Quasi-elastic electron scattering in uranium-238
Blatchley, C.C.
1984-01-01
Electron scattering data from the MIT-Bates linear accelerator were used to derive longitudinal and transverse response functions (S/sub L/, S/sub T/) for the quasi-elastic (QE) kinematic region from uranium targets. Incident energies ranged from 100 to 690 MeV at five laboratory scattering angles: 60, 90, 134.5, 140, and 160C. The Rosenbluth separations using all five angles were obtained at three momentum transfers (q) from 250 to 500 MeV/c. Both response functions compared well to relativistic Fermi Gas Model (FGM) predictions at higher values of q, but the S/sub L/ peak was progressively lower and broader than the FGM at lower q. This difference in response was reflected in the longitudinal sum rule and in the evaluation of y-scaling. The S/sub L/ integrated strength was generally about 30% larger than the transverse FGM strength throughout. The S/sub L/ sum, however, was reduced to about 60% of the model prediction at lower values of q and increased to almost 100% as q increased to 500 MeV/c. No significant quenching in S/sub L/ was observed at the larger values of q.
Tensor Analyzing Powers for Quasi-Elastic Electron Scattering from Deuterium
Z.-L. Zhou; M. Bouwhuis; M. Ferro-Luzzi; E. Passchier; R. Alarcon; M. Anghinolfi; H. Arenhoevel; R. van Bommel; T. Botto; J.F.J. van den Brand; H.J. Bulten; S. Choi; J. Comfort; S.M. Dolfini; R. Ent; C. Gaulard; D.W. Higinbotham; C.W. de Ja ger; E. Konstantinov; J. Lang; W. Leidemann; D.J. de Lange; M.A. Miller; D. Niko lenko; N. Papadakis; I. Passchier; H.R. Poolman; S.G. Popov; I. Rachek; M. Ripan i; E. Six; J.J.M. Steijger; M. Taiuti; O. Unal; N. Vodinas; H. de Vries
1999-01-01
We report on a first measurement of tensor analyzing powers in quasi-elastic electron-deuteron scattering at an average three-momentum transfer of 1.7 fm{sup -1}. Data sensitive to the spin-dependent nucleon density in the deuteron were obtained for missing momenta up to 150 MeV/c with a tensor polarized {sup 2}H target internal to an electron storage ring. The data are well described by a calculation that includes the effects of final-state interaction, meson-exchange and isobar currents, and leading-order relativistic contributions.
Chiral symmetry, constituent quarks and quasi-elastic electron-nucleus scattering
NASA Astrophysics Data System (ADS)
Henley, E. M.; Krein, G.
1989-11-01
The effects of chiral symmetry breaking are examined for quasi-elastic electron scattering on nuclei. Nucleons are assumed to be composed of constituent quarks with masses that depend on density. This density dependence is determined on the basis of the Nambu-Jona-Lasinio model. It is found that the effects of chiral symmetry breaking are in the right direction and the right order of magnitude to explain the discrepancies between theory and experiment. On leave from Departamento de Fisica, Universidade Federal de Santa Maria, 97100 Santa Maria, R.S., Brazil.
Short Range Correlations in Nuclei at Large xbj through Inclusive Quasi-Elastic Electron Scattering
Ye, Zhihong
2013-12-01
The experiment, E08-014, in Hall-A at Jefferson Lab aims to study the short-range correlations (SRC) which are necessary to explain the nuclear strength absent in the mean field theory. The cross sections for 2H, 3He, 4He, 12C, 40Ca and 48Ca, were measured via inclusive quasi-elastic electron scattering from these nuclei in a Q2 range between 0.8 and 2.8 (GeV/c)^{2} for x>1. The cross section ratios of heavy nuclei to 2H were extracted to study two-nucleon SRC for 1
Quasi-Elastic Light Scattering in Ophthalmology
NASA Astrophysics Data System (ADS)
Ansari, Rafat R.
The eye is not just a "window to the soul"; it can also be a "window to the human body." The eye is built like a camera. Light which travels from the cornea to the retina traverses through tissues that are representative of nearly every tissue type and fluid type in the human body. Therefore, it is possible to diagnose ocular and systemic diseases through the eye. Quasi-elastic light scattering (QELS) also known as dynamic light scattering (DLS) is a laboratory technique routinely used in the characterization of macromolecular dispersions. QELS instrumentation has now become more compact, sensitive, flexible, and easy to use. These developments have made QELS/DLS an important tool in ophthalmic research where disease can be detected early and noninvasively before the clinical symptoms appear.
Improved Optics For Quasi-Elastic Light Scattering
NASA Technical Reports Server (NTRS)
Cheung, Harry Michael
1995-01-01
Improved optical train devised for use in light-scattering measurements of quasi-elastic light scattering (QELS) and laser spectroscopy. Measurements performed on solutions, microemulsions, micellular solutions, and colloidal dispersions. Simultaneous measurements of total intensity and fluctuations in total intensity of light scattered from sample at various angles provides data used, in conjunction with diffusion coefficients, to compute sizes of particles in sample.
Quasi-elastic nuclear scattering at high energies
NASA Technical Reports Server (NTRS)
Cucinotta, Francis A.; Townsend, Lawrence W.; Wilson, John W.
1992-01-01
The quasi-elastic scattering of two nuclei is considered in the high-energy optical model. Energy loss and momentum transfer spectra for projectile ions are evaluated in terms of an inelastic multiple-scattering series corresponding to multiple knockout of target nucleons. The leading-order correction to the coherent projectile approximation is evaluated. Calculations are compared with experiments.
Rhodopsin photoactivation dynamics revealed by quasi-elastic neutron scattering
Bhowmik, Debsindhu; Shrestha, Utsab; Perera, Suchithranga M.d.c.; Chawla, Udeep; Mamontov, Eugene; Brown, Michael F.; Chu, Xiang -Qiang
2015-01-27
Rhodopsin is a G-protein-coupled receptor (GPCR) responsible for vision under dim light conditions. During rhodopsin photoactivation, the chromophore retinal undergoes cis-trans isomerization, and subsequently dissociates from the protein yielding the opsin apoprotein [1]. What are the changes in protein dynamics that occur during the rhodopsin photoactivation process? Here, we studied the microscopic dynamics of the dark-state rhodopsin and the ligand-free opsin using quasi-elastic neutron scattering (QENS). The QENS technique tracks the individual hydrogen atom motions in the protein molecules, because the neutron scattering cross-section of hydrogen is much higher than other atoms [2-4]. We used protein (rhodopsin/opsin) samples with CHAPSmore » detergent hydrated with heavy water. The solvent signal is suppressed due to the heavy water, so that only the signals from proteins and detergents are detected. The activation of proteins is confirmed at low temperatures up to 300 K by the mean-square displacement (MSD) analysis. Our QENS experiments conducted at temperatures ranging from 220 K to 300 K clearly indicate that the protein dynamic behavior increases with temperature. The relaxation time for the ligand-bound protein rhodopsin was longer compared to opsin, which can be correlated with the photoactivation. Moreover, the protein dynamics are orders of magnitude slower than the accompanying CHAPS detergent, which forms a band around the protein molecule in the micelle. Unlike the protein, the CHAPS detergent manifests localized motions that are the same as in the bulk empty micelles. Furthermore QENS provides unique understanding of the key dynamics involved in the activation of the GPCR involved in the visual process.« less
Rhodopsin photoactivation dynamics revealed by quasi-elastic neutron scattering
Bhowmik, Debsindhu; Shrestha, Utsab; Perera, Suchithranga M.d.c.; Chawla, Udeep; Mamontov, Eugene; Brown, Michael F.; Chu, Xiang -Qiang
2015-01-27
Rhodopsin is a G-protein-coupled receptor (GPCR) responsible for vision under dim light conditions. During rhodopsin photoactivation, the chromophore retinal undergoes cis-trans isomerization, and subsequently dissociates from the protein yielding the opsin apoprotein [1]. What are the changes in protein dynamics that occur during the rhodopsin photoactivation process? Here, we studied the microscopic dynamics of the dark-state rhodopsin and the ligand-free opsin using quasi-elastic neutron scattering (QENS). The QENS technique tracks the individual hydrogen atom motions in the protein molecules, because the neutron scattering cross-section of hydrogen is much higher than other atoms [2-4]. We used protein (rhodopsin/opsin) samples with CHAPS detergent hydrated with heavy water. The solvent signal is suppressed due to the heavy water, so that only the signals from proteins and detergents are detected. The activation of proteins is confirmed at low temperatures up to 300 K by the mean-square displacement (MSD) analysis. Our QENS experiments conducted at temperatures ranging from 220 K to 300 K clearly indicate that the protein dynamic behavior increases with temperature. The relaxation time for the ligand-bound protein rhodopsin was longer compared to opsin, which can be correlated with the photoactivation. Moreover, the protein dynamics are orders of magnitude slower than the accompanying CHAPS detergent, which forms a band around the protein molecule in the micelle. Unlike the protein, the CHAPS detergent manifests localized motions that are the same as in the bulk empty micelles. Furthermore QENS provides unique understanding of the key dynamics involved in the activation of the GPCR involved in the visual process.
Measurement of muon neutrino quasi-elastic scattering on carbon
Aguilar-Arevalo, A.A.; Bazarko, A.O.; Brice, S.J.; Brown, B.C.; Bugel, L.; Cao, J.; Coney, L.; Conrad, J.M.; Cox, D.C.; Curioni, A.; Djurcic, Z.; /Alabama U. /Bucknell U. /Cincinnati U. /Colorado U. /Columbia U. /Embry-Riddle Aeronautical U. /Fermilab /Indiana U. /Los Alamos /Louisiana State U. /Michigan U.
2007-06-01
Low energy (200 < E{sub v} < 2000 MeV) neutrino oscillation experiments, including MiniBooNE, require a model of charged current quasi-elastic (CCQE) neutrino interactions to predict signal samples. Using a high-statistics sample of muon neutrino CCQE events, MiniBooNE finds that a simple Fermi gas model, with appropriate adjustments, accurately characterizes the CCQE events observed in a carbon-based detector. The extracted parameters include an effective axial mass, M{sub A} = 1.23 {+-} 0.20 GeV, used to describe the four-momentum dependence of the axial-vector form factor of the nucleon; and a Pauli-suppression parameter, {kappa} = 1.019 {+-} 0.011.
Quasi-elastic light scattering from structured particles.
Chen, S H; Holz, M; Tartaglia, P
1977-01-01
We present a formulation by which the scattered field correlation function of a nonstationary structured particle can be calculated. Specifically, we consider the case of micron-size bacteria, where the Rayleigh- Gans-Debye approximation may be used to evaluate the correlation function. We show that the width of the intensity correlation spectrum (as measured, for example, by the photon correlation technique) exhibits I an oscillatory behavior which is characteristic of the interference pattern produced by the internal structure. Two cases are of interest: diffusion and motility are considered in detail, and some evidence of the predicted behavior is shown from the photon correlation measurement of E. coli bacteria. PMID:20168450
Rhodopsin Photoactivation Dynamics Revealed by Quasi-Elastic Neutron Scattering
NASA Astrophysics Data System (ADS)
Bhowmik, Debsindhu; Shrestha, Utsab; Perera, Suchhithranga M. C. D.; Chawla, Udeep; Mamontov, Eugene; Brown, Michael; Chu, Xiang-Qiang
2015-03-01
Rhodopsin is a G-protein-coupled receptor (GPCR) responsible for vision. During photoactivation, the chromophore retinal dissociates from protein yielding the opsin apoprotein. What are the changes in protein dynamics that occur during the photoactivation process? Here, we studied the microscopic dynamics of dark-state rhodopsin and the ligand-free opsin using quasielastic neutron scattering (QENS). The QENS technique tracks individual hydrogen atom motion because of the much higher neutron scattering cross-section of hydrogen than other atoms. We used protein with CHAPS detergent hydrated with heavy water. The activation of proteins is confirmed at low temperatures up to 300 K by mean-square displacement (MSD) analysis. The QENS experiments at temperatures ranging from 220 K to 300 K clearly indicate an increase in protein dynamic behavior with temperature. The relaxation time for the ligand-bound protein rhodopsin is faster compared to opsin, which can be correlated with the photoactivation. Moreover, the protein dynamics are orders of magnitude slower than the accompanying CHAPS detergent, which unlike protein, manifests localized motions.
A quasi-elastic light scattering study of smooth muscle myosin in the presence of ATP.
