y.; Cline, D.; Allmond, J. M.; Bandyopadhyay, D.; Dashdorj, D.; Choudry, S. N.; Hayes, A. B.; Hua, H.; Mynk, M. G.; McEllistrem, M. T.; McKay, C. J.; Orce, J. N.; Teng, R.; Yates, S. W.

    2008-06-01

    The 685 keV excitation energy of the first excited 0+ state in Sm152 makes it an attractive candidate to explore expected two-phonon excitations at low energy. Multiple-step Coulomb excitation and inelastic neutron scattering studies of Sm152 are used to probe the E2 collectivity of excited 0+ states in this “soft” nucleus and the results are compared with model predictions. No candidates for two-phonon Kπ=0+quadrupole vibrational states are found. A 2+,K=2 state with strong E2 decay to the first excited Kπ=0+ band and a probable 3+ band member are established.

  11. Electron-hydrogen atom-impact 1s{yields}2s and 1s{yields}2p excitation with screened Coulomb interaction between the n=2 and n=3 excitation thresholds

    SciTech Connect

    Zhang Songbin; Chen Xiangjun; Wang Jianguo; Janev, R. K.

    2011-03-15

    The effects of Coulomb interaction screening on electron-hydrogen atom 1S {yields} 2S and 1S {yields} 2p excitation scattering between the n = 2 and n = 3 excitation thresholds have been investigated by using the R-matrix method with pseudostates. The excitation collision strengths show dramatic changes when the interaction screening length D varies from {infinity} to 9 a.u., as a result of the convergence of S-type and some p- and D-type Feshbach resonances to the varying 3S or 3p thresholds, and due to the crossover of some other p-, D- and all F-type Feshbach resonances into shape-type resonances when they pass across the 3S or 3p threshold at certain critical values of D. The noncrossover of some p- and D-type Feshbach resonances into shape-type resonances at the 3S (or 3p for those of D-type) threshold is at variance with the behavior of these types of resonances at the 2S (2p for those of D-type) threshold, which results from the threefold splitting of the n = 3 hydrogenic level and, consequently, the more complex nature of the configuration mixing in the n = 3 threshold region. The evolution of the total 1S {yields} 2S, 1S {yields} 2p, and 2S {yields} 2p excitation collision strengths, when the screening strength varies, is presented and discussed.

  12. Low-energy electron scattering on deuterated nanocrystalline diamond films-a model system for understanding the interplay between density-of-states, excitation mechanisms and surface versus lattice contributions.

    PubMed

    Amiaud, L; Martin, I; Milosavljević, A R; Michaelson, Sh; Hoffman, A; Azria, R; Lafosse, A

    2011-06-28

    Electron energy loss spectrum, elastic reflectivity and selected vibrational excitation functions were measured by High Resolution Electron Energy Loss Spectroscopy (HREELS) for deuterated nanocrystalline dc GD CVD diamond films. The electron elastic reflectivity is strongly enhanced at about 13 eV, as a consequence of the second absolute band gap of diamond preserved up to the surface for D-nano-crystallites. The pure bending modes δ(CD(x)) at 88 meV and 107 meV are dominantly excited through the impact mechanism and their vibration excitation functions mimic the electron elastic reflectivity curve. Pure diamond phonon mode ν(CC) can be probed through the resolved fundamental loss located at 152 meV and through the multiple loss located at 300 meV. In addition to the well-known 8 eV resonance, two supplementary resonances located at 4.5 eV and 11.5 eV were identified and clearly resolved for the first time. A comprehensive set of data is now available on low-energy electron scattering at hydride terminated polycrystalline diamond films grown either by HF (microcrystalline) or dc GD (nanocrystalline) chemical vapour deposition. The careful comparison of the vibrational excitation functions for hydrogen/deuterium termination stretching modes ν(sp(3)-CH(x)) and ν(sp(3)-CD(x)), for hydrogen termination bending modes δ(CH(x)) mixed with diamond lattice modes ν(CC), for deuterium termination bending modes δ(CD(x)), and for multiple loss 2ν(CC) demonstrates the close interplay between three characteristics: (i) the density-of-states of the substrate, (ii) the vibrational excitation mechanisms (dipolar and/or impact scattering including resonant scattering) and (iii) the surface versus lattice character of the excited vibrational modes. This work shows clearly that excitation function measurement provides a powerful and sensitive tool to clarify loss attributions, involved excitation mechanisms, and surface versus lattice characters of the excited vibrational

  13. Field-Angle-Dependent Low-Energy Excitations around a Vortex in the Superconducting Topological Insulator CuxBi2Se3

    NASA Astrophysics Data System (ADS)

    Nagai, Yuki

    2014-06-01

    We study the quasiparticle excitations around a single vortex in the superconducting topological insulator CuxBi2Se3, focusing on a superconducting state with point nodes. Inspired by the recent Knight shift measurements, we propose two ways to detect the positions of point nodes, using an explicit formula of the density of states with Kramer-Pesch approximation in the quasiclassical treatment. The zero-energy local density of states around a vortex parallel to the c-axis has a twofold shape and splits along the nodal direction with increasing energy; these behaviors can be detected by the scanning tunneling microscopy. An angular dependence of the density of states with a rotating magnetic field on the a-b plane has deep minima when the magnetic field is parallel to the directions of point nodes, which can be detected by angular-resolved heat capacity and thermal conductivity measurements. All the theoretical predictions are detectable via standard experimental techniques in magnetic fields.

  14. 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.

  15. 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.

  16. 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.

  17. Coulomb-nuclear interference with {sup 6}Li: Isospin character of the 2{sub 1}{sup +} excitation in {sup 70,72,74}Ge

    SciTech Connect

    Barbosa, M.D.L.; Borello-Lewin, T.; Horodynski-Matsushigue, L.B.; Duarte, J.L.M.; Rodrigues, C.L.; Rodrigues, M.R.D.; Ukita, G.M.

    2005-02-01

    Ratios of B(E2) to B(IS2), that is, of the reduced quadrupole transition probabilities related, respectively, to charge and mass were extracted through Coulomb-nuclear interference (CNI) for the excitation of the 2{sub 1}{sup +} states in {sup 70,72,74}Ge, with a relative accuracy of less than 4%. For this purpose, the CNI angular distributions associated with the inelastic scattering of 28-MeV incident {sup 6}Li ions accelerated by the Sao Paulo Pelletron, and momentum analyzed by the Enge magnetic spectrograph were interpreted within the DWBA-DOMP approach (distorted wave approximation for the scattering process and deformed optical model for the structure representation) with global {sup 6}Li optical parameters. The present CNI results demonstrate an abrupt change in the B(E2)/B(IS2) ratio for {sup 74}Ge: although for {sup 70,72}Ge, values of the order of 1.0 or slightly higher were obtained, this ratio is 0.66 (7) for {sup 74}Ge. The heavier Ge isotope is thus one of the few nuclei that, so far, have been shown to present clear mixed symmetry components in their ground-state band.

  18. Magnetic moment and lifetime measurements of Coulomb-excited states in Cd106

    SciTech Connect

    Benczer-Koller, N.; Kumbartzki, G. J.; Speidel, K. -H.; Torres, D. A.; Robinson, S. J. Q.; Sharon, Y. Y.; Allmond, J. M.; Fallon, P.; Abramovic, I.; Bernstein, L. A.; Bevins, J. E.; Crawford, H. L.; Guevara, Z. E.; Hurst, A. M.; Kirsch, L.; Laplace, T. A.; Lo, A.; Matthews, E. F.; Mayers, I.; Phair, L. W.; Ramirez, F.; Wiens, A.

    2016-09-06

    The Cd isotopes are well studied, but experimental data for the rare isotopes are sparse. At energies above the Coulomb barrier, higher states become accessible. Remeasure and supplement existing lifetimes and magnetic moments of low-lying states in 106Cd. Methods: In an inverse kinematics reaction, a 106Cd beam impinging on a 12C target was used to Coulomb excite the projectiles. The high recoil velocities provide a unique opportunity to measure g factors with the transient-field technique and to determine lifetimes from lineshapes by using the Doppler-shift-attenuation method. Large-scale shell-model calculations were carried out for 106Cd. As a result, the g factors of the 2+1 and 4+1 states in 106Cd were measured to be g(2+1) = +0.398(22) and g(4+1) = +0.23(5). A lineshape analysis yielded lifetimes in disagreement with published values. The new results are τ(106Cd; 2+1) = 7.0(3) ps and τ(106Cd; 4+1) = 2.5(2) ps. The mean life τ(106Cd; 2+2) = 0.28(2) ps was determined from the fully-Doppler-shifted γ line. Mean lives of τ(106Cd; 4+3) = 1.1(1) ps and τ(106Cd; 31) = 0.16(1) ps were determined for the first time. In conclusion, the newly measured g(4+1) of 106Cd is found to be only 59% of the g(2+1). This difference cannot be explained by either shell-model or collective-model calculations.

  19. Magnetic moment and lifetime measurements of Coulomb-excited states in Cd106

    SciTech Connect

    Benczer-Koller, N.; Kumbartzki, G. J.; Speidel, K. -H.; Torres, D. A.; Robinson, S. J. Q.; Sharon, Y. Y.; Allmond, J. M.; Fallon, P.; Abramovic, I.; Bernstein, L. A.; Bevins, J. E.; Crawford, H. L.; Guevara, Z. E.; Hurst, A. M.; Kirsch, L.; Laplace, T. A.; Lo, A.; Matthews, E. F.; Mayers, I.; Phair, L. W.; Ramirez, F.; Wiens, A.

    2016-09-06

    The Cd isotopes are well studied, but experimental data for the rare isotopes are sparse. At energies above the Coulomb barrier, higher states become accessible. Remeasure and supplement existing lifetimes and magnetic moments of low-lying states in 106Cd. Methods: In an inverse kinematics reaction, a 106Cd beam impinging on a 12C target was used to Coulomb excite the projectiles. The high recoil velocities provide a unique opportunity to measure g factors with the transient-field technique and to determine lifetimes from lineshapes by using the Doppler-shift-attenuation method. Large-scale shell-model calculations were carried out for 106Cd. As a result, the g factors of the 2+1 and 4+1 states in 106Cd were measured to be g(2+1) = +0.398(22) and g(4+1) = +0.23(5). A lineshape analysis yielded lifetimes in disagreement with published values. The new results are τ(106Cd; 2+1) = 7.0(3) ps and τ(106Cd; 4+1) = 2.5(2) ps. The mean life τ(106Cd; 2+2) = 0.28(2) ps was determined from the fully-Doppler-shifted γ line. Mean lives of τ(106Cd; 4+3) = 1.1(1) ps and τ(106Cd; 31) = 0.16(1) ps were determined for the first time. In conclusion, the newly measured g(4+1) of 106Cd is found to be only 59% of the g(2+1). This difference cannot be explained by either shell-model or collective-model calculations.

  20. 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.

  1. Coulomb Damping

    ERIC Educational Resources Information Center

    Fay, Temple H.

    2012-01-01

    Viscous damping is commonly discussed in beginning differential equations and physics texts but dry friction or Coulomb friction is not despite dry friction being encountered in many physical applications. One reason for avoiding this topic is that the equations involve a jump discontinuity in the damping term. In this article, we adopt an energy…

  2. Coulomb Damping

    ERIC Educational Resources Information Center

    Fay, Temple H.

    2012-01-01

    Viscous damping is commonly discussed in beginning differential equations and physics texts but dry friction or Coulomb friction is not despite dry friction being encountered in many physical applications. One reason for avoiding this topic is that the equations involve a jump discontinuity in the damping term. In this article, we adopt an energy…

  3. 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.

  4. Resonant Auger decay driving intermolecular Coulombic decay in molecular dimers.

    PubMed

    Trinter, F; Schöffler, M S; Kim, H-K; Sturm, F P; Cole, K; Neumann, N; Vredenborg, A; Williams, J; Bocharova, I; Guillemin, R; Simon, M; Belkacem, A; Landers, A L; Weber, Th; Schmidt-Böcking, H; Dörner, R; Jahnke, T

    2014-01-30

    In 1997, it was predicted that an electronically excited atom or molecule placed in a loosely bound chemical system (such as a hydrogen-bonded or van-der-Waals-bonded cluster) could efficiently decay by transferring its excess energy to a neighbouring species that would then emit a low-energy electron. This intermolecular Coulombic decay (ICD) process has since been shown to be a common phenomenon, raising questions about its role in DNA damage induced by ionizing radiation, in which low-energy electrons are known to play an important part. It was recently suggested that ICD can be triggered efficiently and site-selectively by resonantly core-exciting a target atom, which then transforms through Auger decay into an ionic species with sufficiently high excitation energy to permit ICD to occur. Here we show experimentally that resonant Auger decay can indeed trigger ICD in dimers of both molecular nitrogen and carbon monoxide. By using ion and electron momentum spectroscopy to measure simultaneously the charged species created in the resonant-Auger-driven ICD cascade, we find that ICD occurs in less time than the 20 femtoseconds it would take for individual molecules to undergo dissociation. Our experimental confirmation of this process and its efficiency may trigger renewed efforts to develop resonant X-ray excitation schemes for more localized and targeted cancer radiation therapy.

  5. Coulomb blockade and Coulomb staircase behavior observed at room temperature

    NASA Astrophysics Data System (ADS)

    Uky Vivitasari, Pipit; Azuma, Yasuo; Sakamoto, Masanori; Teranishi, Toshiharu; Majima, Yutaka

    2017-02-01

    A single-electron transistor (SET) consists of source, drain, Coulomb island, and gate to modulate the number of electrons and control the current. For practical applications, it is important to operate a SET at room temperature. One proposal towards the ability to operate at room temperature is to decrease Coulomb island size down to a few nanometres. We investigate a SET using Sn-porphyrin (Sn-por) protected gold nanoparticles (AuNPs) with 1.4 nm in core diameter as a Coulomb island. The fabrication method of nanogap electrodes uses the combination of a top-down technique by electron beam lithography (EBL) and a bottom-up process through electroless gold plating (ELGP) as our group have described before. The electrical measurement was conducted at room temperature (300 K). From current-voltage (I d-V d) characteristics, we obtained clear Coulomb blockade phenomena together with a Coulomb staircase due to a Sn-por protected gold NP as a Coulomb island. Experimental results of I d-V d characteristics agree with a theoretical curve based on using the orthodox model. Clear dI d/dV d peaks are observed in the Coulomb staircase at 9 K which suggest the electron transports through excited energy levels of Au NPs. These results are a big step for obtaining SETs that can operate at room temperature.

  6. Coulomb interaction in multiple scattering theory

    NASA Astrophysics Data System (ADS)

    Ray, L.; Hoffmann, G. W.; Thaler, R. M.

    1980-10-01

    The treatment of the Coulomb interaction in the multiple scattering theories of Kerman-McManus-Thaler and Watson is examined in detail. By neglecting virtual Coulomb excitations, the lowest order Coulomb term in the Watson optical potential is shown to be a convolution of the point Coulomb interaction with the distributed nuclear charge, while the equivalent Kerman-McManus-Thaler Coulomb potential is obtained from an averaged, single-particle Coulombic T matrix. The Kerman-McManus-Thaler Coulomb potential is expressed as the Watson Coulomb term plus additional Coulomb-nuclear and Coulomb-Coulomb cross terms, and the omission of the extra terms in usual Kerman-McManus-Thaler applications leads to negative infinite total reaction cross section predictions and incorrect pure Coulomb scattering limits. Approximations are presented which eliminate these anomalies. Using the two-potential formula, the full projectile-nucleus T matrix is separated into two terms, one resulting from the distributed nuclear charge and the other being a Coulomb distorted nuclear T matrix. It is shown that the error resulting from the omission of the Kerman-McManus-Thaler Coulomb terms is effectively removed when the pure Coulomb T matrix in Kerman-McManus-Thaler is replaced by the analogous quantity in the Watson approach. Using the various approximations, theoretical angular distributions are obtained for 800 MeV p+208Pb elastic scattering and compared with experimental data. NUCLEAR REACTIONS 208Pb(p, p), E=0.8 GeV, Kerman, McManus, and Thaler, and Watson multiple scattering theories, Coulomb correction terms, high momentum transfer.

  7. Absence of Magnetic Dipolar Phase Transition and Evolution of Low-Energy Excitations in PrNb2Al20 with Crystal Electric Field Γ3 Ground State: Evidence from 93Nb-NQR Studies

    NASA Astrophysics Data System (ADS)

    Kubo, Tetsuro; Kotegawa, Hisashi; Tou, Hideki; Higashinaka, Ryuji; Nakama, Akihiro; Aoki, Yuji; Sato, Hideyuki

    2015-07-01

    We report measurements of bulk magnetic susceptibility and 93Nb nuclear quadrupole resonance (NQR) in the Pr-based caged compound PrNb2Al20. By analyzing the magnetic susceptibility and magnetization, the crystal electric field (CEF) level scheme of PrNb2Al20 is determined to be Γ3(0 K)-Γ4(21.32 K)-Γ5(43.98 K)-Γ1(51.16 K) within the framework of the localized 4f electron picture. The 93Nb-NQR spectra exhibit neither spectral broadening nor spectral shift upon cooling down to 75 mK. The 93Nb-NQR spin-lattice relaxation rate 1/T1 at 5 K depends on the frequency and remains almost constant below 5 K. The frequency dependence of 1/T1 is attributed to the magnetic fluctuation due to the hyperfine-enhanced 141Pr nuclear moment inherent in the nonmagnetic Γ3 CEF ground state. The present NQR results provide evidence that no symmetry-breaking magnetic dipole order occurs down to 75 mK. Also, considering an invariant form of the quadrupole and octupole couplings between a 93Nb nucleus and Pr 4f electrons, Pr 4f quadrupoles and an octupole can couple with a 93Nb nuclear quadrupole moment and nuclear spin, respectively. Together with the results of bulk measurements, the present NQR results suggest that the possibility of a static quadrupole or octupole ordering can be excluded down to 100 mK. At low temperatures below 500 mK, however, the nuclear spin-echo decay rate gradually increases and the decay curve changes from Gaussian decay to Lorentzian decay, suggesting the evolution of a low-energy excitation.

  8. 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.

  9. Determining the 7Li(n,γ) cross section via Coulomb dissociation of 8Li

    NASA Astrophysics Data System (ADS)

    Izsák, R.; Horváth, Á.; Kiss, Á.; Seres, Z.; Galonsky, A.; Bertulani, C. A.; Fülöp, Zs.; Baumann, T.; Bazin, D.; Ieki, K.; Bordeanu, C.; Carlin, N.; Csanád, M.; Deák, F.; DeYoung, P.; Frank, N.; Fukuchi, T.; Gade, A.; Galaviz, D.; Hoffman, C. R.; Peters, W. A.; Schelin, H.; Thoennessen, M.; Veres, G. I.

    2013-12-01

    The applicability of Coulomb dissociation reactions to determine the cross section for the inverse neutron capture reaction was explored using the reaction 8Li(γ,n)7Li. A 69.5 MeV/nucleon 8Li beam was incident on a Pb target, and the outgoing neutron and 7Li nucleus were measured in coincidence. The deduced (n,γ) excitation function is consistent with data for the direct capture reaction 7Li(n,γ)8Li and with low-energy effective field theory calculations.

  10. Antineutron and antiproton nuclear interactions at very low energies

    NASA Astrophysics Data System (ADS)

    Friedman, E.

    2014-05-01

    Experimental annihilation cross sections of antineutrons and antiprotons at very low energies are compared. Features of Coulomb focusing are observed for pbar annihilation on protons. Direct comparisons for heavier targets are not straightforward due to lack of overlap between targets and energies of experimental results for pbar and nbar. Nevertheless, the annihilation cross sections for nbar on nuclei cannot be described by an optical potential that fits well all the available data on pbar interactions with nuclei. Comparisons made with the help of this potential reveal in the nbar data features similar to Coulomb focusing. Direct comparisons between nbar and pbar annihilations at very low energies would be possible when pbar cross sections are measured on the same targets and at the same energies as the available cross sections for nbar. Such measurements may be possible in the foreseeable future.

  11. Uncertainties of α-particle optical potential assessment around and below the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Avrigeanu, V.; Avrigeanu, M.; Mǎnǎilescu, C.

    2017-06-01

    A competition of the low-energy Coulomb excitation (CE) with the compound nucleus (CN) formation in α-induced reactions below the Coulomb barrier has recently been assumed in order to make possible the description of the latter as well as the α-particle emission by the same optical model (OM) potential. However, we show in the present work that the corresponding partial waves and integration radii provide evidence for the distinct account of the CE cross section and OM total-reaction cross section σR. Thus the largest contribution to CE cross section comes by far from partial waves larger than the ones contributing to the σR values. Finally, effects of statistical model parameters are comparatively discussed.

  12. Low-energy physics of high-temperature superconductors

    SciTech Connect

    Emery, V.J. . Physics Dept.); Kivelson, S.A. . Dept. of Physics)

    1992-01-01

    It is argued that the low-energy properties of high temperature superconductors are dominated by the interaction between the mobile holes and a particular class of collective modes, corresponding to local large-amplitude low-energy fluctuations in the hole density. The latter are a consequence of the competition between the effects of long-range Coulomb interactions and the tendency of a low concentration of holes in an antiferromagnet to phase separate. The low-energy behavior of the system is governed by the same fixed point as the two-channel Kondo problem, which accounts for the universality'' of the properties of the cuprate superconductors. Predictions of the optical properties and the spin dynamics are compared with experiment. The pairing resonance of the two Kondo problem gives a mechanism of high temperature superconductivity with an unconventional symmetry of the order parameter.

  13. Low-energy physics of high-temperature superconductors

    SciTech Connect

    Emery, V.J.; Kivelson, S.A.

    1992-09-01

    It is argued that the low-energy properties of high temperature superconductors are dominated by the interaction between the mobile holes and a particular class of collective modes, corresponding to local large-amplitude low-energy fluctuations in the hole density. The latter are a consequence of the competition between the effects of long-range Coulomb interactions and the tendency of a low concentration of holes in an antiferromagnet to phase separate. The low-energy behavior of the system is governed by the same fixed point as the two-channel Kondo problem, which accounts for the ``universality`` of the properties of the cuprate superconductors. Predictions of the optical properties and the spin dynamics are compared with experiment. The pairing resonance of the two Kondo problem gives a mechanism of high temperature superconductivity with an unconventional symmetry of the order parameter.

  14. 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.

  15. Attosecond Streaking in the Low-Energy Region

    NASA Astrophysics Data System (ADS)

    Geng, Ji-Wei; Peng, Liang-You; Xu, Ming-Hui; Gong, Qihuang

    2014-04-01

    The low-energy photonelectron (PEs) ionized by a single attosecond pulse can be controlled by a moderately intense infrared field (IR). The electric field of the IR pulse can drive part of the PEs back to the parent ion and induce multiple rescattering of the electrons. Interesting interference patterns are observed in the photoelectron momentum distributions, which are formed by the rescattered electrons and the directly ionized PEs. By analyzing the interference patterns with a simple semiclassical model, which considers the particular PE trajectories incorporating the rescattering with the core, we demonstrate that the low-energy attosecond streaking offers a promising method of holographic imaging of atomic and molecular potential. In addition, we show that neither strong field approximation (SFA) or Coulomb-Volkov approximation (CVA) is able to reproduce these interesting structures at the low energy region.

  16. Search for intrinsic collective excitations in {sup 152}Sm

    SciTech Connect

    Kulp, W. D.; Wood, J. L.; Allmond, J. M.; Garrett, P. E.; Wu, C. Y.; Cline, D.; Hayes, A. B.; Hua, H.; Teng, R.; Bandyopadhyay, D.; Choudry, S. N.; McEllistrem, M. T.; McKay, C. J.; Orce, J. N.; Dashdorj, D.; Mynk, M. G.; Yates, S. W.

    2008-06-15

    The 685 keV excitation energy of the first excited 0{sup +} state in {sup 152}Sm makes it an attractive candidate to explore expected two-phonon excitations at low energy. Multiple-step Coulomb excitation and inelastic neutron scattering studies of {sup 152}Sm are used to probe the E2 collectivity of excited 0{sup +} states in this 'soft' nucleus and the results are compared with model predictions. No candidates for two-phonon K{sup {pi}}=0{sup +}quadrupole vibrational states are found. A 2{sup +},K=2 state with strong E2 decay to the first excited K{sup {pi}}=0{sup +} band and a probable 3{sup +} band member are established.

  17. 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.

  18. New approach to folding with the Coulomb wave function

    SciTech Connect

    Blokhintsev, L. D.; Savin, D. A.; Kadyrov, A. S.; Mukhamedzhanov, A. M.

    2015-05-15

    Due to the long-range character of the Coulomb interaction theoretical description of low-energy nuclear reactions with charged particles still remains a formidable task. One way of dealing with the problem in an integral-equation approach is to employ a screened Coulomb potential. A general approach without screening requires folding of kernels of the integral equations with the Coulomb wave. A new method of folding a function with the Coulomb partial waves is presented. The partial-wave Coulomb function both in the configuration and momentum representations is written in the form of separable series. Each term of the series is represented as a product of a factor depending only on the Coulomb parameter and a function depending on the spatial variable in the configuration space and the momentum variable if the momentum representation is used. Using a trial function, the method is demonstrated to be efficient and reliable.

  19. Widespread seismicity excitation throughout central Japan following the 2011 M=9.0 Tohoku earthquake and its interpretation by Coulomb stress transfer

    USGS Publications Warehouse

    Toda, S.; Stein, R.S.; Lin, J.

    2011-01-01

    We report on a broad and unprecedented increase in seismicity rate following the M=9.0 Tohoku mainshock for M ≥ 2 earthquakes over inland Japan, parts of the Japan Sea and Izu islands, at distances of up to 425 km from the locus of high (≥15 m) seismic slip on the megathrust. Such an increase was not seen for the 2004 M=9.1 Sumatra or 2010 M=8.8 Chile earthquakes, but they lacked the seismic networks necessary to detect such small events. Here we explore the possibility that the rate changes are the product of static Coulomb stress transfer to small faults. We use the nodal planes of M ≥ 3.5 earthquakes as proxies for such small active faults, and find that of fifteen regions averaging ~80 by 80 km in size, 11 show a positive association between calculated stress changes and the observed seismicity rate change, 3 show a negative correlation, and for one the changes are too small to assess. This work demonstrates that seismicity can turn on in the nominal stress shadow of a mainshock as long as small geometrically diverse active faults exist there, which is likely quite common.

  20. Widespread seismicity excitation throughout central Japan following the 2011 M=9.0 Tohoku earthquake and its interpretation by Coulomb stress transfer

    NASA Astrophysics Data System (ADS)

    Toda, Shinji; Stein, Ross S.; Lin, Jian

    2011-08-01

    We report on a broad and unprecedented increase in seismicity rate following the M=9.0 Tohoku mainshock for M ≥ 2 earthquakes over inland Japan, parts of the Japan Sea and Izu islands, at distances of up to 425 km from the locus of high (≥15 m) seismic slip on the megathrust. Such an increase was not seen for the 2004 M=9.1 Sumatra or 2010 M=8.8 Chile earthquakes, but they lacked the seismic networks necessary to detect such small events. Here we explore the possibility that the rate changes are the product of static Coulomb stress transfer to small faults. We use the nodal planes of M ≥ 3.5 earthquakes as proxies for such small active faults, and find that of fifteen regions averaging ˜80 by 80 km in size, 11 show a positive association between calculated stress changes and the observed seismicity rate change, 3 show a negative correlation, and for one the changes are too small to assess. This work demonstrates that seismicity can turn on in the nominal stress shadow of a mainshock as long as small geometrically diverse active faults exist there, which is likely quite common.

  1. 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…

  2. 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…

  3. Gamma-Ray Angular Distribution in Coulomb Excitation Experiments at Intermediate Energies as a Signature of Electromagnetic and Nuclear Forces in Peripheral Collisions

    NASA Astrophysics Data System (ADS)

    Bednarczyk, P.; Grębosz, J.; Maj, A.; Kmiecik, M.; Męczyński, W.; Styczeń, J.; Wollersheim, H. J.; Gerl, J.; Górska, M.; Reiter, P.; Bracco, A.; Camera, F.

    2009-03-01

    In Coulex experiments at intermediate beam energies besides electromagnetic forces the nuclear interaction may occur. These two excitation mechanisms result in emission of gamma -rays with a characteristic angular distribution W(theta ). Measurement of W(theta ) was performed at the RISING fast beam set-up to probe the electromagnetic-nuclear interface. Unexpectedly large hadronic-like contribution was observed when high Z projectiles were used.

  4. Low-energy fusion caused by an interference

    NASA Astrophysics Data System (ADS)

    Ivlev, Boris

    2013-04-01

    Fusion of two deuterons of room temperature energy is discussed. The nuclei are in vacuum with no connection to any external source(electric or magnetic field, illumination, surrounding matter, traps, etc.) which may accelerate them. The energy of two nuclei is conserved and remains small during the motion through the Coulomb barrier. The penetration through this barrier, which is the main obstacle for low-energy fusion, strongly depends on a form of the incident flux on the Coulomb center at large distances from it. In contrast to the usual scattering, the incident wave is not a single plane wave but the certain superposition of plane waves of the same energy and various directions, for example, a conergent conical wave. The wave function close to the Coulomb center is determined by cusp caustic which is probed by de Broglie waves. The particle flux gets away from the cusp and moves to the Coulomb center providing a not small probability of fusion (cusp driven tunneling). Getting away from a caustic cusp also occurs in optics and acoustics. arXiv:1211.1243

  5. Low-energy electron rescattering in laser-induced ionization

    NASA Astrophysics Data System (ADS)

    Becker, W.; Goreslavski, S. P.; Milošević, D. B.; Paulus, G. G.

    2014-10-01

    The low-energy structure (LES) in the energy spectrum of above-threshold ionization of rare-gas atoms is reinvestigated from three different points of view. First, the role of forward rescattering in the completely classical simple-man model (SMM) is considered. Then, the corresponding classical electronic trajectories are retrieved in the quantum-mechanical ionization amplitude derived in the strong-field approximation augmented to allow for rescattering. Third, classical trajectories in the presence of both the laser field and the Coulomb field are scrutinized in order to see how they are related to the LES. It is concluded that the LES is already rooted in the SMM. The Coulomb field enhances the structure so that it can successfully compete with other contributions and become visible in the total spectrum.

  6. Low-energy antinucleon-nucleus interaction revisited

    NASA Astrophysics Data System (ADS)

    Friedman, E.

    2015-08-01

    Annihilation cross sections of antiprotons and antineutrons on the proton between 50 and 400 MeV/c show Coulomb focusing below 200 MeV/c and almost no charge-dependence above 200 MeV/c. Similar comparisons for heavier targets are not possible for lack of overlap between nuclear targets studied with and beams. Interpolating between -nucleus annihilation cross sections with the help of an optical potential to compare with -nucleus annihilation cross sections reveal unexpected features of Coulomb interactions in the latter. Direct comparisons between -nucleus and -nucleus annihilations at very low energies could be possible if cross sections are measured on the same targets and at the same energies as the available cross sections for . Such measurements may be feasible in the foreseeable future.

  7. Coulomb dissociation of N,2120

    NASA Astrophysics Data System (ADS)

    Röder, Marko; Adachi, Tatsuya; Aksyutina, Yulia; Alcantara, Juan; Altstadt, Sebastian; Alvarez-Pol, Hector; Ashwood, Nicholas; Atar, Leyla; Aumann, Thomas; Avdeichikov, Vladimir; Barr, M.; Beceiro, Saul; Bemmerer, Daniel; Benlliure, Jose; Bertulani, Carlos; Boretzky, Konstanze; Borge, Maria J. G.; Burgunder, G.; Caamaño, Manuel; Caesar, Christoph; Casarejos, Enrique; Catford, Wilton; Cederkäll, Joakim; Chakraborty, S.; Chartier, Marielle; Chulkov, Leonid; Cortina-Gil, Dolores; Crespo, Raquel; Datta Pramanik, Ushasi; Diaz-Fernandez, Paloma; Dillmann, Iris; Elekes, Zoltan; Enders, Joachim; Ershova, Olga; Estrade, A.; Farinon, F.; Fraile, Luis M.; Freer, Martin; Freudenberger, M.; Fynbo, Hans; Galaviz, Daniel; Geissel, Hans; Gernhäuser, Roman; Göbel, Kathrin; Golubev, Pavel; Gonzalez Diaz, D.; Hagdahl, Julius; Heftrich, Tanja; Heil, Michael; Heine, Marcel; Heinz, Andreas; Henriques, Ana; Holl, Matthias; Ickert, G.; Ignatov, Alexander; Jakobsson, Bo; Johansson, Hâkan; Jonson, Björn; Kalantar-Nayestanaki, Nasser; Kanungo, Rituparna; Kelic-Heil, Aleksandra; Knöbel, Ronja; Kröll, Thorsten; Krücken, Reiner; Kurcewicz, J.; Kurz, Nikolaus; Labiche, Marc; Langer, Christoph; Le Bleis, Tudi; Lemmon, Roy; Lepyoshkina, Olga; Lindberg, Simon; Machado, Jorge; Marganiec, Justyna; Mostazo Caro, Magdalena; Movsesyan, Alina; Najafi, Mohammad Ali; Nilsson, Thomas; Nociforo, Chiara; Panin, Valerii; Paschalis, Stefanos; Perea, Angel; Petri, Marina; Pietri, S.; Plag, Ralf; Prochazka, A.; Rahaman, Md. Anisur; Rastrepina, Ganna; Reifarth, Rene; Ribeiro, Guillermo; Ricciardi, M. Valentina; Rigollet, Catherine; Riisager, Karsten; Rossi, Dominic; Sanchez del Rio Saez, Jose; Savran, Deniz; Scheit, Heiko; Simon, Haik; Sorlin, Olivier; Stoica, V.; Streicher, Branislav; Taylor, Jon; Tengblad, Olof; Terashima, Satoru; Thies, Ronja; Togano, Yasuhiro; Uberseder, Ethan; Van de Walle, J.; Velho, Paulo; Volkov, Vasily; Wagner, Andreas; Wamers, Felix; Weick, Helmut; Weigand, Mario; Wheldon, Carl; Wilson, G.; Wimmer, Christine; Winfield, J. S.; Woods, Philip; Yakorev, Dmitry; Zhukov, Mikhail; Zilges, Andreas; Zuber, Kai; R3B Collaboration

    2016-06-01

    Neutron-rich light nuclei and their reactions play an important role in the creation of chemical elements. Here, data from a Coulomb dissociation experiment on N,2120 are reported. Relativistic N,2120 ions impinged on a lead target and the Coulomb dissociation cross section was determined in a kinematically complete experiment. Using the detailed balance theorem, the 19N (n ,γ )20N and 20N (n ,γ ) 21N excitation functions and thermonuclear reaction rates have been determined. The 19 (n ,γ )20N rate is up to a factor of 5 higher at T <1 GK with respect to previous theoretical calculations, leading to a 10% decrease in the predicted fluorine abundance.