Wu, X; Blank, P S; Carlson, F D
1992-01-01
We have investigated the hydrodynamic properties of turkey gizzard smooth muscle myosin in solution using quasi-elastic light scattering (QELS). The effects of ionic strength (0.05-0.5 M KCl) and light chain phosphorylation on the conformational transition of myosin were examined in the presence of ATP at 20 degrees C. Cumulant analysis and light scattering models were used to describe the myosin system in solution. A nonlinear least squares fitting procedure was used to determine the model that best fits the data. The conformational transition of the myosin monomer from a folded form to an extended form was clearly demonstrated in a salt concentration range of 0.15-0.3 M KCl. Light chain phosphorylation regulates the transition and promotes unfolding of the myosin. These results agree with the findings obtained using sedimentation velocity and electron microscopy (Onishi and Wakabayashi, 1982; Trybus et al., 1982; Trybus and Lowey, 1984). In addition, we present evidence for polymeric myosin coexisting with the two monomeric myosin species over a salt concentration range from 0.05 to 0.5 M KCl. The size of the polymeric myosin varied with salt concentration. This observation supports the hypothesis that, in solution, a dynamic equilibrium exists between the two conformations of myosin monomer and filaments. PMID:1420864
Dorman, Mark Edward
2008-04-01
The Main Injector Neutrino Oscillation Search (MINOS) is a long baseline neutrino oscillation experiment based at the Fermi National Accelerator Laboratory (FNAL) in Chicago, Illinois. MINOS measures neutrino interactions in two large iron-scintillator tracking/sampling calorimeters; the Near Detector on-site at FNAL and the Far Detector located in the Soudan mine in northern Minnesota. The Near Detector has recorded a large number of neutrino interactions and this high statistics dataset can be used to make precision measurements of neutrino interaction cross sections. The cross section for charged-current quasi-elastic scattering has been measured by a number of previous experiments and these measurements disagree by up to 30%. A method to select a quasi-elastic enriched sample of neutrino interactions in the MINOS Near Detector is presented and a procedure to fit the kinematic distributions of this sample and extract the quasi-elastic cross section is introduced. The accuracy and robustness of the fitting procedure is studied using mock data and finally results from fits to the MINOS Near Detector data are presented.
Quasi-elastic light scattering studies of membrane motion in single red blood cells.
Tishler, R B; Carlson, F D
1987-01-01
Studies of red blood cells (RBCs) and RBC ghosts, using a quasi-elastic light scattering (QELS) microscope spectrometer, have identified the membrane as the primary source of the light scattering signal. This is the first report in which motion of the cell membrane has been demonstrated to be the primary source of the QELS signal from a cell. Cytoplasmic changes induced in the RBC by varying the osmotic strength of the medium were also detected using this technique. Comparison of the data from white blood cells (WBCs) with the RBC data demonstrated significant differences between different types of cells. PMID:3607216
Role of triple phonon excitations in large angle quasi-elastic scattering of very heavy mass systems
NASA Astrophysics Data System (ADS)
Zamrun, Muhammad Firihu
2016-07-01
We study the effect of multi-phonon excitations on large-angle quasi-elastic scattering of massive systems using the full order coupled-channels formalism. We especially investigate the role of triple phonon excitations of the target and projectile nuclei on the quasi-elastic scattering cross-section as well as the barrier distribution for 54Cr, 56Fe, 64Ni and 70Zn + 208Pb systems. It is shown that the calculations taken into account, the triple octupole phonon excitations of the target and triple quadrupole phonon excitations of the projectile for these systems can explain the experimental data of the quasi-elastic cross-section and the quasi-elastic barrier distribution. These results indicate that the coupled-channels formalism is still valid even for the very heavy mass systems.
Looking at hydrogen motions in confinement. The uniqueness of Quasi-Elastic Neutron Scattering
NASA Astrophysics Data System (ADS)
Fischer, J.; Tsapatsaris, N.; de Paula, E.; Bordallo, H. N.
2014-09-01
Why in a barren and hot desert, clays can contain a significant fraction of water? Why does concrete crack? How can we demonstrate that complexation of a drug does not alter its conformation in a way that affects its functionality? In this paper we present results on various studies using Quasi-Elastic Neutron Scattering aimed at clarifying these questions. To allow for a better understanding of neutron scattering, a brief introduction to the basics of its theory is presented. Following the theoretical part, experimental results dealing with the effects of confinement on the water dynamics caused by the interfaces in clays and the nano- and micro-pores of concrete are reviewed in detail. At the end, recent Quasi-Elastic Neutron Scattering investigations on the complexation of the local anesthetics Bupivacaine (BVC.HCl, C18H28N20.HCl.H2O) and Ropivacaine (RVC.HCl, C17H26N20.HCl.H2O) into the cyclic β-cyclodextrin oligosaccharide are presented. To conclude, the perspectives that the European Spallation Source brings to this subject are discussed.
Osti, Naresh C.; Mamontov, Eugene; Ramirez-cuesta, A.; Wesolowski, David J.; Diallo, S. O.
2015-12-10
Understanding the molecular behavior of water in spatially restricted environments is important to better understanding its role in many biological, chemical and geological processes. Here we examine the translational diffusion of water confined to a variety of substrates, from flat surfaces to nanoporous media, in the context of a recently proposed universal scaling law (Chiavazzo 2014) [1]. Using over a dozen previous neutron scattering results, we test the validity of this law, evaluating separately the influence of the hydration amount, and the effects of the size and morphology of the confining medium. Additionally, we investigate the effects of changing instrument resolutions and fitting models on the applicability of this law. Finally, we perform quasi-elastic neutron scattering measurements on water confined inside nanoporous silica to further evaluate this predictive law, in the temperature range 250≤T≤290 K.
Osti, Naresh C.; Mamontov, Eugene; Ramirez-cuesta, A.; Wesolowski, David J.; Diallo, S. O.
2015-12-10
Understanding the molecular behavior of water in spatially restricted environments is important to better understanding its role in many biological, chemical and geological processes. Here we examine the translational diffusion of water confined to a variety of substrates, from flat surfaces to nanoporous media, in the context of a recently proposed universal scaling law (Chiavazzo 2014) [1]. Using over a dozen previous neutron scattering results, we test the validity of this law, evaluating separately the influence of the hydration amount, and the effects of the size and morphology of the confining medium. Additionally, we investigate the effects of changing instrumentmore » resolutions and fitting models on the applicability of this law. Finally, we perform quasi-elastic neutron scattering measurements on water confined inside nanoporous silica to further evaluate this predictive law, in the temperature range 250≤T≤290 K.« less
Fast Proton Hopping Detection in Ice Ih by Quasi-Elastic Neutron Scattering
Presiado, Itay; Lal, Jyotsana; Mamontov, Eugene; Kolesnikov, Alexander I; Huppert, Dan I
2011-01-01
Quasi-elastic neutron scattering was employed on samples of HCl-doped polycrystalline ice I{sub h}. The analysis of the scattering signal provides the excess proton hopping time, {tau}{sub hop}, in the temperature range of 140-195 K. The hopping time strongly depends on the temperature of the sample, and the activation energy of a hopping step is 17 kJ/mol. The values of {tau}{sub hop} of the current experiment are in good agreement with calculated values derived from previous photochemical experiments,(1) in which we found that the proton hopping time at T > 242 K is on the order of 200 fs, roughly 10 times shorter than in liquid water at room temperature.
Fast proton hopping detection in ice I{sub h} by quasi-elastic neutron scattering.
Presiado, I.; Lal, J.; Mamontov, E.; Kolesnikov, A. I.; Huppert, D.
2011-01-01
Quasi-elastic neutron scattering was employed on samples of HCl-doped polycrystalline ice I{sub h}. The analysis of the scattering signal provides the excess proton hopping time, {tau}{sub hop}, in the temperature range of 140-195 K. The hopping time strongly depends on the temperature of the sample, and the activation energy of a hopping step is 17 kJ/mol. The values of {tau}{sub hop} of the current experiment are in good agreement with calculated values derived from previous photochemical experiments, in which we found that the proton hopping time at T > 242 K is on the order of 200 fs, roughly 10 times shorter than in liquid water at room temperature.
Quasi elastic and inelastic neutron scattering study of vitamin C aqueous solutions
NASA Astrophysics Data System (ADS)
Migliardo, F.; Branca, C.; Magazù, S.; Migliardo, P.; Coppolino, S.; Villari, A.; Micali, N.
2002-02-01
In this paper, new results obtained by quasi elastic and inelastic neutron scattering experiments performed on vitamin C ( L-ascorbic acid)/H 2O mixtures are reported. The data analysis of the QENS measurements, by a separation of the diffusive dynamics of hydrated L-ascorbic acid from that of water, furnishes quantitative evidences of a random jump diffusion motion of vitamin C and shows that the water dynamics is strongly affected by the presence of L-ascorbic acid. Concerning the INS experiment, we are able, through the behaviour of neutron spectra across the glass transition temperature ( T g≈233 K for the vitamin C/water system), to collocate the investigated system in the Angell “strong-fragile” scheme.
NASA Astrophysics Data System (ADS)
Hagino, K.
2009-05-01
We invert experimental data for heavy-ion fusion cross sections at energies well below the Coulomb barrier in order to directly determine the internucleus potential between the colliding nuclei. In contrast to the previous applications of the inversion formula, we explicitly take into account the effect of channel couplings on fusion reactions, by assuming that fusion cross sections at deep subbarrier energies are governed by the lowest barrier in the barrier distribution. The surface region of the internuclear potential is determined from quasi-elastic scattering at deep subbarrier energies, while the inner part is determined with the WKB formula. We apply this procedure to the 16O+144Sm and 16O+208Pb reactions, and find that the inverted internucleus potential are much thicker than phenomenological potentials.
Hydrogen species motion in piezoelectrics: A quasi-elastic neutron scattering study
NASA Astrophysics Data System (ADS)
Alvine, K. J.; Tyagi, M.; Brown, C. M.; Udovic, T. J.; Jenkins, T.; Pitman, S. G.
2012-03-01
Hydrogen is known to damage or degrade piezoelectric materials, at low pressure for ferroelectric random access memory applications, and at high pressure for hydrogen-powered vehicle applications. The piezoelectric degradation is in part governed by the motion of hydrogen species within the piezoelectric materials. We present here quasi-elastic neutron scattering (QENS) measurements of the local hydrogen species motion within lead zirconate titanate (PZT) and barium titanate (BTO) on samples charged by exposure to high-pressure gaseous hydrogen (≈17 MPa). Neutron vibrational spectroscopy (NVS) studies of the hydrogen-enhanced vibrational modes are presented as well. Results are discussed in the context of theoretically predicted interstitial hydrogen lattice sites and compared to comparable bulk diffusion studies of hydrogen diffusion in lead zirconate titanate.
Quasi-Elastic Light Scattering by Diffusional Fluctuations in RNase Solutions
Rimai, L.; Hickmott, J. T.; Cole, T.; Carew, E. B.
1970-01-01
Using measurements of quasi-elastic light scattering spectra, we have investigated diffusional fluctuations of RNase. The diffusion coefficient for individual protein molecules, together with the corresponding calculated effective molecular radius Reff, were determined. Between room temperature and the point of irreversible denaturation at 63.5°C, Reff increased from 20-250 A. This is comparable to the plateau in Reff of 300 A reached after about 200 min following chemical denaturation in 10 M urea. The measurements indicated the presence of a large size component even in the freshly prepared and chromatographically purified solutions. From the diffusion constants deduced for this large component we obtained effective sizes from 1000-5000 A. Concentration and temperature dependent measurements exclude the possibility that these large particles are impurities and indicate that they are the result of aggregations of RNase molecules. PMID:5409774
Spin observables in quasi-elastic proton-nucleus scattering near 1 GeV
Smith, R.D.; Wallace, S.J.
1985-11-01
The spin dependence of quasi-elastic proton-nucleus scattering is studied using Glauber's eikonal multiple scattering theory, which is extended to include multiple knockout collisions as well as the full spin dependence of the NN amplitudes. Calculations of the cross section d/sup 2/sigma/d..cap omega.. dp and spin observables DNN, DLL, DSS, DSL, DLS, Ay are presented and compared to data for d/sup 2/sigma/d..cap omega.. dp and Ay from inclusive (p,p') experiments on /sup 12/C at T/sub lab/ = 800 MeV. The main feature seen is a drop in the spin observables in the kinematic region where two nucleon knockout dominates the cross section. As an initial study of the contribution of quasi-free ..delta.. production to the inclusive cross section, multiple scattering theory is used to normalize a plane-wave impulse approximation calculation of d/sup 2/sigma/d..cap omega.. dp for p+/sup 12/C..-->..p+..pi..+/sup 12/C(. .AE
Effect of strangeness for neutrino (antineutrino) scattering in the quasi-elastic region
Kim, K. S.; Yu, Byung Geel; Cheoun, Myung-Ki
2008-05-15
We present the neutral- and charged-current reactions by incident neutrino (antineutrino) scattering on the nucleon and on the {sup 12}C target in the quasi-elastic region within the framework of a relativistic single-particle model. The incident energies at 500 MeV and 1 GeV are used for the scattering. Effects of strangeness are studied thoroughly on the cross sections, the ratios between the neutral- and charged-current reactions, and the asymmetries by incident neutrino and antineutrino. We find that there exists some cancellation of the strange quark contributions between the knocked-out protons and neutrons in the neutrino (antineutrino)-nucleus scattering. The effect of strangeness is exhibited more strongly on the asymmetry than on the ratio or cross section. On a difference of the asymmetry, the effect of strangeness appears strongly, but on a summation of the asymmetry, the effect almost disappears in the low and middle kinetic energies of the knocked-out nucleon.