  8. 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

  9. 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.

  10. 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.

  11. Steering continuum electron dynamics by low-energy attosecond streaking

    NASA Astrophysics Data System (ADS)

    Geng, Ji-Wei; Xiong, Wei-Hao; Xiao, Xiang-Ru; Gong, Qihuang; Peng, Liang-You

    2016-08-01

    A semiclassical model is developed to understand the electronic dynamics in the low-energy attosecond streaking. Under a relatively strong infrared (IR) pulse, the low-energy part of photoelectrons initialized by a single attosecond pulse (SAP) can either rescatter with the ionic core and induce interferences structures in the momentum spectra of the ionized electrons or be recaptured into the Rydberg states. The Coulomb potential plays essential roles in both the electron rescattering and recapturing processes. We find that by changing the time delay between the SAP and the IR pulse, the photoelectrons yield or the population of the Rydberg states can be effectively controlled. The present study demonstrates a fascinating way to steer the electron motion in the continuum.

  12. Low-energy electron scattering from cyanamide

    NASA Astrophysics Data System (ADS)

    Wang, Kedong; Guo, Shuangcheng; Meng, Ju; Huang, Xiaotian; Wang, Yongfeng

    2016-09-01

    The low-energy electron collisions with cyanamide molecule are investigated by using the UK molecular R -matrix codes for electron energies ranging from 0.01 eV to 10 eV. Three models including static-exchange, static-exchange plus polarization, and close-coupling (CC) approximations are employed to reveal the dynamic interaction. Elastic (integrated and differential), momentum-transfer, and excitation cross sections from the ground state to the three low-lying electron excited states have been presented. Two shape resonances, two core-excited resonances, and two Feshbach resonances are detected in the CC approximation. The role of active space in the target and scattering problem including the resonances is discussed. The precise resonance parameters are found to be sensitive to the treatment of polarization effects employed. These resonances may be responsible for the fragments observed in a recent experiment of the dissociative electron attachments to cyanamide. Since the cyanamide molecule has a large permanent dipole moment, a Born closure procedure is used to account for the contribution of partial waves higher than l =4 to obtain converged cross sections.

  13. Light element production by low energy nuclei from massive stars

    NASA Technical Reports Server (NTRS)

    Vangioni-Flam, E.; Casse, M.; Ramaty, R.

    1997-01-01

    The Orion complex is a source of gamma rays attributed to the de-excitation of fast carbon and oxygen nuclei excited through interactions with ambient hydrogen and helium. This has consequences for the production and evolution of light isotopes in the Galaxy, as massive stars appear as prolific sources of C-O rich low energy nuclei. The different stages of massive star evolution are considered in relation to the acceleration of nuclei to moderate energies. It is concluded that the low energy nuclear component originating from massive stars plays a larger role than the usual Galactic cosmic rays in shaping the evolution of Li-6, Be-9, B-10 and B-11, especially in the early Galactic evolution. The enhancement of the B-11/B-10 ratio observed in meteorites and in the interstellar medium is attributed to the interaction of low energy carbon nuclei with ambient H and to a lesser degree, to neutrino spallation.

  14. Light element production by low energy nuclei from massive stars

    NASA Technical Reports Server (NTRS)

    Vangioni-Flam, E.; Casse, M.; Ramaty, R.

    1997-01-01

    The Orion complex is a source of gamma rays attributed to the de-excitation of fast carbon and oxygen nuclei excited through interactions with ambient hydrogen and helium. This has consequences for the production and evolution of light isotopes in the Galaxy, as massive stars appear as prolific sources of C-O rich low energy nuclei. The different stages of massive star evolution are considered in relation to the acceleration of nuclei to moderate energies. It is concluded that the low energy nuclear component originating from massive stars plays a larger role than the usual Galactic cosmic rays in shaping the evolution of Li-6, Be-9, B-10 and B-11, especially in the early Galactic evolution. The enhancement of the B-11/B-10 ratio observed in meteorites and in the interstellar medium is attributed to the interaction of low energy carbon nuclei with ambient H and to a lesser degree, to neutrino spallation.

  15. Complete dissociation branching fractions and Coulomb explosion dynamics of SO2 induced by excitation of O 1s pre-edge resonances.

    PubMed

    Salén, Peter; Yatsyna, Vasyl; Schio, Luca; Feifel, Raimund; Af Ugglas, Magnus; Richter, Robert; Alagia, Michele; Stranges, Stefano; Zhaunerchyk, Vitali

    2015-10-07

    Fragmentation processes of SO2 following excitation of the six main O 1s pre-edge resonances, as well as above the ionization threshold and below the resonances, are studied using a position-sensitive time-of-flight ion imaging detector, and the associated dissociation branching ratios and break-up dynamics are determined. In order to distinguish between the O(+) and S(2+) fragments of equal mass-to-charge ratio, the measurements have been performed with the isotopically enriched S(18)O2 sample. By analysis of the complete set of the fragment momentum vectors, the β values for the fragments originating from the SO(+) + O(+) break-up and the kinetic energy release for fragmentation channels of both SO2 (2+) and SO2 (3+) parent ions are determined. We also present results on the three-body break-up dynamics.

  16. Low-energy electron scattering by pyrazine

    SciTech Connect

    Winstead, Carl; McKoy, Vincent

    2007-07-15

    We report cross sections for low-energy elastic electron collisions with the diazabenzene molecule pyrazine, obtained from first-principles calculations. The integral elastic cross section exhibits three sharp peaks that are nominally shape resonances associated with trapping in the vacant {pi}* molecular orbitals. Although the two lowest-energy resonances do in fact prove to be nearly pure single-channel shape resonances, the third contains a considerable admixture of core-excited character, and accounting for this channel coupling effect is essential to obtaining an accurate resonance energy. Such resonant channel coupling has implications for electron interactions with the DNA bases, especially the pyrimidine bases for which pyrazine is a close analog. In the absence of data on pyrazine itself, we compare our elastic differential cross section to measurements on benzene and find close agreement.

  17. Low Energy Transfer Reactions With {sup 11}Be

    SciTech Connect

    Johansen, Jacob

    2009-08-26

    The low-energy transfer reaction {sup 11}Be(d,p){sup 12}Be gives us the opportunity to investigate single particle excitations in {sup 12}Be. The breaking of the magic number N = 8 for {sup 12}Be can be studied by comparing spectroscopic data with theoretical predictions.

  18. 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.-

  19. 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)

  20. Electric-hexadecapole (24-pole) Coulomb integrals

    NASA Astrophysics Data System (ADS)

    Chidichimo, Marita C.; Stastna, Marek

    1996-03-01

    We obtain the quantal zero-energy-loss limit of the radial integrals arising in the nonrelativistic atomic excitation of electric-hexadecapole transitions. We compare these results to the classical limit and the WKB approximation. We show the different behavior of the Coulomb integrals in the WKB approximation in the cases of repulsive and attractive potentials as functions of the Sommerfeld number η.

  1. Non-resonant elastic scattering of low-energy photons by atomic sodium confined in quantum plasmas

    NASA Astrophysics Data System (ADS)

    Ghosh, Avijit; Ray, Debasis

    2015-03-01

    The non-resonant elastic scattering of low-energy photons by the bound valence electron in the ground state 3s of atomic sodium confined in quantum plasmas is investigated theoretically. The incident photon energy is assumed to be much smaller than the 3s-3p excitation energy. The alkali atom sodium is first formulated as an effective one-electron problem in which the attractive interaction between the valence electron and the atomic ion core is simulated by a spherically symmetric model potential. The Shukla-Eliasson oscillatory exponential cosine screened-Coulomb potential model is then used to mimic the effective two-body (valence-core) interaction within quantum plasmas. Non-relativistic calculations performed within the electric dipole approximation indicate that the non-resonant elastic photon scattering cross-section undergoes a dramatic growth by several orders of magnitude as the quantum wave number increases. A qualitative explanation of this phenomenon is presented. In the absence of the oscillatory cosine screening term, a similar growth is observed at larger values of the quantum wave number. Our computed relevant atomic data are in very good agreement with the experimental as well as the previous theoretical data for the zero-screening (free atom) case, and with the very limited, accurate theoretical results available for the case of exponential screened-Coulomb two-body interaction, without the cosine screening term.

  2. Non-resonant elastic scattering of low-energy photons by atomic sodium confined in quantum plasmas

    SciTech Connect

    Ghosh, Avijit Ray, Debasis

    2015-03-15

    The non-resonant elastic scattering of low-energy photons by the bound valence electron in the ground state 3s of atomic sodium confined in quantum plasmas is investigated theoretically. The incident photon energy is assumed to be much smaller than the 3s-3p excitation energy. The alkali atom sodium is first formulated as an effective one-electron problem in which the attractive interaction between the valence electron and the atomic ion core is simulated by a spherically symmetric model potential. The Shukla-Eliasson oscillatory exponential cosine screened-Coulomb potential model is then used to mimic the effective two-body (valence-core) interaction within quantum plasmas. Non-relativistic calculations performed within the electric dipole approximation indicate that the non-resonant elastic photon scattering cross-section undergoes a dramatic growth by several orders of magnitude as the quantum wave number increases. A qualitative explanation of this phenomenon is presented. In the absence of the oscillatory cosine screening term, a similar growth is observed at larger values of the quantum wave number. Our computed relevant atomic data are in very good agreement with the experimental as well as the previous theoretical data for the zero-screening (free atom) case, and with the very limited, accurate theoretical results available for the case of exponential screened-Coulomb two-body interaction, without the cosine screening term.

  3. Investigating Coulomb's Law.

    ERIC Educational Resources Information Center

    Noll, Ellis; Koehlinger, Mervin; Kowalski, Ludwik; Swackhamer, Gregg

    1998-01-01

    Describes the use of a computer-linked camera to demonstrate Coulomb's law. Suggests a way of reducing the difficulties in presenting Coulomb's law by teaching the inverse square law of gravity and the inverse square law of electricity in the same unit. (AIM)

  4. Diffusion in Coulomb crystals.

    PubMed

    Hughto, J; Schneider, A S; Horowitz, C J; Berry, D K

    2011-07-01

    Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions "hop" in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter Γ=175 to Coulomb parameters up to Γ=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous.

  5. Diffusion in Coulomb crystals

    SciTech Connect

    Hughto, J.; Schneider, A. S.; Horowitz, C. J.; Berry, D. K.

    2011-07-15

    Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions ''hop'' in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter {Gamma}=175 to Coulomb parameters up to {Gamma}=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous.

  6. Low-energy structures in strong field ionization revealed by quantum orbits.

    PubMed

    Yan, Tian-Min; Popruzhenko, S V; Vrakking, M J J; Bauer, D

    2010-12-17

    Experiments on atoms in intense laser pulses and the corresponding exact ab initio solutions of the time-dependent Schrödinger equation (TDSE) yield photoelectron spectra with low-energy features that are not reproduced by the otherwise successful work horse of strong field laser physics: the "strong field approximation" (SFA). In the semiclassical limit, the SFA possesses an appealing interpretation in terms of interfering quantum trajectories. It is shown that a conceptually simple extension towards the inclusion of Coulomb effects yields very good agreement with exact TDSE results. Moreover, the Coulomb quantum orbits allow for a physically intuitive interpretation and detailed analysis of all low-energy features in the semiclassical regime, in particular, the recently discovered "low-energy structure" [C. I. Blaga, Nature Phys. 5, 335 (2009) and W. Quan, Phys. Rev. Lett. 103, 093001 (2009).

  7. Low-Energy Structures in Strong Field Ionization Revealed by Quantum Orbits

    SciTech Connect

    Yan, Tian-Min; Popruzhenko, S. V.; Vrakking, M. J. J.; Bauer, D.

    2010-12-17

    Experiments on atoms in intense laser pulses and the corresponding exact ab initio solutions of the time-dependent Schroedinger equation (TDSE) yield photoelectron spectra with low-energy features that are not reproduced by the otherwise successful work horse of strong field laser physics: the 'strong field approximation' (SFA). In the semiclassical limit, the SFA possesses an appealing interpretation in terms of interfering quantum trajectories. It is shown that a conceptually simple extension towards the inclusion of Coulomb effects yields very good agreement with exact TDSE results. Moreover, the Coulomb quantum orbits allow for a physically intuitive interpretation and detailed analysis of all low-energy features in the semiclassical regime, in particular, the recently discovered 'low-energy structure' [C. I. Blaga et al., Nature Phys. 5, 335 (2009) and W. Quan et al., Phys. Rev. Lett. 103, 093001 (2009)].

  8. Low-energy excitations in the S=(1)/(2) molecular nanomagnet K6[V15IVAs6O42(H2O)]•8H2O from proton NMR and μSR

    NASA Astrophysics Data System (ADS)

    Procissi, D.; Lascialfari, A.; Micotti, E.; Bertassi, M.; Carretta, P.; Furukawa, Y.; Kögerler, P.

    2006-05-01

    Zero- and longitudinal-field muon-spin-rotation (μSR) and H1 NMR measurements on the S=(1)/(2) molecular nanomagnet K6[V15IVAs6O42(H2O)]•8H2O are presented. In LF experiments, the muon asymmetry P(t) was fitted by the sum of three different exponential components with fixed weights. The different muon relaxation rates λi (i=1,2,3) and the low-field H=0.23T H1 NMR spin-lattice relaxation rate 1/T1 show a similar behavior for T>50K : starting from room temperature they increase as the temperature is decreased. The increase of λi and 1/T1 can be attributed to the “condensation” of the system toward the lowest-lying energy levels. The gap Δ˜550K between the first and second S=(3)/(2) excited states was determined experimentally. For T<2K , the muon relaxation rates λi stay constant, independently of the field value H⩽0.15T . The behavior for T<2K strongly suggests that, at low T , the spin fluctuations are not thermally driven but rather originate from quasielastic intramolecular or intermolecular magnetic interactions. We suggest that the very-low-temperature relaxation rates could be driven by energy exchanges between two almost degenerate S=(1)/(2) ground states and/or by quantum effects.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Coulomb breakup of 22C in a four-body model

    NASA Astrophysics Data System (ADS)

    Pinilla, E. C.; Descouvemont, P.

    2016-08-01

    Breakup cross sections are determined for the Borromean nucleus 22C by using a four-body eikonal model, including Coulomb corrections. Bound and continuum states are constructed within a 20C+n +n three-body model in hyperspherical coordinates. We compute continuum states with the correct asymptotic behavior through the R -matrix method. For the n +n potential, we use the Minnesota interaction. As there is no precise experimental information on 21C, we define different parameter sets for the 20C+n potentials. These parameter sets provide different scattering lengths, and resonance energies of an expected 3 /2+ excited state. Then we analyze the 22C ground-state energy and rms radius, as well as E 1 strength distributions and breakup cross sections. The E 1 strength distribution presents an enhancement at low energies. Its amplitude is associated with the low binding energy, rather than with a three-body resonance. We show that the shape of the cross section at low energies is sensitive to the ground-state properties. In addition, we suggest the existence of a low-energy 2+ resonance, which should be observable in breakup experiments.

  14. 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.

  15. Saturation of low-energy antiproton annihilation on nuclei

    NASA Astrophysics Data System (ADS)

    Gal, A.; Friedman, E.; Batty, C. J.

    2000-10-01

    Recent measurements of very low-energy (pL<100 MeV//c) /p¯ annihilation on light nuclei reveal apparent suppression of annihilation upon increasing the atomic charge /Z and mass number /A. Using /p¯-nucleus optical potentials Vopt, fitted to /p¯-atom energy-shifts and -widths, we resolve this suppression as due to the strong effective repulsion produced by the very absorptive Vopt. The low-energy /p¯-nucleus wavefunction is kept substantially outside the nuclear surface and the resulting reaction cross section saturates as function of the strength of ImVopt. This feature, for /E>0, parallels the recent prediction, for /E<0, that the level widths of /p¯ atoms saturate and, hence, that /p¯ deeply bound atomic states are relatively narrow. Antiproton annihilation cross sections are calculated at pL=57 MeV//c across the periodic table, and their dependence on /Z and /A is classified and discussed with respect to the Coulomb focussing effect at very low energies.

  16. 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.

  17. 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.

  18. Coulomb effect and threshold effect in electronic stopping power for slow protons

    SciTech Connect

    Semrad, D.

    1986-03-01

    We show how the electronic stopping power for slow protons is influenced by the deceleration and deflection of the projectile in the field of the target nucleus (Coulomb effect) and by the fact that in insulators a finite energy is also required for excitation of the outermost electrons (threshold effect). Estimates are derived from the Fermi-Teller description of the stopping process, from a modified local-density approximation, and from measured inner-shell ionization cross sections. It is found that the introduction of an energy threshold reduces at low energies the stopping cross section by a large factor and hence leads to an appreciable deviation from v/sub 1/ proportionality.

  19. 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.

  20. Intra-half-cycle interference of low-energy photoelectron in strong midinfrared laser fields.

    PubMed

    Xie, Hui; Li, Min; Li, Yang; Zhou, Yueming; Lu, Peixiang

    2016-11-28

    Using semiclassical models with implementing interference effects, we study the low-energy photoelectron intra-half-cycle interferences among nonscattering trajectories and multiple forward scattering trajectories of atoms ionized by a strong mid-infrared laser field. Tracing back to the initial tunneling coordinates, we find that up to three kinds of forward scattering trajectories have substantial contributions to the low-energy photoelectrons. Those multiple forward scattering trajectories depend sensitively on the initial transverse momentum at the tunnel exit and they lead to sign reversal of the transverse momentum of the electrons. We show that the interference of the nonscattering trajectory and the triple-scattered trajectory has the largest contribution to the low-energy structure in mid-infrared laser fields. It is also shown that the long-range Coulomb potential has a significant effect on the low-energy photoelectron interference patterns.

  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. Molecular Dynamics Simulations of Coulomb Explosion

    SciTech Connect

    Bringa, E M

    2002-05-17

    A swift ion creates a track of electronic excitations in the target material. A net repulsion inside the track can cause a ''Coulomb Explosion'', which can lead to damage and sputtering of the material. Here we report results from molecular-dynamics (MD) simulations of Coulomb explosion for a cylindrical track as a function of charge density and neutralization/quenching time, {tau}. Screening by the free electrons is accounted for using a screened Coulomb potential for the interaction among charges. The yield exhibits a prompt component from the track core and a component, which dominates at higher excitation density, from the heated region produced. For the cases studied, the number of atoms ejected per incident ion, i.e. the sputtering yield Y, is quadratic with charge density along the track as suggested by simple models. Y({tau} = 0.2 Debye periods) is nearly 20% of the yield when there is no neutralization ({tau} {yields} {infinity}). The connections between ''Coulomb explosions'', thermal spikes and measurements of electronic sputtering are discussed.

  4. Comment on "Structure effects in the 15N(n ,γ )16N radiative capture reaction from the Coulomb dissociation of 16N"

    NASA Astrophysics Data System (ADS)

    Mohr, Peter

    2016-05-01

    In their recent study Neelam, Shubhchintak, and Chatterjee have claimed that "it would certainly be useful to perform a Coulomb dissociation experiment to find the low-energy capture cross section for the reaction" 15N(n ,γ )16N. However, it is obvious that a Coulomb dissociation experiment cannot constrain this capture cross section because the dominating branchings of the capture reaction lead to excited states in 16N, which do not contribute in a Coulomb dissociation experiment. An estimate of the total 15N(n ,γ )16N cross section from Coulomb dissociation of 16N requires a precise knowledge of the γ -ray branchings in the capture reaction. Surprisingly, the calculation of Neelam, Shubhchintak, and Chatterjee predicts a strongly energy-dependent ground-state branching of the order of 0.05% to 0.6% at energies between 100 and 500 keV, which is almost 2 orders of magnitude below calculations in the direct capture model. Additionally, this calculation of Neelam, Shubhchintak, and Chatterjee deviates significantly from the expected energy dependence for p -wave capture.

  5. Coulomb interactions and screening effects in few-layer black phosphorus: a tight-binding consideration beyond the long-wavelength limit

    NASA Astrophysics Data System (ADS)

    Prishchenko, D. A.; Mazurenko, V. G.; Katsnelson, M. I.; Rudenko, A. N.

    2017-06-01

    Coulomb interaction and its screening play an important role in many physical phenomena of materials ranging from optical properties to many-body effects including superconductivity. Here, we report on a systematic study of dielectric screening in few-layer black phosphorus (BP), a two-dimensional material with promising electronic and optical characteristics. We use a combination of a tight-binding model and rigorously determined bare Coulomb interactions, which allows us to consider relevant microscopic effects beyond the long-wavelength limit. We calculate the dielectric function of few-layer BP in the random phase approximation and show that it exhibits strongly anisotropic behavior even in the static limit. We also estimate the strength of effective local and non-local Coulomb interactions and determine their doping dependence. We find that the p z states responsible for low-energy excitations in BP provide a moderate contribution to the screening, weakening the on-site Coulomb interaction by less that a factor of two. Finally, we calculate the full plasmon spectrum of few-layer BP and discuss the effects beyond long-wavelengths.

  6. Electronic relativistic effects on K-shell ionization by low-energy protons

    SciTech Connect

    Mukoyama, T.; Sarkadi, L.

    1981-01-01

    K-shell ionization cross sections by low-energy proton impact have been calculated in the relativistic plane-wave Born approximation, taking into account the effects of binding-energy increase and Coulomb deflection. The calculated values are compared with the recent experimental cross sections of Zander and Andrews. It is found that the use of Dirac wave functions for target electrons improves agreement with the experimental results, but the theoretical predictions are still systematically higher at the lower proton energies.

  7. The Low-Energy p-d System in Pionless EFT

    NASA Astrophysics Data System (ADS)

    König, Sebastian; Hammer, H.-W.

    2013-03-01

    We summarize results presented at the 5th Asian Pacific Conference on Few Body Problems in Physics, which was held in Seoul in August 2011. We calculate low-energy quartet and doublet channel proton-deuteron scattering in the framework of pionless effective field theory. We obtain good agreement with the available phase shift analyses. Moreover, we calculate the Coulomb contribution to the 3He-3H binding energy difference in first order perturbation theory.

  8. Dynamics of Coulombic and gravitational periodic systems

    NASA Astrophysics Data System (ADS)

    Kumar, Pankaj; Miller, Bruce N.

    2016-04-01

    We study the dynamics and the phase-space structures of Coulombic and self-gravitating versions of the classical one-dimensional three-body system with periodic boundary conditions. We demonstrate that such a three-body system may be reduced isomorphically to a spatially periodic system of a single particle experiencing a two-dimensional potential on a rhombic plane. For the case of both Coulombic and gravitational versions, exact expressions of the Hamiltonian have been derived in rhombic coordinates. We simulate the phase-space evolution through an event-driven algorithm that utilizes analytic solutions to the equations of motion. The simulation results show that the motion exhibits chaotic, quasiperiodic, and periodic behaviors in segmented regions of the phase space. While there is no evidence of global chaos in either the Coulombic or the gravitational system, the former exhibits a transition from a completely nonchaotic phase space at low energies to a mixed behavior. Gradual yet striking transitions from mild to intense chaos are indicated with changing energy, a behavior that differentiates the spatially periodic systems studied in this Rapid Communication from the well-understood free-boundary versions of the three-body problem. Our treatment of the three-body systems opens avenues for analysis of the dynamical properties exhibited by spatially periodic versions of various classes of systems studied in plasma and gravitational physics as well as in cosmology.

  9. Coulomb dissociation of one- and two-neutron halos in halo EFT

    NASA Astrophysics Data System (ADS)

    Acharya, Bijaya; Phillips, Daniel

    2013-10-01

    In neutron halo nuclei the neutron distribution extends significantly beyond the region occupied by the nuclear ``core.'' Halo effective field theory (Halo-EFT) exploits the consequent separation of scales in order to predict relationships between low-energy observables in these systems as a systematic expansion in Rcore /Rhalo . This talk will discuss results for the Coulomb dissociation of neutron halo nuclei in this framework. In particular, we consider the Coulomb dissociation of 19C. We compute the reduced transition probability (dB (E 1) / dE) for excitation of the bound-state neutrons to the continuum up to N2LO in the Halo-EFT expansion. By comparing the predcition with data from RIKEN we are able to extract accurate results for 19C's one-neutron separation energy and asymptotic normalization coefficient. Good agreement between data and Halo-EFT is also found for the longitudinal momentum distribution of 19C. Results from ongoing work to extend ths calculation to two-neutron halos will also be presented. Supported by the US Department of Energy under grant DE-FG02- 93ER40756.

  10. Flux tube spectra from approximate integrability at low energies

    NASA Astrophysics Data System (ADS)

    Dubovsky, S.; Flauger, R.; Gorbenko, V.

    2015-03-01

    We provide a detailed introduction to a method we recently proposed for calculating the spectrum of excitations of effective strings such as QCD flux tubes. The method relies on the approximate integrability of the low-energy effective theory describing the flux tube excitations and is based on the thermodynamic Bethe ansatz. The approximate integrability is a consequence of the Lorentz symmetry of QCD. For excited states, the convergence of the thermodynamic Bethe ansatz technique is significantly better than that of the traditional perturbative approach. We apply the new technique to the lattice spectra for fundamental flux tubes in gluodynamics in D = 3 + 1 and D = 2 + 1, and to k-strings in gluodynamics in D = 2 + 1. We identify a massive pseudoscalar resonance on the worldsheet of the confining strings in SU(3) gluodynamics in D = 3 + 1, and massive scalar resonances on the worldsheet of k = 2.3 strings in SU(6) gluodynamics in D = 2 + 1.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Coulomb gauge ghost propagator and the Coulomb form factor

    NASA Astrophysics Data System (ADS)

    Quandt, M.; Burgio, G.; Chimchinda, S.; Reinhardt, H.

    The ghost propagator and the Coulomb potential are evaluated in Coulomb gauge on the lattice, using an improved gauge fixing scheme which includes the residual symmetry. This setting has been shown to be essential in order to explain the scaling violations in the instantaneous gluon propagator. We find that both the ghost propagator and the Coulomb potential are insensitive to the Gribov problem or the details of the residual gauge fixing, even if the Coulomb potential is evaluated from the A0 -propagator instead of the Coulomb kernel. In particular, no signs of scaling violations could be found in either quantity, at least to well below the numerical accuracy where these violations were visible for the gluon propagator. The Coulomb potential from the A0 -propagator is shown to be in qualitative agreement with the (formally equivalent) expression evaluated from the Coulomb kernel.

  16. 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.

  17. Elementary excitations in homogeneous superfluid neutron star matter: Role of the proton component

    NASA Astrophysics Data System (ADS)

    Baldo, Marcello; Ducoin, Camille

    2011-09-01

    The thermal evolution of neutron stars depends on the elementary excitations affecting the stellar matter. In particular, the low-energy excitations, whose energy is proportional to the transferred momentum, can play a major role in the emission and propagation of neutrinos. In this paper, we focus on the density modes associated with the proton component in the homogeneous matter of the outer core of neutron stars (at density between one and three times the nuclear saturation density, where the baryonic constituents are expected to be neutrons and protons). In this region, it is predicted that the protons are superconducting. We study the respective roles of the proton pairing and Coulomb interaction in determining the properties of the modes associated with the proton component. This study is performed in the framework of the random phase approximation, generalized in order to describe the response of a superfluid system. The formalism we use ensures that the generalized Ward’s identities are satisfied. An important conclusion of this work is the presence of a pseudo-Goldstone mode associated with the superconducting protons in neutron-star matter. Indeed, the Goldstone mode, which characterizes a pure superfluid, is suppressed in usual superconductors because of the long-range Coulomb interaction, which allows a plasmon mode. However, for the proton component of stellar matter, the Coulomb field is screened by the electrons and a pseudo-Goldstone mode occurs, with a velocity increased by the Coulomb interaction.

  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. Low-Energy Charge and Spin Dynamics in Quantum Confined Systems

    NASA Astrophysics Data System (ADS)

    Rice, William D.

    Condensed matter systems exhibit a variety of dynamical phenomena at low energy scales, from gigahertz (GHz) to terahertz (THz) frequencies in particular, arising from complex interplay between charge, spin, and lattice. A large number of collective and elementary excitations in solids occur in this frequency range, which are further modified and enriched by scattering, interactions, and disorder. Recent advancements in spectroscopic methods for probing low-energy dynamics allow us to investigate novel aspects of charge and spin dynamics in solids. In this dissertation work, we used direct current (DC) conductivity, GHz, THz, and mid-infrared (MIR) techniques to provide significant new insights into interaction and disorder effects in low-dimensional systems. Specifically, we have studied temperature-dependent magnetoresistance (MR) and electron spin resonance (ESR) in single-wall carbon nanotubes (SWCNTs), intra-exciton scattering in InGaAs quantum wells, and high-field MIR-induced band gaps in graphene. Temperature-dependent resistance and MR were measured in an ensemble of SWCNTs from 0.3 to 350 K. The resistance temperature behavior followed a 3D variable range hopping (VRH) behavior from 0.3 to ˜100 K. A positive MR was observed at temperatures above 25 K and could be fit with a spin-dependent VRH model; negative MR was seen at low temperatures. In the GHz regime, the ESR linewidth for SWCNTs was observed to narrow by as much as 50% as the temperature was increased from 3 to 300 K, a phenomenon known as motional narrowing, suggesting that we are detecting the ESR of hopping spins. From the linewidth change versus temperature, we find the hopping frequency to be 285 GHz. For excitons in InGaAs quantum wells, we demonstrate the manipulation of intra-excitonic populations using intense, narrow-band THz pulses. The THz radiation temporarily quenches the 1s emission, which is then followed by an enhancement and subsequent decay of 2s emission. After the quenching

  20. Novel Role of Superfluidity in Low-Energy Nuclear Reactions

    NASA Astrophysics Data System (ADS)

    Magierski, Piotr; Sekizawa, Kazuyuki; Wlazłowski, Gabriel

    2017-07-01

    We demonstrate, within symmetry unrestricted time-dependent density functional theory, the existence of new effects in low-energy nuclear reactions which originate from superfluidity. The dynamics of the pairing field induces solitonic excitations in the colliding nuclear systems, leading to qualitative changes in the reaction dynamics. The solitonic excitation prevents collective energy dissipation and effectively suppresses the fusion cross section. We demonstrate how the variations of the total kinetic energy of the fragments can be traced back to the energy stored in the superfluid junction of colliding nuclei. Both contact time and scattering angle in noncentral collisions are significantly affected. The modification of the fusion cross section and possibilities for its experimental detection are discussed.

  1. Low-energy dissociative recombination in small polyatomic molecules.

    PubMed

    Jungen, Ch; Pratt, S T

    2010-12-07

    Indirect dissociative recombination of low-energy electrons and molecular ions often occurs through capture into vibrationally excited Rydberg states. Properties of vibrational autoionization, the inverse of this capture mechanism, are used to develop some general ideas about the indirect recombination process, and these ideas are illustrated by examples from the literature. In particular, the Δv = -1 propensity rule for vibrational autoionization, i.e., that vibrational autoionization occurs by the minimum energetically allowed change in vibrational quantum numbers, leads to the prediction of thresholds in the dissociative recombination cross sections and rates at the corresponding vibrational thresholds. Capture into rotationally excited Rydberg states is also discussed in terms of recent low-temperature studies of the dissociative recombination of H(3)(+).

  2. Semiclassical Coulomb field

    SciTech Connect

    Polonyi, J.

    2008-06-15

    The contribution of different modes of the Coulomb field to decoherence and to the dynamical breakdown of the time reversal invariance is calculated in the one-loop approximation for nonrelativistic electron gas. The dominant contribution was found to come from the usual collective modes in the plasma, namely, the zero-sound and the plasmon oscillations. The length scale of the quantum-classical transition is found to be close to the Thomas-Fermi screening length. It is argued that the extension of these modes to the whole Fock space yields optimal pointer states.

  3. Excited baryons

    SciTech Connect

    Mukhopadhyay, N.C.

    1986-01-01

    The status of the theory of the low-energy approach to hadron structure is reviewed briefly by surveying a few relevant models. A few examples of tests needed to sort out the predictions of different models pertaining to the quark-gluon structure of hadrons are discussed, and given the resulting physics objectives, a few experimental options for excited baryon research at CFBAF are suggested. (LEW)

  4. Striped states in quantum Hall effect: Deriving a low-energy theory from Hartree-Fock

    NASA Astrophysics Data System (ADS)

    Lopatnikova, Anna

    2002-03-01

    In their influential work, MacDonald and Fisher [PRB 61 5724 2000] suggested a phenomenological coupled Luttinger liquid theory to describe the low energy excitations of the striped quantum Hall state. We extend that work and explicitly derive the Luttinger liquid model using a microscopic Hartree-Fock description, in which the low energy excitations are represented by coherent states localized around the edges of the stripes. Our approach allows us to obtain analytical expressions for all of the parameters of the Luttinger liquid theory and of the equivalent hydrodynamic theory, suggested by Fogler and Vinokur [PRL 84 5828 2000]. As examples of the use of these results, we explicitly calculate the low-energy excitation spectrum and study tunneling into the striped state. Addressing a recent controversy regarding the possible instability of the striped state towards crystallization, we use our coherent-state approach to show the existence of the instability and analytically construct the stripe-crystal ground state.

  5. Low-energy control of electrical turbulence in the heart.

    PubMed

    Luther, Stefan; Fenton, Flavio H; Kornreich, Bruce G; Squires, Amgad; Bittihn, Philip; Hornung, Daniel; Zabel, Markus; Flanders, James; Gladuli, Andrea; Campoy, Luis; Cherry, Elizabeth M; Luther, Gisa; Hasenfuss, Gerd; Krinsky, Valentin I; Pumir, Alain; Gilmour, Robert F; Bodenschatz, Eberhard

    2011-07-13

    Controlling the complex spatio-temporal dynamics underlying life-threatening cardiac arrhythmias such as fibrillation is extremely difficult, because of the nonlinear interaction of excitation waves in a heterogeneous anatomical substrate. In the absence of a better strategy, strong, globally resetting electrical shocks remain the only reliable treatment for cardiac fibrillation. Here we establish the relationship between the response of the tissue to an electric field and the spatial distribution of heterogeneities in the scale-free coronary vascular structure. We show that in response to a pulsed electric field, E, these heterogeneities serve as nucleation sites for the generation of intramural electrical waves with a source density ρ(E) and a characteristic time, τ, for tissue depolarization that obeys the power law τ ∝ E(α). These intramural wave sources permit targeting of electrical turbulence near the cores of the vortices of electrical activity that drive complex fibrillatory dynamics. We show in vitro that simultaneous and direct access to multiple vortex cores results in rapid synchronization of cardiac tissue and therefore, efficient termination of fibrillation. Using this control strategy, we demonstrate low-energy termination of fibrillation in vivo. Our results give new insights into the mechanisms and dynamics underlying the control of spatio-temporal chaos in heterogeneous excitable media and provide new research perspectives towards alternative, life-saving low-energy defibrillation techniques. ©2011 Macmillan Publishers Limited. All rights reserved

  6. Low-energy control of electrical turbulence in the heart

    NASA Astrophysics Data System (ADS)

    Luther, Stefan; Fenton, Flavio H.; Kornreich, Bruce G.; Squires, Amgad; Bittihn, Philip; Hornung, Daniel; Zabel, Markus; Flanders, James; Gladuli, Andrea; Campoy, Luis; Cherry, Elizabeth M.; Luther, Gisa; Hasenfuss, Gerd; Krinsky, Valentin I.; Pumir, Alain; Gilmour, Robert F.; Bodenschatz, Eberhard

    2011-07-01

    Controlling the complex spatio-temporal dynamics underlying life-threatening cardiac arrhythmias such as fibrillation is extremely difficult, because of the nonlinear interaction of excitation waves in a heterogeneous anatomical substrate. In the absence of a better strategy, strong, globally resetting electrical shocks remain the only reliable treatment for cardiac fibrillation. Here we establish the relationship between the response of the tissue to an electric field and the spatial distribution of heterogeneities in the scale-free coronary vascular structure. We show that in response to a pulsed electric field, E, these heterogeneities serve as nucleation sites for the generation of intramural electrical waves with a source density ρ(E) and a characteristic time, τ, for tissue depolarization that obeys the power law τ~Eα. These intramural wave sources permit targeting of electrical turbulence near the cores of the vortices of electrical activity that drive complex fibrillatory dynamics. We show in vitro that simultaneous and direct access to multiple vortex cores results in rapid synchronization of cardiac tissue and therefore, efficient termination of fibrillation. Using this control strategy, we demonstrate low-energy termination of fibrillation in vivo. Our results give new insights into the mechanisms and dynamics underlying the control of spatio-temporal chaos in heterogeneous excitable media and provide new research perspectives towards alternative, life-saving low-energy defibrillation techniques.

  7. Striped states in quantum Hall effect: Deriving a low-energy theory from Hartree-Fock

    NASA Astrophysics Data System (ADS)

    Lopatnikova, Anna; Simon, Steven H.; Halperin, Bertrand I.; Wen, Xiao-Gang

    2001-10-01

    There is growing experimental and theoretical evidence that very clean two-dimensional electron systems form unidirectional charge density waves (UCDW) or ``striped'' states at low temperatures and at Landau level filling fractions of the form ν=M+x with 4low-energy excitations of the system by making smooth deformations of the stripe edges analogous to the construction of edge state excitations of quantum Hall droplets. These low-energy excitations are described as a coupled Luttinger liquid theory, as discussed previously by MacDonald and Fisher [Phys. Rev. B 61, 5724 (2000)]. Here, we extend that work and explicitly derive all of the parameters of this low energy theory using a Hartree-Fock approach. We also make contact with the equivalent low-energy hydrodynamic approach of Fogler and Vinokur [Phys. Rev. Lett. 84, 5828 (2000)] and similarly derive the parameters of this theory. As examples of the use of these results, we explicitly calculate the low-energy excitation spectrum and study tunneling into the striped state.

  8. Reconciling Coulomb breakup and neutron radiative capture

    NASA Astrophysics Data System (ADS)

    Capel, P.; Nollet, Y.

    2017-07-01

    The Coulomb-breakup method to extract the cross section for neutron radiative capture at astrophysical energies is analyzed in detail. In particular, its sensitivity to the description of the neutron-core continuum is ascertained. We consider the case of 14C(n ,γ )15C for which both the radiative capture at low energy and the Coulomb breakup of 15C into 14C+n on Pb at 68 MeV/nucleon have been measured with accuracy. We confirm the direct proportionality of the cross section for both reactions to the square of the asymptotic normalization constant of 15C observed by Summers and Nunes [Phys. Rev. C 78, 011601(R) (2008), 10.1103/PhysRevC.78.011601], but we also show that the 14C-n continuum plays a significant role in the calculations. Fortunately, the method proposed by Summers and Nunes can be improved to absorb that continuum dependence. We show that a more precise radiative-capture cross section can be extracted selecting the breakup data at forward angles and low 14C-n relative energies.

  9. 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.}

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Efros-Shklovskii Coulomb gap in the absence of disorder

    NASA Astrophysics Data System (ADS)

    Rademaker, Louk; Mahmoudian, Samiyeh; Ralko, Arnaud; Fratini, Simone; Dobrosavljevic, Vladimir

    2015-03-01

    Certain models of frustrated electron systems have been shown to self-generate glassy behavior, in the absence of disorder. Possible candidate materials contain quarter-filled triangular lattices with long-range Coulomb interactions, as found in the θ-family of organic BEDT-TTF crystals. In disordered insulators with localized electronic states, the so-called Coulomb glass, the single particle excitation spectrum displays the well-known Efros-Shklovskii gap. The same excitation spectrum is investigated in a class of models that display self-generated electronic glassiness, showing pseudogap formation related to the Efros-Shklovskii Coulomb gap. Our study suggests universal characteristics of all electron glasses, regardless of disorder.

  17. Low-energy D-wave positronium-hydrogen scattering

    NASA Astrophysics Data System (ADS)

    Woods, Denton; van Reeth, P.; Ward, S. J.

    2014-03-01

    We are investigating the four-body Coulomb process of positronium-hydrogen (Ps-H) scattering below the Ps(n=2) excitation threshold using the Kohn variational method and variants. Our Ps-H 1 D -wave phase shifts compare reasonably well with the close-coupling results, but our 3 D -wave phase shifts are appreciably lower. In an attempt to improve the accuracy of these, we are employing a sectors-based approach and the modification of the short-range Hylleraas terms with an exponential in the r12 coordinate. We are investigating the use of the Born approximation for higher partial waves. We plan also to present our latest S-wave and P-wave results using the Kohn variational method. S.J. Ward acknowledges support from NSF under grant no. PHYS-968638.

  18. A new look at low-energy nuclear reaction research.

    PubMed

    Krivit, Steven B; Marwan, Jan

    2009-10-01

    This paper presents a new look at low-energy nuclear reaction research, a field that has developed from one of the most controversial subjects in science, "cold fusion." Early in the history of this controversy, beginning in 1989, a strong polarity existed; many scientists fiercely defended the claim of new physical effects as well as a new process in which like-charged atomic nuclei overcome the Coulomb barrier at normal temperatures and pressures. Many other scientists considered the entire collection of physical observations-along with the hypothesis of a "cold fusion"--entirely a mistake. Twenty years later, some people who had dismissed the field in its entirety are considering the validity of at least some of the reported experimental phenomena. As well, some researchers in the field are wondering whether the underlying phenomena may be not a fusion process but a neutron capture/absorption process. In 2002, a related tabletop form of thermonuclear fusion was discovered in the field of acoustic inertial confinement fusion. We briefly review some of this work, as well.

  19. A statistical model for simulating the emission of light particles from excited nuclei

    NASA Astrophysics Data System (ADS)

    Sannikov, A. V.; Savitskaya, E. N.

    2016-05-01

    The algorithms and basic equations of a novel evaporation model that have been implemented in the program package EVAP15 are detailed. The level density of an excited nucleus is described by the composite Gilbert-Cameron formula with parameter values as suggested by the IAEA working group RIPL-3. Special attention is paid to the cross sections of inverse reactions and, in particular, to those for the interactions of low-energy neutrons with nuclei and for crossing of the Coulomb barrier by low-energy charged particles. The model predictions are compared with a large volume of experimental data on the spectra of particles emitted in the reactions ( n, xn), ( n, xp), and ( n, xα) induced by neutrons with energy near 14 MeV and on the four spectra for the reaction ( p, xp) induced by 62-MeV protons.

  20. Traceable Coulomb blockade thermometry

    NASA Astrophysics Data System (ADS)

    Hahtela, O.; Mykkänen, E.; Kemppinen, A.; Meschke, M.; Prunnila, M.; Gunnarsson, D.; Roschier, L.; Penttilä, J.; Pekola, J.

    2017-02-01

    We present a measurement and analysis scheme for determining traceable thermodynamic temperature at cryogenic temperatures using Coulomb blockade thermometry. The uncertainty of the electrical measurement is improved by utilizing two sampling digital voltmeters instead of the traditional lock-in technique. The remaining uncertainty is dominated by that of the numerical analysis of the measurement data. Two analysis methods are demonstrated: numerical fitting of the full conductance curve and measuring the height of the conductance dip. The complete uncertainty analysis shows that using either analysis method the relative combined standard uncertainty (k  =  1) in determining the thermodynamic temperature in the temperature range from 20 mK to 200 mK is below 0.5%. In this temperature range, both analysis methods produced temperature estimates that deviated from 0.39% to 0.67% from the reference temperatures provided by a superconducting reference point device calibrated against the Provisional Low Temperature Scale of 2000.

  1. Energies of Screened Coulomb Potentials.

    ERIC Educational Resources Information Center

    Lai, C. S.

    1979-01-01

    This article shows that, by applying the Hellman-Feynman theorem alone to screened Coulomb potentials, the first four coefficients in the energy series in powers of the perturbation parameter can be obtained from the unperturbed Coulomb system. (Author/HM)

  2. Low energy cyclotron for radiocarbon dating

    SciTech Connect

    Welch, J.J.

    1985-01-01

    The author built and tested a low energy cyclotron for radiocarbon dating similar to a conventional mass spectrometer. These tests clearly show that with the addition of a conventional ion source, the low energy cyclotron can perform the extremely high sensitivity /sup 14/C measurements that are now done at accelerator facilities. The author found that no significant background is present when the cyclotron is tuned to accelerate /sup 14/C negative ions and the transmission efficiency is adequate to perform radiocarbon dating on milligram samples of carbon. The internal ion source used did not produce sufficient current to detect /sup 14/C directly at modern concentrations. The author shows how a conventional carbon negative ion source located outside the cyclotron magnet, would produce sufficient beam and provide for quick sample changing to make radiocarbon dating milligram samples with a modest laboratory instrument feasible.

  3. Low-Energy Polymeric Phases of Alanates

    NASA Astrophysics Data System (ADS)

    Huan, Tran Doan; Amsler, Maximilian; Marques, Miguel A. L.; Botti, Silvana; Willand, Alexander; Goedecker, Stefan

    2013-03-01

    Low-energy structures of alanates are currently known to be described by patterns of isolated, nearly ideal tetrahedral [AlH4] anions and metal cations. We discover that the novel polymeric motif recently proposed for LiAlH4 plays a dominant role in a series of alanates, including LiAlH4, NaAlH4, KAlH4, Mg(AlH4)2, Ca(AlH4)2, and Sr(AlH4)2. In particular, most of the low-energy structures discovered for the whole series are characterized by networks of corner-sharing [AlH6] octahedra, forming wires and/or planes throughout the materials. Finally, for Mg(AlH4)2 and Sr(AlH4)2, we identify two polymeric phases to be lowest in energy at low temperatures.

  4. 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.

  5. Physics with ultra-low energy antiprotons

    SciTech Connect

    Holtkamp, D.B.; Holzscheiter, M.H.; Hughes, R.J. )

    1989-01-01

    The experimental observation that all forms of matter experience the same gravitational acceleration is embodied in the weak equivalence principle of gravitational physics. However no experiment has tested this principle for particles of antimatter such as the antiproton or the antihydrogen atom. Clearly the question of whether antimatter is in compliance with weak equivalence is a fundamental experimental issue, which can best be addressed at an ultra-low energy antiproton facility. This paper addresses the issue. 20 refs.

  6. PHYSICS WITH ULTRA-LOW ENERGY ANTIPROTONS

    SciTech Connect

    M. HOLZSCHEITER

    2001-02-01

    In this report the author describes the current status of the antiproton deceleration (AD) facility at CERN, and highlights the physics program with ultra-low energy antiproton at this installation. He also comments on future possibilities provided higher intensity antiproton beams become available at Fermilab, and review possibilities for initial experiments using direct degrading of high energy antiprotons in material has been developed and proven at CERN.

  7. Experimental Measurement of Low Energy Neutrino Interactions

    SciTech Connect

    Scholberg, Kate

    2011-11-23

    Neutrino interactions in the few to few tens of MeV range are of importance for several physics topics, including solar, supernova and reactor neutrinos, as well as future proposed oscillation and Standard Model test experiments. Although interaction cross-sections for some simple targets are well understood, very little experimental data exist for interactions with nuclei. This talk will discuss the motivation for measuring low energy neutrino interactions, the state of knowledge, and possible future strategies.

  8. Low energy {bar p} physics at FNAL

    SciTech Connect

    Hsueh, S.Y.

    1992-12-01

    The charmonium formation experiment is the only low energy {bar p} experiment at FNAL. This paper describes the performance of the Fermilab {bar p} Accumulator during fixed target run for the experiment and the planned upgrades. We also discuss the proposal for the direct CP violation search in {bar p} + p {yields} {bar {Lambda}} + {Lambda} {yields} {bar p}{pi}{sup +} + p{pi}{sup {minus}}.

  9. Study on low-energy positron polarimetry

    NASA Astrophysics Data System (ADS)

    Schälicke, A.; Alexander, G.; Dollan, R.; Laihem, K.; Lohse, T.; Riemann, S.; Starovoitov, P.; Ushakov, A.

    2007-12-01

    A polarised positron source has been proposed for the design of the international linear collider (ILC). In order to optimise the positron beam, a measurement of its degree of polarisation close to the positron creation point is desired. In this contribution, methods for determining the positron polarisation at low energies are reviewed. A newly developed polarisation extension to GEANT4 will provide the basis for further polarimeter investigations.

  10. Low-energy sterile neutrinos: Theory

    NASA Astrophysics Data System (ADS)

    Palazzo, Antonio

    2013-04-01

    Several experimental anomalies seem to point towards the existence of light sterile neutrinos. We focus on the low-energy anomalous results (the so-called gallium and reactor anomalies), which indicate a non-zero admixture U of the electron neutrino with a fourth (mostly) sterile mass eigenstate ν4. We point out that solar sector data, in combination with the precision measurement of θ13, provide the constraint |<0.041 (90% C.L.), independent of the reactor flux determinations.

  11. Targeting Low-Energy Ballistic Lunar Transfers

    NASA Technical Reports Server (NTRS)

    Parker, Jeffrey S.

    2010-01-01

    Numerous low-energy ballistic transfers exist between the Earth and Moon that require less fuel than conventional transfers, but require three or more months of transfer time. An entirely ballistic lunar transfer departs the Earth from a particular declination at some time in order to arrive at the Moon at a given time along a desirable approach. Maneuvers may be added to the trajectory in order to adjust the Earth departure to meet mission requirements. In this paper, we characterize the (Delta)V cost required to adjust a low-energy ballistic lunar transfer such that a spacecraft may depart the Earth at a desirable declination, e.g., 28.5(white bullet), on a designated date. This study identifies the optimal locations to place one or two maneuvers along a transfer to minimize the (Delta)V cost of the transfer. One practical application of this study is to characterize the launch period for a mission that aims to launch from a particular launch site, such as Cape Canaveral, Florida, and arrive at a particular orbit at the Moon on a given date using a three-month low-energy transfer.

  12. Targeting Low-Energy Ballistic Lunar Transfers

    NASA Technical Reports Server (NTRS)

    Parker, Jeffrey S.

    2010-01-01

    Numerous low-energy ballistic transfers exist between the Earth and Moon that require less fuel than conventional transfers, but require three or more months of transfer time. An entirely ballistic lunar transfer departs the Earth from a particular declination at some time in order to arrive at the Moon at a given time along a desirable approach. Maneuvers may be added to the trajectory in order to adjust the Earth departure to meet mission requirements. In this paper, we characterize the (Delta)V cost required to adjust a low-energy ballistic lunar transfer such that a spacecraft may depart the Earth at a desirable declination, e.g., 28.5(white bullet), on a designated date. This study identifies the optimal locations to place one or two maneuvers along a transfer to minimize the (Delta)V cost of the transfer. One practical application of this study is to characterize the launch period for a mission that aims to launch from a particular launch site, such as Cape Canaveral, Florida, and arrive at a particular orbit at the Moon on a given date using a three-month low-energy transfer.

  13. Coulomb energy differences in isobaric multiplets

    SciTech Connect

    Lenzi, S. M.; Farnea, E.; Bazzacco, D.; Brandolini, F.; Lunardi, S.; Mason, P.; Menegazzo, R.; Nespolo, M.; Ur, C. A.; Della Vedova, F.; Marginean, N.; Napoli, D. R.; De Angelis, G.; Axiotis, M.; Gadea, A.; Ionescu-Bujor, M.; Bucurescu, D.; Iordachescu, A.; Bizzeti-Sona, A. M.; Bizzeti, P. G.

    2007-02-12

    By comparing the excitation energies of analogue states in isobaric multiplets, several nuclear structure properties can be studied as a function of the angular momentum up to high spin states. In particular, the mirror nuclei 35Ar and 35Cl show large differences between the excitation energies of analogue negative-parity states at high spin, confirming the important contribution of the relativistic electromagnetic spin-orbit interaction to the Coulomb energy. The single-particle character of the configuration of these states is reproduced with very good accuracy by shell model calculations in the sd and pf shells valence space. In addition, evidence of isospin mixing is deduced from the El transitions linking positive and negative parity states.

  14. Angular asymmetry of low-energy electron emission in ion-atom collisions

    SciTech Connect

    Fainstein, P.D.; Gulyas, L.; Martin, F.; Salin, A.

    1996-05-01

    We show that two factors contribute to the forward-backward angular asymmetry in low-energy electron emission by ion impact: the deviation of the target potential from a pure Coulomb potential and the two-center effect. We perform calculations with various theories that include these two effects: the continuum-distorted-wave{endash}eikonal-initial-state (CDW-EIS) and the CDW approximations based on distorted-wave perturbation theory and a close-coupling calculation using a discrete representation of the continuum. The various theories give consistent results on the asymmetry but discrepancies remain between theory and experiment. {copyright} {ital 1996 The American Physical Society.}

  15. Nonexistence of the Oppenheimer-Phillips process in low-energy deuteron-nucleus collisions

    SciTech Connect

    Bencze, G.; Chandler, C.

    1996-02-01

    It is shown that the electric polarizability of the deuteron produces negligible effect on the cross section of deuteron induced rearrangement reactions even at extremely low energies. This assessment is based on simple analytical formulas, derived on the basis of {ital N}-particle scattering theory by means of the general two-potential formalism, including Coulomb and exchange effects. It is shown on the basis of general physical arguments that the polarizability effects at very low energies are entirely contained in a multiplicative enhancement factor that differs from 1 by at most a few percent. As a result enhancement of ({ital d},{ital p}) relative to ({ital d},{ital n}) reactions is not possible by the Oppenheimer-Phillips mechanism.

  16. Nonexistence of the Oppenheimer-Phillips process in low-energy deuteron-nucleus collisions

    NASA Astrophysics Data System (ADS)

    Bencze, Gy.; Chandler, Colston

    1996-02-01

    It is shown that the electric polarizability of the deuteron produces negligible effect on the cross section of deuteron induced rearrangement reactions even at extremely low energies. This assessment is based on simple analytical formulas, derived on the basis of N-particle scattering theory by means of the general two-potential formalism, including Coulomb and exchange effects. It is shown on the basis of general physical arguments that the polarizability effects at very low energies are entirely contained in a multiplicative enhancement factor that differs from 1 by at most a few percent. As a result enhancement of (d,p) relative to (d,n) reactions is not possible by the Oppenheimer-Phillips mechanism.

  17. RHIC low energy beam loss projections

    SciTech Connect

    Satogata,T.

    2009-08-01

    For RHIC low-energy operations, we plan to collide Au beams with energies of E = 2:5-10 GeV/u in RHIC. Beams are injected into collision optics, and RHIC runs as a storage ring with no acceleration. At these low energies, observed beam lifetimes are minutes, with measured beam lifetimes of 3.5 min (fast) and 50 min (slow) at E=4.6 GeV/u in the March 2008 test run. With these lifetimes we can operate RHIC as a storage ring to produce reasonable integrated luminosity. This note estimates beam losses and collimator/dump energy deposition in normal injection modes of low energy operation. The main question is whether a normal injection run is feasible for an FY10 10-15 week operations run from a radiation safety perspective. A peripheral question is whether continuous injection operations is feasible from a radiation safety perspective. In continuous injection mode, we fill both rings, then continuously extract and reinject the oldest bunches that have suffered the most beam loss to increase the overall integrated luminosity. We expect to gain a factor of 2-3 in integrated luminosity from continuous injection at lowest energies if implemented[1]. Continuous injection is feasible by FY11 from an engineering perspective given enough effort, but the required extra safety controls and hardware dose risk make it unappealing for the projected luminosity improvement. Low-energy electron cooling will reduce beam losses by at least an order of magnitude vs normal low-energy operations, but low energy cooling is only feasible in the FY13 timescale and therefore beyond the scope of this note. For normal injection low energy estimates we assume the following: (1) RHIC beam total energies are E=2.5-10 GeV/u. (Continuous injection mode is probably unnecessary above total energies of E=7-8 GeV/u.); (2) RHIC operates only as a storage ring, with no acceleration; (3) 110 bunches of about 0.5-1.0 x 10{sup 9} initial bunch intensities (50-100% injection efficiency, likely conservative

  18. Momentum-space treatment of Coulomb distortions in a multiple-scattering expansion

    NASA Astrophysics Data System (ADS)

    Chinn, C. R.; Elster, Ch.; Thaler, R. M.

    1991-10-01

    The momentum-space treatment of the Coulomb interaction within the framework of the Watson multiple-scattering expansion is derived and tested numerically. By neglecting virtual Coulomb excitations and higher-order terms, the lowest-order optical potential for proton-nucleus scattering is shown to be the sum of the convolutions of a two-body nucleon-nucleon t matrix with the nuclear density and the point Coulomb interaction with the nuclear charge density. The calculation of the optical potential, as well as the treatment of the Coulomb interaction, is performed entirely in momentum space in an exact and numerically stable procedure. Elastic-scattering observables are presented for 16O, 40Ca, and 208Pb at energies up to 500 MeV. Comparisons are made with approximate treatments of the Coulomb interaction. The interference of nonlocality effects in the nuclear optical potential with different treatments of the Coulomb interaction is investigated.

  19. 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.

  20. Low Energy Nuclear Structure Modeling: Can It Be Improved?

    NASA Astrophysics Data System (ADS)

    Stone, Jirina R.

    Since the discovery of the atomic nucleus in 1911 generations of physicists have devoted enormous effort to understand low energy nuclear structure. Properties of nuclei in their ground state, including mass, binding energy and shape, provide vital input to many areas of sub-atomic physics as well as astrophysics and cosmology. Low energy excited states are equally important for understanding nuclear dynamics. Yet, no consensus exists as to what is the best path to a theory which would not only consistently reproduce a wide variety of experimental data but also have enough predictive power to yield credible predictions in areas where data are still missing. In this contribution some of the main obstacles preventing building such a theory are discussed. These include modification of the free nucleon-nucleon force in the nuclear environment and effects of the sub-nucleon (quark) structure of the nucleon. Selected classes of nuclear models, mean-field, shell and ab-initio models are briefly outlined. Finally, suggestions are made for, at least partial, progress that can be achieved with the quark-meson coupling model, as reported in recent publication [1].

  1. Low energy electron magnetometer using a monoenergetic electron beam

    NASA Technical Reports Server (NTRS)

    Singh, J. J.; Wood, G. M.; Rayborn, G. H.; White, F. A. (Inventor)

    1983-01-01

    A low energy electron beam magnetometer utilizes near-monoenergetic electrons thereby reducing errors due to electron energy spread and electron nonuniform angular distribution. In a first embodiment, atoms in an atomic beam of an inert gas are excited to a Rydberg state and then electrons of near zero energy are detached from the Rydberg atoms. The near zero energy electrons are then accelerated by an electric field V(acc) to form the electron beam. In a second embodiment, a filament emits electrons into an electrostatic analyzer which selects electrons at a predetermined energy level within a very narrow range. These selected electrons make up the electron beam that is subjected to the magnetic field being measured.

  2. NRV web knowledge base on low-energy nuclear physics

    SciTech Connect

    Karpov, V. Denikin, A. S.; Alekseev, A. P.; Zagrebaev, V. I.; Rachkov, V. A.; Naumenko, M. A.; Saiko, V. V.

    2016-09-15

    Principles underlying the organization and operation of the NRV web knowledge base on low-energy nuclear physics (http://nrv.jinr.ru) are described. This base includes a vast body of digitized experimental data on the properties of nuclei and on cross sections for nuclear reactions that is combined with a wide set of interconnected computer programs for simulating complex nuclear dynamics, which work directly in the browser of a remote user. Also, the current situation in the realms of application of network information technologies in nuclear physics is surveyed. The potential of the NRV knowledge base is illustrated in detail by applying it to the example of an analysis of the fusion of nuclei that is followed by the decay of the excited compound nucleus formed.

  3. NRV web knowledge base on low-energy nuclear physics

    NASA Astrophysics Data System (ADS)

    Karpov, V.; Denikin, A. S.; Alekseev, A. P.; Zagrebaev, V. I.; Rachkov, V. A.; Naumenko, M. A.; Saiko, V. V.

    2016-09-01

    Principles underlying the organization and operation of the NRV web knowledge base on low-energy nuclear physics (http://nrv.jinr.ru) are described. This base includes a vast body of digitized experimental data on the properties of nuclei and on cross sections for nuclear reactions that is combined with a wide set of interconnected computer programs for simulating complex nuclear dynamics, which work directly in the browser of a remote user. Also, the current situation in the realms of application of network information technologies in nuclear physics is surveyed. The potential of the NRV knowledge base is illustrated in detail by applying it to the example of an analysis of the fusion of nuclei that is followed by the decay of the excited compound nucleus formed.

  4. Low energy intake plus low energy expenditure (low energy flux), not energy surfeit, predicts future body fat gain12

    PubMed Central

    Yokum, Sonja; Stice, Eric

    2016-01-01

    Background: There is a paucity of studies that have prospectively tested the energy surfeit theory of obesity with the use of objectively estimated energy intake and energy expenditure in humans. An alternative theory is that homeostatic regulation of body weight is more effective when energy intake and expenditure are both high (high energy flux), implying that low energy flux should predict weight gain. Objective: We aimed to examine the predictive relations of energy balance and energy flux to future weight gain and tested whether results were replicable in 2 independent samples. Design: Adolescents (n = 154) and college-aged women (n = 75) underwent 2-wk objective doubly labeled water, resting metabolic rate, and percentage of body fat measures at baseline. Percentage of body fat was measured annually for 3 y of follow-up for the adolescent sample and for 2 y of follow-up for the young adult sample. Results: Low energy flux, but not energy surfeit, predicted future increases in body fat in both studies. Furthermore, high energy flux appeared to prevent fat gain in part because it was associated with a higher resting metabolic rate. Conclusion: Counter to the energy surfeit model of obesity, results suggest that increasing energy expenditure may be more effective for reducing body fat than caloric restriction, which is currently the treatment of choice for obesity. This trial was registered at clinicaltrials.gov as NCT02084836. PMID:27169833

  5. Low energy intake plus low energy expenditure (low energy flux), not energy surfeit, predicts future body fat gain.

    PubMed

    Hume, David John; Yokum, Sonja; Stice, Eric

    2016-06-01

    There is a paucity of studies that have prospectively tested the energy surfeit theory of obesity with the use of objectively estimated energy intake and energy expenditure in humans. An alternative theory is that homeostatic regulation of body weight is more effective when energy intake and expenditure are both high (high energy flux), implying that low energy flux should predict weight gain. We aimed to examine the predictive relations of energy balance and energy flux to future weight gain and tested whether results were replicable in 2 independent samples. Adolescents (n = 154) and college-aged women (n = 75) underwent 2-wk objective doubly labeled water, resting metabolic rate, and percentage of body fat measures at baseline. Percentage of body fat was measured annually for 3 y of follow-up for the adolescent sample and for 2 y of follow-up for the young adult sample. Low energy flux, but not energy surfeit, predicted future increases in body fat in both studies. Furthermore, high energy flux appeared to prevent fat gain in part because it was associated with a higher resting metabolic rate. Counter to the energy surfeit model of obesity, results suggest that increasing energy expenditure may be more effective for reducing body fat than caloric restriction, which is currently the treatment of choice for obesity. This trial was registered at clinicaltrials.gov as NCT02084836. © 2016 American Society for Nutrition.

  6. Low energy dipole strength from large scale shell model calculations

    NASA Astrophysics Data System (ADS)

    Sieja, Kamila

    2017-09-01

    Low energy enhancement of radiative strength functions has been deduced from experiments in several mass regions of nuclei. Such an enhancement is believed to impact the calculated neutron capture rates which are crucial input for reaction rates of astrophysical interest. Recently, shell model calculations have been performed to explain the upbend of the γ-strength as due to the M1 transitions between close-lying states in the quasi-continuum in Fe and Mo nuclei. Beyond mean-↓eld calculations in Mo suggested, however, a non-negligible role of electric dipole in the low energy enhancement. So far, no calculations of both dipole components within the same theoretical framework have been presented in this context. In this work we present newly developed large scale shell model appraoch that allows to treat on the same footing natural and non-natural parity states. The calculations are performed in a large sd - pf - gds model space, allowing for 1p{1h excitations on the top of the full pf-shell con↓guration mixing. We restrict the discussion to the magnetic part of the dipole strength, however, we calculate for the ↓rst time the magnetic dipole strength between states built of excitations going beyond the classical shell model spaces. Our results corroborate previous ↓ndings for the M1 enhancement for the natural parity states while we observe no enhancement for the 1p{1h contributions. We also discuss in more detail the e↑ects of con↓guration mixing limitations on the enhancement coming out from shell model calculations.

  7. Evidence for the importance of extended Coulomb interactions and forward scattering in cuprate superconductors.

    PubMed

    Johnston, S; Vishik, I M; Lee, W S; Schmitt, F; Uchida, S; Fujita, K; Ishida, S; Nagaosa, N; Shen, Z X; Devereaux, T P

    2012-04-20

    The prevalent view of the high-temperature superconducting cuprates is that their essential low-energy physics is captured by local Coulomb interactions. However, this view been challenged recently by studies indicating the importance of longer-range components. Motivated by this, we demonstrate the importance of these components by examining the electron-phonon (e-ph) interaction with acoustic phonons in connection with the recently discovered renormalization in the near-nodal low-energy (~8-15 meV) dispersion of Bi(2)Sr(2)CaCu(2)O(8+δ). By studying its nontrivial momentum and doping dependence we conclude a predominance of forward scattering arising from the direct interplay between the e-ph and extended Coulomb interactions. Our results thus demonstrate how the low-energy renormalization can provide a pathway to new insights into how these interactions interplay with one another and influence pairing and dynamics in the cuprates.

  8. A Very Low Energy Electrostatic Analyzer,

    DTIC Science & Technology

    1979-12-31

    SCIENTFI C-1 AFGL-TR-80-0023 NL... mlllEllilllE EIIIIIIIIIEEI IIIIIIIIIw SAFGL-T -0023 LEYE " - A VERY LOW ENERGY ELECTROSTATIC ANALYZER ROBERT E. LA...probably be per- formed for less than $200,000 in a period of about one year. ~1 -3t - i L..i. Cr L- 4 z iu 0 . SI ’ a D, Io rl 7 I a ZcrT a- / Clio) ~ ’ r~ !- 2 ’I - L~J~ ~AIo -~ C arLC) T IA1

  9. Low energy source for seismic operation

    SciTech Connect

    Martin, P.N.

    1980-09-23

    A lightweight, mobile, low-energy seismic source comprises an industrial shotgun, having a solid projectile combined with a base structure to support the gun in a substantially vertical position, slightly above the surface of the earth. The muzzle velocity of the projectile is sufficiently high that it can provide up to 9,000 foot pounds of energy impacting on the earth, which is comparable to that of some of the larger weight drop machines. Wheels or carrying bars can be provided for manual transport of the source.

  10. RHIC CHALLENGES FOR LOW ENERGY OPERATIONS

    SciTech Connect

    SATOGATA,T.; BRENNAN, J.M.; DREES, A.; FEDOTOV, A.; ROSER, T.; TSOUPAS, N.

    2007-06-25

    There is significant interest in RHIC heavy ion collisions at {radical}s =5-50 GeV/u, motivated by a search for the QCD phase transition critical point. The lowest energies are well below the nominal RHIC gold injection {radical}s = 19.6 GeV/u. There are several challenges that face RHIC operations in this regime, including longitudinal acceptance, magnet field quality, lattice control, and luminosity monitoring. We report on the status of work to address these challenges, including results from beam tests of low energy RHIC operations with protons and gold.

  11. The Low-Energy Telescopes on EXIST

    NASA Astrophysics Data System (ADS)

    Ramsey, Brian; Kaaret, P.; Jernigan, J. G.; Remillard, R. A.; Rothschild, R.; Hong, J.; Grindlay, J. E.

    2007-05-01

    The low-energy telescopes on EXIST are a coded aperture system that will continually image the 5-30 keV sky with 1' angular resolution and 12" source localization accuracy. The good source localization accuracy is essential to uniquely identify counterparts to obscured AGN and gamma-ray bursts. A total detector area of about one square meter with 200 micron square pixel is required. We are evaluating two silicon-based technologies capable of achieving the required performance: active pixel sensors with integrated DEPFET readout, and fully pixellated hybrid sensors with CMOS readout multiplexers optimized for X-ray detection.

  12. The Low-Energy Telescopes on EXIST

    NASA Astrophysics Data System (ADS)

    Ramsey, Brian; Kaaret, Philip E.; Jernigan, J. G.; Remillard, R. A.; Rothschild, R. E.; Hong, J.; Grindlay, J. E.

    2006-12-01

    The low-energy telescopes on EXIST are a coded aperture system that will continually image the 5-30 keV sky with 1' angular resolution and 12" source localization accuracy. The good source localization accuracy is essential to uniquely identify counterparts to obscured AGN and gamma-ray bursts. A total detector area of about one square meter with 200 micron square pixel is required. We are evaluating two silicon-based technologies capable of achieving the required performance: active pixel sensors with integrated DEPFET readout, and fully pixellated hybrid sensors with CMOS readout multiplexers optimized for X-ray detection.