Quasi-elastic neutron scattering studies of the slow dynamics of supercooled and glassy aspirin
NASA Astrophysics Data System (ADS)
Zhang, Yang; Tyagi, Madhusudan; Mamontov, Eugene; Chen, Sow-Hsin
2012-02-01
Aspirin, also known as acetylsalicylic acid (ASA), is not only a wonderful drug, but also a good glass former. Therefore, it serves as an important molecular system to study the near-arrest and arrested phenomena. In this paper, a high-resolution quasi-elastic neutron scattering (QENS) technique is used to investigate the slow dynamics of supercooled liquid and glassy aspirin from 410 down to 350 K. The measured QENS spectra can be analyzed with a stretched exponential model. We find that (i) the stretched exponent β(Q) is independent of the wavevector transfer Q in the measured Q range and (ii) the structural relaxation time τ(Q) follows a power-law dependence on Q. Consequently, the Q-independent structural relaxation time τ0 can be extracted for each temperature to characterize the slow dynamics of aspirin. The temperature dependence of τ0 can be fitted with the mode-coupling power law, the Vogel-Fulcher-Tammann equation and a universal equation for fragile glass forming liquids recently proposed by Tokuyama in the measured temperature range. The calculated dynamic response function χT(Q, t) using the experimentally determined self-intermediate scattering function of the hydrogen atoms of aspirin shows direct evidence of the enhanced dynamic fluctuations as the aspirin is increasingly supercooled, in agreement with the fixed-time mean squared displacement langx2rang and the non-Gaussian parameter α2 extracted from the elastic scattering.
Quasi-Elastic Neutron Scattering Studies of the Slow Dynamics of Supercooled and Glassy Aspirin
Zhang, Yang; Tyagi, M.; Mamontov, Eugene; Chen, Sow-hsin H
2011-01-01
Aspirin, also known as acetylsalicylic acid (ASA), is not only a wonderful drug, but also a good glass former. Therefore, it serves as an important molecular system to study the near-arrest and arrested phenomena. In this paper, a high-resolution quasi-elastic neutron scattering (QENS) technique is used to investigate the slow dynamics of supercooled liquid and glassy aspirin from 410 K down to 350 K. The measured QENS spectra can be analyzed with a stretched exponential model. We find that (i) the stretched exponent (Q) is independent of the wave vector transfer Q in the measured Q-range, and (ii) the structural relaxation time (Q) follows a power law dependence on Q. Consequently, the Q-independent structural relaxation time 0 can be extracted for each temperature to characterize the slow dynamics of aspirin. The temperature dependence of 0 can be fitted with the mode coupling power law, the Vogel-Fulcher-Tammann equation and a universal equation for fragile glass forming liquids recently proposed by M. Tokuyama in the measured temperature range. The calculated dynamic response function T(Q,t) using the experimentally determined self-intermediate scattering function of the hydrogen atoms of aspirin shows a direct evidence of the enhanced dynamic fluctuations as the aspirin is increasingly supercooled, in agreement with the fixed-time mean squared displacement x2 and non-Gaussian parameter 2 extracted from the elastic scattering.
A Quasi-Elastic Neutron Scattering Study of the Dynamics of Electrically Constrained Water.
Fuchs, Elmar C; Bitschnau, Brigitte; Wexler, Adam D; Woisetschläger, Jakob; Freund, Friedemann T
2015-12-31
We have measured the quasi-elastic neutron scattering (QENS) of an electrohydrodynamic liquid bridge formed between two beakers of pure water when a high voltage is applied, a setup allowing to investigate water under high-voltage without high currents. From this experiment two proton populations were distinguished: one consisting of protons strongly bound to oxygen atoms (immobile population, elastic component) and a second one of quasi-free protons (mobile population, inelastic component) both detected by QENS. The diffusion coefficient of the quasi-free protons was found to be D = (26 ± 10) × 10(-5) cm(2) s(-1) with a jump length lav ∼ 3 Å and an average residence time of τ0 = 0.55 ± 0.08 ps. The associated proton mobility in the proton channel of the bridge is ∼9.34 × 10(-7) m(2) V(-1) s(-1), twice as fast as diffusion-based proton mobility in bulk water. It also matches the so-called electrohydrodynamic or "apparent" charge mobility, an experimental quantity which so far has lacked molecular interpretation. These results further corroborate the proton channel model for liquid water under high voltage and give new insights into the molecular mechanisms behind electrohydrodynamic charge transport phenomena and delocalization of protons in liquid water. PMID:26643863
Molecular dynamics force-field refinement against quasi-elastic neutron scattering data
Borreguero Calvo, Jose M.; Lynch, Vickie E.
2015-11-23
Quasi-elastic neutron scattering (QENS) is one of the experimental techniques of choice for probing the dynamics at length and time scales that are also in the realm of full-atom molecular dynamics (MD) simulations. This overlap enables extension of current fitting methods that use time-independent equilibrium measurements to new methods fitting against dynamics data. We present an algorithm that fits simulation-derived incoherent dynamical structure factors against QENS data probing the diffusive dynamics of the system. We showcase the difficulties inherent to this type of fitting problem, namely, the disparity between simulation and experiment environment, as well as limitations in the simulationmore » due to incomplete sampling of phase space. We discuss a methodology to overcome these difficulties and apply it to a set of full-atom MD simulations for the purpose of refining the force-field parameter governing the activation energy of methyl rotation in the octa-methyl polyhedral oligomeric silsesquioxane molecule. Our optimal simulated activation energy agrees with the experimentally derived value up to a 5% difference, well within experimental error. We believe the method will find applicability to other types of diffusive motions and other representation of the systems such as coarse-grain models where empirical fitting is essential. In addition, the refinement method can be extended to the coherent dynamic structure factor with no additional effort.« less
Quasi-Elastic Neutron Scattering: an insight into life at extreme conditions
NASA Astrophysics Data System (ADS)
Foglia, Fabrizia; Hazael, Rachael; Simeoni, Giovanna; Appavou, Marie-Sousai; Meersman, Filip; Daniel, Isabelle; Forsyth, Trevor; McMillan, Paul
2013-06-01
Microbes have been found to thrive in diverse environments characterised by a wide range of pressure-temperature-composition conditions. The range of physicochemical conditions under which microbial life has been observed has continually expanded as microbiologists explore additional remote and apparently hostile environments. The studies provide us with clues about the current extent of biological organisms and allow us to explore the fundamental limits to survival of bacterial life forms under extreme conditions. We are developing quasi-elastic neutron scattering (QENS) studies to help us to understand the dynamic processes associated with H-/D-containing microbes under high P conditions. We have begun our study using samples of Shewanella oneidensis. We obtained pioneering QENS results carried out in situ on live organisms into the 200 MPa range that provide new information on H2O/D2O exchange dynamics across the cell walls. To achieve this result we prepared D2O-substituted bacteria within the Deuteration Facility in Grenoble and transferred samples to the Munich FRM-II neutron reactor for QENS experiments at the high resolution TOFTOF spectrometer station. Our initial results show clear P dependence of H2O/D2O transfer dynamics across the bacterial cell walls. DCO
Molecular dynamics force-field refinement against quasi-elastic neutron scattering data
Borreguero Calvo, Jose M.; Lynch, Vickie E.
2015-11-23
Quasi-elastic neutron scattering (QENS) is one of the experimental techniques of choice for probing the dynamics at length and time scales that are also in the realm of full-atom molecular dynamics (MD) simulations. This overlap enables extension of current fitting methods that use time-independent equilibrium measurements to new methods fitting against dynamics data. We present an algorithm that fits simulation-derived incoherent dynamical structure factors against QENS data probing the diffusive dynamics of the system. We showcase the difficulties inherent to this type of fitting problem, namely, the disparity between simulation and experiment environment, as well as limitations in the simulation due to incomplete sampling of phase space. We discuss a methodology to overcome these difficulties and apply it to a set of full-atom MD simulations for the purpose of refining the force-field parameter governing the activation energy of methyl rotation in the octa-methyl polyhedral oligomeric silsesquioxane molecule. Our optimal simulated activation energy agrees with the experimentally derived value up to a 5% difference, well within experimental error. We believe the method will find applicability to other types of diffusive motions and other representation of the systems such as coarse-grain models where empirical fitting is essential. In addition, the refinement method can be extended to the coherent dynamic structure factor with no additional effort.
A Quasi-Elastic Neutron Scattering Study of the Dynamics of Electrically Constrained Water.
Fuchs, Elmar C; Bitschnau, Brigitte; Wexler, Adam D; Woisetschläger, Jakob; Freund, Friedemann T
2015-12-31
We have measured the quasi-elastic neutron scattering (QENS) of an electrohydrodynamic liquid bridge formed between two beakers of pure water when a high voltage is applied, a setup allowing to investigate water under high-voltage without high currents. From this experiment two proton populations were distinguished: one consisting of protons strongly bound to oxygen atoms (immobile population, elastic component) and a second one of quasi-free protons (mobile population, inelastic component) both detected by QENS. The diffusion coefficient of the quasi-free protons was found to be D = (26 ± 10) × 10(-5) cm(2) s(-1) with a jump length lav ∼ 3 Å and an average residence time of τ0 = 0.55 ± 0.08 ps. The associated proton mobility in the proton channel of the bridge is ∼9.34 × 10(-7) m(2) V(-1) s(-1), twice as fast as diffusion-based proton mobility in bulk water. It also matches the so-called electrohydrodynamic or "apparent" charge mobility, an experimental quantity which so far has lacked molecular interpretation. These results further corroborate the proton channel model for liquid water under high voltage and give new insights into the molecular mechanisms behind electrohydrodynamic charge transport phenomena and delocalization of protons in liquid water.
Energy dissipation in heavy systems: the transition from quasi-elastic to deep-inelastic scattering
Rehm, K.E.; van den Berg, A.; Kolata, J.J.; Kovar, D.G.; Kutschera, W.; Rosner, G.; Stephans, G.S.F.; Yntema, J.L.; Lee, L.L.
1984-01-01
The interaction of medium mass projectiles (A = 28 - 64) with /sup 208/Pb has been studied using a split-pole spectrograph which allows single mass and charge identification. The reaction process in all systems studied so far is dominated by quasi-elastic neutron transfer reactions, especially at incident energies in the vicinity of the Coulomb barrier. In addition to the quasi-elastic component deep inelastic contributions are present in all reaction channels. The good mass and charge separation allows to generate Wilczynski plots for individual channels; for the system /sup 48/Ti + /sup 208/Pb we observe that the transition between the quasi-elastic and deep-inelastic reactions occurs around Q = -(30 to 35) MeV.
Study of quasi-elastic scattering in the NOνA near detector prototype
Betancourt, M.
2015-05-15
NOvA is a 14 kTon long-baseline neutrino oscillation experiment currently being installed in the NuMI off-axis neutrino beam produced at Fermilab. A 222 Ton prototype NOνA detector was built and operated in the neutrino beam for over a year to understand the response of the detector and its construction. Muon neutrino interaction data collected in this test are being analyzed to identify quasi-elastic charged-current interactions and measure the behavior of the quasi-elastic muon neutrino cross section.
Study of the Quasi-Elastic Scattering in the NOvA Detector Prototype
Betancourt, Minerba
2013-06-01
NOvA is a 810 km long base-line neutrino oscillation experiment with two detectors (far 14 KTon and near detector 300 Ton) currently being installed in the NUMI o -axis neutrino beam produced at Fermilab. A 222 Ton prototype NOvA detector (NDOS) was built and operated in the neutrino beam for over a year to understand the response of the detector and its construction. The goal of this thesis is to study the muon neutrino interaction data collected in this test, specifically the identification of quasi-elastic charged-current interactions and measure the behavior of the quasi-elastic muon neutrino cross section.
Frank Wesselmann
2004-11-01
We determined the electric form factor of the neutron GEn via the reaction d(e,e?n)p using a longitudinally polarized electron beam and a frozen, polarized 15ND3 target at Jefferson Lab. The knocked out neutrons were detected in a segmented plastic scintillator in coincidence with the quasi-elastically scattered electrons which were tracked in Hall C's High Momentum Spectrometer. To extract GEn, we compared the experimental beam-target asymmetry with theoretical calculations based on different GEn models. We report the results of the fall 2001 run at Q2=0.5 and 1.0 (GeV/c)2.
Anti-Neutrino Charged Current Quasi-Elastic Scattering in MINER$\
Chvojka, Jesse John
2012-01-01
The phenomenon of neutrino oscillation is becoming increasingly understood with results from accelerator-based and reactor-based experiments, but unanswered questions remain. The proper ordering of the neutrino mass eigenstates that compose the neutrino avor eigenstates is not completely known. We have yet to detect CP violation in neutrino mixing, which if present could help explain the asymmetry between matter and anti-matter in the universe. We also have not resolved whether sterile neutrinos, which do not interact in any Standard Model interaction, exist. Accelerator-based experiments appear to be the most promising candidates for resolving these questions; however, the ability of present and future experiments to provide answers is likely to be limited by systematic errors. A significant source of this systematic error comes from limitations in our knowledge of neutrino-nucleus interactions. Errors on cross-sections for such interactions are large, existing data is sometimes contradictory, and knowledge of nuclear effects is incomplete. One type of neutrino interaction of particular interest is charged current quasi-elastic (CCQE) scattering, which yields a final state consisting of a charged lepton and nucleon. This process, which is the dominant interaction near energies of 1 GeV, is of great utility to neutrino oscillation experiments since the incoming neutrino energy and the square of the momentum transferred to the final state nucleon, Q^{2}, can be reconstructed using the final state lepton kinematics. To address the uncertainty in our knowledge of neutrino interactions, many experiments have begun making dedicated measurements. In particular, the MINER A experiment is studying neutrino-nucleus interactions in the few GeV region. MINERvA is a fine-grained, high precision, high statistics neutrino scattering experiment that will greatly improve our understanding of neutrino cross-sections and nuclear effects that affect the final state particles
Garvey, G. T.; Harris, D. A.; Tanaka, H. A.; Tayloe, R.; Zeller, G. P.