  13. FLSR - The Frankfurt low energy storage ring

    NASA Astrophysics Data System (ADS)

    Stiebing, K. E.; Alexandrov, V.; Dörner, R.; Enz, S.; Kazarinov, N. Yu.; Kruppi, T.; Schempp, A.; Schmidt Böcking, H.; Völp, M.; Ziel, P.; Dworak, M.; Dilfer, W.

    2010-02-01

    An electrostatic storage ring for low-energy ions with a design energy of 50 keV is presently being set up at the Institut für Kernphysik der Johann Wolfgang Goethe-Universität Frankfurt am Main, Germany (IKF). This new device will provide a basis for new experiments on the dynamics of ionic and molecular collisions, as well as for high precision and time resolved laser spectroscopy. In this article, the design parameters of this instrument are reported.

  14. Performance monitoring of low energy house, Macclesfield

    NASA Astrophysics Data System (ADS)

    Stephen, F. R.

    1980-01-01

    The monitoring of the energy balance of a very well insulated low-energy house in Macclesfield, England is discussed. The house is an existing dwelling which had been converted into a low-energy-requiring house by the reduction of heat loss through a high level of thermal insulation and the collection of solar energy by a water cascade solar panel with warm water storage. Measurements of house temperatures, radiation, off-peak electricity consumption and hot water and heating using were performed from January to August, 1978 and reveal that the house used less than 22,000 kWh electricity during that period, compared to 55,000 kWh expected if the house had been constructed to average insulation levels. Solar energy is found to contribute only 2% of house energy requirements, with the use of a heat pump combined with the solar panel leading to greater efficiency and thus utilization. In addition, the large thermal mass and good insulation are found to improve comfort by reducing temperature fluctuations, and the ventilation and low-temperature water return system employed provided satisfactory results.

  15. Low Energy Ion-Molecule Reactions

    SciTech Connect

    James M. Farrar

    2004-05-01

    This objective of this project is to study the dynamics of the interactions of low energy ions important in combustion with small molecules in the gas phase and with liquid hydrocarbon surfaces. The first of these topics is a long-standing project in our laboratory devoted to probing the key features of potential energy surfaces that control chemical reactivity. The project provides detailed information on the utilization of specific forms of incident energy, the role of preferred reagent geometries, and the disposal of total reaction energy into product degrees of freedom. We employ crossed molecular beam methods under single collision conditions, at collision energies from below one eV to several eV, to probe potential surfaces over a broad range of distances and interaction energies. These studies allow us to test and validate dynamical models describing chemical reactivity. Measurements of energy and angular distributions of the reaction products with vibrational state resolution provide the key data for these studies. We employ the crossed beam low energy mass spectrometry methods that we have developed over the last several years.

  16. Low Energy Accelerator Facility Upgrade and test

    SciTech Connect

    Alford, K.; Chemerisov, S.; Gromov, R.; Hafenrichter, L.; Jonah, C. D.; Tafoya, R.; Wesolowski, K.; Brown, D.; Forknall, S.; Gardner, James; Macrillo, Dave; Zulpo, A.

    2015-01-01

    The Low Energy Accelerator Facility (LEAF) contains a low-energy linac with high average beam power, which was designed and built in the late 1960’s primarily for radiation-chemistry experiments. The maximum beam energy in that configuration was 21 MeV. Although, the installation is old, it is still reliable. The accelerator was repurposed for development of accelerator-based technologies for the production of 99Mo with funding provided by the National Nuclear Security Administration’s Office of Material Management and Minimization (M3 ). An extensive scientific program on the production of radioactive isotopes demanded an upgrade of the accelerator to fit the experimental requirements. Several possible LEAF upgrades were proposed to increase the electron beam energy. The final design proposed the replacement of the old accelerating structures with new ones. In 2011-2012, the new structures were manufactured, installed, and tested with the beam energy up to 50 MeV and average beam power up to 20 kW. LEAF now is an attractive installation for performing research into medical isotope production.

  17. Low energy neutrinos in Super-Kamiokande

    NASA Astrophysics Data System (ADS)

    Sekiya, Hiroyuki

    2016-05-01

    Super-Kamiokande (SK), a 50 kton water Cherenkov detector, observes 8B solar neutrinos via neutrino-electron elastic scattering. The analysis threshold was successfully lowered to 3.5 MeV (recoil electron kinetic energy) in SK-IV. To date SK has observed solar neutrinos for 18 years. An analysis regarding possible correlations between the solar neutrino flux and the 11 year solar activity cycle is shown. With large statistics, SK searches for distortions of the solar neutrino energy spectrum caused by the MSW resonance in the core of the sun. SK also searches for a day/night solar neutrino flux asymmetry induced by the matter in the Earth. The Super-Kamiokande Gd (SK-Gd) project is the upgrade of the SK detector via the addition of water-soluble gadolinium (Gd) salt. This modification will enable it to efficiently identify low energy anti-neutrinos. SK-Gd will pursue low energy physics currently inaccessible to SK due to backgrounds. The most important will be the world’s first observation of the diffuse supernova neutrino background. The main R&D program towards SK-Gd is EG ADS: a 200 ton, fully instrumented tank built in a new cavern in the Kamioka mine.

  18. Low energy cyclotron for radiocarbon dating

    SciTech Connect

    Welch, J.J.

    1984-12-01

    The measurement of naturally occurring radioisotopes whose half lives are less than a few hundred million years but more than a few years provides information about the temporal behavior of geologic and climatic processes, the temporal history of meteoritic bodies as well as the production mechanisms of these radioisotopes. A new extremely sensitive technique for measuring these radioisotopes at tandem Van de Graaff and cyclotron facilities has been very successful though the high cost and limited availability have been discouraging. We have built and tested a low energy cyclotron for radiocarbon dating similar in size to a conventional mass spectrometer. These tests clearly show that with the addition of a conventional ion source, the low energy cyclotron can perform the extremely high sensitivity /sup 14/C measurements that are now done at accelerator facilities. We found that no significant background is present when the cyclotron is tuned to accelerate /sup 14/C negative ions and the transmission efficiency is adequate to perform radiocarbon dating on milligram samples of carbon. The internal ion source used did not produce sufficient current to detect /sup 14/C directly at modern concentrations. We show how a conventional carbon negative ion source, located outside the cyclotron magnet, would produce sufficient beam and provide for quick sampling to make radiocarbon dating milligram samples with a modest laboratory instrument feasible.

  19. Low-Energy Polymeric Phases of Alanates

    NASA Astrophysics Data System (ADS)

    Tran, Huan; Amsler, Maximilian; Marques, Miguel; Botti, Silvana; Willand, Alexander; Goedecker, Stefan

    2013-03-01

    Low-energy structures of alanates are currently known to be described by patterns of isolated, nearly ideal tetrahedral [AlH4] anions and metal cations. We discover that the novel polymeric motif recently proposed for LiAlH4 plays a dominant role in a series of alanates, including LiAlH4, NaAlH4, KAlH4, Mg(AlH4)2, Ca(AlH4)2 and Sr(AlH4)2. In particular, most of the low-energy structures discovered for the whole series are characterized by networks of corner-sharing [AlH6] octahedra, forming wires and/or planes throughout the materials. Finally, for Mg(AlH4)2 and Sr(AlH4)2, we identify two polymeric phases to be lowest in energy at low temperatures. Work supported by Swiss NSF. Computational resources were provided by the Swiss National Supercomputing Center (CSCS) in Lugano.

  20. Low energy antiproton possibilities at BNL

    SciTech Connect

    Lee, Y.Y.; Lowenstein, D.I.

    1987-01-01

    Antinuclear physics in the energy range of 0 to 20 GeV has long been a mainstay of the high energy physics program at BNL. The emphasis of the experimental program in the last couple of years has however moved to other areas as new facilities in the world have come on line. The initiatives stimulated by the USAF has caused a renewed interest in the low energy capabilities at BNL, which are still very competitive and considerable for the production of low energy antiprotons. A synopsis is given of the present BNL accelerator plans and the near term possibilities for a high yield antiproton production experiment. This paper does not address the longer term facility possibilities of producing ''large'' amounts of antimatter. Parenthetically, even though several aspects of the program are of little interest for this audience, such as the Relativistic Heavy Ion Collider (RHIC) and the Stretcher, it is important to understand their parameters and impact upon various possible antinucleon initiatives at BNL.

  1. Large Regular QCD Coupling at Low Energy?

    NASA Astrophysics Data System (ADS)

    Shirkov, Dmitry V.

    2008-10-01

    The issue is the expediency of the QCD notions' use in the low energy region down to the confinement scale, and, in particular, the efficacy of the QCD invariant coupling {bar α }s (Q2 ) with a minimal analytic modification in this domain. To this goal, we overview a quite recent progress in application of the ghost-free Analytic Perturbative Theory approach (with no adjustable parameters) for QCD in the region below 1 GeV. Among them the Bethe-Salpeter analysis of the meson spectra and spin-dependent (polarization) Bjorken sum rule. The impression is that there is a chance for theoretically consistent and numerically correlated description of hadronic events from the Z0 till few hundred MeV scale by combination of analytic pQCD and some explicit non-perturbative contribution in the spirit of duality. This is an invitation to practitioner community for a more courageous use of ghost-free models for data analysis in the low energy region.

  2. Detectors for low energy electron cooling in RHIC

    SciTech Connect

    Carlier, F. S.

    2016-02-15

    Low energy operation of RHIC is of particular interest to study the location of a possible critical point in the QCD phase diagram. The performance of RHIC at energies equal to or lower than 10 GV/nucleon is limited by nonlinearities, Intra-BeamScattering (IBS) processes and space-charge effects. To successfully address the luminosity and ion store lifetime limitations imposed by IBS the method of electron cooling has been envisaged. During electron cooling processes electrons are injected along with the ion beam at the nominal ion bunch velocities. The velocity spread of the ion beam is reduced in all planes through Coulomb interactions between the cold electron beam and the ion beam. The electron cooling system proposed for RHIC will be the first of its kind to use bunched beams for the delivery of the electron bunches, and will therefore be accompanied by the necessary challenges. The designed electron cooler will be located in IP2. The electron bunches will be accelerated by a linac before being injected along side the ion beams. Thirty consecutive electron bunches will be injected to overlap with a single ion bunch. They will first cool the yellow beam before being extracted turned by 180-degrees and reinjected into the blue beam for cooling. As such, both the yellow and blue beams will be cooled by the same ion bunches. This will pose considerable challenges to ensure proper electron beam quality to cool the second ion beam. Furthermore, no ondulator will be used in the electron cooler so radiative recombination between the ions and the electrons will occur.

  3. 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.

  4. Low energy high pressure miniature screw valve

    DOEpatents

    Fischer, Gary J.; Spletzer, Barry L.

    2006-12-12

    A low energy high pressure screw valve having a valve body having an upper portion and a lower portion, said lower portion of said valve body defining an inlet flow passage and an outlet flow passage traversing said valve body to a valve seat, said upper portion of said valve body defining a cavity at said valve seat, a diaphragm restricting flow between said upper portion of said valve body and said lower portion, said diaphragm capable of engaging said valve seat to restrict fluid communication between said inlet passage and said outlet passage, a plunger within said cavity supporting said diaphragm, said plunger being capable of engaging said diaphragm with said valve seat at said inlet and outlet fluid passages, said plunger being in point contact with a drive screw having threads engaged with opposing threads within said upper portion of said valve body such engagement allowing motion of said drive screw within said valve body.

  5. Low-energy pion-nucleon scattering

    SciTech Connect

    Gibbs, W.R.; Ai, L.; Kaufmann, W.B.

    1998-02-01

    An analysis of low-energy charged pion-nucleon data from recent {pi}{sup {plus_minus}}p experiments is presented. From the scattering lengths and the Goldberger-Miyazawa-Oehme (GMO) sum rule we find a value of the pion-nucleon coupling constant of f{sup 2}=0.0756{plus_minus}0.0007. We also find, contrary to most previous analyses, that the scattering volumes for the P{sub 31} and P{sub 13} partial waves are equal, within errors, corresponding to a symmetry found in the Hamiltonian of many theories. For the potential models used, the amplitudes are extrapolated into the subthreshold region to estimate the value of the {Sigma} term. Off-shell amplitudes are also provided. {copyright} {ital 1998} {ital The American Physical Society}

  6. Low-energy dynamics of gravitation

    NASA Astrophysics Data System (ADS)

    Torma, Tibor

    The present status of theories of quantum gravity are reviewed from the low energy point of view. String theory relates classical black-hole type solutions of Einstein- like equations (e.g. axidilaton gravity) to the string vacuum. Several such solutions are proposed and their properties are investigated, including their behavior under supersymmetry transformations. A general feature of all possible quantum theories of gravitation is that they lead to a field theory description at low (as compared to the Planck mass) energies. The theoretical consistency, uniqueness and consequences of such an effective theory are investigated. I show that a power counting theorem allows for the momentum expansion that defines the effective theory even in the presence of large masses. I also show that graviton-graviton scattering is free of potential infrared and collinear divergencies that plague perturbative discussions of Yang-Mills theories.

  7. Low energy ion-molecule reactions

    SciTech Connect

    Farrar, J.M.

    1993-12-01

    This project is concerned with elucidating the dynamics of elementary ion-molecule reactions at collision energies near and below 1 eV. From measurements of the angular and energy distributions of the reaction products, one can infer intimathe details about the nature of collisions leading to chemical reaction, the geometries and lifetimes of intermediate complexes that govern the reaction dynamics, and the collision energy dependence of these dynamical features. The author employs crossed-beam low energy mass spectrometry technology developed over the last several years, with the focus of current research on proton transfer and hydrogen atom transfer reactions of te O{sup {minus}} ion with species such as HF, H{sub 2}O, and NH{sub 3}.

  8. Low energy consumption spintronics using multiferroic heterostructures.

    PubMed

    Trassin, Morgan

    2016-01-27

    We review the recent progress in the field of multiferroic magnetoelectric heterostructures. The lack of single phase multiferroic candidates exhibiting simultaneously strong and coupled magnetic and ferroelectric orders led to an increased effort into the development of artificial multiferroic heterostructures in which these orders are combined by assembling different materials. The magnetoelectric coupling emerging from the created interface between the ferroelectric and ferromagnetic layers can result in electrically tunable magnetic transition temperature, magnetic anisotropy or magnetization reversal. The full potential of low energy consumption magnetic based devices for spintronics lies in our understanding of the magnetoelectric coupling at the scale of the ferroic domains. Although the thin film synthesis progresses resulted into the complete control of ferroic domain ordering using epitaxial strain, the local observation of magnetoelectric coupling remains challenging. The ability to imprint ferroelectric domains into ferromagnets and to manipulate those solely using electric fields suggests new technological advances for spintronics such as magnetoelectric memories or memristors.

  9. Low-energy irradiation effects in cellulose

    SciTech Connect

    Polvi, Jussi; Nordlund, Kai

    2014-01-14

    Using molecular dynamics simulations, we determined the threshold energy for creating defects as a function of the incident angle for all carbon and oxygen atoms in the cellulose monomer. Our analysis shows that the damage threshold energy is strongly dependent on the initial recoil direction and on average slightly higher for oxygen atoms than for carbon atoms in cellulose chain. We also performed cumulative bombardment simulations mimicking low-energy electron irradiation (such as TEM imaging) on cellulose. Analyzing the results, we found that formation of free molecules and broken glucose rings were the most common forms of damage, whereas cross-linking and chain scission were less common. Pre-existing damage was found to increase the probability of cross-linking.

  10. Low-energy neutrino factory design

    SciTech Connect

    Ankenbrandt, C.; Bogacz, S.A.; Bross, A.; Geer, S.; Johnstone, C.; Neuffer, D.; Popovic, M.; /Fermilab

    2009-07-01

    The design of a low-energy (4 GeV) neutrino factory (NF) is described, along with its expected performance. The neutrino factory uses a high-energy proton beam to produce charged pions. The {pi}{sup {+-}} decay to produce muons ({mu}{sup {+-}}), which are collected, accelerated, and stored in a ring with long straight sections. Muons decaying in the straight sections produce neutrino beams. The scheme is based on previous designs for higher energy neutrino factories, but has an improved bunching and phase rotation system, and new acceleration, storage ring, and detector schemes tailored to the needs of the lower energy facility. Our simulations suggest that the NF scheme we describe can produce neutrino beams generated by {approx} 1.4 x 10{sup 21} {mu}{sup +} per year decaying in a long straight section of the storage ring, and a similar number of {mu}{sup -} decays.

  11. Low-energy pion-nucleon scattering

    NASA Astrophysics Data System (ADS)

    Gibbs, W. R.; Ai, Li; Kaufmann, W. B.

    1998-02-01

    An analysis of low-energy charged pion-nucleon data from recent π+/-p experiments is presented. From the scattering lengths and the Goldberger-Miyazawa-Oehme (GMO) sum rule we find a value of the pion-nucleon coupling constant of f2=0.0756+/-0.0007. We also find, contrary to most previous analyses, that the scattering volumes for the P31 and P13 partial waves are equal, within errors, corresponding to a symmetry found in the Hamiltonian of many theories. For the potential models used, the amplitudes are extrapolated into the subthreshold region to estimate the value of the Σ term. Off-shell amplitudes are also provided.

  12. RHIC low energy tests and initial operations

    SciTech Connect

    Satogata,T.; Ahrens, L.; Bai, M.; Brennan, J.M.; Bruno, D.; Butler, J.; Drees, A.; Fedotov, A.; Fischer, W.; Harvey, M.; Hayes, T.; Jappe, W.; Lee, R.C.; Mackay, W.W.; Malitsky, N.; Marr, G.; Michnoff, R.; Oerter, B.; Pozdeyev, E.; Roser, T.; Severino, F.; Smith, K.; Tepikian, S.; Tsoupas, N.

    2009-05-04

    Future Relativistic Heavy Ion Collider (RHIC) runs, including a portion of FY10 heavy ion operations, will explore collisions at center of mass energies of 5-50 GeV/n (GeV/nucleon). Operations at these energies is motivated by a search for the QCD phase transition critical point. The lowest end of this energy range is nearly a factor of four below the nominal RHIC injection center of mass energy of {radical} s = 20.8 GeV/n. There are several operational challenges in the RHIC low-energy regime, including harmonic number changes, small longitudinal acceptance, lowered magnet field quality, nonlinear orbit control, and luminosity monitoring. We report on the experience with some of these challenges during beam tests with gold in March 2008, including first RHIC operations at {radical}s = 9.18 GeV/n and first beam experience at {radical}s = 5 GeV/n.

  13. Bluetooth Low Energy Mesh Networks: A Survey.

    PubMed

    Darroudi, Seyed Mahdi; Gomez, Carles

    2017-06-22

    Bluetooth Low Energy (BLE) has gained significant momentum. However, the original design of BLE focused on star topology networking, which limits network coverage range and precludes end-to-end path diversity. In contrast, other competing technologies overcome such constraints by supporting the mesh network topology. For these reasons, academia, industry, and standards development organizations have been designing solutions to enable BLE mesh networks. Nevertheless, the literature lacks a consolidated view on this emerging area. This paper comprehensively surveys state of the art BLE mesh networking. We first provide a taxonomy of BLE mesh network solutions. We then review the solutions, describing the variety of approaches that leverage existing BLE functionality to enable BLE mesh networks. We identify crucial aspects of BLE mesh network solutions and discuss their advantages and drawbacks. Finally, we highlight currently open issues.

  14. Low energy dislocation structures in epitaxy

    NASA Technical Reports Server (NTRS)

    Van Der Merwe, Jan H.; Woltersdorf, J.; Jesser, W. A.

    1986-01-01

    The principle of minimum energy was applied to epitaxial interfaces to show the interrelationship beteen misfit, overgrowth thickness and misfit dislocation spacing. The low energy dislocation configurations were presented for selected interfacial geometries. A review of the interfacial energy calculations was made and a critical assessment of the agreement between theory and experiment was presented. Modes of misfit accommodation were presented with emphasis on the distinction between kinetic effects and equilibrium conditions. Two-dimensional and three-dimensional overgrowths were treated together with interdiffusion-modified interfaces, and several models of interfacial structure were treated including the classical and the current models. The paper is concluded by indicating areas of needed investigation into interfacial structure.

  15. Low energy wearable body-sensor-network.

    PubMed

    Yoo, Hoi-Jun; Cho, Namjun; Yoo, Jerald

    2009-01-01

    Wearable body sensor network (WBSN) is realized with wireless and wireline techniques. Body channel communication (BCC), which uses the human body as a signal transmission medium, can reduce energy consumption of a wireless on-body transceiver to less than 0.5nJ/b. The 3 pulse-based transceivers for BCC are reviewed in this paper, and their interference issues are discussed. To enhance BCC robustness, an adaptive frequency hopping scheme is applied. Fabric Area Network (FAN) is introduced with a low energy inductive coupling transceiver and a fault-tolerant switch to realize intra- and inter-layer WBSN at once. Unique wearable environment issues and the adaptation technique to overcome those issues are discussed.

  16. Spin polarized low-energy positron source

    NASA Astrophysics Data System (ADS)

    Petrov, V. N.; Samarin, S. N.; Sudarshan, K.; Pravica, L.; Guagliardo, P.; Williams, J. F.

    2015-06-01

    This paper presents an investigation of spin polarization of positrons from a source based on the decay of 22Na isotopes. Positrons are moderated by transmission through a tungsten film and electrostatically focussed and transported through a 90 deg deflector to produce a slow positron beam with polarization vector normal to the linear momentum. The polarization of the beam was determined to be about 10% by comparison with polarized electron scattering asymmetries from a thin Fe film on W(110) at 10-10 Torr. Low energy electron emission from Fe layer on W(100) surfaces under positron impact is explored. It is shown that the intensity asymmetry of the electron emission as a function of the incident positron energy can be used to estimate the polarization of the positron beam. Also several materials with long mean free paths for spin relaxation are considered as possible moderators with increased polarization of the emergent positrons.

  17. Low-energy neutral-atom spectrometer

    SciTech Connect

    Voss, D.E.; Cohen, S.A.

    1982-04-01

    The design, calibration, and performance of a low energy neutral atom spectrometer are described. Time-of-flight analysis is used to measure the energy spectrum of charge-exchange deuterium atoms emitted from the PLT tokamak plasma in the energy range from 20 to 1000 eV. The neutral outflux is gated on a 1 ..mu..sec time scale by a slotted rotating chopper disc, supported against gravity in vacuum by magnetic levitation, and is detected by secondary electron emission from a Cu-Be plate. The energy dependent detection efficiency has been measured in particle beam experiments and on the tokamak so that the diagnostic is absolutely calibrated, allowing quantitative particle fluxes to be determined with 200 ..mu..sec time resolution. In addition to its present application as a plasma diagnostic, the instrument is capable of making a wide variety of measurements relevant to atomic and surface physics.

  18. Bluetooth Low Energy Mesh Networks: A Survey

    PubMed Central

    Darroudi, Seyed Mahdi; Gomez, Carles

    2017-01-01

    Bluetooth Low Energy (BLE) has gained significant momentum. However, the original design of BLE focused on star topology networking, which limits network coverage range and precludes end-to-end path diversity. In contrast, other competing technologies overcome such constraints by supporting the mesh network topology. For these reasons, academia, industry, and standards development organizations have been designing solutions to enable BLE mesh networks. Nevertheless, the literature lacks a consolidated view on this emerging area. This paper comprehensively surveys state of the art BLE mesh networking. We first provide a taxonomy of BLE mesh network solutions. We then review the solutions, describing the variety of approaches that leverage existing BLE functionality to enable BLE mesh networks. We identify crucial aspects of BLE mesh network solutions and discuss their advantages and drawbacks. Finally, we highlight currently open issues. PMID:28640183

  19. 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.

  20. Low energy demonstration accelerator technical area 53

    SciTech Connect

    1996-04-01

    As part of the Department of Energy`s (DOE) need to maintain the capability of producing tritium in support of its historic and near-term stewardship of the nation`s nuclear weapons stockpile, the agency has recently completed a Programmatic Environmental Impact Statement for Tritium Supply and Recycling. The resulting Record of Decision (ROD) determined that over the next three years the DOE would follow a dual-track acquisition strategy that assures tritium production for the nuclear weapon stockpile in a rapid, cost effective, and safe manner. Under this strategy the DOE will further investigate and compare two options for producing tritium: (1) purchase of an existing commercial light-water reactor or irradiation services with an option to purchase the reactor for conversion to a defense facility; and (2) design, build, and test critical components of a system for accelerator production of tritium (APT). The final decision to select the primary production option will be made by the Secretary of Energy in the October 1998 time frame. The alternative not chosen as the primary production method, if feasible, would be developed as a back-up tritium supply source. This Environmental Assessment (EA) analyzes the potential environmental effects that would be expected to occur if the DOE were to design, build, and test critical prototypical components of the accelerator system for tritium production, specifically the front-end low-energy section of the accelerator, at Los Alamos National Laboratory. The Low Energy Demonstration Accelerator (LEDA) would be incrementally developed and tested in five separate stages over the next seven years. The following issues were evaluated for the proposed action: utility demands, air, human health, environmental restoration, waste management, transportation, water, threatened and endangered species, wetlands, cultural resources, and environmental justice.

  1. Low energy AMS of americium and curium

    NASA Astrophysics Data System (ADS)

    Christl, Marcus; Dai, Xiongxin; Lachner, Johannes; Kramer-Tremblay, Sheila; Synal, Hans-Arno

    2014-07-01

    Accelerator mass spectrometry (AMS) has evolved over the past years as one of the most sensitive, selective, and robust techniques for actinide analyses. While analyses of U and Pu isotopes have already become routine at the ETH Zurich 0.5 MV AMS system "Tandy", there is an increasing demand for highly sensitive analyses of the higher actinides such as Am and Cm for bioassay applications and beyond. In order to extend the actinide capabilities of the compact ETH Zurich AMS system and to develop new, more sensitive bioassay routines, a pilot study was carried out. The aim was to investigate and document the performance and the potential background of Am and Cm analyses with low energy AMS. Our results show that 241Am and Cm isotopes can be determined relative to a 243Am tracer if samples and AMS standards are prepared identically with regard to the matrix elements, in which the sample is dispersed. In this first test, detection limits for Cm and Am isotopes are all in the sub-femtogram range and even below 100 ag for Cm isotopes. In a systematic background study in the mass range of the Cm isotopes, two formerly unknown metastable triply charged Th molecules were found on amu(244) and amu(248). The presence of such a background is not a principal problem for AMS if the stripper pressure is increased accordingly. Based on our first results, we conclude that ultra-trace analyses of Am and Cm isotopes for bioassay are very well possible with low energy AMS.

  2. 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

  3. The Low Energy Effective Area of the Chandra Low Energy Transmission Grating Spectrograph

    NASA Technical Reports Server (NTRS)

    Pease, D.; Drake, J. J.; Johnson, C. O.; Kashya, V.; Ratzlaff, P. W.; Wargelin, B. J.; Brinkman, A. C.; Kaastra, J. S.; vanderMeer, R.; Paerels, F. B.

    2000-01-01

    The Chandra X-ray Observatory was successfully launched on July 23, 1999, and subsequently began an intensive calibration phase. We present the preliminary results from the in-flight calibration of the low energy response of the High Resolution Camera spectroscopic readout (HRC-S) combined with the Low Energy Transmission Grating (LETG) aboard Chandra. These instruments comprise the Low Energy Transmission Grating Spectrograph (LETGS). For this calibration study, we employ a pure hydrogen non-LTE white dwarf emission model (T = 25000 K and log g = 9.0) for comparison with the Chandra observations of Sirius B. The pre-flight calibration of the LETGS effective area only covered wavelengths shortward of 44 A (E less than 277 eV). Our Sirius B analysis shows that the HRC-S quantum efficiency (QE) model assumed for longer wavelengths leads to an overestimate of the effective area by an average factor of about 1.6. We derive a correction to the low energy HRC-S QE model to match the predicted and observed Sirius B spectra over the wavelength range of 44-185 A. We make an independent test of our results by the comparison of a Chandra LETGS observation of HZ 43 with pure hydrogen model atmosphere predictions and find good agreement.

  4. Location of Low-Energy Charged Particle Instrument

    NASA Image and Video Library

    2012-12-03

    This graphic shows the NASA Voyager 1 spacecraft and the location of its low-energy charged particle instrument. A labeled close-up of the low-energy charged particle instrument appears as the inset image.

  5. Low energy ion distribution around the Moon

    NASA Astrophysics Data System (ADS)

    Saito, Y.; Yokota, S.; Tanaka, T.; Asamura, K.; Nishino, M. N.; Yamamoto, T.; Tsunakawa, H.

    2009-04-01

    More than a year has passed since MAP-PACE onboard KAGUYA (SELENE) started continuous observation of the low energy charged particles around the Moon from 100km-altitude polar orbit. MAP (MAgnetic field and Plasma experiment) was developed for the comprehensive measurement of the magnetic field and three-dimensional plasma around the Moon. MAP consists of MAP-LMAG (Lunar MAGnetometer) and MAP-PACE (Plasma energy Angle and Composition Experiment). MAP-PACE consists of 4 sensors: ESA (Electron Spectrum Analyzer)-S1, ESA-S2, IMA (Ion Mass Analyzer), and IEA (Ion Energy Analyzer). Since each sensor has hemispherical field of view, two electron sensors and two ion sensors that are installed on the spacecraft panels opposite to each other can make full 3-dimensional measurements of low energy electrons and ions. One of the ion sensors IMA is an energy mass spectrometer. IMA measures mass identified ion energy spectra that have never been obtained at 100km altitude around the Moon. Low energy charged particles around the Moon were vigorously observed by Moon orbiting satellites and plasma instrumentation placed on the lunar surface in 1960s and 1970s. Though there were some satellites that explored the Moon afterwards, most of them were dedicated to the global mapping of the lunar surface. There has been almost no new information about the low energy charged particles around the Moon except the low energy electron measurement by Lunar Prospector, the lunar wake plasma data obtained by WIND during its Moon fly-by, and reports on remote detection of the lunar ions, lunar electrons and ULF waves generated by electron beams around the lunar wake. The newly observed data show characteristic ion distributions around the Moon. Besides the solar wind, MAP-PACE-IMA discovered four clearly distinguishable ion distributions: 1) Solar wind ions reflected/scattered at the lunar surface, 2) Solar wind ions reflected by magnetic anomalies on the lunar surface, 3) Ions that are

  6. Radiative capture versus Coulomb dissociation.

    SciTech Connect

    Esbensen, H.; Physics

    2006-01-01

    Measurements of the Coulomb dissociation of {sup 8}B have been used to infer the rate of the inverse radiative proton capture on {sup 7}Be. The analysis is usually based on the assumptions that the two processes are related by detailed balance and described by E1 transitions. However, there are corrections to this relation. The Coulomb form factors for the two processes, for example, are not identical. There are also E2 transitions and higher-order effects in the Coulomb dissociation, and the nuclear induced breakup cannot always be ignored. While adding first-order E2 transitions enhances the decay energy spectrum, the other mechanisms cause a suppression at low relative energies. The net result may accidentally be close to the conventional first-order E1 calculation, but there are differences which cannot be ignored if accuracies of 10% or better are needed.

  7. 21 CFR 878.4410 - Low energy ultrasound wound cleaner.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Low energy ultrasound wound cleaner. 878.4410... (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4410 Low energy ultrasound wound cleaner. (a) Identification. A low energy ultrasound wound cleaner is a device that...

  8. 21 CFR 878.4410 - Low energy ultrasound wound cleaner.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Low energy ultrasound wound cleaner. 878.4410... (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4410 Low energy ultrasound wound cleaner. (a) Identification. A low energy ultrasound wound cleaner is a device that...

  9. 21 CFR 878.4410 - Low energy ultrasound wound cleaner.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Low energy ultrasound wound cleaner. 878.4410... (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4410 Low energy ultrasound wound cleaner. (a) Identification. A low energy ultrasound wound cleaner is a device that...

  10. 21 CFR 878.4410 - Low energy ultrasound wound cleaner.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Low energy ultrasound wound cleaner. 878.4410... (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4410 Low energy ultrasound wound cleaner. (a) Identification. A low energy ultrasound wound cleaner is a device that...

  11. 21 CFR 878.4410 - Low energy ultrasound wound cleaner.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Low energy ultrasound wound cleaner. 878.4410... (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4410 Low energy ultrasound wound cleaner. (a) Identification. A low energy ultrasound wound cleaner is a device that...

  12. Role of the Permanent Dipole Moment in Coulomb Explosion

    NASA Astrophysics Data System (ADS)

    Zhang, Cai-Ping; Miao, Xiang-Yang

    2013-10-01

    By numerically solving the non-Born—Oppenheimer time-dependent Schrödinger equation in a few-cycle chirped laser field (5-fs, 800-nm), the effect of the permanent dipole moment on the Coulomb explosion is studied by the kinetic-energy-release spectra with the “virtual detector" method. The results indicate that with the effect of the permanent dipole moment, different multiphoton processes for heteronuclear and homonuclear diatomic molecular ions may take place when the wave packets transit from the ground state (1sσg) to the first excited state (2pσu), and then move along the excited potential curve, and finally charge-resonant enhanced ionization occurs at critical internuclear distance. As a result, despite the similar ionization probabilities for these two systems at higher vibrational level with larger chirp parameter β, the structure of the Coulomb explosion spectrum for the former is prominently different from that for the latter.

  13. Coulomb interactions in particle beams

    SciTech Connect

    Jansen, G.H. )

    1990-01-01

    This book develops analytical and computer models for beams in which Coulomb interactions are important. The research into the different phenomena of Coulomb interactions in particle beams is stimulated by developments in the field of electron beam lithography for VLSI electronics. The standard theory of charged particle optics breaks down for intense beams in which interactions between particles are significant. This monograph is devoted to the theory of these intense beams, which are not only used in VLSI electronics but also in scanning electron microscopes. The theory is also applicable to focused ion beams, which are used in VLSI mask repair.

  14. Abnormal Heating of Low-Energy Electrons in Low-Pressure Capacitively Coupled Discharges

    SciTech Connect

    Park, G. Y.; You, S. J.; Iza, F.; Lee, J. K.

    2007-02-23

    In low-pressure capacitively coupled plasmas, high-energy electrons are collisionlessly heated by large rf fields in the sheaths while low-energy electrons are confined in the bulk plasma by the ambipolar potential. Low-energy electrons are typically inefficiently heated due to their low collisionality and the weak rf electric field present in the bulk. It is shown, however, that as a result of the nonlinear interaction between the electron motion and the weak rf field present in the bulk, low-energy electrons can be efficiently heated. Electrons in the bulk that bounce inside the electrostatic potential well with a frequency equal to the rf excitation frequency are efficiently heated by the coherent interaction with the rf field. This resonant collisionless heating can be very efficient and manifest itself as a plateau in the electron energy probability function.

  15. Abnormal heating of low-energy electrons in low-pressure capacitively coupled discharges.

    PubMed

    Park, G Y; You, S J; Iza, F; Lee, J K

    2007-02-23

    In low-pressure capacitively coupled plasmas, high-energy electrons are collisionlessly heated by large rf fields in the sheaths while low-energy electrons are confined in the bulk plasma by the ambipolar potential. Low-energy electrons are typically inefficiently heated due to their low collisionality and the weak rf electric field present in the bulk. It is shown, however, that as a result of the nonlinear interaction between the electron motion and the weak rf field present in the bulk, low-energy electrons can be efficiently heated. Electrons in the bulk that bounce inside the electrostatic potential well with a frequency equal to the rf excitation frequency are efficiently heated by the coherent interaction with the rf field. This resonant collisionless heating can be very efficient and manifest itself as a plateau in the electron energy probability function.

  16. Soft X-ray bremsstrahlung and fluorescent line production in the atmosphere by low energy electrons

    NASA Technical Reports Server (NTRS)

    Kraushaar, W. L.

    1974-01-01

    The effect of low energy quasi-trapped or precipitating electrons which impact on the counter windows of soft X-ray detectors are discussed. The errors caused by X-rays produced in the residual atmosphere above a rocket-borne detector because of the resemblance to X-rays of cosmic origin are examined. The design and development of counter windows which make it possible to identify the atmospherically produced X-rays are described. Curves are presented to show the following: (1) preliminary low energy electron data from Atmospheric Explorer C, (2) X-ray flux in electron-excited nitrogen and oxygen, (3) typical proportional counter response to low energy cosmic rays, and (4) proportional counter response to X-radiation produced by electrons incident upon a gas of oxygen to nitrogen number of 0.4.

  17. MicroBooNE: The Search For The MiniBooNE Low Energy Excess

    NASA Astrophysics Data System (ADS)

    Kaleko, David

    This thesis describes work towards the search for a low energy excess of electromagnetic events in the MicroBooNE detector. A background primer on the current state of neutrino physics is provided, including a description of the MiniBooNE detector and its published observation of an excess of electromagnetic events at low energies. A description of the MicroBooNE Liquid Argon Time Projection Chamber (LArTPC) detector is given, along with a description of the event selection and reconstruction algorithms developed to select electron neutrino charge-current interactions. A MiniBooNE-like signal is simulated in MicroBooNE with assumptions about the origin of the excess, and the sensitivity to observe such a signal above backgrounds in MicroBooNE is computed. An additional analysis is presented which constrains a dominant background in the MicroBooNE low energy excess search: the beam-intrinsic electron neutrino interactions which come from kaon decay in the beam-line. An essential step in this analysis is to reconstruct the energy of muon neutrino charge-current interactions in which the muon produced in the interaction escapes the detector. A publication detailing the algorithm which leverages the phenomenon of multiple Coulomb scattering to reconstruct the energy of escaping muons is provided as an appendix.

  18. Low Energy Electron Scattering from Fuels

    NASA Astrophysics Data System (ADS)

    Lopes, M. Cristina A.

    2012-06-01

    We report an investigation of processes that occur during the ignition of the plasma and its consequences in post-discharge time for an internal combustion engine, in order to find the appropriate parameters to be used in cars that operate with lean mixtures air-fuel. The relevance of this theme has attracted much attention, and has been one of the subjects of collaboration between experimental and theoretical groups in the USA and Brazil. We have produced some basic information necessary to modeling spark ignition in alcohol- fuelled engines. Total cross sections of electron scattering by methanol and ethanol molecules were obtained, using the linear transmission method based on the Beer-Lambert law to first approximation. Measurements and calculations of differential cross sections for low-energy (rotationally unresolved) electron scattering were also obtained, for scattering angles of 5 --130 . The measurements were taken using the relative flow method with an aperture source, and calculations using two different implementations of the Schwinger multichannel method, one that takes all electrons into account and is adapted for parallel computers, and another that uses pseudopotentials and considers only the valence electrons. Additionally to these, computer simulation studies of electronic discharge in mixtures of ethanol were performed, using a Zero-Dimensional Plasma Kinetic solver. Previous reported models for combustion of ethanol and cross sections data for momentum transfer of electron collisions with ethanol were used. The time evolutions of the main species densities are reported and the ignition time delay discussed.

  19. Low Energy Electron Scattering from Fuels

    NASA Astrophysics Data System (ADS)

    Lopes, M. C. A.; Silva, D. G. M.; Bettega, M. H. F.; da Costa, R. F.; Lima, M. A. P.; Khakoo, M. A.; Winstead, C.; McKoy, V.

    2012-11-01

    In order to understand and optimize processes occurring during the ignition of plasma and its consequences in post-discharge for an internal combustion engine, especially considering the spark plug, we have produced in this work some basic information necessary to modeling spark ignition in alcohol- fuelled engines. Total cross sections of electron scattering by methanol and ethanol molecules in the energy range from 60 to 500 eV are reported, using the linear transmission method based on the Beer-Lambert law to first approximation. Aditionally to that, measurements and calculations of differential cross sections for elastic low-energy (rotationally unresolved) electron scattering were also discussed, for impact energies of 1, 2, 5, 10, 15, 20, 30, 50, and 100 eV and for scattering angles of 5°-130°. The measurements were obtained using the relative flow method with an aperture source, and calculations using two different implementations of the Schwinger multichannel method, one that takes all electrons into account and is adapted for parallel computers, and another that uses pseudopotentials and considers only the valence electrons.

  20. Discrete R symmetries and low energy supersymmetry

    SciTech Connect

    Dine, Michael; Kehayias, John

    2010-09-01

    If nature exhibits low energy supersymmetry, discrete (non-Z{sub 2}) R symmetries may well play an important role. In this paper, we explore such symmetries. We generalize gaugino condensation, constructing large classes of models which are classically scale invariant, and which spontaneously break discrete R symmetries (but not supersymmetry). The order parameters for the breaking include chiral singlets. These simplify the construction of models with metastable dynamical supersymmetry breaking. We explain that in gauge mediation, the problem of the cosmological constant makes ''retrofitting'' particularly natural--almost imperative. We describe new classes of models, with interesting scales for supersymmetry breaking, and which allow simple solutions of the {mu} problem. We argue that models exhibiting such R symmetries can readily solve not only the problem of dimension four operators and proton decay, but also dimension five operators. On the other hand, in theories of ''gravity mediation,'' the breaking of an R symmetry is typically of order M{sub p}; R parity is required to suppress dimension four B and L violating operators, and dimension five operators remain problematic.

  1. Shadowing in low-energy photonuclear reactions

    NASA Astrophysics Data System (ADS)

    Das, Swapan

    2017-09-01

    The photonuclear reaction in the multi-GeV region occurs because of the electromagnetic and hadronic interactions. The latter originates due to the hadronic fluctuation, i.e., vector meson, of the photon. The total cross section of the reaction is shadowed because of the vector meson-nucleus (hadronic) interaction. To estimate it quantitatively, the cross section of the photonuclear reaction was calculated in the low energy region (˜1 -3 GeV) using the simple vector-meson dominance (SVMD) model, i.e., the low-lying vector mesons (ρ0, ω , and ϕ mesons) were considered. The nuclear shadowing is reinvestigated using the generalized vector meson (GVMD) model, where the higher ρ meson effective state (ρ' meson) is taken into account along with the low-lying vector mesons. Using the GVMD model, the total cross section of the photonuclear reaction are calculated in the above mentioned energy region. The calculated results are compared with the measured spectra.

  2. Low energy CMOS for space applications

    NASA Technical Reports Server (NTRS)

    Panwar, Ramesh; Alkalaj, Leon

    1992-01-01

    The current focus of NASA's space flight programs reflects a new thrust towards smaller, less costly, and more frequent space missions, when compared to missions such as Galileo, Magellan, or Cassini. Recently, the concept of a microspacecraft was proposed. In this concept, a small, compact spacecraft that weighs tens of kilograms performs focused scientific objectives such as imaging. Similarly, a Mars Lander micro-rover project is under study that will allow miniature robots weighing less than seven kilograms to explore the Martian surface. To bring the microspacecraft and microrover ideas to fruition, one will have to leverage compact 3D multi-chip module-based multiprocessors (MCM) technologies. Low energy CMOS will become increasingly important because of the thermodynamic considerations in cooling compact 3D MCM implementations and also from considerations of the power budget for space applications. In this paper, we show how the operating voltage is related to the threshold voltage of the CMOS transistors for accomplishing a task in VLSI with minimal energy. We also derive expressions for the noise margins at the optimal operating point. We then look at a low voltage CMOS (LVCMOS) technology developed at Stanford University which improves the power consumption over conventional CMOS by a couple of orders of magnitude and consider the suitability of the technology for space applications by characterizing its SEU immunity.

  3. Low energy stable plasma calibration facility.

    PubMed

    Frederick-Frost, K M; Lynch, K A

    2007-07-01

    We have designed and fabricated a low energy plasma calibration facility for testing and calibration of rocket-borne charged-particle detectors and for the investigation of plasma sheath formation in an environment with ionospheric plasma energies, densities, and Debye lengths. We describe the vacuum system and associated plasma source, which was modified from a Naval Research Laboratory design [Bowles et al. Rev. Sci. Instrum. 67, 455 (1996)]. Mechanical and electrical modifications to this cylindrical microwave resonant source are outlined together with a different method of operating the magnetron that achieves a stable discharge. This facility produces unmagnetized plasmas with densities from 1x10(3)/cm(3) to 6x10(5)/cm(3), electron temperatures from 0.1 to 1.7 eV, and plasma potentials from 0.5 to 8 V depending on varying input microwave power and neutral gas flow. For the range of input microwave power explored (350-600 W), the energy density of the plasma remains constant because of an inverse relationship between density and temperature. This relationship allows a wide range of Debye lengths (0.3-8.4 cm) to be investigated, which is ideal for simulating the ionospheric plasma sheaths we explore.

  4. Low energy neutral atom imaging techniques

    SciTech Connect

    Funsten, H.O. McComas, D.J.; Scime, E.E.

    1993-01-01

    The potential scientific return from low energy neutral atom (LENA) imaging of the magnetosphere is extraordinary. The technical challenges of LENA detection include (1) removal of LENAs from the tremendous ambient UV without losing information of their incident trajectories, (2) quantification of their trajectories, and (3) obtaining high sensitivity measurements. Two techniques that have been proposed for this purpose are based on fundamentally different atomic interaction mechanisms between LENAs and a solid: LENA transmission through an ultrathin foil and LENA reflection from a solid surface. Both of these methods provide LENA ionization (for subsequent removal from the UV by electrostatic deflection) and secondary electron emission (for start pulse generation for time-of-flight and/or coincidence). We present a comparative study of the transmission and reflection techniques based on differences in atomic interactions with solids and surfaces. We show that transmission methods yield an order of magnitude greater secondary electron emission than reflection methods. Transmission methods are shown to be sufficient for LENA energies of approximately 1 keV to greater than 30 keV. Reflection methods using low work function surfaces could be employed for LENA ionization for energies less than several keV.

  5. Studies in Low-Energy Nuclear Science

    SciTech Connect

    Brune, Carl R; Grimes, Steven M

    2006-03-30

    This report presents a summary of research projects in the area of low energy nuclear reactions and structure, carried out between 1 January 2003 and 31 December 2005 and supported by U.S. DOE grant number DE-FG03-03NA00074. Cross sections measured with high resolution have been subjected to an Ericson theory analysis to infer information about the nuclear level density. Other measurements were made of the spectral shape of particles produced in evaporation processes; these also yield level density information. A major project was the development of a new Hauser-Feshbach code for analyzing such spectra. Other measurements produced information on the spectra of gamma rays emitted in reactions on heavy nuclei and gave a means of refining our understanding of gamma-ray strength functions. Finally,reactions on light nuclei were studied and subjected to an R-matrix analysis. Cross sections fora network of nuclear reactions proceedingthrough a given compound nucleus shouldgreatly constrain the family of allowed parameters. Modifications to the formalism andcomputer code are also discussed.

  6. Optimal Low Energy Earth-Moon Transfers

    NASA Technical Reports Server (NTRS)

    Griesemer, Paul Ricord; Ocampo, Cesar; Cooley, D. S.

    2010-01-01

    The optimality of a low-energy Earth-Moon transfer is examined for the first time using primer vector theory. An optimal control problem is formed with the following free variables: the location, time, and magnitude of the transfer insertion burn, and the transfer time. A constraint is placed on the initial state of the spacecraft to bind it to a given initial orbit around a first body, and on the final state of the spacecraft to limit its Keplerian energy with respect to a second body. Optimal transfers in the system are shown to meet certain conditions placed on the primer vector and its time derivative. A two point boundary value problem containing these necessary conditions is created for use in targeting optimal transfers. The two point boundary value problem is then applied to the ballistic lunar capture problem, and an optimal trajectory is shown. Additionally, the ballistic lunar capture trajectory is examined to determine whether one or more additional impulses may improve on the cost of the transfer.

  7. Oscillations of very low energy atmospheric neutrinos

    SciTech Connect

    Peres, Orlando L. G.; Smirnov, A. Yu.

    2009-06-01

    There are several new features in the production, oscillations, and detection of the atmospheric neutrinos of low energies E < or approx. 100 MeV. The flavor ratio r of muon to electron neutrino fluxes is substantially smaller than 2 and decreases with energy, a significant part of events is due to the decay of invisible muons at rest, etc. Oscillations in a two-layer medium (atmosphere-Earth) should be taken into account. We derive analytical and semianalytical expressions for the oscillation probabilities of these 'sub-sub-GeV' neutrinos. The energy spectra of the e-like events in water Cherenkov detectors are computed, and the dependence of the spectra on the 2-3 mixing angle {theta}{sub 23}, the 1-3 mixing, and the CP-violation phase are studied. We find that variations of {theta}{sub 23} in the presently allowed region change the number of e-like events by about 15%-20% as well as lead to distortion of the energy spectrum. The 1-3 mixing and CP violation can lead to {approx}10% effects. Detailed study of the sub-sub-GeV neutrinos will be possible in future megaton-scale detectors.

  8. RHIC low-energy challenges and plans

    SciTech Connect

    Satogata,T.; Ahrens, L.; Bai, M.; Brennan, J.M.; Bruno, D.; Butler, J.; Drees, A.; Fedotov, A.; Fischer, W.; Harvey, M.; Hayes, T.; Jappe, W.; Lee, R.C.; MacKay, W.W.; Malitsky, N.; Marr, G.; Michnoff, R.; Oerter, B.; Pozdeyev, E.; Roser, T.; Schoefer, V.; Severino, F.; Smith, K.; Tepikian, S.; Tsoupas, N.

    2009-06-08

    Future Relativistic Heavy Ion Collider (RHIC) runs, including a portion of FY10 heavy ion operations, will explore collisions at center of mass energies of 5-50 GeV/n (GeV/nucleon). Operations at these energies is motivated by the search for a possible QCD phase transition critical point. The lowest end of this energy range is nearly a factor of four below the nominal RHIC injection center of mass energy {radical}s = 19.6 GeV/n. There are several operational challenges in the RHIC low-energy regime, including harmonic number changes, small longitudinal acceptance, lowered magnet field quality, nonlinear orbit control, and luminosity monitoring. We report on the experience with these challenges during beam tests with gold beams in March 2008. This includes first operations at {radical}s = 9.18 GeV/n, first beam experience at {radical}s = 5 GeV/n, and luminosity projections for near-term operations.

  9. Decomposition of methionine by low energy electrons.

    PubMed

    Kopyra, Janina; Szamrej, Iwona; Abdoul-Carime, Hassan; Farizon, Bernadette; Farizon, Michel

    2012-06-14

    In this work, we present the results from low energy (<12 eV) electron impact on isolated methionine, Met. We show that dissociative electron attachment is the operative mechanism for the sulfur content amino-acid fragmentation. The two most dominant fragments are attributed to the (Met-H)(-) and (C(4)NOH(5))(-) ions that are formed at energy below 2 eV. The formation of the latter anion is accompanied by the loss of neutral counterparts, which are most likely a water molecule and highly toxic methanethiol, CH(3)SH. Further fragments are associated with the damage at the sulfur end of the amino acid, producing the methyl sulfide anion CH(3)S(-) or sulfur containing neutrals. In the context of radiation induced damage to biological material at the nano-scale level, the present interest of methionine arises from the implication of the molecule in biological processes (e.g., S-adenosyl methionine for the stimulation of DNA methyltransferase reactions or protein synthesis).

  10. Low-energy electron collisions with biomolecules

    NASA Astrophysics Data System (ADS)

    Winstead, Carl; McKoy, Vincent

    2012-11-01

    We report recent progress in applying the Schwinger multichannel computational method to the interactions of slow electrons with biomolecules. Calculations on constituents of DNA, including nucleobases, phosphate esters, and models of the backbone sugar, have provided insight into the nature of the low-energy shape resonances, and thereby into possible sites and mechanisms for electron attachment that may lead to strand-breaking. At the same time, more approximate calculations on larger assemblies such as nucleosides and deoxyadenosine monophosphate indicate how the resonance properties of the subunits will or will not persist in DNA itself. We are pursuing a similar strategy for another major class of biomolecules, the proteins, by beginning with fixed-nuclei studies of the constituent amino acids; here we present preliminary results for the simplest amino acid, glycine. We also describe efforts directed at an improved understanding electron collisions with alcohols, which, in addition to basic scientific interest, may prove useful in the modeling of ignition and combustion within biofuel-powered engines.

  11. Low-energy structure of the even-A {sup 96-104}Ru isotopes via g-factor measurements

    SciTech Connect

    Taylor, M. J.; Bentley, M. A.; Guerdal, G.; Kumbartzki, G.; Benczer-Koller, N.; Sharon, Y. Y.; Stuchbery, A. E.; Berant, Z.; Casperson, R. J.; Casten, R. F.; Heinz, A.; Ilie, G.; McCutchan, E. A.; Qian, J.; Werner, V.; Williams, E.; Winkler, R.; Luettke, R.; Shoraka, B.

    2011-04-15

    The transient-field-perturbed angular correlation technique was used with Coulomb excitation in inverse kinematics to perform a systematic measurement of the g factors of the first excited 2{sub 1}{sup +} states in the stable even-A isotopes {sup 96-104}Ru. The measurements have been made relative to one another under matched kinematic conditions and include a measurement of g(2{sub 1}{sup +})=+0.47(3) in {sup 96}Ru.

  12. Information Content of the Low-Energy Electric Dipole Strength: Correlation Analysis

    SciTech Connect

    Reinhard, P.-G.; Nazarewicz, Witold

    2013-01-01

    Background: Recent experiments on the electric dipole (E1) polarizability in heavy nuclei have stimulated theoretical interest in the low-energy electric dipole strength, both isovector and isoscalar. Purpose: We study the information content carried by the electric dipole strength with respect to isovector and isoscalar indicators characterizing bulk nuclear matter and finite nuclei. To separate isoscalar and isovector modes, and low-energy strength and giant resonances, we analyze the E1 strength as a function of the excitation energy E and momentum transfer q. Methods: We use the self-consistent nuclear density functional theory with Skyrme energy density functionals, augmented by the random phase approximation, to compute the E1 strength and covariance analysis to assess correlations between observables. Calculations are performed for the spherical, doubly magic nuclei 208Pb and 132Sn. Results: We demonstrate that E1 transition densities in the low-energy region below the giant dipole resonance exhibit appreciable state dependence and multinodal structures, which are fingerprints of weak collectivity. The correlation between the accumulated low-energy strength and the symmetry energy is weak, and dramatically depends on the energy cutoff assumed. On the other hand, a strong correlation is predicted between isovector indicators and the accumulated isovector strength at E around 20 MeV and momentum transfer q 0.65 fm 1. Conclusions: Momentum- and coordinate-space patterns of the low-energy dipole modes indicate a strong fragmentation into individual particle-hole excitations. The global measure of low-energy dipole strength correlates poorly with the nuclear symmetry energy and other isovector characteristics. Consequently, our results do not support the suggestion that there exists a collective pygmy dipole resonance, which is a strong indicator of nuclear isovector properties. By considering nonzero values of momentum transfer, one can isolate individual

  13. Low energy x-ray spectrometer

    SciTech Connect

    Woodruff, W.R.

    1981-06-05

    A subkilovolt spectrometer has been produced to permit high-energy-resolution, time-dependent x-ray intensity measurements. The diffracting element is a curved mica (d = 9.95A) crystal. To preclude higher order (n > 1) diffractions, a carbon x-ray mirror that reflects only photons with energies less than approx. 1.1 keV is utilized ahead of the diffracting element. The nominal energy range of interest is 800 to 900 eV. The diffracted photons are detected by a gold-surface photoelectric diode designed to have a very good frequency response, and whose current is recorded on an oscilloscope. A thin, aluminium light barrier is placed between the diffracting crystal and the photoelectric diode detector to keep any uv generated on or scattered by the crystal from illuminating the detector. High spectral energy resolution is provided by many photocathodes between 8- and 50-eV wide placed serially along the diffracted x-ray beam at the detector position. The spectrometer was calibrated for energy and energy dispersion using the Ni L..cap alpha../sub 1/ /sub 2/ lines produced in the LLNL IONAC accelerator and in third order using a molybdenum target x-ray tube. For the latter calibration the carbon mirror was replaced by one surfaced with rhodium to raise the cut-off energy to about 3 keV. The carbon mirror reflection dependence on energy was measured using one of our Henke x-ray sources. The curved mica crystal diffraction efficiency was measured on our Low-Energy x-ray (LEX) machine. The spectrometer performs well although some changes in the way the x-ray mirror is held are desirable. 16 figures.

  14. Low energy beam transport system developments

    SciTech Connect

    Dudnikov, V.; Han, B.; Stockli, M.; Welton, R.; Dudnikova, G.

    2015-04-08

    For high brightness beam production it is important to preserve the brightness in the low energy beam transport system (LEBT) used to transport and match the ion beams to the next stage of acceleration, usually an RFQ. While electrostatic focusing can be problematic for high current beam transport, reliable electrostatic LEBT operation has been demonstrated with H{sup −} beams up to 60 mA. Now, however, it is commonly accepted that an optimal LEBT for high current accelerator applications consists of focusing solenoids with space charge compensation. Two-solenoid LEBTs are successfully used for high current (>100 mA) proton beam transport. Preservation of low emittances (~0.15 π mm-mrad) requires the addition of a heavy gas (Xe, Kr), which causes ~5% of proton loss in a 1 m long LEBT. Similar Xe densities would be required to preserve low emittances of H{sup −} beams, but such gas densities cause unacceptably high H{sup −} beam losses. A short LEBT with only one short solenoid, movable for RFQ matching, can be used for reduced negative ion stripping. A strong electrostatic-focusing LEBT has been successfully adopted for transport of high current H{sup −} beams in the SNS Front End. Some modifications of such electrostatic LEBTs are expected to improve the reliable transport of intense positive and negative ion beams without greatly degrading their low emittances. We concentrate on processes that determine the beam brightness degradation and on their prevention. Proposed improvements to the SNS electrostatic LEBT are discussed.

  15. Low energy beam transport for HIDIF

    NASA Astrophysics Data System (ADS)

    Meusel, O.; Pozimski, J.; Jakob, A.; Lakatos, A.

    2001-05-01

    Low energy beam transport (LEBT) for a heavy ion inertial fusion (HIDIF, I. Hofmann and G. Plass, Report of the European Study Group on Heavy Ion Driven Inertial Fusion for the Period 1995-1998) facility suffers from high space charge forces and high ion mass. Space charge compensation reduces the necessary focusing force of the lenses and the radius of the beam in the LEBT, and therefrom the emittance growth due to aberrations and self fields is reduced. Gabor lenses (D. Gabor, Nature 160 (1947)) providing a stable space charge cloud for focusing and combine strong cylinder symmetric focusing with partly space charge compensation and low emittance growth. A high tolerance against source noise and current fluctuations and reduced investment costs could be other possible advantages. The proof of principle has already been demonstrated (J.A. Palkovic, Measurements on a Gabor lens for Neutralizing and Focusing a 30 keV Proton beam, University of Wisconsin, Madison, 1989; J. Pozimski, P. Groß, R. Dölling and T. Weis, First experimental studies of a Gabor plasma-lens in Frankfurt, Proceedings of the 3rd EPAC Conference, Berlin, 1992). To broaden the experiences and to investigate the realisation of a LEBT concept for the HIDIF injector an experimental program using two Gabor lenses for independent variation of beam radius and envelope angel at RFQ injection was started. Therefrom the first experimental results using a double Gabor lens (DGPL) LEBT system for transporting an high perveance Xe + beam are presented and the results of numerical simulations are shown.

  16. 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

  17. Photodetachment of hydrogen negative ions with screened Coulomb interaction

    SciTech Connect

    Zhang, Song Bin; Chen, Xiang Jun; Wang, Jian Guo; Janev, R. K.; Qu, Yi Zhi

    2010-06-15

    The effects of Coulomb interaction screening on photodetachment cross sections of hydrogen negative ions below the n =2 excitation threshold is investigated by using the R-matrix method with pseudostates. The contributions of Feshbach and shape resonances to H{sup -} photodetachment cross section are presented when screening length (D) varies from D = {infinity} to D = 4.6 a.u. It is found that the interaction screening has dramatic effects on the photodetachment cross sections of hydrogen negative ions in the photoelectron energy region around the n = 2 excitation threshold by strongly affecting the evolution of near-threshold resonances.

  18. Imaging of Acoustic Waves in Piezoelectric Ceramics by Coulomb Coupling

    NASA Astrophysics Data System (ADS)

    Habib, Anowarul; Shelke, Amit; Pluta, Mieczyslaw; Kundu, Tribikram; Pietsch, Ullrich; Grill, Wolfgang

    2012-07-01

    The transport properties of bulk and guided acoustic waves travelling in a lead zirconate titanate (PZT) disc, originally manufactured to serve as ultrasonic transducer, have been monitored by scanned Coulomb coupling. The images are recorded by excitation and detection of ultrasound with local electric field probes via piezoelectric coupling. A narrow pulse has been used for excitation. Broadband coupling is achieved since neither mechanical nor electrical resonances are involved. The velocities of the traveling acoustic waves determined from the images are compared with characteristic velocities calculated from material properties listed by the manufacturer of the PZT plate.

  19. Analytical expressions for partial wave two-body Coulomb transition matrices at ground-state energy

    NASA Astrophysics Data System (ADS)

    Kharchenko, V. F.

    2016-11-01

    Leaning upon the Fock method of the stereographic projection of the three-dimensional momentum space onto the four-dimensional unit sphere the possibility of the analytical solving of the Lippmann-Schwinger integral equation for the partial wave two-body Coulomb transition matrix at the ground bound state energy has been studied. In this case new expressions for the partial p-, d- and f-wave two-body Coulomb transition matrices have been obtained in the simple analytical form. The developed approach can also be extended to determine analytically the partial wave Coulomb transition matrices at the energies of excited bound states.

  20. Carrier scattering processes and low energy phonon spectroscopy in hybrid perovskites crystals

    NASA Astrophysics Data System (ADS)

    Even, Jacky; Paofai, Serge; Bourges, Philippe; Letoublon, Antoine; Cordier, Stéphane; Durand, Olivier; Katan, Claudine

    2016-03-01

    Despite the wealth of research conducted the last three years on hybrid organic perovskites (HOP), several questions remain open including: to what extend the organic moiety changes the properties of the material as compared to allinorganic (AIP) related perovskite structures. To ultimately reach an answer to this question, we have recently introduced two approaches that were designed to take the stochastic molecular degrees of freedom into account, and suggested that the high temperature cubic phase of HOP and AIP is an appropriate reference phase to rationalize HOP's properties. In this paper, we recall the main concepts and discuss more specifically the various possible couplings between charge carriers and low energy excitations such as acoustic and optical phonons. As available experimental or simulated data on low energy excitations are limited, we also present preliminary neutron scattering and ultrasonic measurements obtained and freshly prepared single crystals of CH3NH3PbBr3.

  1. Reactions induced by low energy electrons in cryogenic films (Review)

    NASA Astrophysics Data System (ADS)

    Bass, A. D.; Sanche, L.

    2003-03-01

    We review recent research on reactions (including dissociation) initiated by low-energy electron bombardment of monolayer and multilayer molecular solids at cryogenic temperatures. With incident electrons of energies below 20 eV, dissociation is observed by the electron stimulated desorption (ESD) of anions from target films and is attributed to the processes of dissociative electron attachment (DEA) and to dipolar dissociation. It is shown that DEA to condensed molecules is sensitive to environmental factors such as the identity of co-adsorbed species and film morphology. The effects of image-charge induced polarization on cross sections for DEA to CH3Cl are also discussed. Taking as example, the electron-induced production of CO within multilayer films of methanol and acetone, it is shown that the detection of electronic excited states by high-resolution electron energy loss spectroscopy can be used to monitor electron beam damage. In particular, the incident energy dependence of the CO indicates that below 19 eV, dissociation proceeds via the decay of transient negative ions (TNI) into electronically excited dissociative states. The electron-induced dissociation of biomolecular targets is also considered, taking as examples the ribose analog tetrahydrofuran and DNA bases adenine and thymine, cytosine and guanine. The ESD of anions from such films also show dissociation via the formation of TNI. In multilayer molecular solids, fragment species resulting from dissociation, may react with neighboring molecules, as is demonstrated in anion ESD measurements from films containing O2 and various hydrocarbon molecules. X-ray photoelectron spectroscopy measurements reported for electron-irradiated monolayers of H2O and CF4 on a Si-H passivated surface further show that DEA is an important initial step in the electron-induced chemisorption of fragment species.

  2. Collisions of low-energy electrons with cyclohexane

    SciTech Connect

    Barbosa, Alessandra Souza; Bettega, Márcio H. F.

    2014-12-28

    We report calculated cross sections for elastic scattering of low-energy electrons by cyclohexane (c-C{sub 6}H{sub 12}). We employed the Schwinger multichannel method implemented with norm-conserving pseudopotentials in the static-exchange and static-exchange plus polarization approximations, for impact energies up to 30 eV. We compare our calculated integral cross section with experimental total cross sections available in the literature. We also compare our calculated differential cross sections (DCSs) with experimental results for benzene and experimental and theoretical results for 1,4-dioxane, in order to investigate the similarities between those molecules under electron collisions. Although benzene is a cyclic six-carbon molecule, as cyclohexane, we found that the differential cross sections of the latter are more similar to those of 1,4-dioxane than those of benzene. These similarities suggest that the geometry may play an important role in the behavior of the DCSs of these molecules. Our integral cross section displays a broad structure at around 8.5 eV, in agreement with the total cross section experimental data of 8 eV and vibrational excitation data of 7.5 eV. The present integral cross section also shows the presence of a Ramsauer-Townsend minimum at around 0.12 eV. In general, our integral cross section shows a qualitative agreement with the experimental total cross section.

  3. A compact, versatile low-energy electron beam ion source

    SciTech Connect

    Zschornack, G.; König, J.; Schmidt, M.; Thorn, A.

    2014-02-15

    A new compact Electron Beam Ion Source, the Dresden EBIT-LE, is introduced as an ion source working at low electron beam energies. The EBIT-LE operates at an electron energy ranging from 100 eV to some keV and can easily be modified to an EBIT also working at higher electron beam energies of up to 15 keV. We show that, depending on the electron beam energy, electron beam currents from a few mA in the low-energy regime up to about 40 mA in the high-energy regime are possible. Technical solutions as well as first experimental results of the EBIT-LE are presented. In ion extraction experiments, a stable production of low and intermediate charged ions at electron beam energies below 2 keV is demonstrated. Furthermore, X-ray spectroscopy measurements confirm the possibility of using the machine as a source of X-rays from ions excited at low electron energies.

  4. A compact, versatile low-energy electron beam ion source.

    PubMed

    Zschornack, G; König, J; Schmidt, M; Thorn, A

    2014-02-01

    A new compact Electron Beam Ion Source, the Dresden EBIT-LE, is introduced as an ion source working at low electron beam energies. The EBIT-LE operates at an electron energy ranging from 100 eV to some keV and can easily be modified to an EBIT also working at higher electron beam energies of up to 15 keV. We show that, depending on the electron beam energy, electron beam currents from a few mA in the low-energy regime up to about 40 mA in the high-energy regime are possible. Technical solutions as well as first experimental results of the EBIT-LE are presented. In ion extraction experiments, a stable production of low and intermediate charged ions at electron beam energies below 2 keV is demonstrated. Furthermore, X-ray spectroscopy measurements confirm the possibility of using the machine as a source of X-rays from ions excited at low electron energies.

  5. Low-energy Cathodoluminescence for (Oxy)Nitride Phosphors

    PubMed Central

    Cho, Yujin; Dierre, Benjamin; Sekiguchi, Takashi; Suehiro, Takayuki; Takahashi, Kohsei; Takeda, Takashi; Xie, Rong-Jun; Yamamoto, Yoshinobu; Hirosaki, Naoto

    2016-01-01

    Nitride and oxynitride (Sialon) phosphors are good candidates for the ultraviolet and visible emission applications. High performance, good stability and flexibility of their emission properties can be achieved by controlling their composition and dopants. However, a lot of work is still required to improve their properties and to reduce the production cost. A possible approach is to correlate the luminescence properties of the Sialon particles with their local structural and chemical environment in order to optimize their growth parameters and find novel phosphors. For such a purpose, the low-voltage cathodoluminescence (CL) microscopy is a powerful technique. The use of electron as an excitation source allows detecting most of the luminescence centers, revealing their luminescence distribution spatially and in depth, directly comparing CL results with the other electron-based techniques, and investigating the stability of their luminescence properties under stress. Such advantages for phosphors characterization will be highlighted through examples of investigation on several Sialon phosphors by low-energy CL. PMID:27911365

  6. Photon strength and the low-energy enhancement

    NASA Astrophysics Data System (ADS)

    Wiedeking, M.; Bernstein, L. A.; Krtička, 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.