2015-06-15
The study of neutrino–nucleus interactions has recently seen rapid development with a new generation of accelerator-based neutrino experiments employing medium and heavy nuclear targets for the study of neutrino oscillations. A few unexpected results in the study of quasi-elastic scattering and single photon production have spurred a revisiting of the underlying nuclear physics and connections to electron–nucleus scattering. A thorough understanding and resolution of these issues is essential for future progress in the study of neutrino oscillations.
Effect of coupling in the 28Si+154Sm reaction studied by quasi-elastic scattering
NASA Astrophysics Data System (ADS)
Kaur, Gurpreet; Behera, B. R.; Jhingan, A.; Nayak, B. K.; Dubey, R.; Sharma, Priya; Thakur, Meenu; Mahajan, Ruchi; Saneesh, N.; Banerjee, Tathagata; Khushboo, Kumar, A.; Mandal, S.; Saxena, A.; Sugathan, P.; Rowley, N.
2016-09-01
The study of the coupling to collective states of the 28Si projectile and 154Sm target in fusion mechanism is reported. Understanding such couplings is important as they influence the barrier height and the formation probability of the compound nuclei, which in turn may be related to the synthesis of superheavy elements in heavier systems. In the present work, before performing the coupled-channel calculations, we wish to obtain an experimental signature of coupling to projectile and target excitation through barrier distribution (BD) study. To this end, the BDs of the 28Si+154Sm and 16O+154Sm systems have been compared using existing fusion data, scaled to compensate for the differences between the nominal Coulomb barriers and the respective coupling strengths. However, the large error bars on the high-energy side of the fusion BD prevent any definite identification of such signatures. We have, therefore, performed a quasi-elastic (QE) scattering experiment for the heavier 28Si+154Sm system and compared its results with existing QE data for the 16O projectile. Since QE BDs are precise at higher energies, the comparison has shown that the BD of 28Si+154Sm is similar to that of 16O+154Sm to a large extent except for a peaklike structure on the higher energy side. The similarity shows that the 154Sm deformation plays a major role in the fusion mechanism of 28Si+154Sm system. The peaklike structure is attributed to 28Si excitation. In contrast with previous studies, it is found that a coupled-channel calculation with vibrational coupling to the first 2+ state of 28Si reproduces this structure rather well. However, an almost identical result is found with the rotational coupling scheme if one considers the large positive hexadecapole deformation of the projectile. A value around that given by Möller and Nix (β4≈0.25 ) leads to a strong cancellation in the re-orientation term that couples the 2+ state back to itself, making that state look vibrational in this
Study of Quasi-Elastic Scattering in the NOnuA Detector Prototype
NASA Astrophysics Data System (ADS)
Betancourt, Minerba
NOvA is a 810 km long base-line neutrino oscillation experiment with two detectors (far 14 KTon and near detector 300 Ton) currently being installed in the NUMI off-axis neutrino beam produced at Fermilab. A 222 Ton prototype NOvA detector (NDOS) was built and operated in the neutrino beam for over a year to understand the response of the detector and its construction. The goal of this thesis is to study the muon neutrino interaction data collected in this test, specifically the identification of quasi-elastic charged-current interactions and measure the behavior of the quasi-elastic muon neutrino cross section. This thesis presents the analysis of the data from two detector configurations, the first configuration collected data from 1e19 protons on target (POT) from April to May 2011 and the second configuration collected data from 1.7e20POT from October 2011 to April 2012. The charged current quasi-elastic muon neutrino events collected with each configuration were analyzed to extract the cross section as a function of energy as well as the single differential cross sections with respect to outgoing muon momentum, outgoing muon angle from the incident neutrino direction; and the momentum dP, and transfer squared of the interaction.
NASA Astrophysics Data System (ADS)
Serebrov, A. P.; Fomin, A. K.
2009-12-01
Motivated by the strong disagreement of a recent result for the neutron lifetime with the previous world average value we report results of a Monte Carlo simulation of the neutron lifetime experiment MAMBO I, which was carried out some 20 years ago. In addition to all experimental parameters and procedures known to us, the analysis included quasi-elastic neutron scattering on the surface of liquid fomblin oil wall coatings of the UCN storage vessel, and above-barrier neutrons. The original analysis, leading to the published result of 887.6 ± 3 s, did not take into account these effects. For an exemplary set of model parameters we find a negative correction of 6.0 seconds, which demonstrates that these hitherto neglected effects may be very important also in the analysis of other neutron lifetime experiments using UCN storage vessels with fomblin oil coating close to room temperature.
Wolcott, Jeremy
2016-01-01
Appearance-type neutrino oscillation experiments, which observe the transition from muon neutrinos to electron neutrinos, promise to help answer some of the fundamental questions surrounding physics in the post-Standard-Model era. Because they wish to observe the interactions of electron neutrinos in their detectors, and because the power of current results is typically limited by their systematic uncertainties, these experiments require precise estimates of the cross-section for electron neutrino interactions. Of particular interest is the charged-current quasi-elastic (CCQE) process, which gures signi cantly in the composition of the reactions observed at the far detector. However, no experimental measurements of this crosssection currently exist for electron neutrinos; instead, current experiments typically work from the abundance of muon neutrino CCQE cross-section data and apply corrections from theoretical arguments to obtain a prediction for electron neutrinos. Veri cation of these predictions is challenging due to the di culty of constructing an electron neutrino beam, but the advent of modern high-intensity muon neutrino beams|together with the percent-level electron neutrino impurity inherent in these beams| nally presents the opportunity to make such a measurement. We report herein the rst-ever measurement of a cross-section for an exclusive state in electron neutrino scattering, which was made using the MINER A detector in the NuMI neutrino beam at Fermilab. We present the electron neutrino CCQE di erential cross-sections, which are averaged over neutrinos of energies 1-10 GeV (with mean energy of about 3 GeV), in terms of various kinematic variables: nal-state electron angle, nal-state electron energy, and the square of the fourmomentum transferred to the nucleus by the neutrino , Q^{2}. We also provide a total cross-section vs. neutrino energy. While our measurement of this process is found to be in agreement with the predictions of the GENIE
Mazer, N A; Carey, M C
1983-01-18
We have employed quasi-elastic light-scattering methods to characterize micellar aggregates and microprecipitates formed in aqueous solutions containing sodium taurocholate (TC), egg lecithin (L), and cholesterol (Ch). Particle size and polydispersity were studied as functions of Ch mole fraction (XCh = 0-15%), L/TC molar ratio (0-1.6), temperature (5-85 degrees C), and total lipid concentration (3 and 10 g/dL in 0.15 M NaCl). For XCh values below the established solubilization limits (XChmax) [Carey, M. C., & Small, D. M. (1978) J. Clin. Invest. 61, 998], added Ch has little influence on the size of simple TC micelles (type 1 systems), on the coexistence of simple and mixed TC-L micelles (type 2 systems), or on the growth of "mixed disc" TC-L micelles (type 3 systems). For supersaturated systems (XCh/XChmax greater than 1), 10 g/dL type 1 systems (L/TC = 0) exist as metastable micellar solutions even at XCh/XChmax = 5.3. Metastability is decreased in type 2 systems (0 less than L/TC less than 0.6), and "labile" microprecipitation occurs when XCh/XChmax exceeds approximately 1.6. In 10 g/dL mixtures, the microprecipitates initially range in size from 500 to 20000 A and later coalesce to form a buoyant macroscopic precipitate phase. In 3 g/dL mixtures, the microprecipitates are smaller (200-400 A) and remain as a stable, noncoalesced microdispersion. Transmission electron microscopy of the microprecipitates formed at both concentrations indicates a globular noncrystalline structure, and lipid analysis reveals the presence of cholesterol and lecithin in a molar ratio (Ch/L) of approximately 2/1, suggesting that the microprecipitates represent a metastable cholesterol-rich liquid-crystalline phase. In supersaturated type 3 systems (0.6 less than L/TC less than 2.0), the precipitate phase is a lecithin-rich liquid-crystalline phase which likewise coalesces in a 10 g/dL system but forms stable vesicle (liposomal) structures (600-800 A radius) in 3 g/dL systems. In
Millot, B.; Methivier, A.; Jobic, H.; Moueddeb, H.; Bee, M.
1999-02-18
The use of ZSM-5 zeolites is widely recommended for adsorption separation processes mainly in the field of refining and for gas processing. One of the most promising applications of ZSM-5 zeolites is the kinetic separation of alkane isomers for upgrading the octane number of gasoline. Isobutane diffusivities in ZSM-5 zeolite have been measured by quasi-elastic neutron scattering (QENS) and supported membrane techniques. This is the first diffusivity measurement of a branched alkane inside a zeolite of MFI type using a microscopic method. The self-diffusion coefficient derived from QENS is 3 {times} 10{sup {minus}12} m{sup 2}/s at 500 K. The diffusivity obtained with the supported membrane is 1 order of magnitude larger. In view of the large differences usually reported in the literature between microscopic and macroscopic techniques, the comparison between QENS and supported membrane data is quite satisfactory. The activation energy for diffusion determined from QENS is 27 kJ/mol. Because of the variation of loading due to temperature changes, an apparent activation energy is obtained with the supported membrane; it is 34 kJ/mol. In this zeolite, the diffusion of branched hydrocarbons is much slower than that of linear alkanes; the diffusion coefficient of isobutane is found to be 3 orders of magnitude lower than that of n-butane by QENS.
Shrestha, Utsab R.; Perera, Suchithranga M. D. C.; Bhowmik, Debsindhu; Chawla, Udeep; Mamontov, Eugene; Brown, Michael F.; Chu, Xiang -Qiang
2016-09-15
Light activation of the visual G-protein-coupled receptor (GPCR) rhodopsin leads to significant structural fluctuations of the protein embedded within the membrane yielding the activation of cognate G-protein (transducin), which initiates biological signaling. Here, we report a quasi-elastic neutron scattering study of the activation of rhodopsin as a GPCR prototype. Our results reveal a broadly distributed relaxation of hydrogen atom dynamics of rhodopsin on a picosecond–nanosecond time scale, crucial for protein function, as only observed for globular proteins previously. Interestingly, the results suggest significant differences in the intrinsic protein dynamics of the dark-state rhodopsin versus the ligand-free apoprotein, opsin. These differencesmore » can be attributed to the influence of the covalently bound retinal ligand. Moreover, an idea of the generic free-energy landscape is used to explain the GPCR dynamics of ligand-binding and ligand-free protein conformations, which can be further applied to other GPCR systems.« less
NASA Astrophysics Data System (ADS)
Patrick, Cheryl Elizabeth
Next-generation neutrino oscillation experiments, such as DUNE and Hyper-Kamiokande, hope to measure charge-parity (CP) violation in the lepton sector. In order to do this, they must dramatically reduce their current levels of uncertainty, particularly those due to neutrino-nucleus interaction models. As CP violation is a measure of the difference between the oscillation properties of neutrinos and antineutrinos, data about how the less-studied antineutrinos interact is especially valuable. We present the MINERvA experiment's first double-differential scattering cross sections for antineutrinos on scintillator, in the few-GeV range relevant to experiments such as DUNE and NOvA. We also present total antineutrino-scintillator quasi-elastic cross sections as a function of energy, which we compare to measurements from previous experiments. As well as being useful to help reduce oscillation experiments' uncertainty, our data can also be used to study the prevalence of various correlation and final-state interaction effects within the nucleus. We compare to models produced by different model generators, and are able to draw first conclusions about the predictions of these models.
Trantham, E.C.; Rorschach, H.E.; Clegg, J.S.; Hazlewood, C.F.; Nicklow, R.M.; Wakabayashi, N.
1984-05-01
Results have been obtained on the quasi-elastic spectra of neutrons scattered from pure water, 20% agarose gel (hydration four grams H/sub 2/O per gram of dry solid) and cysts of the brine shrimp Artemia for hydrations between 0.10 and 1.2 grams H/sub 2/O per gram of dry solids. The spectra were interpreted using a two-component model that included contributions from the covalently bonded protons and the hydration water, and a mobile water fraction. The mobile fraction was described by a jump-diffusion correlation function for the translation motion and a simple diffusive orientational correlation function. The results for the line widths ..gamma..(Q/sup 2/) for pure water were in good agreement with previous measurements. The agarose results were consistent with NMR measurements that show a slightly reduced translational diffusion for the mobile water fraction. The Artemia results show that the translational diffusion coefficient of the mobile water fraction was greatly reduced from that of pure water. The line width was determined mainly by the rotational motion, which was also substantially reduced from the pure water value as determined from dielectric relaxation studies. The translational and rotational diffusion parameters were consistent with the NMR measurements of diffusion and relaxation. Values for the hydration fraction and the mean square thermal displacement as determined from the Q-dependence of line areas were also obtained.