    2014-08-01

    Several measurements in medium mass nuclei have reported a low-energy enhancement in the photon strength function. Although, much effort has been invested in unraveling the mysteries of this effect, its physical origin is still not conclusively understood. Here, a completely model-independent experimental approach to investigate the existence of this enhancement is presented. The experiment was designed to study statistical feeding from the quasi-continuum (below the neutron separation energy) to individual low-lying discrete levels in 95Mo produced in the (d, p) reaction. A key aspect to successfully study gamma decay from the region of high-level density is the detection and extraction of correlated particle-gamma-gamma events which was accomplished using an array of Clover HPGe detectors and large area annular silicon detectors. The entrance channel excitation energy into the residual nucleus produced in the reaction was inferred from the detected proton energies in the silicon detectors. Gating on gamma-transitions originating from low-lying discrete levels specifies the state fed by statistical gamma-rays. Any particle-gamma-gamma event in combination with specific energy sum requirements ensures a clean and unambiguous determination of the initial and final state of the observed gamma rays. With these requirements the statistical feeding to individual discrete levels is extracted on an event-by-event basis. The results are presented and compared to 95Mo photon strength function data measured at the University of Oslo.

  7. Projectile - Mass asymmetry systematics for low energy incomplete fusion

    NASA Astrophysics Data System (ADS)

    Singh, Pushpendra P.; Yadav, Abhishek; Sharma, Vijay R.; Sharma, Manoj K.; Kumar, Pawan; Sahoo, Rudra N.; Kumar, R.; Singh, R. P.; Muralithar, S.; Singh, B. P.; Bhowmik, R. K.; Prasad, R.

    2015-06-01

    In the present work, low energy incomplete fusion (ICF) in which only a part of projectile fuses with target nucleus has been investigated in terms of various entrance channel parameters. The ICF strength function has been extracted from the analysis of experimental excitation functions (EFs) measured for different projectile-target combinations from near- to well above- barrier energies in 12C,16O(from 1.02Vb to 1.64Vb)+169Tm systems. Experimental EFs have been analysed in the framework statistical model code PACE4 based on the idea of equilibrated compound nucleus decay. It has been found that the value of ICF fraction (FICF) increases with incident projectile energy. A substantial fraction of ICF (FICF ≈ 7 %) has been accounted even at energy as low as ≈ 7.5% above the barrier (at relative velocity νrel ≈0.027) in 12C+169Tm system, and FICF ≈ 10 % at νrel ≈0.014 in 16O+169Tm system. The probability of ICF is discussed in light of the Morgenstern's mass-asymmetry systematics. The value of FICF for 16O+169Tm systems is found to be 18.3 % higher than that observed for 12C+169Tm systems. Present results together with the re-analysis of existing data for nearby systems conclusively demonstrate strong competition of ICF with CF even at slightly above barrier energies, and strong projectile dependence that seems to supplement the Morgenstern's systematics.

  8. 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.

  9. Low-energy effective Hamiltonians for correlated electron systems beyond density functional theory

    NASA Astrophysics Data System (ADS)

    Hirayama, Motoaki; Miyake, Takashi; Imada, Masatoshi; Biermann, Silke

    2017-08-01

    We propose a refined scheme of deriving an effective low-energy Hamiltonian for materials with strong electronic Coulomb correlations beyond density functional theory (DFT). By tracing out the electronic states away from the target degrees of freedom in a controlled way by a perturbative scheme, we construct an effective Hamiltonian for a restricted low-energy target space incorporating the effects of high-energy degrees of freedom in an effective manner. The resulting effective Hamiltonian can afterwards be solved by accurate many-body solvers. We improve this "multiscale ab initio scheme for correlated electrons" (MACE) primarily in two directions by elaborating and combining two frameworks developed by Hirayama et al. [M. Hirayama, T. Miyake, and M. Imada, Phys. Rev. B 87, 195144 (2013), 10.1103/PhysRevB.87.195144] and Casula et al. [M. Casula, P. Werner, L. Vaugier, F. Aryasetiawan, T. Miyake, A. J. Millis, and S. Biermann, Phys. Rev. Lett. 109, 126408 (2012), 10.1103/PhysRevLett.109.126408]: (1) Double counting of electronic correlations between the DFT and the low-energy solver is avoided by using the constrained G W scheme; and (2) the frequency dependent interactions emerging from the partial trace summation are successfully separated into a nonlocal part that is treated following ideas by Hirayama et al. and a local part treated nonperturbatively in the spirit of Casula et al. and are incorporated into the renormalization of the low-energy dispersion. The scheme is favorably tested on the example of SrVO3.

  10. Langevin model of low-energy fission

    DOE PAGES

    Sierk, Arnold John

    2017-09-05

    Since the earliest days of fission, stochastic models have been used to describe and model the process. For a quarter century, numerical solutions of Langevin equations have been used to model fission of highly excited nuclei, where microscopic potential-energy effects have been neglected. In this paper I present a Langevin model for the fission of nuclei with low to medium excitation energies, for which microscopic effects in the potential energy cannot be ignored. I solve Langevin equations in a five-dimensional space of nuclear deformations. The macroscopic-microscopic potential energy from a global nuclear structure model well benchmarked to nuclear masses ismore » tabulated on a mesh of approximately 107 points in this deformation space. The potential is defined continuously inside the mesh boundaries by use of a moving five-dimensional cubic spline approximation. Because of reflection symmetry, the effective mesh is nearly twice this size. For the inertia, I use a (possibly scaled) approximation to the inertia tensor defined by irrotational flow. A phenomenological dissipation tensor related to one-body dissipation is used. A normal-mode analysis of the dynamical system at the saddle point and the assumption of quasiequilibrium provide distributions of initial conditions appropriate to low excitation energies, and are extended to model spontaneous fission. A dynamical model of postscission fragment motion including dynamical deformations and separation allows the calculation of final mass and kinetic-energy distributions, along with other interesting quantities. The model makes quantitative predictions for fragment mass and kinetic-energy yields, some of which are very close to measured ones. Varying the energy of the incident neutron for induced fission allows the prediction of energy dependencies of fragment yields and average kinetic energies. With a simple approximation for spontaneous fission starting conditions, quantitative predictions are made for

  11. Langevin model of low-energy fission

    NASA Astrophysics Data System (ADS)

    Sierk, Arnold J.

    2017-09-01

    Background: Since the earliest days of fission, stochastic models have been used to describe and model the process. For a quarter century, numerical solutions of Langevin equations have been used to model fission of highly excited nuclei, where microscopic potential-energy effects have been neglected. Purpose: In this paper I present a Langevin model for the fission of nuclei with low to medium excitation energies, for which microscopic effects in the potential energy cannot be ignored. Method: I solve Langevin equations in a five-dimensional space of nuclear deformations. The macroscopic-microscopic potential energy from a global nuclear structure model well benchmarked to nuclear masses is tabulated on a mesh of approximately 107 points in this deformation space. The potential is defined continuously inside the mesh boundaries by use of a moving five-dimensional cubic spline approximation. Because of reflection symmetry, the effective mesh is nearly twice this size. For the inertia, I use a (possibly scaled) approximation to the inertia tensor defined by irrotational flow. A phenomenological dissipation tensor related to one-body dissipation is used. A normal-mode analysis of the dynamical system at the saddle point and the assumption of quasiequilibrium provide distributions of initial conditions appropriate to low excitation energies, and are extended to model spontaneous fission. A dynamical model of postscission fragment motion including dynamical deformations and separation allows the calculation of final mass and kinetic-energy distributions, along with other interesting quantities. Results: The model makes quantitative predictions for fragment mass and kinetic-energy yields, some of which are very close to measured ones. Varying the energy of the incident neutron for induced fission allows the prediction of energy dependencies of fragment yields and average kinetic energies. With a simple approximation for spontaneous fission starting conditions

  12. Low-energy electron collisions with thiophene

    NASA Astrophysics Data System (ADS)

    da Costa, R. F.; Varella, M. T. do N.; Lima, M. A. P.; Bettega, M. H. F.

    2013-05-01

    We report on elastic integral, momentum transfer, and differential cross sections for collisions of low-energy electrons with thiophene molecules. The scattering calculations presented here used the Schwinger multichannel method and were carried out in the static-exchange and static-exchange plus polarization approximations for energies ranging from 0.5 eV to 6 eV. We found shape resonances related to the formation of two long-lived π* anion states. These resonant structures are centered at the energies of 1.00 eV (2.85 eV) and 2.82 eV (5.00 eV) in the static-exchange plus polarization (static-exchange) approximation and belong to the B1 and A2 symmetries of the C2v point group, respectively. Our results also suggest the existence of a σ* shape resonance in the B2 symmetry with a strong d-wave character, located at around 2.78 eV (5.50 eV) as obtained in the static-exchange plus polarization (static-exchange) calculation. It is worth to mention that the results obtained at the static-exchange plus polarization level of approximation for the two π* resonances are in good agreement with the electron transmission spectroscopy results of 1.15 eV and 2.63 eV measured by Modelli and Burrow [J. Phys. Chem. A 108, 5721 (2004), 10.1021/jp048759a]. The existence of the σ* shape resonance is in agreement with the observations of Dezarnaud-Dandiney et al. [J. Phys. B 31, L497 (1998), 10.1088/0953-4075/31/11/004] based on the electron transmission spectra of dimethyl(poly)sulphides. A comparison among the resonances of thiophene with those of pyrrole and furan is also performed and, altogether, the resonance spectra obtained for these molecules point out that electron attachment to π* molecular orbitals is a general feature displayed by these five-membered heterocyclic compounds.

  13. Low-energy electron collisions with thiophene.

    PubMed

    da Costa, R F; Varella, M T do N; Lima, M A P; Bettega, M H F

    2013-05-21

    We report on elastic integral, momentum transfer, and differential cross sections for collisions of low-energy electrons with thiophene molecules. The scattering calculations presented here used the Schwinger multichannel method and were carried out in the static-exchange and static-exchange plus polarization approximations for energies ranging from 0.5 eV to 6 eV. We found shape resonances related to the formation of two long-lived π∗ anion states. These resonant structures are centered at the energies of 1.00 eV (2.85 eV) and 2.82 eV (5.00 eV) in the static-exchange plus polarization (static-exchange) approximation and belong to the B1 and A2 symmetries of the C2v point group, respectively. Our results also suggest the existence of a σ∗ shape resonance in the B2 symmetry with a strong d-wave character, located at around 2.78 eV (5.50 eV) as obtained in the static-exchange plus polarization (static-exchange) calculation. It is worth to mention that the results obtained at the static-exchange plus polarization level of approximation for the two π∗ resonances are in good agreement with the electron transmission spectroscopy results of 1.15 eV and 2.63 eV measured by Modelli and Burrow [J. Phys. Chem. A 108, 5721 (2004)]. The existence of the σ∗ shape resonance is in agreement with the observations of Dezarnaud-Dandiney et al. [J. Phys. B 31, L497 (1998)] based on the electron transmission spectra of dimethyl(poly)sulphides. A comparison among the resonances of thiophene with those of pyrrole and furan is also performed and, altogether, the resonance spectra obtained for these molecules point out that electron attachment to π∗ molecular orbitals is a general feature displayed by these five-membered heterocyclic compounds.

  14. Low energy lepton scattering -- recent results for electron and positron interactions

    NASA Astrophysics Data System (ADS)

    Sullivan, J. P.; Vizcaino, V.; Mondal, S.; Lower, J. C.; Jones, A.; Caradonna, P.; Makochekanwa, C.; Buckman, S. J.

    2008-07-01

    The interaction of low energy electrons with atoms, molecules and materials underpin a large number of technological, environmental and biomedical processes that impact on our everyday lives. Many of these areas have been well studied over the years and in some cases a large body of important and relevant cross section data has been gathered to assist in the understanding and development of the technology or phenomena. A perfect example of this is the area of low energy gaseous electronics where microscopic cross section information for a whole host of scattering processes (vibrational and electronic excitation, dissociation, ionization) have been critical to an understanding of the macroscopic behaviour of a range of gas discharge environments -- large area plasma processing discharges being a case in point. More recently there has been a realisation that fundamental information about both low energy electron and positron interactions also have significant bearing on issues of radiation damage in biological materials. Low energy electrons have been shown to cause significant damage to DNA strands, for instance, as a result of processes such as dissociative attachment -- a process which can occur at energies down to 0 eV. These processes result from the production of copious low energy electrons (< 20 eV) when high energy ionizing radiation thermalises in the body. This realisation has provided an enormous boost to the field of low energy electron physics and spawned an enormous number of new studies of interactions with biologically relevant molecules. In a similar fashion, low energy positron interactions are thought to be fundamentally important for an understanding of the atomic and molecular processes that underpin technologies such as Positron Emission Tomography (PET). PET scans image the coincident 511 keV gamma-rays that arise form the annihilation of an electron-positron pair. During a PET scan, high energy positrons thermalise in the body through

  15. Coincident excitation and radiative decay in electron-nucleus collisions

    NASA Astrophysics Data System (ADS)

    Jakubassa-Amundsen, D. H.; Ponomarev, V. Yu.

    2017-02-01

    The distorted-wave Born approximation formalism for the description of the (e ,e'γ ) reaction, in which emitted photons and scattered electrons are simultaneously detected, is outlined. Both the Coulomb and the magnetic scattering are fully taken into account. The influence of electron bremsstrahlung is estimated within the plane-wave Born approximation. Recoil effects are also discussed. The formalism is applied for the low-energy (e ,e'γ )92Zr reaction with excitation of the first collective (21+) and mixed-symmetry (22+) states. The corresponding transition charge and current densities are taken from a random-phase approximation (RPA) calculation within the quasiparticle phonon model. It is shown, by this example, in which way the magnetic subshell population of the excited state influences the angular distribution of the decay photon. For these quadrupole excitations the influence of magnetic scattering is only prominent at the backmost scattering angles, where a clear distinction of the photon pattern pertaining to the two states is predicted.

  16. Low-energy extensions of the eikonal approximation to heavy-ion scattering

    SciTech Connect

    Aguiar, C.E.; Aguiar, C.E.; Zardi, F.; Vitturi, A.

    1997-09-01

    We discuss different schemes devised to extend the eikonal approximation to the regime of low bombarding energies (below 50 MeV per nucleon) in heavy-ion collisions. From one side we consider the first- and second-order corrections derived from Wallace{close_quote}s expansion. As an alternative approach we examine the procedure of accounting for the distortion of the eikonal straight-line trajectory by shifting the impact parameter to the corresponding classical turning point. The two methods are tested for different combinations of colliding systems and bombarding energies, by comparing the angular distributions they provide with the exact solution of the scattering problem. We find that the best results are obtained with the shifted trajectories, the Wallace expansion showing a slow convergence at low energies, in particular for heavy systems characterized by a strong Coulomb field. {copyright} {ital 1997} {ital The American Physical Society}

  17. Low-energy description of the metal-insulator transition in the rare-earth nickelates

    NASA Astrophysics Data System (ADS)

    Subedi, Alaska; Peil, Oleg E.; Georges, Antoine

    2015-02-01

    We propose a simple theoretical description of the metal-insulator transition of rare-earth nickelates. The theory involves only two orbitals per nickel site, corresponding to the low-energy antibonding eg states. In the monoclinic insulating state, bond-length disproportionation splits the manifold of eg bands, corresponding to a modulation of the effective on-site energy. We show that, when subject to a local Coulomb repulsion U and Hund's coupling J , the resulting bond-disproportionated state is a paramagnetic insulator for a wide range of interaction parameters. Furthermore, we find that when U -3 J is small or negative, a spontaneous instability to bond disproportionation takes place for large enough J . This minimal theory emphasizes that a small or negative charge-transfer energy, a large Hund's coupling, and a strong coupling to bond disproportionation are the key factors underlying the transition. Experimental consequences of this theoretical picture are discussed.

  18. Coulomb blockade in graphene nanoribbons.

    PubMed

    Sols, F; Guinea, F; Neto, A H

    2007-10-19

    We propose that recent transport experiments revealing the existence of an energy gap in graphene nanoribbons may be understood in terms of Coulomb blockade. Electron interactions play a decisive role at the quantum dots which form due to the presence of necks arising from the roughness of the graphene edge. With the average transmission as the only fitting parameter, our theory shows good agreement with the experimental data.

  19. Interaction between Low Energy Ions and the Complicated Organism

    NASA Astrophysics Data System (ADS)

    Yu, Zeng-liang

    1999-12-01

    Low energy ions exist widely in natural world, but people pay a little attention on the interaction between low energy ions and matter, it is even more out of the question of studying on the relation of low energy ions and the complicated organism. The discovery of bioeffect induced by ion implantation has, however, opened a new branch in the field of ion beam application in life sciences. This paper reports recent advances in research on the role of low energy ions in chemical synthesis of the biomolecules and application in genetic modification.

  20. Low-Energy Ballistic Transfers to Lunar Halo Orbits

    NASA Technical Reports Server (NTRS)

    Parker, Jeffrey S.

    2009-01-01

    Recent lunar missions have begun to take advantage of the benefits of low-energy ballistic transfers between the Earth and the Moon rather than implementing conventional Hohmann-like lunar transfers. Both Artemis and GRAIL plan to implement low-energy lunar transfers in the next few years. This paper explores the characteristics and potential applications of many different families of low-energy ballistic lunar transfers. The transfers presented here begin from a wide variety of different orbits at the Earth and follow several different distinct pathways to the Moon. This paper characterizes these pathways to identify desirable low-energy lunar transfers for future lunar missions.

  1. Low-Energy Ballistic Transfers to Lunar Halo Orbits

    NASA Technical Reports Server (NTRS)

    Parker, Jeffrey S.

    2009-01-01

    Recent lunar missions have begun to take advantage of the benefits of low-energy ballistic transfers between the Earth and the Moon rather than implementing conventional Hohmann-like lunar transfers. Both Artemis and GRAIL plan to implement low-energy lunar transfers in the next few years. This paper explores the characteristics and potential applications of many different families of low-energy ballistic lunar transfers. The transfers presented here begin from a wide variety of different orbits at the Earth and follow several different distinct pathways to the Moon. This paper characterizes these pathways to identify desirable low-energy lunar transfers for future lunar missions.

  2. Development of a Low-energy Trigger for VERITAS

    SciTech Connect

    Kildea, J.

    2008-12-24

    During the 2007/2008 observing season a low-energy trigger configuration was developed and tested for VERITAS. The configuration makes uses of the small ({approx}35 m) baseline between two of the VERITAS telescopes and employs a much lower discriminator threshold and tighter coincidence window compared to the standard VERITAS trigger. Five hours of Crab Nebula ON/OFF observations were obtained in low-energy mode and were used to test new low-energy analysis algorithms. We present some details of the VERITAS low-energy trigger and the associated data analysis.

  3. Ordering in classical Coulombic systems.

    SciTech Connect

    Schiffer, J. P.

    1998-01-22

    The author discusses the properties of classical Coulombic matter at low temperatures. It has been well known for some time [1,2] that infinite Coulombic matter will crystallize in body-centered cubic form when the quantity {Lambda} (the dimensionless ratio of the average two-particle Coulomb energy to the kinetic energy per particle) is larger than {approximately}175. But the systems of such particles that have been produced in the laboratory in ion traps, or ion beams, are finite with surfaces defined by the boundary conditions that have to be satisfied. This results in ion clouds with sharply defined curved surfaces, and interior structures that show up as a set of concentric layers that are parallel to the outer surface. The ordering does not appear to be cubic, but the charges on each shell exhibit a ''hexatic'' pattern of equilateral triangles that is the characteristic of liquid crystals. The curvature of the surfaces prevents the structures on successive shells from interlocking in any simple fashion. This class of structures was first found in simulations [3] and later in experiments [4].

  4. α scattering and α -induced reaction cross sections of 64Zn at low energies

    NASA Astrophysics Data System (ADS)

    Ornelas, A.; Mohr, P.; Gyürky, Gy.; Elekes, Z.; Fülöp, Zs.; Halász, Z.; Kiss, G. G.; Somorjai, E.; Szücs, T.; Takács, M. P.; Galaviz, D.; Güray, R. T.; Korkulu, Z.; Özkan, N.; Yalçın, C.

    2016-11-01

    Background: α -nucleus potentials play an essential role for the calculation of α -induced reaction cross sections at low energies in the statistical model. Uncertainties of these calculations are related to ambiguities in the adjustment of the potential parameters to experimental elastic scattering angular distributions and to the energy dependence of the effective α -nucleus potentials. Purpose: The present work studies the total reaction cross section σreac of α -induced reactions at low energies which can be determined from the elastic scattering angular distribution or from the sum over the cross sections of all open nonelastic channels. Method: Elastic and inelastic 64Zn(α ,α )64Zn angular distributions were measured at two energies around the Coulomb barrier, at 12.1 and 16.1 MeV. Reaction cross sections of the (α ,γ ) , (α ,n ) , and (α ,p ) reactions were measured at the same energies using the activation technique. The contributions of missing nonelastic channels were estimated from statistical model calculations. Results: The total reaction cross sections from elastic scattering and from the sum of the cross sections over all open nonelastic channels agree well within the uncertainties. This finding confirms the consistency of the experimental data. At the higher energy of 16.1 MeV, the predicted significant contribution of compound-inelastic scattering to the total reaction cross section is confirmed experimentally. As a by-product it is found that most recent global α -nucleus potentials are able to describe the reaction cross sections for 64Zn around the Coulomb barrier. Conclusions: Total reaction cross sections of α -induced reactions can be well determined from elastic scattering angular distributions. The present study proves experimentally that the total cross section from elastic scattering is identical to the sum of nonelastic reaction cross sections. Thus, the statistical model can reliably be used to distribute the total reaction

  5. Charge-Density-Excitation Spectrum in the t-t'-J-V Model

    NASA Astrophysics Data System (ADS)

    Greco, Andrés; Yamase, Hiroyuki; Bejas, Matías

    2017-03-01

    We study the density-density correlation function in a large-N scheme of the t-t'-J-V model. When the nearest-neighbor Coulomb interaction V is zero, our model exhibits phase separation in a wide doping region and we obtain large spectral weight near momentum q = (0,0) at low energy, which originates from the proximity to phase separation. These features are much stronger for electron doping than for hole doping. However, once phase separation is suppressed by including a finite V, the low-energy spectral weight around q = (0,0) is substantially suppressed. Instead a sharp zero-sound mode is stabilized above the particle-hole continuum. We discuss that the presence of a moderate value of V, which is frequently neglected in the t-J model, is important to understand low-energy charge excitations especially close to q = (0,0) for electron doping. This insight should be taken into account in a future study of x-ray scattering measurements.

  6. 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.

  7. Computational Analysis of Intermolecular Coulombic Decay Effects in DNA nucleotide Photoionization

    NASA Astrophysics Data System (ADS)

    Vargas, E. L.; Robertson, J.; Andrianarijaona, V. M.

    2016-03-01

    Intermolecular Coulombic Decay (ICD) is the process of how electrons return to their original state after excitation and how this affects their immediate environment. In a previous research presentationwe had considered the hypothetical applications of Intermolecular Coulombic Decay on the adhesiveness of coding proteins within DNA molecules. This presentation is a continuation of the previous in that the results of our DFT-based computational calculations of the ionization potentials of nucleotides and their excitation energies will be presented, as well as how they influence their surroundings. Author would like to acknowledge the PUC Student Senate for financial assistance.

  8. Unified optical-model approach to low-energy antiproton annihilation on nuclei and to antiprotonic atoms

    NASA Astrophysics Data System (ADS)

    Batty, C. J.; Friedman, E.; Gal, A.

    2001-07-01

    A successful unified description of p¯ nuclear interactions near E=0 is achieved using a p¯ optical potential within a folding model, V opt˜ v¯∗ρ , where a p¯p potential v¯ is folded with the nuclear density ρ. The potential v¯ fits very well the measured p¯p -annihilation cross sections at low energies ( p L<200 MeV /c) and the 1s and 2p spin-averaged level shifts and widths for the p¯H atom. The density-folded optical potential V opt reproduces satisfactorily the strong-interaction level shifts and widths over the entire periodic table, for A>10, as well as the few low-energy p¯-annihilation cross sections measured on Ne. Both v¯ and V opt are found to be highly absorptive, which leads to a saturation of reaction cross sections in hydrogen and on nuclei. Predictions are made for p¯-annihilation cross sections over the entire periodic table at these very low energies and the systematics of the calculated cross sections as function of A, Z and E is discussed and explained in terms of a Coulomb-modified strong-absorption model. Finally, optical potentials which fit simultaneously low-energy p¯- 4He observables for E<0 as well as for E>0 are used to assess the reliability of extracting Coulomb modified p¯ nuclear scattering lengths directly from the data. The relationship between different kinds of scattering lengths is discussed and previously published systematics of the p¯ nuclear scattering lengths is updated.

  9. What is a low-energy house and who cares?

    SciTech Connect

    Litt, B.R.

    1994-12-01

    Most energy analysts view low-energy houses as good things, yet differ in their expectations of what exactly a low energy house is. There are two intertwining threads to this report. The first is an evaluation of 50 buildings that have been claimed to be low-energy residences, for which monitored energy performance data have been collected. These data represent the preliminary effort in the ongoing update of the Buildings Energy-Use Compilation and Analysis (BECA) data base for new residences. The second thread concerns the definition of a low-energy house. After the elements of a definition are presented, their implications for actors involved in providing housing are identified. Several more tractable definitions are applied to the houses in this compilation. The outcomes illustrate ways in which different interests are served by various definitions. Different definitions can yield very different energy rankings. No single definition of a low-energy house is universally applicable.

  10. Nanoscale Dynamics of Radiosensitivity: Role of Low Energy Electrons

    NASA Astrophysics Data System (ADS)

    Sanche, Léon

    This chapter addresses the nanoscale dynamics involved in the sensitization of biological cells to ionizing radiation. More specifically, it describes the role of low energy electrons (LEE) in radiosensitization by gold nanoparticles and chemotherapeutic agents, as well as potential applications to radiotherapy. The basic mechanisms of action of the LEE generated within nanoscopic volumes by ionizing radiation are described in solid water ice and various forms of DNA. These latter include the subunits (i.e., a base, a sugar or the phosphate group), short single strands (i.e., oligonucleotides) and plasmid and linear DNA. By comparing the results from experiments with the different forms of the DNA molecule and theory, it is possible to determine fundamental mechanisms that are involved in the dissociation of the subunits, base release and the production of single, double-strand breaks and cross-links. Below 15 eV, LEE localize on DNA subunits to form transient negative ions. Such states can damage DNA by dissociating into a stable anion and radical fragment(s), via dissociative electron attachment, or by decaying into dissociative electronically excited states. LEE can also transfer from one DNA subunit to another, particularly from a base to the phosphate group, where they can induce cleavage of the C-O bond (i.e., break a strand). DNA damage and the corresponding nanoscale dynamics are found to be modified in the presence of other cellular constituents. For example, condensing on DNA the most abundant cellular molecule, H2O, induces the formation of a new type of transient anion whose parent is a H2O-DNA complex.

  11. Low energy electron-driven damage in biomolecules

    NASA Astrophysics Data System (ADS)

    Sanche, L.

    2005-08-01

    The damage induced by the impact of low energy electrons (LEE) on biomolecules is reviewed from a radiobiological perspective with emphasis on transient anion formation. The major type of experiments, which measure the yields of fragments produced as a function of incident electron energy (0.1{-}30 eV), are briefly described. Theoretical advances are also summarized. Several examples are presented from the results of recent experiments performed in the gas-phase and on biomolecular films bombarded with LEE under ultra-high vacuum conditions. These include the results obtained from DNA films and those obtained from the fragmentation of elementary components of the DNA molecule (i.e., the bases, sugar and phosphate group analogs and oligonucleotides) and of proteins (e.g. amino acids). By comparing the results from different experiments and theory, it is possible to determine fundamental mechanisms that are involved in the dissociation of the biomolecules and the production of single- and double-strand breaks in DNA. Below 15 eV, electron resonances (i.e., the formation of transient anions) play a dominant role in the fragmentation of all biomolecules investigated. These transient anions fragment molecules by decaying into dissociative electronically excited states or by dissociating into a stable anion and a neutral radical. These fragments can initiate further reactions within large biomolecules or with nearby molecules and thus cause more complex chemical damage. Dissociation of a transient anion within DNA may occur by direct electron attachment at the location of dissociation or by electron transfer from another subunit. Damage to DNA is dependent on the molecular environment, topology, type of counter ion, sequence context and chemical modifications.

  12. Low energy cross sections for electron scattering from tetrafluoroallene

    NASA Astrophysics Data System (ADS)

    Gupta, Dhanoj; Choi, Heechol; Song, Mi-Young; Chakrabarti, Kalyan; Yoon, Jung-Sik

    2017-08-01

    We report elastic, total, excitation, differential and momentum-transfer cross sections for scattering of low-energy electrons by tetrafluoroallene (C3F4) using the close-coupling (CC) approximation in the R-matrix method with Quantemol-N. We have tested various target models initially to check for the convergence of the result and the final results are provided with the best target model. We have detected shape resonances of symmetry 2 E(2B1,2B2) at 3.08 eV and 3.71 eV with a close-coupling and static exchange models which is seen as a sharp feature in the elastic and momentum transfer cross sections. We also detected other resonances of symmetry 2 E at 11.26 eV and of symmetry 2A2 at 11.12 eV below the ionization threshold of the target respectively. The present elastic and total cross sections are compared with the elastic and total cross sections of allene (C3H4), propene (C3H6) and hexafluoropropene (C3F6) as there were no results available for C3F4. The effect of fluorination is clearly seen with the shape resonance for C3F4 getting slightly shifted to higher energies compared to allene. Finally, we also report the ionization cross section calculated using the Binary-Encounter Bethe (BEB) method. The present calculation is a maiden attempt to find cross sections for C3F4 molecule which could be useful for fluorocarbon plasma modeling.

  13. Fusion of {sup 48}Ca+{sup 90,96}Zr above and below the Coulomb barrier

    SciTech Connect

    Stefanini, A.M.; Behera, B.R.; Corradi, L.; Fioretto, E.; Gadea, A.; Wu, Y.W.; Scarlassara, F.; Beghini, S.; Montagnoli, G.; Silvestri, R.; Trotta, M.; Szilner, S.; Zhang, H.Q.; Liu, Z.H.; Ruan, M.; Yang, F.; Rowley, N.

    2006-03-15

    Fusion-evaporation cross sections were measured in the two systems {sup 48}Ca+{sup 90,96}Zr in an energy range from well below to well above the Coulomb barrier. The sub-barrier fusion of {sup 48}Ca+{sup 90}Zr is reproduced by coupled-channels calculations including the lowest quadrupole and octupole vibrations of {sup 90}Zr, and using a Woods-Saxon potential with a standard diffuseness parameter a = 0.68 fm. However, the fusion cross sections are overestimated above the barrier. The low-energy slope of the excitation function for {sup 48}Ca+{sup 96}Zr is steeper. This implies a larger diffuseness parameter a = 0.85 fm. Fusion cross sections are well fit in the whole energy range, and the effect of the strong octupole vibration in {sup 96}Zr is predominant. The extracted fusion barrier distributions are reasonably well reproduced by calculations for both systems. A comparison with previous data for {sup 40}Ca+{sup 90,96}Zr is made in an attempt to clarify the role of transfer couplings in sub-barrier fusion.

  14. Complex time contours in tunnel ionization and low-energy structures

    NASA Astrophysics Data System (ADS)

    Pisanty, Emilio; Ivanov, Misha

    2015-03-01

    In tunnel ionization, a strong low-frequency laser field removes an electron from an atom by setting up a slowly-varying potential energy barrier that the electron can tunnel through. During its subsequent oscillations in the laser field, the electron can revisit the neighbourhood of the remaining ion one or more times. Frequently, this is a soft recollision which affects the momentum distribution, although more substantial effects can happen. We use the Analytical R-Matrix theory to investigate the effect of these soft recollisions, focusing on low drift momenta, where the laser-induced trajectory has a turning point near the nucleus. Our framework provides a complex-valued trajectory perspective on the electron propagation, from first principles. We show that the presence of the Coulomb interaction, which is responsible for the soft recollisions, forbids certain common choices of contour within the complex time plane, and we describe an algorithm for safely circumventing the associated branch cuts. We find quantum analogues to the classical turning points near the ion, and we investigate their relation to the recently-discovered low-energy and very-low-energy structures in above-threshold ionization. We acknowledge funding from CONACYT (Mexico) and the MC-ITN CORINF network.

  15. The low-energy N = 4 SYM effective action in diverse harmonic superspaces

    NASA Astrophysics Data System (ADS)

    Buchbinder, I. L.; Ivanov, E. A.; Samsonov, I. B.

    2017-05-01

    We review various superspace approaches to the description of the low-energy effective action in N = 4 super Yang-Mills (SYM) theory. We consider the four-derivative part of the low-energy effective action in the Coulomb branch. The typical components of this effective action are the gauge field F 4/ X 4 and the scalar field Wess-Zumino terms. We construct N = 4 supersymmetric completions of these terms in the framework of different harmonic superspaces supporting N = 2,3,4 supersymmetries. These approaches are complementary to each other in the sense that they make manifest different subgroups of the total SU(4) R-symmetry group. We show that the effective action acquires an extremely simple form in those superspaces which manifest the non-anomalous maximal subgroups of SU(4). The common characteristic feature of our construction is that we restore the superfield effective actions exclusively by employing the N = 4 supersymmetry and/or superconformal PSU(2, 2| 4) symmetry.

  16. Low-energy physics of three-orbital impurity model with Kanamori interaction

    NASA Astrophysics Data System (ADS)

    Horvat, Alen; Žitko, Rok; Mravlje, Jernej

    2016-10-01

    We discuss the low-energy physics of the three-orbital Anderson impurity model with the Coulomb interaction term of the Kanamori form which has orbital SO(3) and spin SU(2) symmetry and describes systems with partially occupied t2 g shells. We focus on the case with two electrons in the impurity that is relevant to Hund's metals. Using the Schrieffer-Wolff transformation we derive an effective Kondo model with couplings between the bulk and impurity electrons expressed in terms of spin, orbital, and orbital quadrupole operators. The bare spin-spin Kondo interaction is much smaller than the orbit-orbit and spin-orbital couplings or is even ferromagnetic. Furthermore, the perturbative scaling equations indicate faster renormalization of the couplings related to orbital degrees of freedom compared to spin degrees of freedom. Both mechanisms lead to a slow screening of the local spin moment. The model thus behaves similarly to the related quantum impurity problem with a larger SU(3) orbital symmetry (Dworin-Narath interaction) where this was first observed. We find that the two problems actually describe the same low-energy physics since the SU(3) symmetry is dynamically established through the renormalization of the splittings between the orbital and quadrupole coupling constants to zero. The perturbative renormalization group results are corroborated with the numerical-renormalization group (NRG) calculations. The dependence of spin Kondo temperatures and orbital Kondo temperatures as a function of interaction parameters, the hybridization, and the impurity occupancy is calculated and discussed.