Patrick, Cheryl
2016-01-01
Next-generation neutrino oscillation experiments, such as DUNE and Hyper-Kamiokande, hope to measure charge-parity (CP) violation in the lepton sector. In order to do this, they must dramatically reduce their current levels of uncertainty, particularly those due to neutrino-nucleus interaction models. As CP violation is a measure of the difference between the oscillation properties of neutrinos and antineutrinos, data about how the less-studied antineutrinos interact is especially valuable. We present the MINERvA experiment's first double-differential scattering cross sections for antineutrinos on scintillator, in the few-GeV range relevant to experiments such as DUNE and NOvA. We also present total antineutrino-scintillator quasi-elastic cross sections as a function of energy, which we compare to measurements from previous experiments. As well as being useful to help reduce oscillation experiments' uncertainty, our data can also be used to study the prevalence of various cor relation and final-state interaction effects within the nucleus. We compare to models produced by different model generators, and are able to draw first conclusions about the predictions of these models.
Foglia, Fabrizia; Hazael, Rachael; Simeoni, Giovanna G.; Appavou, Marie-Sousai; Moulin, Martine; Haertlein, Michael; Trevor Forsyth, V.; Seydel, Tilo; Daniel, Isabelle; Meersman, Filip; McMillan, Paul F.
2016-01-01
Quasielastic neutron scattering (QENS) is an ideal technique for studying water transport and relaxation dynamics at pico- to nanosecond timescales and at length scales relevant to cellular dimensions. Studies of high pressure dynamic effects in live organisms are needed to understand Earth’s deep biosphere and biotechnology applications. Here we applied QENS to study water transport in Shewanella oneidensis at ambient (0.1 MPa) and high (200 MPa) pressure using H/D isotopic contrast experiments for normal and perdeuterated bacteria and buffer solutions to distinguish intracellular and transmembrane processes. The results indicate that intracellular water dynamics are comparable with bulk diffusion rates in aqueous fluids at ambient conditions but a significant reduction occurs in high pressure mobility. We interpret this as due to enhanced interactions with macromolecules in the nanoconfined environment. Overall diffusion rates across the cell envelope also occur at similar rates but unexpected narrowing of the QENS signal appears between momentum transfer values Q = 0.7–1.1 Å−1 corresponding to real space dimensions of 6–9 Å. The relaxation time increase can be explained by correlated dynamics of molecules passing through Aquaporin water transport complexes located within the inner or outer membrane structures. PMID:26738409
NASA Astrophysics Data System (ADS)
Foglia, Fabrizia; Hazael, Rachael; Simeoni, Giovanna G.; Appavou, Marie-Sousai; Moulin, Martine; Haertlein, Michael; Trevor Forsyth, V.; Seydel, Tilo; Daniel, Isabelle; Meersman, Filip; McMillan, Paul F.
2016-01-01
Quasielastic neutron scattering (QENS) is an ideal technique for studying water transport and relaxation dynamics at pico- to nanosecond timescales and at length scales relevant to cellular dimensions. Studies of high pressure dynamic effects in live organisms are needed to understand Earth’s deep biosphere and biotechnology applications. Here we applied QENS to study water transport in Shewanella oneidensis at ambient (0.1 MPa) and high (200 MPa) pressure using H/D isotopic contrast experiments for normal and perdeuterated bacteria and buffer solutions to distinguish intracellular and transmembrane processes. The results indicate that intracellular water dynamics are comparable with bulk diffusion rates in aqueous fluids at ambient conditions but a significant reduction occurs in high pressure mobility. We interpret this as due to enhanced interactions with macromolecules in the nanoconfined environment. Overall diffusion rates across the cell envelope also occur at similar rates but unexpected narrowing of the QENS signal appears between momentum transfer values Q = 0.7-1.1 Å-1 corresponding to real space dimensions of 6-9 Å. The relaxation time increase can be explained by correlated dynamics of molecules passing through Aquaporin water transport complexes located within the inner or outer membrane structures.
NASA Astrophysics Data System (ADS)
Foglia, Fabrizia; Hazael, Rachael; Simeoni, Giovanna G.; Appavou, Marie-Sousai; Moulin, Martine; Haertlein, Michael; Trevor Forsyth, V.; Seydel, Tilo; Daniel, Isabelle; Meersman, Filip; McMillan, Paul F.
2016-01-01
Quasielastic neutron scattering (QENS) is an ideal technique for studying water transport and relaxation dynamics at pico- to nanosecond timescales and at length scales relevant to cellular dimensions. Studies of high pressure dynamic effects in live organisms are needed to understand Earth’s deep biosphere and biotechnology applications. Here we applied QENS to study water transport in Shewanella oneidensis at ambient (0.1 MPa) and high (200 MPa) pressure using H/D isotopic contrast experiments for normal and perdeuterated bacteria and buffer solutions to distinguish intracellular and transmembrane processes. The results indicate that intracellular water dynamics are comparable with bulk diffusion rates in aqueous fluids at ambient conditions but a significant reduction occurs in high pressure mobility. We interpret this as due to enhanced interactions with macromolecules in the nanoconfined environment. Overall diffusion rates across the cell envelope also occur at similar rates but unexpected narrowing of the QENS signal appears between momentum transfer values Q = 0.7–1.1 Å‑1 corresponding to real space dimensions of 6–9 Å. The relaxation time increase can be explained by correlated dynamics of molecules passing through Aquaporin water transport complexes located within the inner or outer membrane structures.
Coherent Dynamics of meta-Toluidine Investigated by QuasiElastic Neutron Scattering
Faraone, Antonio; Hong, Kunlun; Kneller, Larry; Ohl, Michael E; Copley, John R. D.
2012-01-01
The coherent dynamics of a typical fragile glass former, meta-toluidine, was investigated at the molecular level using quasielastic neutron scattering, with time-of-flight and neutron spin echo spectrometers. It is well known that the static structure factor of meta-toluidine shows a prepeak originating from clustering of the molecules through hydrogen bonding between the amine groups. The dynamics of meta-toluidine was measured for several values of the wavevector transfer Q, which is equivalent to an inverse length scale, in a range encompassing the prepeak and the structure factor peak. Data were collected in the temperature range corresponding to the liquid and supercooled states, down to the glass transition. At least two dynamical processes were identified. This paper focuses on the slowest relaxation process in the system, the {alpha}-relaxation, which was found to scale with the macroscopic shear viscosity at all the investigated Q values. No evidence of 'de Gennes' narrowing associated with the prepeak was observed, in contrast with what happens at the Q value corresponding to the interparticle distance. Moreover, using partially deuterated samples, the dynamics of the clusters was found to be correlated to the single-particle dynamics of the meta-toluidine molecules.
Foglia, Fabrizia; Hazael, Rachael; Simeoni, Giovanna G; Appavou, Marie-Sousai; Moulin, Martine; Haertlein, Michael; Trevor Forsyth, V; Seydel, Tilo; Daniel, Isabelle; Meersman, Filip; McMillan, Paul F
2016-01-01
Quasielastic neutron scattering (QENS) is an ideal technique for studying water transport and relaxation dynamics at pico- to nanosecond timescales and at length scales relevant to cellular dimensions. Studies of high pressure dynamic effects in live organisms are needed to understand Earth's deep biosphere and biotechnology applications. Here we applied QENS to study water transport in Shewanella oneidensis at ambient (0.1 MPa) and high (200 MPa) pressure using H/D isotopic contrast experiments for normal and perdeuterated bacteria and buffer solutions to distinguish intracellular and transmembrane processes. The results indicate that intracellular water dynamics are comparable with bulk diffusion rates in aqueous fluids at ambient conditions but a significant reduction occurs in high pressure mobility. We interpret this as due to enhanced interactions with macromolecules in the nanoconfined environment. Overall diffusion rates across the cell envelope also occur at similar rates but unexpected narrowing of the QENS signal appears between momentum transfer values Q = 0.7-1.1 Å(-1) corresponding to real space dimensions of 6-9 Å. The relaxation time increase can be explained by correlated dynamics of molecules passing through Aquaporin water transport complexes located within the inner or outer membrane structures. PMID:26738409
Craig, T; Hallett, F R; Nickel, B
1982-04-01
The Rayleigh-Gans-Debye approximation is used to predict the electric field autocorrelation functions of light scattered from circularly swimming bull spermatozoa. Using parameters determined from cinematography and modeling the cells as coated ellipsoids of semiaxes a = 0.5 micrometers, b = 2.3 micrometers, and c = 9.0 micrometers, we were able to obtain model spectra that mimic the data exactly. A coat is found to be a necessary attribute of the particle. It is also clear that these model functions at 15 degrees may be represented by the relatively simple function used before by Hallett et al. (1978) to fit data from circularly swimming cells, thus giving some physical meaning to these functional shapes. Because of this agreement the half-widths of experimental functions can now be interpreted in terms of an oscillatory frequency for the movement of the circularly swimming cell. The cinematographic results show a trend to chaotic behavior as the temperature of the sample is increased, with concomitant decrease in overall efficiency. This is manifested by a decrease in oscillatory frequency and translational speed.
Kyriakos, Konstantinos; Philipp, Martine; Silvi, Luca; Lohstroh, Wiebke; Petry, Winfried; Müller-Buschbaum, Peter; Papadakis, Christine M
2016-05-26
The solvent dynamics of concentrated solutions of poly(N-isopropylacrylamide) (PNIPAM, 25 wt %) in water/methanol mixtures (85:15 v/v) are measured with the aim of shedding light onto the cononsolvency effect. Quasi-elastic neutron scattering (QENS) with contrast variation has been carried out at temperatures below and above the cloud point by using in the first set of experiments the mixture H2O:d-MeOD (d-MeOD denotes fully deuterated methanol) as a solvent and in the second set of experiments the mixture D2O:MeOH (MeOH denotes methanol). As a reference, bulk H2O, bulk MeOH and the mixtures H2O:d-MeOD and D2O:MeOH (both 85:15 v/v) have been investigated as well. In the PNIPAM solution in H2O:d-MeOD, two water populations are identified, namely strongly and less strongly arrested water. At the cloud point, the former is partially released from PNIPAM. The diffusion coefficient of the latter one is similar to the one in the water/methanol mixture, and its residence time decreases at the cloud point. The PNIPAM solution in D2O:MeOH reveals similar dynamics to the one in H2O:d-MeOD which may reflect that the dynamics of MeOH near the PNIPAM chain is similar to the one of H2O. The similarity may, however, partially be due to H/D exchange between D2O and MeOH. In both PNIPAM solutions, the mean-square displacement of the PNIPAM chain decreases gradually above the cloud point.
Measurement of the nu(mu) Charged Current pi+ Production to Quasi-elastic Scattering Cross Section
Nowak, Jaroslaw A.; /Louisiana State U.
2009-09-01
Using high statistics samples of charged current interactions, MiniBooNE reports a model independent measurement of the single charged pion production to quasi-elastic cross section ratio on mineral oil without corrections for pion re-interactions in the target nucleus [1]. The result is provided as a function of neutrino energy in the range 0.4 GeV < E < 2.4 GeV with 11% precision in the region of highest statistics.
Al-Wahish, Amal; Armitage, D.; Hill, B.; Mills, R.; Santodonato, L.; Herwig, K. W.; Al-Binni, U.; Jalarvo, N.; Mandrus, D.
2015-09-15
A design for a sample cell system suitable for high temperature Quasi-Elastic Neutron Scattering (QENS) experiments is presented. The apparatus was developed at the Spallation Neutron Source in Oak Ridge National Lab where it is currently in use. The design provides a special sample cell environment under controlled humid or dry gas flow over a wide range of temperature up to 950 °C. Using such a cell, chemical, dynamical, and physical changes can be studied in situ under various operating conditions. While the cell combined with portable automated gas environment system is especially useful for in situ studies of microscopic dynamics under operational conditions that are similar to those of solid oxide fuel cells, it can additionally be used to study a wide variety of materials, such as high temperature proton conductors. The cell can also be used in many different neutron experiments when a suitable sample holder material is selected. The sample cell system has recently been used to reveal fast dynamic processes in quasi-elastic neutron scattering experiments, which standard probes (such as electrochemical impedance spectroscopy) could not detect. In this work, we outline the design of the sample cell system and present results demonstrating its abilities in high temperature QENS experiments.
Wang, P C; Chen, S H
1986-01-01
A series of light scattering experiments have been performed to study both macroscopic aspects of band formation and propagation and microscopic motility parameters of Escherichia coli in the combined substrate gradients of oxygen and serine. From the band formation experiment the conclusion is drawn that a minimum threshold gradient of the substrate is required for bacteria to form a band. From the band propagation experiment in the serine substrate the motility coefficient mu and chemotactic coefficient delta are determined. A separate quasi-elastic scattering experiment has been made with a propagating band to obtain three microscopic motility parameters: mean twiddle time tau 1, mean run time tau 2, and mean run speed V2. Finally, a scaling argument is made to connect the macroscopic parameters mu and delta with the microscopic parameters tau 1, tau 2, and V2, thus achieving a unified understanding of macroscopic and microscopic aspect of chemotaxis. Images FIGURE 1 PMID:3087435
Djurado, David; Bée, Marc; Sniechowski, Maciej; Howells, Spencer; Rannou, Patrice; Pron, Adam; Travers, J P; Luzny, Wojciech
2005-03-21
Proton dynamics in films of poly(aniline) "plastdoped" with di-esters of sulfophthalic (or sulfosuccinic) acids have been investigated by using quasi-elastic neutron scattering techniques. A broad time range (10(-13)-10(-9) s) has been explored by using four different spectrometers. In this time range, the dynamics is exclusively due to protons attached to the flexible tails of the counter-ions. A model of limited diffusion in spheres whose radii are distributed in size gives a realistic view of the geometry of molecular motions. However, it is found that the characteristic times of these motions are widely distributed over several orders of magnitude. The time decay of the intermediate scattering function is well described by a time power law. This behaviour is qualitatively discussed in connection with the structure of the systems and by comparison with other so-called complex systems.
Frauenfelder, Hans; Young, Robert D; Fenimore, Paul W
2013-10-24
The Mössbauer effect and quasi-elastic neutron scattering (QENS) from hydrated proteins yield sharp elastic lines that are accompanied by broad wings. Conventionally, the elastic line and the broad wings are treated as separate phenomena. We show that there is no separation; the entire spectrum consists of Lorentzians with the natural line width. In protein crystals, the shifts of the individual lines from the elastic center above about 150 K are caused by beta fluctuations in the hydration shell. Vibrations cause shifts in the entire temperature range but are best seen below about 150 K. We construct a microscopic model for the dynamics that is based on a random walk of the proteins in their free-energy landscape. The model yields approximate values for the steps in the energy landscape. Remarkably, the quantum electrodynamic concept of gamma rays is needed to justify the model. PMID:23962200
Guilbert, Anne A Y; Zbiri, Mohamed; Jenart, Maud V C; Nielsen, Christian B; Nelson, Jenny
2016-06-16
The molecular dynamics of organic semiconductor blend layers are likely to affect the optoelectronic properties and the performance of devices such as solar cells. We study the dynamics (5-50 ps) of the poly(3-hexylthiophene) (P3HT): phenyl-C61-butyric acid methyl ester (PCBM) blend by time-of-flight quasi-elastic neutron scattering, at temperatures in the range 250-360 K, thus spanning the glass transition temperature region of the polymer and the operation temperature of an OPV device. The behavior of the QENS signal provides evidence for the vitrification of P3HT upon blending, especially above the glass transition temperature, and the plasticization of PCBM by P3HT, both dynamics occurring on the picosecond time scale. PMID:27192930
NASA Astrophysics Data System (ADS)
Cheoun, Myung-Ki; Kim, K. S.; Kim, Hungchong; So, W. Y.; Maruyama, Tomoyuki; Kajino, Toshitaka
2015-04-01
We investigated the in-medium effect by density-dependent axial and weak-vector form factors on muon-neutrino ({{ν }μ }) and anti-muon-neutrino ({{\\bar{ν }}μ }) scattering in the quasi-elastic (QE) region from nucleons (N*) bound in a nucleus or immersed in a nuclear medium via neutral current (NC) and charged current (CC). For the density-dependent form factors, we exploited a quark-meson-coupling (QMC) model. We found that the {{ν }μ }({{\\bar{ν }}μ })-{{N}*} scattering cross sections via NC in the QE region usually decrease with an increased medium density, while those using CC were increased. However, their rate of change was sensitive to the four-momentum transfer given to a bound nucleon through scattering. We compared these results obtained by the elementary process corrected by the in-medium effect to the BNL and MiniBooNE data, which measured {{ν }μ } scattering cross sections per nucleon through {{ν }μ } - 12C scattering in 12C composite targets. The incident energy range was 550 \\lt {{E}ν }\\lt 3000 MeV. We increased the energy up to 100 GeV to compare our results to the NOMAD experimental data. In order to study the density effects on a nucleon embedded in 12C, we exploited the QMC form factors evaluated at ρ =0.5{{ρ }o}, where the normal density {{ρ }o}˜ 0.15 f{{m}-3}. The strangeness contributions in NC scattering are also incorporated into the form factors for comparison with experimental data. Our numerical results show that most of the experimental data can be explained in a satisfactory manner by the density-dependent elementary process, but there are some remaining deviations resulting from the nuclear structure, particularly in the low and high momentum-transfer regions.
Toyota, Taro; Uchiyama, Koyo; Kimura, Takahiro; Nomoto, Tomonori; Fujinami, Masanori
2013-01-01
We used a time-resolved interfacial tension measurement method with quasi-elastic laser scattering to investigate the effects of electrolytes and various surfactants on the nonlinear dynamics of the chemical oscillation that occurred at a water/nitrobenzene interface when a surfactant was added to the interface through a capillary. For both cationic and anionic surfactants, an electrolyte in the water phase was required for slow desorption of the surfactant from the interface. In the absence of an electrolyte, repulsion between the polar head groups of the ionic surfactants hindered adsorption of the surfactant molecules at the interface, resulting in their rapid desorption. In contrast, the presence of an electrolyte induced adsorption of the surfactant ions by screening their charged polar heads. Zwitterionic and nonionic surfactants were also examined and we deduced that the salting out effect of the surfactant produced by the presence of an electrolyte results in strongly attractive interactions between the surfactant molecules and the water/nitrobenzene interface.
Mavila Chathoth, Suresh; Mamontov, Eugene; Melnichenko, Yuri B; Zamponi, Michaela M
2010-01-01
The diffusion of methane confined in nano-porous carbon aerogel with the average pore size 48 {angstrom} and porosity 60% was investigated as a function of pressure at T = 298 K using quasi-elastic neutron scattering (QENS). The diffusivity of methane shows a clear effect of confinement: it is about two orders of magnitude lower than in bulk at the same thermodynamic conditions and is close to the diffusivity of liquid methane at 100 K (i.e. {approx} 90 K below the liquid-gas critical temperature T{sub C} {approx} 191 K). The diffusion coefficient (D) of methane initially increases with pressure by a factor of {approx}2.5 from 3.47 {+-} 0.41 x 10{sup -10} m{sup 2} s{sup -1} at 0.482 MPa to D = 8.55 {+-} 0.33 x 10{sup -10} m{sup 2} s{sup -1} at 2.75 MPa and starts to decrease at higher pressures. An explanation of the observed non-monotonic behavior of the diffusivity in the confined fluid is based on the results of small-angle neutron scattering experiments of the phase behavior of methane in a similar carbon aerogel sample. The initial increase of the diffusion coefficient with pressure is explained as due to progressive filling of bigger pores in which molecular mobility in the internal pore volume is less affected by the sluggish liquid-like molecular mobility in the adsorbed phase. Subsequent decrease of D, is associated with the effect of intermolecular collisions, which result in a lower total molecular mobility with pressure, as in the bulk state. The results are compared with the available QENS data on the methane diffusivity in zeolites, metal organic frameworks, and porous silica as well as with the molecular dynamics simulations of methane in nano-porous carbons and silica zeolites.
NASA Astrophysics Data System (ADS)
Yi, Zhou; Deng, Pei-Na; Zhang, Li-Li; Li, Hua
2016-10-01
The dynamic behaviors of water contained in calcium-silicate-hydrate (C-S-H) gel with different water content values from 10% to 30% (by weight), are studied by using an empirical diffusion model (EDM) to analyze the experimental data of quasi-elastic neutron scattering (QENS) spectra at measured temperatures ranging from 230 K to 280 K. In the study, the experimental QENS spectra with the whole Q-range are considered. Several important parameters including the bound/immobile water elastic coefficient A, the bound water index BWI, the Lorentzian with a half-width at half-maximum (HWHM) Γ 1(Q) and Γ 2(Q), the self-diffusion coefficients D t1 and D t2 of water molecules, the average residence times τ 01 and τ 02, and the proton mean squared displacement (MSD) are obtained. The results show that the QENS spectra can be fitted very well not only for small Q (≤ 1 Å-1) but also for large Q. The bound/immobile water fraction in a C-S-H gel sample can be shown by the fitted BWI. The distinction between bound/immobile and mobile water, which includes confined water and ultra-confined water, can be seen by the fitted MSD. All the MSD tend to be the smallest value below 0.25 Å2 (the MSD of bound/immobile water) as the Q increases to 1.9 Å-1, no matter what the temperature and water content are. Furthermore, by the abrupt changes of the fitted values of D t1, τ 01, and Γ 1(Q), a crossover temperature at 250 K, namely the liquid-to-crystal-like transition temperature, can be identified for confined water in large gel pores (LGPs) and/or small gel pores (SGPs) contained in the C-S-H gel sample with 30% water content.
Etampawala, Thusitha; Ratnaweera, Dilru; Morgan, Brian; Diallo, Souleymane; Mamontov, Eugene; Dadmun, Mark
2015-02-02
Our work reports on the detailed molecular dynamic behavior of miscible blends of Poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and their pure counterparts by quasi-elastic neutron scattering measurements (QENS). The study provides the measure of relaxation processes on pico-to-nanosecond time scales. A single relaxation process was observed in pure P3HT and PCBM while two relaxation processes, one fast and one slow, were observed in the blends. The fast process was attributed to the dynamics of P3HT while the slow process was correlated to the dynamics of PCBM. The results show that the relaxation process is a balance betweenmore » two opposing effects: increased mobility due to thermal activation of P3HT molecules and decrease mobility due to the presence of PCBM which is correlated to the percent crystallinity of P3HT and local packing density of PCBM in the amorphous phase. The threshold for the domination of the thermally activated relaxation is between 5 and 9 vol.% of PCBM loading. Two distinct spatial dependences of the relaxation processes, in which the crossover length scale depends neither on temperature nor composition, were observed for all the samples. They were attributed to the collective motions of the hexyl side chains and the rotational motions of the C-C single bonds of the side chains. Finally, these results provide an understanding of the effects of PCBM loading and temperature on the dynamics of the polymer-fullerene blends which provides a tool to optimize the efficiency of charge carrier and exciton transport within the organic photovoltaic (OPV) active layer to improve the high performance of organic solar cells.« less
Etampawala, Thusitha; Ratnaweera, Dilru; Morgan, Brian; Diallo, Souleymane; Mamontov, Eugene; Dadmun, Mark
2015-02-02
Our work reports on the detailed molecular dynamic behavior of miscible blends of Poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and their pure counterparts by quasi-elastic neutron scattering measurements (QENS). The study provides the measure of relaxation processes on pico-to-nanosecond time scales. A single relaxation process was observed in pure P3HT and PCBM while two relaxation processes, one fast and one slow, were observed in the blends. The fast process was attributed to the dynamics of P3HT while the slow process was correlated to the dynamics of PCBM. The results show that the relaxation process is a balance between two opposing effects: increased mobility due to thermal activation of P3HT molecules and decrease mobility due to the presence of PCBM which is correlated to the percent crystallinity of P3HT and local packing density of PCBM in the amorphous phase. The threshold for the domination of the thermally activated relaxation is between 5 and 9 vol.% of PCBM loading. Two distinct spatial dependences of the relaxation processes, in which the crossover length scale depends neither on temperature nor composition, were observed for all the samples. They were attributed to the collective motions of the hexyl side chains and the rotational motions of the C-C single bonds of the side chains. Finally, these results provide an understanding of the effects of PCBM loading and temperature on the dynamics of the polymer-fullerene blends which provides a tool to optimize the efficiency of charge carrier and exciton transport within the organic photovoltaic (OPV) active layer to improve the high performance of organic solar cells.