  17. PREFACE: Strongly Coupled Coulomb Systems Strongly Coupled Coulomb Systems

    NASA Astrophysics Data System (ADS)

    Neilson, David; Senatore, Gaetano

    2009-05-01

    This special issue contains papers presented at the International Conference on Strongly Coupled Coulomb Systems (SCCS), held from 29 July-2 August 2008 at the University of Camerino. Camerino is an ancient hill-top town located in the Apennine mountains of Italy, 200 kilometres northeast of Rome, with a university dating back to 1336. The Camerino conference was the 11th in a series which started in 1977: 1977: Orleans-la-Source, France, as a NATO Advanced Study Institute on Strongly Coupled Plasmas (hosted by Marc Feix and Gabor J Kalman) 1982: Les Houches, France (hosted by Marc Baus and Jean-Pierre Hansen) 1986: Santa Cruz, California, USA (hosted by Forrest J Rogers and Hugh E DeWitt) 1989: Tokyo, Japan (hosted by Setsuo Ichimaru) 1992: Rochester, New York, USA (hosted by Hugh M Van Horn and Setsuo Ichimaru) 1995: Binz, Germany (hosted by Wolf Dietrich Kraeft and Manfred Schlanges) 1997: Boston, Massachusetts, USA (hosted by Gabor J Kalman) 1999: St Malo, France (hosted by Claude Deutsch and Bernard Jancovici) 2002: Santa Fe, New Mexico, USA (hosted by John F Benage and Michael S Murillo) 2005: Moscow, Russia (hosted by Vladimir E Fortov and Vladimir Vorob'ev). The name of the series was changed in 1996 from Strongly Coupled Plasmas to Strongly Coupled Coulomb Systems to reflect a wider range of topics. 'Strongly Coupled Coulomb Systems' encompasses diverse many-body systems and physical conditions. The purpose of the conferences is to provide a regular international forum for the presentation and discussion of research achievements and ideas relating to a variety of plasma, liquid and condensed matter systems that are dominated by strong Coulomb interactions between their constituents. Each meeting has seen an evolution of topics and emphases that have followed new discoveries and new techniques. The field has continued to see new experimental tools and access to new strongly coupled conditions, most recently in the areas of warm matter, dusty plasmas

  18. Coulomb interaction effect in tilted Weyl fermion in two dimensions

    NASA Astrophysics Data System (ADS)

    Isobe, Hiroki; Nagaosa, Naoto

    Weyl fermions with tilted linear dispersions characterized by several different velocities appear in some systems including the quasi-two-dimensional organic semiconductor α-(BEDT-TTF)2I3 and three-dimensional WTe2. The Coulomb interaction between electrons modifies the velocities in an essential way in the low energy limit, where the logarithmic corrections dominate. Taking into account the coupling to both the transverse and longitudinal electromagnetic fields, we derive the renormalization group equations for the velocities of the tilted Weyl fermions in two dimensions, and found that they increase as the energy decreases and eventually hit the velocity of light c to result in the Cherenkov radiation. Especially, the system restores the isotropic Weyl cone even when the bare Weyl cone is strongly tilted and the velocity of electrons becomes negative in certain directions.

  19. Charge-equilibrium and radiation of low-energy cosmic rays passing through interstellar medium

    NASA Technical Reports Server (NTRS)

    Rule, D. W.; Omidvar, K.

    1977-01-01

    The charge equilibrium and radiation of an oxygen and an iron beam in the MeV per nucleon energy range, representing a typical beam of low-energy cosmic rays passing through the interstellar medium, is considered. Electron loss of the beam has been taken into account by means of the First Born approximation allowing for the target atom to remain unexcited, or to be excited to all possible states. Electron capture cross sections have been calculated by means of the scaled Oppenheimer-Brinkman-Kramers approximation, taking into account all atomic shells of the target atoms. Radiation of the beam due to electron capture into the excited states of the ion, collisional excitation and collisional inner-shell ionization of the ions has been considered. Effective X-ray production cross sections and multiplicities for the most energetic X-ray lines emitted by the Fe and O beams have been calculated.

  20. Interplay between short-range correlated disorder and Coulomb interaction in nodal-line semimetals

    NASA Astrophysics Data System (ADS)

    Wang, Yuxuan; Nandkishore, Rahul M.

    2017-09-01

    In nodal-line semimetals, Coulomb interactions and short-range correlated disorder are both marginal perturbations to the clean noninteracting Hamiltonian. We analyze their interplay using a weak-coupling renormalization group approach. In the clean case, the Coulomb interaction has been found to be marginally irrelevant, leading to Fermi liquid behavior. We extend the analysis to incorporate the effects of disorder. The nodal line structure gives rise to kinematical constraints similar to that for a two-dimensional Fermi surface, which plays a crucial role in the one-loop renormalization of the disorder couplings. For a twofold degenerate nodal loop (Weyl loop), we show that disorder flows to strong coupling along a unique fixed trajectory in the space of symmetry inequivalent disorder couplings. Along this fixed trajectory, all symmetry inequivalent disorder strengths become equal. For a fourfold degenerate nodal loop (Dirac loop), disorder also flows to strong coupling, however, the strengths of symmetry inequivalent disorder couplings remain different. We show that feedback from disorder reverses the sign of the beta function for the Coulomb interaction, causing the Coulomb interaction to flow to strong coupling as well. However, the Coulomb interaction flows to strong coupling asymptotically more slowly than disorder. Extrapolating our results to strong coupling, we conjecture that at low energies nodal line semimetals should be described by a noninteracting nonlinear sigma model. We discuss the relation of our results with possible many-body localization at zero temperatures in such materials.

  1. Low-energy ion beam-based deposition of gallium nitride

    SciTech Connect

    Vasquez, M. R.; Wada, M.

    2016-02-15

    An ion source with a remote plasma chamber excited by a 13.56 MHz radio frequency power was used for low-energy broad ion beam extraction. Optical emission spectral analyses showed the sputtering and postionization of a liquid gallium (Ga) target placed in a chamber separated from the source bombarded by argon (Ar) plasma guided by a bent magnetic field. In addition, an E × B probe successfully showed the extraction of low-energy Ga and Ar ion beams using a dual-electrode extractor configuration. By introducing dilute amounts of nitrogen gas into the system, formation of thin Ga-based films on a silicon substrate was demonstrated as determined from X-ray diffraction and X-ray reflectivity studies.

  2. Protonium formation in the p-H collision at low energies by a diabatic approach

    SciTech Connect

    Hesse, M.; Le, A.T.; Lin, C.D.

    2004-05-01

    We present a diabatization technique in combination with the recently developed hyperspherical close coupling (HSCC) method. In contrast to the strict diabatization, our simple diabatization procedure transforms only sharp avoided crossings in the adiabatic hyperspherical potential curves into real crossings. With this approach, the weak collision channels can be removed from the close-coupling calculations. This method is used to study the antiproton-hydrogen collision at low energies. In the case of a scaled down (anti)proton mass, we show that a 10-channel calculation is enough to obtain converged cross sections at low energies. The results also indicate that protonium formation occurs mostly to the lowest states of the different excited protonium manifolds.

  3. Low-energy ion beam-based deposition of gallium nitride.

    PubMed

    Vasquez, M R; Wada, M

    2016-02-01

    An ion source with a remote plasma chamber excited by a 13.56 MHz radio frequency power was used for low-energy broad ion beam extraction. Optical emission spectral analyses showed the sputtering and postionization of a liquid gallium (Ga) target placed in a chamber separated from the source bombarded by argon (Ar) plasma guided by a bent magnetic field. In addition, an E × B probe successfully showed the extraction of low-energy Ga and Ar ion beams using a dual-electrode extractor configuration. By introducing dilute amounts of nitrogen gas into the system, formation of thin Ga-based films on a silicon substrate was demonstrated as determined from X-ray diffraction and X-ray reflectivity studies.

  4. Low-energy ion beam-based deposition of gallium nitride

    NASA Astrophysics Data System (ADS)

    Vasquez, M. R.; Wada, M.

    2016-02-01

    An ion source with a remote plasma chamber excited by a 13.56 MHz radio frequency power was used for low-energy broad ion beam extraction. Optical emission spectral analyses showed the sputtering and postionization of a liquid gallium (Ga) target placed in a chamber separated from the source bombarded by argon (Ar) plasma guided by a bent magnetic field. In addition, an E × B probe successfully showed the extraction of low-energy Ga and Ar ion beams using a dual-electrode extractor configuration. By introducing dilute amounts of nitrogen gas into the system, formation of thin Ga-based films on a silicon substrate was demonstrated as determined from X-ray diffraction and X-ray reflectivity studies.

  5. 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.

  6. 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.

  7. The Low-Energy Background in XENON1T

    NASA Astrophysics Data System (ADS)

    Gao, Fei; Stein, Alec; Xenon1T Collaboration

    2017-01-01

    The XENON1T dark matter direct-detection experiment looks for hypothetical Weakly Interacting Massive Particles (WIMPs). WIMPs are expected to scatter off xenon nuclei at low energies, so understanding the low-energy background of the detector is crucial. In XENON1T, the background in the WIMP search region is due to radioactive decays stemming from the detector construction materials and impurities in the xenon itself. We show that our predicted low-energy background rate of 10-4events .kg-1 .day-1 .keV-1 matches XENON1T's design goals and is in agreement with the data taken during the commissioning of the detector.

  8. States of low energy on Robertson Walker spacetimes

    NASA Astrophysics Data System (ADS)

    Olbermann, Heiner

    2007-10-01

    We construct a new class of physical states of the free Klein Gordon field in Robertson Walker spacetimes. This is done by minimizing the expectation value of smeared stress energy. We get an explicit expression for the state depending on the smearing function. We call it a state of low energy. States of low energy are an improvement of the concept of adiabatic vacua on Robertson Walker spacetimes. The latter are approximations of the former. It is shown that states of low energy are Hadamard states.

  9. Low Energy X-Ray and Electron Interactions within Matter.

    DTIC Science & Technology

    1980-03-01

    0-C3962 HAWAII] UNIV HONOLULU DEPT OF PHYSICS AND AST/RONiOMY FmI SelfLOW ENERGY X-RAY AND ELECTRON INTERACTIONS WITHIN MATTER.1U) 14M a L HEM Ai -79...U UNCLASSIFIED AFMWTI olL E iiEEEEEsoE II,,,,hEEIN Eh~hEhh~hhhmmEEmhEEAhE Xbo R-TE. 8oo194 DV , LOW ENERGY X-RAY AND ELECTRON INTERACTIONS WITHIN...ACCESSION NO 3. RECiPIENT’S CATALOG NUMBER TITLE (and SublIII.) 5. TYPE OF REPORT & PERIOD COVERE? LOW ENERGY X-RAY AND ELECTRON INTERACTIONS // Interim A

  10. Coulomb interaction effects on the Majorana states in quantum wires.

    PubMed

    Manolescu, A; Marinescu, D C; Stanescu, T D

    2014-04-30

    The stability of the Majorana modes in the presence of a repulsive interaction is studied in the standard semiconductor wire-metallic superconductor configuration. The effects of short-range Coulomb interaction, which is incorporated using a purely repulsive δ-function to model the strong screening effect due to the presence of the superconductor, are determined within a Hartree-Fock approximation of the effective Bogoliubov-De Gennes Hamiltonian that describes the low-energy physics of the wire. Through a numerical diagonalization procedure we obtain interaction corrections to the single particle eigenstates and calculate the extended topological phase diagram in terms of the chemical potential and the Zeeman energy. We find that, for a fixed Zeeman energy, the interaction shifts the phase boundaries to a higher chemical potential, whereas for a fixed chemical potential this shift can occur either at lower or higher Zeeman energies. These effects can be interpreted as a renormalization of the g-factor due to the interaction. The minimum Zeeman energy needed to realize Majorana fermions decreases with the increasing strength of the Coulomb repulsion. Furthermore, we find that in wires with multi-band occupancy this effect can be enhanced by increasing the chemical potential, i.e. by occupying higher energy bands.

  11. Laser-Driven Recollisions under the Coulomb Barrier

    NASA Astrophysics Data System (ADS)

    Keil, Th.; Popruzhenko, S. V.; Bauer, D.

    2016-12-01

    Photoelectron spectra obtained from the ab initio solution of the time-dependent Schrödinger equation can be in striking disagreement with predictions by the strong-field approximation (SFA), not only at low energy but also around twice the ponderomotive energy where the transition from the direct to the rescattered electrons is expected. In fact, the relative enhancement of the ionization probability compared to the SFA in this regime can be several orders of magnitude. We show for which laser and target parameters such an enhancement occurs and for which the SFA prediction is qualitatively good. The enhancement is analyzed in terms of the Coulomb-corrected action along analytic quantum orbits in the complex-time plane, taking soft recollisions under the Coulomb barrier into account. These recollisions in complex time and space prevent a separation into sub-barrier motion up to the "tunnel exit" and subsequent classical dynamics. Instead, the entire quantum path up to the detector determines the ionization probability.

  12. Past, present and future low energy antiproton facilities at CERN

    NASA Astrophysics Data System (ADS)

    Bartmann, W.; Belochitskii, P.; Breuker, H.; Butin, F.; Carli, C.; Eriksson, T.; Maury, S.; Oelert, W.; Pasinelli, S.; Tranquille, G.

    2014-05-01

    Low energy antiprotons are available for physics experiments at CERN since the 1980s and have been used by a large variety of experiments. The Low Energy Antiproton Ring LEAR has been constructed as a complementary use of antiprotons available at that time for high energy physics and delivered beam to experiments mainly using slow extraction. After completion of LEAR exploitation, the Antiproton Decelerator (AD) was constructed (adaptation of the existing Antiproton Collector, AC) to allow for a simpler low energy antiproton scheme (only one accelerator operated with Antiprotons) with fast extraction well suited for trap experiments. The Extra Low ENergy Antiproton ring ELENA is a small synchrotron presently constructed to further decelerate antiprotons from the AD in a controlled manner, and to reduce emittances with the help of an electron cooler to improve the capture efficiencies of existing experiments and allow for additional ones.

  13. 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)

  14. Biological assessments for the low energy demonstration accelerator, 1996

    SciTech Connect

    Cross, S.

    1997-03-01

    This report discusses the biological impact to the area around the Los Alamos National Laboratory of the Low Energy Demonstration Accelerator. In particular the impact to the soils, water quality, vegetation, and wildlife are discussed.

  15. 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)

  16. Beam lifetime and limitations during low-energy RHIC operation

    SciTech Connect

    Fedotov, A.V.; Bai, M.; Blaskiewicz, M.; Fischer, W.; Kayran, D.; Montag, C.; Satogata, T.; Tepikian, S.; Wang, G.

    2011-03-28

    The low-energy physics program at the Relativistic Heavy Ion Collider (RHIC), motivated by a search for the QCD phase transition critical point, requires operation at low energies. At these energies, large nonlinear magnetic field errors and large beam sizes produce low beam lifetimes. A variety of beam dynamics effects such as Intrabeam Scattering (IBS), space charge and beam-beam forces also contribute. All these effects are important to understand beam lifetime limitations in RHIC at low energies. During the low-energy RHIC physics run in May-June 2010 at beam {gamma} = 6.1 and {gamma} = 4.1, gold beam lifetimes were measured for various values of space-charge tune shifts, transverse acceptance limitation by collimators, synchrotron tunes and RF voltage. This paper summarizes our observations and initial findings.

  17. Implosive Interatomic Coulombic decay in the simplest molecular anion

    NASA Astrophysics Data System (ADS)

    Greene, Chris H.; Perez-Rios, Jesus; Slipchenko, Lyudmila

    2016-05-01

    Interatomic Coulombic decay (ICD) has been extensively studied in different systems: from diatomic systems such as He2 up to more complex chemical systems with interest in biochemistry. Independently of the size and complexity of the system, the ICD process proposed involves the emission of an electron through exchange of a virtual photon. The present theoretical study investigates the ICD process in the helium hydride anion, which involves two final product states that can be produced through a Coulomb implosion following high energy ejection of a He 1s electron accompanied by excitation to He+(n = 2) . One of the subsequent decay channels is associated with the usual emission of a single electron, to produce a stable molecule: HeH+, which can compete with the usual dissociated final state of the system. The second channel involves the emission of two electrons, leading to the usual Coulomb explosion of the final product ions He+(1 s) + H + . In addition, the process of formation of the helium hydride anion is analyzed in terms of the existing technology of ionic molecular beams and buffer gas cooling techniques. This work is supported by the National Science Foundation under Grant PHY-1306905.

  18. Dynamical Coulomb blockade of tunnel junctions driven by alternating voltages

    NASA Astrophysics Data System (ADS)

    Grabert, Hermann

    2015-12-01

    The theory of the dynamical Coulomb blockade is extended to tunneling elements driven by a time-dependent voltage. It is shown that, for standard setups where an external voltage is applied to a tunnel junction via an impedance, time-dependent driving entails an excitation of the modes of the electromagnetic environment by the applied voltage. Previous approaches for ac driven circuits need to be extended to account for the driven bath modes. A unitary transformation involving also the variables of the electromagnetic environment is introduced which allows us to split off the time dependence from the Hamiltonian in the absence of tunneling. This greatly simplifies perturbation-theoretical calculations based on treating the tunneling Hamiltonian as a perturbation. In particular, the average current flowing in the leads of the tunnel junction is studied. Explicit results are given for the case of an applied voltage with a constant dc part and a sinusoidal ac part. The connection with standard dynamical Coulomb blockade theory for constant applied voltage is established. It is shown that an alternating voltage source reveals significant additional effects caused by the electromagnetic environment. The hallmark of the dynamical Coulomb blockade in ac driven devices is a suppression of higher harmonics of the current by the electromagnetic environment. The theory presented basically applies to all tunneling devices driven by alternating voltages.

  19. Low-energy triggering for Hyper-Kamiokande

    NASA Astrophysics Data System (ADS)

    Dealtry, T.; Barr, G.; Dewhurst, D.; Nicholls, T.; Nova, F.; O’Keeffe, H. M.; Richards, B.; Short, S.; Stewart, T.; Hyper-Kamiokande proto-collaboration

    2017-09-01

    Hyper-Kamiokande is a proposed neutrino physics and proton decay experiment in Japan, due to start operations in 2026. In order to successfully achieve the low-energy (≲10 MeV) physics aims, a dedicated high-efficiency low-energy trigger is required. The test vertices trigger can, for a fixed noise trigger rate, reduce the electron energy trigger threshold by ∼2 MeV, compared with the simple NHITS trigger.

  20. Surface Passivation and Junction Formation Using Low Energy Hydrogen Implants

    NASA Technical Reports Server (NTRS)

    Fonash, S. J.

    1985-01-01

    New applications for high current, low energy hydrogen ion implants on single crystal and polycrystal silicon grain boundaries are discussed. The effects of low energy hydrogen ion beams on crystalline Si surfaces are considered. The effect of these beams on bulk defects in crystalline Si is addressed. Specific applications of H+ implants to crystalline Si processing are discussed. In all of the situations reported on, the hydrogen beams were produced using a high current Kaufman ion source.

  1. 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.

  2. The Trapping of Low-Energy Particles by Interplanetary Shocks

    NASA Astrophysics Data System (ADS)

    Al Dayeh, M.; Dwyer, J.; Rassoul, H.; Mason, G.; Mazur, J.; Desai, M.

    2007-12-01

    Using ~0.045-10 MeV/nucleon ion data from ACE/ULEIS, we have found that a substantial number of shock- associated solar energetic particle events (20 events) have significant delays in the arrival of the low-energy component beyond what is expected from the travel time of energetic particles from the sun to the earth at 1 AU. Indeed, for some events, after correcting for the velocity dispersion, the low energy component (E < 0.1 MeV/nucleon) is almost completely absent while the high-energy component (E > 1 MeV/nucleon) has very large enhancements. SEP events with the most dramatic initial depletion of low-energy particles are accompanied by large proton fluxes and have large enhancements of the low-energy particles later, in coincidence with the arrival of the interplanetary shock, a day or two after the start of the event. In addition, these events show Fe/O enhancements during the periods in which the low-energy component is depleted and lower Fe/O values once the shock arrives. These new observations appear to be explained by the trapping of particles with low energy-to-charge (E/Q) ratios in the vicinity of the shock by magnetohydrodynamic waves, possibly generated by high energy protons streaming along the magnetic field lines.

  3. PREFACE: Strongly Coupled Coulomb Systems

    NASA Astrophysics Data System (ADS)

    Fortov, Vladimir E.; Golden, Kenneth I.; Norman, Genri E.

    2006-04-01

    This special issue contains papers presented at the International Conference on Strongly Coupled Coulomb Systems (SCCS) which was held during the week of 20 24 June 2005 in Moscow, Russia. The Moscow conference was the tenth in a series of conferences. The previous conferences were organized as follows. 1977: Orleans-la-Source, France, as a NATO Advanced Study Institute on Strongly Coupled Plasmas (organized by Marc Feix and Gabor J Kalman) 1982: Les Houches, France (organized by Marc Baus and Jean-Pierre Hansen) 1986: Santa Cruz, California, USA (hosted by Forrest J Rogers and Hugh E DeWitt) 1989: Tokyo, Japan (hosted by Setsuo Ichimaru) 1992: Rochester, NY, USA (hosted by Hugh M Van Horn and Setsuo Ichimaru) 1995: Binz, Germany (hosted by Wolf Dietrich Kraeft and Manfred Schlanges) 1997: Boston, Massachusetts, USA (hosted by Gabor J Kalman) 1999: St Malo, France (hosted by Claude Deutsch and Bernard Jancovici) 2002: Santa Fe, New Mexico, USA (hosted by John F Benage and Michael S Murillo) After 1995 the name of the series was changed from `Strongly Coupled Plasmas' to the present name in order to extend the topics of the conferences. The planned frequency for the future is once every three years. The purpose of these conferences is to provide an international forum for the presentation and discussion of research accomplishments and ideas relating to a variety of plasma liquid and condensed matter systems, dominated by strong Coulomb interactions between their constituents. Strongly coupled Coulomb systems encompass diverse many-body systems and physical conditions. Each meeting has seen an evolution of topics and emphasis as new discoveries and new methods appear. This year, sessions were organized for invited presentations and posters on dense plasmas and warm matter, astrophysics and dense hydrogen, non-neutral and ultracold plasmas, dusty plasmas, condensed matter 2D and layered charged-particle systems, Coulomb liquids, and statistical theory of SCCS. Within

  4. Low energy dynamics of non-perturbative structures in high energy and condensed matter systems

    NASA Astrophysics Data System (ADS)

    Peterson, Adam Joseph

    This dissertation presents some results on the application of low energy effective field theory vortex dynamics in condensed matter and materials systems. For the first half of the presentation we discuss the possibility of non-Abelian gapless excitations appearing on U(1) vortices in the B phase of superfluid 3He. Specifically, we focus on superfluid 3He-like systems with an enhanced SO(3) L rotational symmetry allowing for non-Abelian excitations to exist in the gapless spectrum of vortices. We consider a variety of vortices in the B-phase with different levels of symmetry breaking in the vortex core, and show conditions on the phenomenological parameters for certain vortices to be stable in the bulk. We then proceed to develope the low energy effective field theory of the various vortex types and consider the quantization of excitations. The process of quantization leads to interesting surprises due to non-lorentz symmetry that are not typically encountered in the analogous cases of U(1) x SU(N) gauge models discussed in high energy theory. The second half of this dissertation focuses on two types of vortices that appear in a particular model that is a modification of the well known Abelian-Higgs model. The specific modification includes a vector spin field in addition to the U(1) Higgs field and gauge fields of the original model. The particular form of the lagrangian results in a cholesteric vacuum structure, with interesting consequences for the vortices in the model. We observe the effects of such a modification on the well known U (1) vortex appearing in the original model due to the emergent spin field in the vortex core. We also consider a new type of vortex that is most closely related to a spin vortex. This vortex appears due to the topology introduced by the new spin field. The low energy effective field theory is also investigated for this type of vortex.

  5. Coulombic contribution and fat center vortex model

    SciTech Connect

    Rafibakhsh, Shahnoosh; Deldar, Sedigheh

    2007-02-27

    The fat (thick) center vortex model is one of the phenomenological models which is fairly successful to interpret the linear potential between static sources. However, the Coulombic part of the potential has not been investigated by the model yet. In an attempt to get the Coulombic contribution and to remove the concavity of the potentials, we are studying different vortex profiles and vortex sizes.

  6. Correlated wave functions for three-particle systems with Coulomb interaction - The muonic helium atom

    NASA Technical Reports Server (NTRS)

    Huang, K.-N.

    1977-01-01

    A computational procedure for calculating correlated wave functions is proposed for three-particle systems interacting through Coulomb forces. Calculations are carried out for the muonic helium atom. Variational wave functions which explicitly contain interparticle coordinates are presented for the ground and excited states. General Hylleraas-type trial functions are used as the basis for the correlated wave functions. Excited-state energies of the muonic helium atom computed from 1- and 35-term wave functions are listed for four states.

  7. Quantum magnetotransport in two-dimensional Coulomb liquids

    NASA Astrophysics Data System (ADS)

    Monarkha, Yu. P.; Teske, E.; Wyder, P.

    2002-11-01

    In this article we review recent progress in understanding of many-electron effects on the quantum magnetotransport in two-dimensional (2D) Coulomb liquids in which the interaction potential energy per electron can be approximately a hundred times larger than the mean kinetic energy. The conventional Fermi-liquid approach based on the introduction of weakly interacting excitations being not applicable, it is remarkable that a quantitative theoretical description of the equilibrium and transport properties of the 2D Coulomb liquid appears to be possible. An account of basic properties of the strongly interacting 2D electron system under magnetic field realized on a free surface of liquid helium is given. Due to the high magnetic field applied perpendicular to the system, the electron liquid constituted of strongly interacting electrons can be described as a collection of statistically independent electrons, each of them having the discrete Landau spectrum in a local reference frame moving ultra-fast with regard to the center-of-mass frame of the entire electron liquid. We found it surprising that the narrowing of Landau levels induced by Coulomb forces in local frames is accompanied by a strong Coulomb broadening of the electron dynamical structure factor (DSF) in the laboratory reference frame. We discuss in detail the magnetotransport theories in two-dimensions, especially the force-balance equation method and the memory function formalism which allow to reduce the electron transport problem to the description of the equilibrium electron DSF. We show that the whole body of the DC magnetoconductivity and cyclotron resonance absorption data measured and reported within the last two decades (even previously conflicting with theory) can be very well described by means of a simple model for the electron DSF entering the imaginary part of the memory function or the effective collision frequency of the electrons.

  8. Evidence for the Dipole Nature of the Low-Energy γ Enhancement in 56Fe

    NASA Astrophysics Data System (ADS)

    Larsen, A. C.; Blasi, N.; Bracco, A.; Camera, F.; Eriksen, T. K.; Görgen, A.; Guttormsen, M.; Hagen, T. W.; Leoni, S.; Million, B.; Nyhus, H. T.; Renstrøm, T.; Rose, S. J.; Ruud, I. E.; Siem, S.; Tornyi, T.; Tveten, G. M.; Voinov, A. V.; Wiedeking, M.

    2013-12-01

    The γ-ray strength function of Fe56 has been measured from proton-γ coincidences for excitation energies up to ≈11MeV. The low-energy enhancement in the γ-ray strength function, which was first discovered in the (He3,αγ)Fe56 reaction, is confirmed with the (p,p'γ)Fe56 experiment reported here. Angular distributions of the γ rays give for the first time evidence that the enhancement is dominated by dipole transitions.

  9. Low-energy elastic electron scattering from chloromethane, CH3Cl

    NASA Astrophysics Data System (ADS)

    Navarro, C.; Sakaamini, A.; Cross, J.; Hargreaves, L. R.; Khakoo, M. A.; Fedus, Kamil; Winstead, C.; McKoy, V.

    2015-10-01

    We report theoretical as well as (normalized) experimental differential and integral cross sections for vibrationally elastic scattering of low-energy electrons from chloromethane, CH3Cl, also known as methyl chloride. The theoretical cross sections were computed using the Schwinger multichannel variational method in the single-channel approximation, with polarization effects included via virtual excitations. Cross section measurements were made at incident energies ranging from 0.5 to 100 eV and at scattering angles from {5}\\circ to {125}\\circ . We compare our data to earlier previous results for this molecule.

  10. Low-energy elastic electron scattering form chloroethane, C2H5Cl

    NASA Astrophysics Data System (ADS)

    Sakaamini, A.; Navarro, C.; Cross, J.; Hargreaves, L. R.; Khakoo, M. A.; Fedus, Kamil; Winstead, C.; McKoy, V.

    2015-10-01

    We report theoretical as well as (normalized) experimental differential and integral cross sections for vibrationally elastic scattering of low-energy electrons from chloroethane, C2H5Cl, also known as ethyl chloride. The theoretical cross sections were computed using the Schwinger multichannel variational method in the single-channel approximation, with polarization effects included via virtual excitations. Cross section measurements were made at incident energies ranging from 1 to 30 eV and at scattering angles from {10}\\circ to {125}\\circ . We compare our data to previous results for C2H5Cl and for the related molecule chloromethane.

  11. Dependence of low energy incomplete fusion on projectile's α-Q-value

    NASA Astrophysics Data System (ADS)

    Yadav, Abhishek; Singh, Pushpendra P.; Kumar, P.; Shuaib, Mohd; Sharma, Vijay R.; Bala, Indu; Singh, D. P.; Gupta, Sunita; Gupta, U.; Sharma, M. K.; Kumar, R.; Muralithar, S.; Singh, R. P.; Singh, B. P.; Prasad, R.

    2015-06-01

    An attempt has been made to understand the effect of entrance-channel parameters on low-energy incomplete fusion and a strong projectile dependence in terms of projectile's α-Q-value has been observed. In the present work, the excitation functions of 16O,13,12C+159Tb systems have been measured and compared with PACE4 predictions to study the involvement of different reaction processes. The strength of incomplete fusion reactions for all the studied systems have been extraced and compared to find out the systematics.

  12. Theoretical modeling of low-energy electronic absorption bands in reduced cobaloximes.

    PubMed

    Bhattacharjee, Anirban; Chavarot-Kerlidou, Murielle; Dempsey, Jillian L; Gray, Harry B; Fujita, Etsuko; Muckerman, James T; Fontecave, Marc; Artero, Vincent; Arantes, Guilherme M; Field, Martin J

    2014-10-06

    The reduced Co(I) states of cobaloximes are powerful nucleophiles that play an important role in the hydrogen-evolving catalytic activity of these species. In this work we analyze the low-energy electronic absorption bands of two cobaloxime systems experimentally and use a variety of density functional theory and molecular orbital ab initio quantum chemical approaches. Overall we find a reasonable qualitative understanding of the electronic excitation spectra of these compounds but show that obtaining quantitative results remains a challenging task.

  13. Theoretical Modeling of Low Energy Electronic Absorption Bands in Reduced Cobaloximes

    PubMed Central

    Bhattacharjee, Anirban; Chavarot-Kerlidou, Murielle; Dempsey, Jillian L.; Gray, Harry B.; Fujita, Etsuko; Muckerman, James T.; Fontecave, Marc; Artero, Vincent; Arantes, Guilherme M.; Field, Martin J.

    2015-01-01

    The reduced Co(I) states of cobaloximes are powerful nucleophiles that play an important role in the hydrogen-evolving catalytic activity of these species. In this work we have analyzed the low energy electronic absorption bands of two cobaloxime systems experimentally and using a variety of density functional theory and molecular orbital ab initio quantum chemical approaches. Overall we find a reasonable qualitative understanding of the electronic excitation spectra of these compounds but show that obtaining quantitative results remains a challenging task. PMID:25113847

  14. Evidence for the dipole nature of the low-energy γ enhancement in Fe56

    DOE PAGES

    Larsen, A. C.; Blasi, N.; Bracco, A.; ...

    2013-12-11

    Here, the γ-ray strength function of 56Fe has been measured from proton-γ coincidences for excitation energies up to ≈11 MeV. The low-energy enhancement in the γ-ray strength function, which was first discovered in the (3He,αγ)56Fe reaction, is confirmed with the (p,p'γ)56Fe experiment reported here. Angular distributions of the γ rays give for the first time evidence that the enhancement is dominated by dipole transitions.

  15. Antiproton stopping at low energies: confirmation of velocity-proportional stopping power.

    PubMed

    Møller, S P; Csete, A; Ichioka, T; Knudsen, H; Uggerhøj, U I; Andersen, H H

    2002-05-13

    The stopping power for antiprotons in various solid targets has been measured in the low-energy range of 1-100 keV. In agreement with most models, in particular free-electron gas models, the stopping power is found to be proportional to the projectile velocity below the stopping-power maximum. Although a stopping power proportional to velocity has also been observed for protons, the interpretation of such measurements is difficult due to the presence of charge exchange processes. Hence, the present measurements constitute the first unambiguous support for a velocity-proportional stopping power due to target excitations by a pointlike projectile.

  16. Theoretical modeling of low-energy electronic absorption bands in reduced cobaloximes

    DOE PAGES

    Bhattacharjee, Anirban; Chavarot-Kerlidou, Murielle; Dempsey, Jillian L.; ...

    2014-08-11

    Here, we report that the reduced Co(I) states of cobaloximes are powerful nucleophiles that play an important role in the hydrogen-evolving catalytic activity of these species. In this work we have analyzed the low energy electronic absorption bands of two cobaloxime systems experimentally and using a variety of density functional theory and molecular orbital ab initio quantum chemical approaches. Overall we find a reasonable qualitative understanding of the electronic excitation spectra of these compounds but show that obtaining quantitative results remains a challenging task.

  17. Theoretical modeling of low-energy electronic absorption bands in reduced cobaloximes

    SciTech Connect

    Bhattacharjee, Anirban; Chavarot-Kerlidou, Murielle; Dempsey, Jillian L.; Gray, Harry B.; Fujita, Etsuko; Muckerman, James T.; Fontecave, Marc; Artero, Vincent; Arantes, Guilherme M.; Field, Martin J.

    2014-08-11

    Here, we report that the reduced Co(I) states of cobaloximes are powerful nucleophiles that play an important role in the hydrogen-evolving catalytic activity of these species. In this work we have analyzed the low energy electronic absorption bands of two cobaloxime systems experimentally and using a variety of density functional theory and molecular orbital ab initio quantum chemical approaches. Overall we find a reasonable qualitative understanding of the electronic excitation spectra of these compounds but show that obtaining quantitative results remains a challenging task.

  18. Evidence for the dipole nature of the low-energy γ enhancement in 56Fe.

    PubMed

    Larsen, A C; Blasi, N; Bracco, A; Camera, F; Eriksen, T K; Görgen, A; Guttormsen, M; Hagen, T W; Leoni, S; Million, B; Nyhus, H T; Renstrøm, T; Rose, S J; Ruud, I E; Siem, S; Tornyi, T; Tveten, G M; Voinov, A V; Wiedeking, M

    2013-12-13

    The γ-ray strength function of 56Fe has been measured from proton-γ coincidences for excitation energies up to ≈11  MeV. The low-energy enhancement in the γ-ray strength function, which was first discovered in the (3He,αγ)56Fe reaction, is confirmed with the (p,p'γ)56Fe experiment reported here. Angular distributions of the γ rays give for the first time evidence that the enhancement is dominated by dipole transitions.