Mazer, N A; Schurtenberg, P; Carey, M C; Preisig, R; Weigand, K; Känzig, W
1984-04-24
Using quasi-elastic light scattering ( QLS ), we have characterized the macromolecular components in hepatic bile obtained from the dog and compared these results with data from model bile solutions containing the bile salt (BS) sodium taurocholate (TC), egg lecithin (L), and cholesterol (Ch). Native bile samples were obtained by direct catheterization of the common bile duct in a previously cholecystectomized dog fitted with a Thomas duodenal cannula. Hepatic bile was sampled during three secretory states: (A) unstimulated "fasting" bile, (B) "stimulated" secretion during an intravenous TC infusion, and (C) "secretin-stimulated" secretion. All three samples had comparable molar ratios of L/BS (0.21 +/- 0.03) and Ch/L (0.027 +/- 0.006) but differed in the total lipid concentration (BS + L + Ch): (A) 13.1 +/- 0.8, (B) 6.7 +/- 0.8, and (C) 3.0 +/- 0.4 g/dL. From the QLS autocorrelation functions measured on samples B and C, three macromolecular components (denoted 1 alpha, 1 beta, and 2) were resolved. Component 1 alpha (hydrodynamic radius R1 alpha = 10 +/- 2 A) is comparable in size to the micellar aggregates of model systems. Component 1 beta (R1 beta = 67 +/- 7 A) appears to reflect an average of biliary proteins. Component 2 (R2 = 650 +/- 15 A) is a trace component whose size and sedimentation behavior are compatible with those of the canalicular membrane vesicles postulated to be present in bile [ Godfrey , P. P., Warner, M. J., & Coleman , R. (1981) Biochem. J. 196, 11]. Serial dilution of the B and C bile samples with Tris buffer (0.15 M NaCl, pH 8.0) showed a remarkable similarity in the behavior of the 1 alpha component as compared to the mean hydrodynamic radius Rh of similarly diluted model bile solutions. When a critical dilution factor, d gamma, is reached, Rh increases abruptly from approximately 30 to approximately 400 A. Above a second dilution factor, d alpha, it then decreases to a value of approximately 150 A. Similar results were obtained on
NASA Astrophysics Data System (ADS)
Soong, Shiao-Bin
We report in this thesis the simultaneous measurement of the longitudinal-transverse response functions, fLT and fLT' , and the transverse-transverse response function fTT of the deuteron. The quasi- elastic H2(e->, e'p)n experiment reported here was conducted at the MIT/Bates Linear Accelerator Center in February, 1997. The experiment was carried out with a 40% polarized, 800 MeV electron beam. The measurement took place in the Bates South Hall using the One Hundred Inch Proton Spectrometer (OHIPS) as the electron spectrometer. It was placed at an angle of 37.27° and the energy transfer, ω, was set for quasi-elastic kinematics with the square of the four-momentum transfer, Q 2, equal to -0.22(GeV/c) 2 . Three out-of- plane proton spectrometers (OOPS) were positioned at fcmpq = (0°, 90°, 180°), respectively, for a given qlabpq of 23.5°. This allowed the simultaneous measurement of fLT,fTT and fLT' at a central missing momentum of ~200 (MeV/ c). The measured asymmetries, cross sections and response functions are compared with different theoretical models. (Copies available exclusively from MIT Libraries, Rm. 14- 0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)
Wang Xu; Dipangkar Dutta; Feng Xiong; Brian Anderson; Leonard Auerbach; Todd Averett; William Bertozzi; Tim Black; John Calarco; Lawrence Cardman; Gordon Cates; Zhengwei Chai; Jian-ping Chen; Seonho Choi; Eugene Chudakov; Steve Churchwell; G.S. Corrado; C. Crawford; Daniel Dale; Alexandre Deur; Pibero Djawotho; Bradley Filippone; John Finn; Haiyan Gao; Ronald Gilman; Oleksandr Glamazdin; Charles Glashausser; Walter Gloeckle; J. Golak; Javier Gomez; Viktor Gorbenko; Jens-ole Hansen; F. Hersman; Douglas Higinbotham; Richard Holmes; Calvin Howell; Emlyn Hughes; Thomas Humensky; Sebastien Incerti; Cornelis De Jager; John Jensen; Xiaodong Jiang; C.E. Jones; Mark Jones; R. Kahl; H. Kamada; A. Kievsky; Ioannis Kominis; Wolfgang Korsch; Kevin Kramer; Gerfried Kumbartzki; Michael Kuss; Enkeleida Lakuriqi; Meihua Liang; Nilanga Liyanage; John Lerose; Sergey Malov; Demetrius Margaziotis; J.W. Martin; Kathy Mccormick; Robert Mckeown; Kevin Mcilhany; Zein-eddine Meziani; Robert Michaels; G.W. Miller; Joseph Mitchell; Sirish Nanda; E. Pace; Tina Pavlin; Gerassimos Petratos; Roman Pomatsalyuk; D. Pripstein; David Prout; Ronald Ransome; Yves Roblin; Marat Rvachev; Arunava Saha; G. Salme; Michael Schnee; Taeksu Shin; Karl Slifer; Paul Souder; Steffen Strauch; Riad Suleiman; Mark Sutter; Bryan Tipton; Luminita Todor; Michele Viviani; Branislav Vlahovic; J. Watson; Claude Williamson; H. Witala; Bogdan Wojtsekhowski; Jen-chuan Yeh; Piotr Zolnierczuk
2000-10-01
We have measured the transverse asymmetry from inclusive scattering of longitudinally polarized electrons from polarized {sup 3}He nuclei at quasi-elastic kinematics in Hall A at Jefferson Lab with high statistical and systematic precision. The neutron magnetic form factor was extracted based on Faddeev calculations with an experimental uncertainty of less than 2%.
NASA Astrophysics Data System (ADS)
Krivorotov, V. F.; Mirzaev, S. Z.; Nuzhdov, G. S.
2016-07-01
Low-frequency light scattering in superionic crystals of the LaF3 structural type was studied. The laser light scattering spectra of LnF3 single crystals at 90o scattering geometry were obtained over a wide temperature range. The scattering intensity increased sharply in the temperature range in which the mobility of the fl uoride ions increased. The experimental scattering curves were represented as the sum of three central Lorentz contours. The "narrow" Lorentzian had width Γ1 = 0.8-4.2 cm-1; the "medium" Lorentzian, Γ2 = 4.2-27 cm-1; and the "wide" Lorentzian, Γ3 = 42-96 cm-1. These corresponded to relaxation times τ1 ≈ (0.13-0.67) × 10-11 s, τ2 ≈ (0.20-1.27) × 10-12 s, and τ3 ≈ (0.56-1.27) × 10-13 s that were associated with different types of displacement of fl uoride ions into interstices. The activation energy ΔEd obtained from the temperature dependence of the Lorentz contour width was found to be many times less than the energy Ed determining the dynamic parameters of ion motion in the LnF3 lattice.
Studying neutrino oscillations using quasi-elastic events in MINOS
Kumaratunga, Sujeewa Terasita
2008-02-01
MINOS (Main Injector Neutrino Oscillation Search), is a long baseline neutrino experiment designed to search for neutrino oscillations using two detectors at Fermi National Accelerator Laboratory, IL (Near Detector) and Soudan, MN (Far Detector). It will study v_{μ} → v_{τ} oscillations and make a measurement on the oscillation parameters, Δm$2\\atop{23}$ and sin^{2} 2θ_{23}, via a v_{μ} beam made at Fermilab. Charge current neutrino interactions in the MINOS detectors are of three types: quasi-elastic scattering (QEL), resonance scattering (RES) and deep inelastic scattering (DIS). Of these, quasi-elastic scattering leaves the cleanest signal with just one μ and one proton in the final state, thus rendering the reconstruction of the neutrino energy more accurate. This thesis will outline a method to separate QEL events from the others in the two detectors and perform a calculation of Δm$2\\atop{23}$ and sin^{2} 2θ_{23} using those events. The period under consideration was May 2005 to February 2006. The number of observed quasi-elastic events with energies below 10 GeV was 29, where the expected number was 60 ± 3. A fit to the energy distribution of these events gives Δm$2\\atop{23}$ = 2.91$+0.49\\atop{-0.53}$(stat)$+0.08\\atop{-0.09}$(sys) x 10^{-3} eV^{2} and sin^{2} 2θ_{23} = 0.990_{-0.180}(stat)_{-0.030}(sys).
Inclusive Inelastic Electron Scattering from Nuclei
Fomin, Nadia
2007-10-26
Inclusive electron scattering from nuclei at large x and Q{sup 2} is the result of a reaction mechanism that includes both quasi-elastic scattering from nucleons and deep inelastic scattering from the quark consitituents of the nucleons. Data in this regime can be used to study a wide variety of topics, including the extraction of nuclear momentum distributions, the infiuence of final state interactions and the approach to y-scaling, the strength of nucleon-nucleon correlations, and the approach to x-scaling, to name a few. Selected results from the recent experiment E02-019 at the Thomas Jefferson National Accelerator Facility will be shown and their relevance discussed.
Applications of effective field theory to electron scattering
NASA Astrophysics Data System (ADS)
Diaconescu, Luca Radu
In this work two calculations are presented. In the first, we compute the vector analyzing power (VAP) for the elastic scattering of transversely polarized electrons from protons at low energies, using an effective theory of electrons, protons, and photons. We study all contributions through second order in E/M, where E and M are the electron energy and nucleon mass, respectively. The leading order VAP arises from the imaginary part of the interference of one- and two-photon exchange amplitudes. Sub-leading contributions are generated by the nucleon magnetic moment and charge radius, as well as recoil corrections to the leading-order amplitude. Working to second order in E/M), we obtain a prediction for A_n that is free of unknown parameters and that agrees with the recent measurement of the VAP in backward angle electron proton scattering. In the second part of this thesis the longitudinal asymmetry due to Z exchange is calculated in quasi-elastic electron-deuteron scattering at momentum transfers |Q^2| of about 0.1 GeV^2 relevant for the SAMPLE experiment. The deuteron and pn scattering-state wave functions are obtained from solutions of a Schrodinger equation with the Argonne v18 potential. Electromagnetic and weak neutral one- and two-nucleon currents are included in the calculation. The two-nucleon currents of pion range are shown to be identical to those derived in Effective Field Theory. The results indicate that two-body contributions to the asymmetry are small (about 0.2%) around the quasi-elastic peak, but become relatively more significant (about 3%) in the high-energy wing of the quasi-elastic peak.
How well do we understand quasi-elastic reactions at energies close to the barrier
Rehm, K.E.
1988-01-01
In collisions between too heavy nuclei a wide spectrum of different reaction modes is observed covering the range from simple processes like elastic scattering to complicated multistep transfers and fusion. On the theoretical side heavy ion reactions are usually analyzed using models that were developed first for light ion induced reactions: the optical model for elastic scattering and the DWBA for more inelastic processes like transfer and inelastic scattering. Some of the assumptions going into these approximations, however, are not valid for heavy ion induced reactions. The region between fusion and quasi-elastic reactions is not well understood theoretically. This region is associated with deep inelastic collisions, which are complex multiparticle reactions involving transfer of several protons and neutrons. In this paper, the author discusses to what extent experiments in the field of quasi-elastic scattering are understood within the framework of various theoretical models and in what areas more work is needed.
Charged current quasi-elastic neutrino analysis at MINERνA
Fiorentini, G. A.
2015-05-15
MINERνA (Main INjector Experiment for ν-A) is a neutrino scattering experiment in the NuMI high-intensity neutrino beam at the Fermi National Accelerator Laboratory. MINERvA was designed to make precision measurements of low energy neutrino and antineutrino cross sections on a variety of different materials (plastic scintillator, C, Fe, Pb, He and H2O). We present the current status of the charged current quasi-elastic scattering in plastic scintillator.
NASA Astrophysics Data System (ADS)
Gustafson, Gösta; Lönnblad, Leif; Ster, András; Csörgő, Tamás
2015-10-01
In order to understand the initial partonic state in proton-nucleus and electron-nucleus collisions, we investigate the total, inelastic, and (quasi-)elastic cross sections in p A and γ ⋆ A collisions, as these observables are insensitive to possible collective effects in the final state interactions. We used as a tool the DIPSY dipole model, which is based on BFKL dynamics including non-leading effects, saturation, and colour interference, which we have extended to describe collisions of protons and virtual photons with nuclei. We present results for collisions with O, Cu, and Pb nuclei, and reproduce preliminary data on the pPb inelastic cross section at LHC by CMS and LHCb. The large NN cross section results in p A scattering that scales approximately with the area. The results are compared with conventional Glauber model calculations, and we note that the more subtle dynamical effects are more easily studied in the ratios between the total, inelastic and (quasi-)elastic cross sections. The smaller photon interaction makes the γ ⋆ A collisions more closely proportional to A, and we see here that future electron-ion colliders would be valuable complements to the p A collisions in studies of dynamical effects from correlations, coherence and fluctuations in the initial state in high energy nuclear collisions.
Nanowire electron scattering spectroscopy
NASA Technical Reports Server (NTRS)
Hunt, Brian D. (Inventor); Bronikowski, Michael (Inventor); Wong, Eric W. (Inventor); von Allmen, Paul (Inventor); Oyafuso, Fabiano A. (Inventor)
2009-01-01
Methods and devices for spectroscopic identification of molecules using nanoscale wires are disclosed. According to one of the methods, nanoscale wires are provided, electrons are injected into the nanoscale wire; and inelastic electron scattering is measured via excitation of low-lying vibrational energy levels of molecules bound to the nanoscale wire.
Electron Scattering Experiments with Polarized Hydrogen/Deuterium Internal Targets
van Buuren, L.D.; 97-01 Collaboration
2000-12-31
A high-density polarized hydrogen/deuterium internal gas target is presented. The target is based on a setup previously used in electron scattering experiments with tensor-polarized deuterium. To increase the target thickness, new state-of-the-art permanent sextupole magnets and a more powerful pumping system were installed together with a longer (60 cm) and colder ({approximately}70 K) cylindrical storage cell. Electro-nuclear spin observables were measured by scattering longitudinally polarized electrons stored in the AmPS ring (NIFHEF) from the target gas. The product of electron beam and target polarization was determined from the known e{prime}p (quasi) elastic asymmetries. A target thickness of 1.1 {times} 10{sup 14} atoms/cm{sup 2} was achieved which with typical beam currents of 110 mA corresponds to a luminosity of about 7.5 {times} 10{sup 31} cm{sup {minus}2}s{sup {minus}1}. Target and beam polarizations up to 0.7 and 0.65, respectively, were obtained.
Transition from quasi-elastic to deep-inelastic reactions
Rehm, K.E.