  19. Low-energy limit of scalar electrodynamics in M/sup 6/

    SciTech Connect

    Svetovoi, V.B.; Khariton, N.G.

    1988-10-01

    We consider scalar electrodynamics in the space M/sup 6/ with a nontrivial vacuum with respect to the two extra dimensions. Reduction to four-dimensional space is carried out. The low-energy sector turns out to possess U/sup loc/(1) x O/sup glob/(2) symmetry, which is broken by nonperturbative effects. The gap in the mass spectrum between heavy and light excitations is due to the breaking of the symmetry of the space by the vacuum. The model studied here provides an example of a natural hierarchy of mass scales.

  20. The Coulombic Lattice Potential of Ionic Compounds: The Cubic Perovskites.

    ERIC Educational Resources Information Center

    Francisco, E.; And Others

    1988-01-01

    Presents coulombic models representing the particles of a system by point charges interacting through Coulomb's law to explain coulombic lattice potential. Uses rubidium manganese trifluoride as an example of cubic perovskite structure. Discusses the effects on cluster properties. (CW)

  1. The Coulombic Lattice Potential of Ionic Compounds: The Cubic Perovskites.

    ERIC Educational Resources Information Center

    Francisco, E.; And Others

    1988-01-01

    Presents coulombic models representing the particles of a system by point charges interacting through Coulomb's law to explain coulombic lattice potential. Uses rubidium manganese trifluoride as an example of cubic perovskite structure. Discusses the effects on cluster properties. (CW)

  2. Transient and chaotic low-energy transfers in a system with bistable nonlinearity

    SciTech Connect

    Romeo, F.; Manevitch, L. I.; Bergman, L. A.; Vakakis, A.

    2015-05-15

    The low-energy dynamics of a two-dof system composed of a grounded linear oscillator coupled to a lightweight mass by means of a spring with both cubic nonlinear and negative linear components is investigated. The mechanisms leading to intense energy exchanges between the linear oscillator, excited by a low-energy impulse, and the nonlinear attachment are addressed. For lightly damped systems, it is shown that two main mechanisms arise: Aperiodic alternating in-well and cross-well oscillations of the nonlinear attachment, and secondary nonlinear beats occurring once the dynamics evolves solely in-well. The description of the former dissipative phenomenon is provided in a two-dimensional projection of the phase space, where transitions between in-well and cross-well oscillations are associated with sequences of crossings across a pseudo-separatrix. Whereas the second mechanism is described in terms of secondary limiting phase trajectories of the nonlinear attachment under certain resonance conditions. The analytical treatment of the two aformentioned low-energy transfer mechanisms relies on the reduction of the nonlinear dynamics and consequent analysis of the reduced dynamics by asymptotic techniques. Direct numerical simulations fully validate our analytical predictions.

  3. Transient and chaotic low-energy transfers in a system with bistable nonlinearity

    NASA Astrophysics Data System (ADS)

    Romeo, F.; Manevitch, L. I.; Bergman, L. A.; Vakakis, A.

    2015-05-01

    The low-energy dynamics of a two-dof system composed of a grounded linear oscillator coupled to a lightweight mass by means of a spring with both cubic nonlinear and negative linear components is investigated. The mechanisms leading to intense energy exchanges between the linear oscillator, excited by a low-energy impulse, and the nonlinear attachment are addressed. For lightly damped systems, it is shown that two main mechanisms arise: Aperiodic alternating in-well and cross-well oscillations of the nonlinear attachment, and secondary nonlinear beats occurring once the dynamics evolves solely in-well. The description of the former dissipative phenomenon is provided in a two-dimensional projection of the phase space, where transitions between in-well and cross-well oscillations are associated with sequences of crossings across a pseudo-separatrix. Whereas the second mechanism is described in terms of secondary limiting phase trajectories of the nonlinear attachment under certain resonance conditions. The analytical treatment of the two aformentioned low-energy transfer mechanisms relies on the reduction of the nonlinear dynamics and consequent analysis of the reduced dynamics by asymptotic techniques. Direct numerical simulations fully validate our analytical predictions.

  4. Low Energy Electrons as Probing Tool for Astrochemical Reaction Mechanisms

    NASA Astrophysics Data System (ADS)

    Hendrik Bredehöft, Jan; Swiderek, Petra; Hamann, Thorben

    hitting anything solid, they will create secondary electrons. These electrons are in fact the energy source needed to run interstellar chemistry. Slow electrons can in principle trigger three different primary processes in a molecule. The first is ionisation by electron impact (EI), which is used to create ions in mass spectrometry. In this process an electron hits a molecule M and knocks an outer shell electron to create a cation. This occurs whenever the electron energy is above the ionisation threshold of the target molecule. Another possibility is the attachment of a slow electron to a molecule to create an anion. This can occur at sharply defined resonance energies specific to the molecule M. A third possibility is to excite the molecule M to a neutral state M∗ .[9] M + e- -> M+ + 2 e- (Electron impact ionisation) M + e- -> M- (Electron attachment) M + e- -> M∗ + e- (Neutral excitation) The created states M+ , M- and M∗ are usually not stable states so they very often dissociate into ions and radicals, which can then further react with neighbouring molecules to form new chemical species. In these chemical reactions some products can be formed even at very low temperatures that would otherwise require a lot of thermal energy and/or special catalysts. The formation of ethylamine from ethylene and ammonia by hydroamination is one such example. The reaction is characterized by a high activation barrier caused by the electronic repulsion between the electron density rich C=C double bound and the lone pair electrons of ammo-nia. The reaction also has a highly negative entropy, so it becomes less favourable at higher temperatures, ruling out heat as a means to facilitate the reaction. In classical chemistry this problem is overcome by the use of catalysts. Unfortunately there still is no general catalyst for this kind of reaction. Recently it was shown that the reaction can efficiently be induced by low energy electron radiation.[10] One of the reaction partners is

  5. 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

  6. Low-energy photoelectron imaging of HS{sub 2} anion

    SciTech Connect

    Qin, Zhengbo; Cong, Ran; Liu, Zhiling; Xie, Hua; Tang, Zichao

    2014-11-28

    Low-energy photoelectron imaging of HS{sub 2}{sup −} has been investigated, which provides the vibrational frequencies of the ground state as well as the first excited state of HS{sub 2}. It allows us to determine more accurate electron affinity of HS{sub 2}, 1.9080 ± 0.0018 eV. Combined with Frank-Condon simulation, the vibrational features have been unveiled related to S-S stretching and S-S-H bending modes for the ground state and S-S stretching, S-S-H bending, and S-H stretching modes for the first excited state. Photoelectron angular distributions are mainly characteristic of electron detachment from two different molecular orbitals (MOs) in HS{sub 2}{sup −}. With the aid of accurate electron affinity value of HS{sub 2}, corresponding thermochemical quantities can be accessed.

  7. Density-matrix based determination of low-energy model Hamiltonians from ab initio wavefunctions.

    PubMed

    Changlani, Hitesh J; Zheng, Huihuo; Wagner, Lucas K

    2015-09-14

    We propose a way of obtaining effective low energy Hubbard-like model Hamiltonians from ab initio quantum Monte Carlo calculations for molecular and extended systems. The Hamiltonian parameters are fit to best match the ab initio two-body density matrices and energies of the ground and excited states, and thus we refer to the method as ab initio density matrix based downfolding. For benzene (a finite system), we find good agreement with experimentally available energy gaps without using any experimental inputs. For graphene, a two dimensional solid (extended system) with periodic boundary conditions, we find the effective on-site Hubbard U(∗)/t to be 1.3 ± 0.2, comparable to a recent estimate based on the constrained random phase approximation. For molecules, such parameterizations enable calculation of excited states that are usually not accessible within ground state approaches. For solids, the effective Hamiltonian enables large-scale calculations using techniques designed for lattice models.

  8. Nuclear Astrophysical studies using low-energy RI beams at CRIB

    SciTech Connect

    Yamaguchi, H.; Wakabayashi, Y.; Hayakawa, S.; Binh, D. N.; Kahl, D.; Kurihara, Y.; Kubono, S.; Niikura, M.; Teranishi, T.; He, J. J.; Kwon, Y. K.; Nishimura, S.; Togano, Y.; Iwasa, N.; Khiem, L. H.

    2009-05-04

    CRIB (CNS Radioactive Ion Beam separator) is a low-energy RI beam separator at the Center for Nuclear Study (CNS) of the University of Tokyo, used for various studies covering nuclear-astrophysical topics. An application of the RI beam at CRIB for the astrophysical studies is a new measurement of the proton resonance scattering on {sup 7}Be. The measurement was performed up to the excitation energy of 6.8 MeV, ans the excitation function above 3.5 MeV was successfully measured for the first time, providing important information about the reaction rate of {sup 7}Be(p,{gamma}){sup 8}B, which is the key reaction in the solar {sup 8}B neutrino production. A preliminary result of the {sup 7}Be+p experiment is presented.

  9. 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.

  10. The problem of low energy particle measurements in the magnetosphere

    NASA Technical Reports Server (NTRS)

    Whipple, E. C., Jr.

    1978-01-01

    The accurate measurement of low energy (less than 100 eV) particle properties in the magnetosphere has been difficult, partly because of the low density of such particles, but more particularly because of spacecraft interference effects. Some early examples of how these phenomena have affected particle measurements on an OGO spacecraft are presented. Data obtained with the UCSD particle detectors on ATS-6 are then presented showing how some of these difficulties have been partially overcome. Future measurements of low energy particles in the magnetosphere can be improved by: (1) improving the low energy resolution of detectors; (2) building electrostatically clean spacecraft; (3) controlling spacecraft potential; and (4) using auxiliary measurements, particularly wave data.

  11. EVOLUTION OF THE CRAB NEBULA IN A LOW ENERGY SUPERNOVA

    SciTech Connect

    Yang, Haifeng; Chevalier, Roger A. E-mail: rac5x@virginia.edu

    2015-06-20

    The nature of the supernova leading to the Crab Nebula has long been controversial because of the low energy that is present in the observed nebula. One possibility is that there is significant energy in extended fast material around the Crab but searches for such material have not led to detections. An electron capture supernova model can plausibly account for the low energy and the observed abundances in the Crab. Here, we examine the evolution of the Crab pulsar wind nebula inside a freely expanding supernova and find that the observed properties are most consistent with a low energy event. Both the velocity and radius of the shell material, and the amount of gas swept up by the pulsar wind point to a low explosion energy (∼10{sup 50} erg). We do not favor a model in which circumstellar interaction powers the supernova luminosity near maximum light because the required mass would limit the freely expanding ejecta.

  12. Evolution of the Crab Nebula in a Low Energy Supernova

    NASA Astrophysics Data System (ADS)

    Yang, Haifeng; Chevalier, Roger A.

    2015-06-01

    The nature of the supernova leading to the Crab Nebula has long been controversial because of the low energy that is present in the observed nebula. One possibility is that there is significant energy in extended fast material around the Crab but searches for such material have not led to detections. An electron capture supernova model can plausibly account for the low energy and the observed abundances in the Crab. Here, we examine the evolution of the Crab pulsar wind nebula inside a freely expanding supernova and find that the observed properties are most consistent with a low energy event. Both the velocity and radius of the shell material, and the amount of gas swept up by the pulsar wind point to a low explosion energy (∼1050 erg). We do not favor a model in which circumstellar interaction powers the supernova luminosity near maximum light because the required mass would limit the freely expanding ejecta.

  13. 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.

  14. Spectroscopy of Light Nuclei with Low Energy Nuclear Reactions

    NASA Astrophysics Data System (ADS)

    Lombardo, I.; Dell'Aquila, D.; Vigilante, M.

    2016-07-01

    We discuss new results concerning the investigation of the 19F(p,α 0)16O and 10B(p,α 0)7Be reactions at low energies. Both reactions are important for the nuclear spectroscopy of the formed compound nucleus, i.e. 20Ne and 11C respectively, and play a role in nuclear astrophysics. For the 10B(p,α 0)7Be case, a comprehensive analysis of our reaction data and other scattering data points out the possible presence of an unreported state in 11C at Ex ≈ 9.36 MeV. For the 19F(p,α 0)16O case, the study of the low energy angular distributions testifies the role played by low energy resonances in the S-factor, leading to an enhanced reaction rate at stellar energies.

  15. Low energy particle composition. [cosmic rays produced in solar system

    NASA Technical Reports Server (NTRS)

    Gloeckler, G.

    1975-01-01

    A review is given of current knowledge of low-energy cosmic ray particles produced in the solar system. It is argued that the notion that the sun alone can accelerate particles in the solar system must be abandoned in light of evidence that Jupiter and earth may be sources of observed low-energy particles. Measurements of the composition and energy spectra of low-energy particles during quiet times are examined, emphasizing the abundance of protons and helium and of anomalous N, O, and Ne. The abundance of heavy particles (B, C, N, O, Ne, Ca and Fe) of unknown origin in the earth magnetosphere is examined. Reported observations of Jovian electrons are discussed and solar particle events with anomalous compositions (He-3 rich events and Fe rich events) are treated in detail. Nuclear abundances of solar particles, emphasizing their temporal and spatial variations are considered together with the nature of nuclear reaction products in solar flares.

  16. Low energy analyzing powers in pion-proton elastic scattering

    NASA Astrophysics Data System (ADS)

    Meier, R.; Cröni, M.; Bilger, R.; van den Brandt, B.; Breitschopf, J.; Clement, H.; Comfort, J. R.; Denz, H.; Erhardt, A.; Föhl, K.; Friedman, E.; Gräter, J.; Hautle, P.; Hofman, G. J.; Konter, J. A.; Mango, S.; Pätzold, J.; Pavan, M. M.; Wagner, G. J.; von Wrochem, F.

    2004-05-01

    Analyzing powers of pion-proton elastic scattering have been measured at PSI with the Low Energy Pion Spectrometer LEPS and a novel polarized scintillator target. Angular distributions between 40 and 120 deg (c.m.) were taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic energy for π+p scattering, and at 67.3 and 87.2 MeV for π-p scattering. These new measurements constitute a substantial extension of the polarization data base at low energies. Predictions from phase shift analyses are compared with the experimental results, and deviations are observed at low energies.

  17. Low energy impact detection on carbon fiber reinforced materials

    SciTech Connect

    Gros, X.E.

    1995-03-01

    Impact damages, even of small magnitude, affect the mechanical properties of a composite material by reducing its structural integrity. Low energy impacts are not always visible to the naked eye, and they need to be accurately localized for safety and quality reasons. The results of low energy impact detection (0.5--6.0 J) on carbon fiber reinforced materials, carried out with four different NDT techniques--visual, infrared, X-rays, and eddy current--are presented in this paper. Probability of detection (POD) curves are plotted to compare the potential of each technique in regards to carbon fiber reinforced materials. Inspection results have shown that eddy currents are well suited to detect and quantify low energy impacts in carbon fiber composites.

  18. Nondestructive low-energy photon analysis of environmental samples

    SciTech Connect

    Larsen, I.L.; Cutshall, N.H.; Olsen, C.R.

    1984-01-01

    Low-energy photons that accompany the decay of alpha- or beta-emitting radionuclides (e.g., /sup 241/Am, /sup 210/Pb, and /sup 238/U-/sup 234/Th) may be used to quantify concentrations of these radionuclides in environmental samples. Previous attempts to quantify these low-energy photons have had limited success because of the uncertainty associated with photon attenuation in samples of variable matrix composition. A method for directly measuring and applying the self-absorption correction factor is presented. Results obtained by this nondestructive technique for counting low-energy photons are in agreement with values obtained from intracalibrated samples using radiochemical separations and alpha or beta analysis. 8 references, 1 figure, 3 tables.

  19. IONS (ANURADHA): Ionization states of low energy cosmic rays

    NASA Technical Reports Server (NTRS)

    Biswas, S.; Chakraborti, R.; Cowsik, R.; Durgaprasad, N.; Kajarekar, P. J.; Singh, R. K.; Vahia, M. N.; Yadav, J. S.; Dutt, N.; Goswami, J. N.

    1987-01-01

    IONS (ANURADHA), the experimental payload designed specifically to determine the ionization states, flux, composition, energy spectra and arrival directions of low energy (10 to 100 MeV/amu) anomalous cosmic ray ions of helium to iron in near-Earth space, had a highly successful flight and operation Spacelab-3 mission. The experiment combines the accuracy of a highly sensitive CR-39 nuclear track detector with active components included in the payload to achieve the experimental objectives. Post-flight analysis of detector calibration pieces placed within the payload indicated no measurable changes in detector response due to its exposure in spacelab environment. Nuclear tracks produced by alpha-particles, oxygen group and Fe ions in low energy anomalous cosmic rays were identified. It is calculated that the main detector has recorded high quality events of about 10,000 alpha-particles and similar number of oxygen group and heavier ions of low energy cosmic rays.

  20. Dynamics of Coulomb correlations in semiconductors in high magnetic fields

    SciTech Connect

    Fromer, Neil Alan

    2002-01-01

    Current theories have been successful in explaining many nonlinear optical experiments in undoped semiconductors. However, these theories require a ground state which is assumed to be uncorrelated. Strongly correlated systems of current interest, such as a two dimensional electron gas in a high magnetic field, cannot be explained in this manner because the correlations in the ground state and the low energy collective excitations cause a breakdown of the conventional techniques. We perform ultrafast time-resolved four-wave mixing on $n$-modulation doped quantum wells, which contain a quasi-two dimensional electron gas, in a large magnetic field, when only a single Landau level is excited and also when two levels are excited together. We find evidence for memory effects and as strong coupling between the Landau levels induced by the electron gas. We compare our results with simulations based on a new microscopic approach capable of treating the collective effects and correlations of the doped electrons, and find a good qualitative agreement. By looking at the individual contributions to the model, we determine that the unusual correlation effects seen in the experiments are caused by the scattering of photo-excited electron-hole pairs with the electron gas, leading to new excited states which are not present in undoped semiconductors, and also by exciton-exciton interactions mediated by the long-lived collective excitations of the electron gas, inter-Landau level magnetoplasmons.

  1. Numerical approach to Coulomb gauge QCD

    SciTech Connect

    Matevosyan, Hrayr H.; Szczepaniak, Adam P.; Bowman, Patrick O.

    2008-07-01

    We calculate the ghost two-point function in Coulomb gauge QCD with a simple model vacuum gluon wave function using Monte Carlo integration. This approach extends the previous analytic studies of the ghost propagator with this ansatz, where a ladder-rainbow expansion was unavoidable for calculating the path integral over gluon field configurations. The new approach allows us to study the possible critical behavior of the coupling constant, as well as the Coulomb potential derived from the ghost dressing function. We demonstrate that IR enhancement of the ghost correlator or Coulomb form factor fails to quantitatively reproduce confinement using Gaussian vacuum wave functional.

  2. Low-energy microscopic models for iron-based superconductors: a review

    NASA Astrophysics Data System (ADS)

    Fernandes, Rafael M.; Chubukov, Andrey V.

    2017-01-01

    The development of sensible microscopic models is essential to elucidate the normal-state and superconducting properties of the iron-based superconductors. Because these materials are mostly metallic, a good starting point is an effective low-energy model that captures the electronic states near the Fermi level and their interactions. However, in contrast to cuprates, iron-based high-T c compounds are multi-orbital systems with Hubbard and Hund interactions, resulting in a rather involved 10-orbital lattice model. Here we review different minimal models that have been proposed to unveil the universal features of these systems. We first review minimal models defined solely in the orbital basis, which focus on a particular subspace of orbitals, or solely in the band basis, which rely only on the geometry of the Fermi surface. The former, while providing important qualitative insight into the role of the orbital degrees of freedom, do not distinguish between high-energy and low-energy sectors and, for this reason, generally do not go beyond mean-field. The latter allow one to go beyond mean-field and investigate the interplay between superconducting and magnetic orders as well as Ising-nematic order. However, they cannot capture orbital-dependent features like spontaneous orbital order. We then review recent proposals for a minimal model that operates in the band basis but fully incorporates the orbital composition and symmetries of the low-energy excitations. We discuss the results of the renormalization group study of such a model, particularly of the interplay between superconductivity, magnetism, and spontaneous orbital order, and compare theoretical predictions with experiments on iron pnictides and chalcogenides. We also discuss the impact of the glide-plane symmetry on the low-energy models, highlighting the key role played by the spin-orbit coupling.

  3. Low-Energy Shockwave Therapy Improves Ischemic Kidney Microcirculation.

    PubMed

    Zhang, Xin; Krier, James D; Amador Carrascal, Carolina; Greenleaf, James F; Ebrahimi, Behzad; Hedayat, Ahmad F; Textor, Stephen C; Lerman, Amir; Lerman, Lilach O

    2016-12-01

    Microvascular rarefaction distal to renal artery stenosis is linked to renal dysfunction and poor outcomes. Low-energy shockwave therapy stimulates angiogenesis, but the effect on the kidney microvasculature is unknown. We hypothesized that low-energy shockwave therapy would restore the microcirculation and alleviate renal dysfunction in renovascular disease. Normal pigs and pigs subjected to 3 weeks of renal artery stenosis were treated with six sessions of low-energy shockwave (biweekly for 3 consecutive weeks) or left untreated. We assessed BP, urinary protein, stenotic renal blood flow, GFR, microvascular structure, and oxygenation in vivo 4 weeks after completion of treatment, and then, we assessed expression of angiogenic factors and mechanotransducers (focal adhesion kinase and β1-integrin) ex vivo A 3-week low-energy shockwave regimen attenuated renovascular hypertension, normalized stenotic kidney microvascular density and oxygenation, stabilized function, and alleviated fibrosis in pigs subjected to renal artery stenosis. These effects associated with elevated renal expression of angiogenic factors and mechanotransducers, particularly in proximal tubular cells. In additional pigs with prolonged (6 weeks) renal artery stenosis, shockwave therapy also decreased BP and improved GFR, microvascular density, and oxygenation in the stenotic kidney. This shockwave regimen did not cause detectable kidney injury in normal pigs. In conclusion, low-energy shockwave therapy improves stenotic kidney function, likely in part by mechanotransduction-mediated expression of angiogenic factors in proximal tubular cells, and it may ameliorate renovascular hypertension. Low-energy shockwave therapy may serve as a novel noninvasive intervention in the management of renovascular disease. Copyright © 2016 by the American Society of Nephrology.

  4. Importance of Electronic Relaxation for Inter-Coulombic Decay in Aqueous Systems

    NASA Astrophysics Data System (ADS)

    Schwartz, Craig P.; Fatehi, Shervin; Saykally, Richard J.; Prendergast, David

    2010-11-01

    Inspired by recent photoelectron spectroscopy experiments on hydroxide solutions, we have examined the conditions necessary for enhanced (and, in the case of solutions, detectable) inter-Coulombic decay (ICD)—Auger emission from an atomic site other than that originally excited. We present general guidelines, based on energetic and spatial overlap of molecular orbitals, for this enhancement of inter-Coulombic decay-based energy transfer in solutions. These guidelines indicate that this decay process should be exhibited by broad classes of biomolecules and suggest a design criterion for targeted radiooncology protocols. Our findings show that photoelectron spectroscopy cannot resolve the current hydroxide coordination controversy.

  5. Coulomb Energy Differences in T = 1 Mirror Rotational Bands in 50Fe and 50Cr

    NASA Astrophysics Data System (ADS)

    Lenzi, S. M.; Mărginean, N.; Napoli, D. R.; Ur, C. A.; Zuker, A. P.; de Angelis, G.; Algora, A.; Axiotis, M.; Bazzacco, D.; Belcari, N.; Bentley, M. A.; Bizzeti, P. G.; Bizzeti-Sona, A.; Brandolini, F.; von Brentano, P.; Bucurescu, D.; Cameron, J. A.; Chandler, C.; de Poli, M.; Dewald, A.; Eberth, H.; Farnea, E.; Gadea, A.; Garces-Narro, J.; Gelletly, W.; Grawe, H.; Isocrate, R.; Joss, D. T.; Kalfas, C. A.; Klug, T.; Lampman, T.; Lunardi, S.; Martínez, T.; Martínez-Pinedo, G.; Menegazzo, R.; Nyberg, J.; Podolyak, Zs.; Poves, A.; Ribas, R. V.; Rossi Alvarez, C.; Rubio, B.; Sánchez-Solano, J.; Spolaore, P.; Steinhardt, T.; Thelen, O.; Tonev, D.; Vitturi, A.; von Oertzen, W.; Weiszflog, M.

    2001-09-01

    Gamma rays from the N = Z-2 nucleus 50Fe have been observed, establishing the rotational ground state band up to the state Jπ = 11+ at 6.994 MeV excitation energy. The experimental Coulomb energy differences, obtained by comparison with the isobaric analog states in its mirror 50Cr, confirm the qualitative interpretation of the backbending patterns in terms of successive alignments of proton and neutron pairs. A quantitative agreement with experiment has been achieved by exact shell model calculations, incorporating the differences in radii along the yrast bands, and properly renormalizing the Coulomb matrix elements in the pf model space.

  6. Electron polarimetry at low energies in Hall C at JLab

    NASA Astrophysics Data System (ADS)

    Gaskell, D.

    2013-11-01

    Although the majority of Jefferson Lab experiments require multi-GeV electron beams, there have been a few opportunities to make electron beam polarization measurements at rather low energies. This proceedings will discuss some of the practical difficulties encountered in performing electron polarimetry via Mo/ller scattering at energies on the order of a few hundred MeV. Prospects for Compton polarimetry at very low energies will also be discussed. While Mo/ller scattering is likely the preferred method for electron polarimetry at energies below 500 MeV, there are certain aspects of the polarimeter and experiment design that must be carefully considered.

  7. Electron polarimetry at low energies in Hall C at JLab

    SciTech Connect

    Gaskell, D.

    2013-11-07

    Although the majority of Jefferson Lab experiments require multi-GeV electron beams, there have been a few opportunities to make electron beam polarization measurements at rather low energies. This proceedings will discuss some of the practical difficulties encountered in performing electron polarimetry via Mo/ller scattering at energies on the order of a few hundred MeV. Prospects for Compton polarimetry at very low energies will also be discussed. While Mo/ller scattering is likely the preferred method for electron polarimetry at energies below 500 MeV, there are certain aspects of the polarimeter and experiment design that must be carefully considered.

  8. Diffuse Galactic low energy gamma ray continuum emission

    NASA Technical Reports Server (NTRS)

    Skibo, J. G.; Ramaty, R.

    1993-01-01

    We investigate the origin of diffuse low-energy Galactic gamma-ray continuum down to about 30 keV. We calculate gamma-ray emission via bremsstrahlung and inverse Compton scattering by propagating an unbroken electron power law injection spectrum and employing a Galactic emmissivity model derived from COSB observations. To maintain the low energy electron population capable of producing the observed continuum via bremsstrahlung, a total power input of 4 x 10 exp 41 erg/s is required. This exceeds the total power supplied to the nuclear cosmic rays by about an order of magnitude.

  9. Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope.

    PubMed

    Govyadinov, Alexander A; Konečná, Andrea; Chuvilin, Andrey; Vélez, Saül; Dolado, Irene; Nikitin, Alexey Y; Lopatin, Sergei; Casanova, Fèlix; Hueso, Luis E; Aizpurua, Javier; Hillenbrand, Rainer

    2017-07-21

    Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

  10. The production of low-energy neutral oxygen beams by grazing-incidence neutralization

    NASA Technical Reports Server (NTRS)

    Albridge, R. G.; Haglund, R. F.; Tolk, N. H.; Daech, A. F.

    1987-01-01

    The Vanderbilt University neutral oxygen facility produces beams of low-energy neutral oxygen atoms by means of grazing-incidence collisions between ion beams and metal surfaces. Residual ions are reflected by applied electric fields. This method can utilize initial ion beams of either O(+) or O2(+) since a very large percentage of molecular oxygen ions are dissociated when they undergo grazing-incidence neutralization. The method of neutralization is applicable to low-energy beams and to all ions. Particular emphasis is on O and N2 beams for simulation of the low Earth orbit space environment. Since the beam is a pure O-neutral beam and since measurements of the interaction of the beam with solid surfaces are made spectroscopically, absolute reaction rates can be determined. The technique permits the beams to be used in conjunction with electron and photon irradiation for studies of synergistic effects. Comparisons of optical spectra of Kapton excited by 2.5-keV O, O(+), and O2(+) show significant differences. Optical spectra of Kapton excited by neutral oxygen beams of less than 1 keV have been recorded.

  11. Space-charge effects in the excitation of a cavity resonator by steady flow of excited classical oscillators

    SciTech Connect

    Petelin, M.I.

    1985-09-01

    This paper studies the conditions for self-excitation of oscillations in microwave autogenerators, based on the induced bremsstrahlung radiation of classical electron oscillators by an analytical method (a variant of the Laplace transform) with allowance for Coulomb interaction between particles. The method described here for taking into account the proper (Coulomb) field of the electron beam can be generalized also to more complex theoretical models of high-frequency generators based on the induced emission of excited classical electron oscillators.

  12. Crystallization in two-component Coulomb systems.

    PubMed

    Bonitz, M; Filinov, V S; Fortov, V E; Levashov, P R; Fehske, H

    2005-12-02

    The analysis of Coulomb crystallization is extended from one-component to two-component plasmas. Critical parameters for the existence of Coulomb crystals are derived for both classical and quantum crystals. In the latter case, a critical mass ratio of the two charged components is found, which is of the order of 80. Thus, holes in semiconductors with sufficiently flat valence bands are predicted to spontaneously order into a regular lattice. Such hole crystals are intimately related to ion Coulomb crystals in white dwarf and neutron stars as well as to ion crystals produced in the laboratory. A unified phase diagram of two-component Coulomb crystals is presented and is verified by first-principles computer simulations.

  13. Analytic form for the nonrelativistic Coulomb propagator

    NASA Astrophysics Data System (ADS)

    Blinder, S. M.

    1991-01-01

    An analytic form for the nonrelativistic Coulomb propagator is derived, thus resolving a long-standing problem in Feynman's path-integral formulation of quantum mechanics. Hostler's formula for the Coulomb Green's function is expanded according to the theorem of Mittag-Leffler, then Fourier transformed term by term to give the Coulomb propagator. The result is a discrete summation over the principal quantum number n, involving Whittaker, Laguerre, Hermite, and error functions. As is the case for other nonquadratic potentials, the Coulomb propagator does not have the canonical structure K=F exp(iS/ħ). Part of the expansion resembles a form derived by Crandall [J. Phys. A 16, 3005 (1983)] for the case of reflectionless potentials.

  14. Coulomb flux tube on the lattice

    NASA Astrophysics Data System (ADS)

    Chung, Kristian; Greensite, Jeff

    2017-08-01

    In Coulomb gauge a longitudinal electric field is generated instantaneously with the creation of a static quark-antiquark pair. The field due to the quarks is a sum of two contributions, one from the quark and one from the antiquark, and there is no obvious reason that this sum should fall off exponentially with distance from the sources. We show here, however, from numerical simulations in pure SU(2) lattice gauge theory, that the color Coulomb electric field does in fact fall off exponentially with transverse distance away from a line joining static quark-antiquark sources, indicating the existence of a color Coulomb flux tube, and the absence of long-range Coulomb dipole fields.

  15. Recent developments in Coulomb breakup calculations

    SciTech Connect

    Capel, P.

    2008-05-12

    The theory of reactions applied to Coulomb breakup of loosely-bound projectiles is reviewed. Both the Continuum Discretized Coupled Channel (CDCC) and time-dependent models are described. Recent results about sensitivity of breakup calculations to the projectile wave function are reviewed. Analyses of the extraction of radiative-capture cross section from Coulomb breakup measurements are presented. Current developments in breakup theory are also mentioned.

  16. Study of Intrabeam Scattering in Low Energy Electron Rings

    SciTech Connect

    Venturini, Marco

    2002-08-08

    The paper contains a study of intrabeam scattering in a low energy electron storage ring to be used as part of a Compton back-scattering x-ray source. We discuss time evolution of emittance and dependence of IBS growth rates on lattice parameters.

  17. Low-energy plasma observations at synchronous orbit

    NASA Technical Reports Server (NTRS)

    Lennartsson, W.; Reasoner, D. L.

    1978-01-01

    The University of California at San Diego Auroral Particles Experiment on the ATS 6 satellite in synchronous orbit has detected a low-energy plasma population which is separate and distinct from both the ring current and the plasma sheet populations. The density and temperature of this low-energy population are highly variable, with temperatures in the range kT = 1-30 eV and densities ranging from less than 1 per cu cm to more than 10 per cu cm. The occurrence of a dense low-energy plasma is most likely in the afternoon and dusk local time sectors, whereas n greater than 1 per cu cm is seen in the local night sector only during magnetically quiet periods. These observations suggest that this plasma is the outer zone of the plasmasphere. During magnetically active periods this low-energy plasma is often observed flowing sunward. In the dusk sector, strong sunward plasma flow is often observed for 1-2 hours prior to the onset of a substorm-associated particle injection.

  18. Nuclear phenomena in low-energy nuclear reaction research.

    PubMed

    Krivit, Steven B

    2013-09-01

    This is a comment on Storms E (2010) Status of Cold Fusion, Naturwissenschaften 97:861-881. This comment provides the following remarks to other nuclear phenomena observed in low-energy nuclear reactions aside from helium-4 make significant contributions to the overall energy balance; and normal hydrogen, not just heavy hydrogen, produces excess heat.

  19. Nuclear phenomena in low-energy nuclear reaction research

    NASA Astrophysics Data System (ADS)

    Krivit, Steven B.

    2013-09-01

    This is a comment on Storms (Naturwissenschaften 97:861-881, 2010) Status of Cold Fusion, Naturwissenschaften, 97:861-881. This comment provides the following corrections: other nuclear phenomena observed in low-energy nuclear reactions aside from helium-4 make significant contributions to the overall energy balance; and normal hydrogen, not just heavy hydrogen, produces excess heat.

  20. Physics overview of the Fermilab Low Energy Antiproton Facility Workshop

    SciTech Connect

    Chanowitz, M.S.

    1986-05-01

    A physics overview is presented of the Fermilab workshop to consider a possible high flux, low energy antiproton facility that would use cooled antiprotons from the accumulator ring of the Tevatron collider. Two examples illustrate the power of each a facility to produce narrow states at high rates. Physics topics to which such a facility may be applied are reviewed.