1986-01-01
Heavy ion induced transfer reactions are usually considered to fall into two categories. Quasi-elastic processes, on one hand, are characterized by small energy transfers, with one-nucleon transfer reactions being a typical example. These processes are dominant for grazing collisions, and are generally described within simple one-step DWBA calculations. Deep inelastic reactions, on the other hand, occur for more central collisions where the interaction time is longer and subsequently more energy and particles can be exchanged. Quasi-elastic collisions dominate transfer reactions induced by light heavy ions (e.g., /sup 16/O) at energies not too high above the barrier, while deep inelastic collisions are observed mainly in reactions induced by heavier projectiles (Kr, Xe). In this contribution, we discuss the transition between these two processes for the system /sup 48/Ti + /sup 208/Pb. /sup 48/Ti is located between light (/sup 16/O) and heavy (Kr) projectiles and should be well suited for a study of the interrelation between quasi- and deep-inelastic reactions. The experiments were performed with a 300 MeV /sup 48/Ti beam obtained from the Argonne National Laboratory superconducting linac. The outgoing particles were momentum analyzed in a split pole magnetic spectrograph and detected in the focal plane by a position sensitive ionization chamber. The specific energy loss, the magnetic rigidity and the total energy of the outgoing particles were measured enabling mass and Z-identification. The energy resolution was about 3 MeV, determined by the thickness of the /sup 208/Pb target, and thus excluded study of transfer reactions to discrete final states. Angular distributions were measured in the range theta/sub lab/ = 20/sup 0/ to 80/sup 0/ in steps of 5/sup 0/. 8 refs.
Nanowire Electron Scattering Spectroscopy
NASA Technical Reports Server (NTRS)
Hunt, Brian; Bronikowsky, Michael; Wong, Eric; VonAllmen, Paul; Oyafuso, Fablano
2009-01-01
Nanowire electron scattering spectroscopy (NESS) has been proposed as the basis of a class of ultra-small, ultralow-power sensors that could be used to detect and identify chemical compounds present in extremely small quantities. State-of-the-art nanowire chemical sensors have already been demonstrated to be capable of detecting a variety of compounds in femtomolar quantities. However, to date, chemically specific sensing of molecules using these sensors has required the use of chemically functionalized nanowires with receptors tailored to individual molecules of interest. While potentially effective, this functionalization requires labor-intensive treatment of many nanowires to sense a broad spectrum of molecules. In contrast, NESS would eliminate the need for chemical functionalization of nanowires and would enable the use of the same sensor to detect and identify multiple compounds. NESS is analogous to Raman spectroscopy, the main difference being that in NESS, one would utilize inelastic scattering of electrons instead of photons to determine molecular vibrational energy levels. More specifically, in NESS, one would exploit inelastic scattering of electrons by low-lying vibrational quantum states of molecules attached to a nanowire or nanotube.
Electron Scattering from Nuclei
J. Wallace Van Orden
2002-08-01
The description of nuclei at distances on the order of a fermi or less poses a difficult challenge for theoretical physicists. At larger distances the traditional description of the nucleus as a collection of interacting nucleons has been quite successful and substantial progress has been made in recent years in describing few-nucleon systems using this approach. However, it has been known for several decades that the nucleons themselves are composite objects which are believed to be described by Quantum Chromodynamics (QCD). QCD is a complicated nonlinear strongly interacting field theory which can only be used for calculation in special circumstances. Due to the property of asymptotic freedom exhibited by QCD, perturbative calculations of QCD can be made at large momentum transfers and have achieved substantial success for a variety of processes. Understanding the transition from traditional pictures of nuclei to QCD is a substantial challenge. As an example of this problem, this paper describes recent calculations of elastic electron-deuteron scattering based on a relativistic extension of the traditional nuclear physics approach. The results of this work are compared to new data obtained at the Thomas Jefferson National Laboratory and to the predictions of perturbative QCD.
A sub-GeV charged-current quasi-elastic $\
Walding, Joseph James
2009-12-01
Neutrino-nucleus charged-current quasi-elastic scattering is the signal interaction used by many neutrino oscillation experiments. For muon disappearance studies the signal mode is ν_{μ}n → μp. Modern oscillation experiments, such as T2K, produce neutrino beams with peak beam energies of order a few-GeV. It is therefore vitally important to have accurate measurements of the charged-current quasi-elastic crosssection for future neutrino oscillation experiments. Neutrino-nucleus cross-sections in the few-GeV region are not well understood, with the main uncertainties coming from understanding of the neutrino beam flux and the final state interactions within nuclei. SciBooNE is a sub-GeV neutrino-nucleus cross-section experiment based at Fermilab, Batavia, USA, with the goal to measure neutrino cross-sections with precision of order 5%. SciBooNE took data from June 2007 until August 2008, in total 0.99×10^{20} and 1.53×10^{20} protons on target were collected in neutrino and anti-neutrino mode, respectively. In this thesis a ν_{μ} charged-current quasi-elastic (CCQE) cross-section contained within the SciBar sub-detector is presented. A method to tag muons in SciBar was developed and three samples were isolated. An excess in backwards tracks in the one-track sample is observed. A Poisson maximum likelihood is used to extract the CCQE cross-section. The fit was applied using a basic fit parameter model, successfully used to obtain the cross-section in the SciBar-MRD matched CCQE analysis. This method was found to be insufficient in describing the data for the SciBarcontained CCQE analysis. By adding two migration parameters the cross-section was calculated to be 1.004 ± 0.031 (stat)^{+0.101} _{-0.150}(sys) × 10^{-38} cm^{2}/neutron, excluding backwards tracks with a χ^{2} = 203.8/76 d.o.f. and 1.083 ± 0.030(stat)^{+0.115} _{-0.177}(sys) × 10^{-38} cm^{2 }
Concept of a multichannel spin-resolving electron analyzer based on Mott scattering
Strocov, Vladimir N.; Petrov, Vladimir N.; Dil, J. Hugo
2015-01-01
The concept of a multichannel electron spin detector based on optical imaging principles and Mott scattering (iMott) is presented. A multichannel electron image produced by a standard angle-resolving (photo) electron analyzer or microscope is re-imaged by an electrostatic lens at an accelerating voltage of 40 kV onto the Au target. Quasi-elastic electrons bearing spin asymmetry of the Mott scattering are imaged by magnetic lenses onto position-sensitive electron CCDs whose differential signals yield the multichannel spin asymmetry image. Fundamental advantages of this concept include acceptance of inherently divergent electron sources from the electron analyzer or microscope focal plane as well as small aberrations achieved by virtue of high accelerating voltages, as demonstrated by extensive ray-tracing analysis. The efficiency gain compared with the single-channel Mott detector can be a factor of more than 104 which opens new prospects of spin-resolved spectroscopies in application not only to standard bulk and surface systems (Rashba effect, topological insulators, etc.) but also to buried heterostructures. The simultaneous spin detection combined with fast CCD readout enables efficient use of the iMott detectors at X-ray free-electron laser facilities. PMID:25931087
Precursor of pion condensation: The softening of the quasi-elastic peak
NASA Astrophysics Data System (ADS)
Alberico, W. M.; Ericson, M.; Molinari, A.
1980-05-01
The phase transition of pion condensation is heralded in the disordered phase by an increase in the life time of the fluctuations for the staggered magnetization. This precursor phenomenon entails, in ordinary nuclei, a showing down of the nuclear quasi-elastic response when observed with spin-sensitive probes. Permanent address: Istituto di Fisica Teorica dell'Università di Torino, Turin, Italy.
Parity Violation in Electron Scattering
Beise, Elizabeth
2007-10-26
About thirty years ago, electron scattering from nucleons was used [1] to identify, and then measure, the properties of the weak interaction, the only force of nature known to violate the symmetry parity. The basic technique has not fundamentally changed, which is to look for a small asymmetry in count rate from scattering a polarized electron beam from an unpolarized target. Since then, parity-violating (PV) electron scattering has developed substantially, a result of significant improvements in polarized electron beams, accelerator advancements, and developments in cryogenic targets that make it possible to carry out experiments with much higher statistical precision. In the last decade PV experiments have focused on using the complementary electron-quark flavor coupling of the weak interaction to identify and place limits on contributions of strange quark-antiquark pairs to the charge and magnetism of the proton. This observable provides a unique window into the structure of the proton since strange quark contributions can arise only from the sea of quarks and gluons that are responsible for the vast majority of the nucleon's mass. This paper will report on recent results aimed at this goal, along with a brief overview of future directions.
Rukhlenko, Ivan D; Fedorov, Anatoly V; Baymuratov, Anvar S; Premaratne, Malin
2011-08-01
We develop a low-temperature theory of quasi-elastic secondary emission from a semiconductor quantum dot, the electronic subsystem of which is resonant with the confined longitudinal-optical (LO) phonon modes. Our theory employs a generalized model for renormalization of the quantum dot's energy spectrum, which is induced by the polar electron-phonon interaction. The model takes into account the degeneration of electronic states and allows for several LO-phonon modes to be involved in the vibrational resonance. We give solutions to three fundamental problems of energy-spectrum renormalization--arising if one, two, or three LO-phonon modes resonantly couple a pair of electronic states--and discuss the most general problem of this kind that admits an analytical solution. With these results, we solve the generalized master equation for the reduced density matrix, in order to derive an expression for the differential cross section of secondary emission from a single quantum dot. The obtained expression is then analyzed to establish the basics of optical spectroscopy for measuring fundamental parameters of the quantum dot's polaron-like states.
Spectroscopic study of sub-barrier quasi-elastic nuclear reactions
Pass, C.N.; Evans, P.M.; Smith, A.E.; Stuttge, L.; Betts, R.R.; Lilley, J.S.; Connell, K.A.; Simpson, J.; Smith, J.R.; James, A.N.
1988-01-01
The technique developed in this paper is particularly well suited to the detailed spectroscopic study of low energy quasi-elastic nuclear reactions and by overcoming the limitations of conventional procedure, the prospect of detailed studies of inclusive reaction mechanism may be realised. With only limited statistics we find evidence for strong multistep character in the transfer of a single nucleon from spherical vibrational target to spherical projectile nuclei. The suggestive measurements reported here may be made definitive through extended runs based on this technique and experiments planned for the future offer the real prospect of developing a quantified interpretation of the reaction process. 9 refs. 5 figs.
Positronium and Electron Scattering on Helium
NASA Technical Reports Server (NTRS)
DiRienzi, Joseph
2011-01-01
A recent work [1] establishes experimentally that Positronium scattering by atoms of various elements is surprisingly close in total cross-section to that of an isolated electron of the same velocity. In this work we will look at the scattering of Ps on Helium and compare it to a determination of the scattering of an e- with the same element. For both the Ps scattering and the e- scattering on He, we assume the symmetrization of the e- with the closed shell He electrons is the dominant interaction. A local effective potential employed in [2] and [3] is used to model the electron exchange and cross- sections are determined for a set of partial waves. For the Ps scattering we include as a secondary effect the Van der Waals interaction. For single e- scattering of He, we also employ a short range Coulomb potential and dispersion as contributing effects. Results of the cross-sections determined in each case are then compared
Rutherford scattering of electron vortices
NASA Astrophysics Data System (ADS)
Van Boxem, Ruben; Partoens, Bart; Verbeeck, Johan
2014-03-01
By considering a cylindrically symmetric generalization of a plane wave, the first-order Born approximation of screened Coulomb scattering unfolds two new dimensions in the scattering problem: transverse momentum and orbital angular momentum of the incoming beam. In this paper, the elastic Coulomb scattering amplitude is calculated analytically for incoming Bessel beams. This reveals novel features occurring for wide-angle scattering and quantitative insights for small-angle vortex scattering. The result successfully generalizes the well-known Rutherford formula, incorporating transverse and orbital angular momentum into the formalism.
Wang Xu
2002-06-01
Electromagnetic form factors are fundamental quantities in describing the underlying electromagnetic structure of nucleons. While proton electromagnetic form factors have been determined with good precision, neutron form factors are known poorly, largely due to the lack of free neutron targets. Jefferson Lab Hall A experiment E95-001, a ''precise measurement of the transverse asymmetry A{sub T}' from the quasielastic {sup 3}He(e, e') process,'' was therefore designed to determine precisely the neutron magnetic form factor, G{sub M}{sup n} at low momentum transfer values and was successfully completed in Spring 1999. High precision A{sub T}'data in the quasi-elastic region at Q{sup 2} values of 0.1 to 0.6 (GeV/c){sup 2} were obtained using a high-pressure spin-exchange optically-pumped polarized {sup 3}He gas target with an average polarization of 30%, a longitudinally polarized e{sup -} beam, and two High Resolution Spectrometers: HRSe and HRSh. HRSe was employed to detect scattered electrons from the quasi-elastic kinematic region, and HRSh was employed as a elastic polarimetry to monitor the product of the beam and target polarizations. The extraction of form factors is usually model-dependent. Significant constraints on theoretical calculations are provided bu additional high precision quasi-elastic asymmetry data at Q{sup 2} values of 0.1 and 0.2 (GeV/c){sup 2} in {sup 3}He breakup region, where effects of final state interactions (FSI) and meson exchange currents (MEC) are expected to be large [71]. G{sub M}{sup n} is extracted from a non-relativistic Faddeev calculation which includes both FSI and MEC at Q{sup 2} values of 0.1 and 0.2 (GeV/c){sup 2}. The uncertainties of G{sub M}{sup n} at these Q{sup 2} values are comparable to those of recent experiments with deuterium targets [58]. At the higher Q{sup 2} values from this experiment, G{sub M}{sup n} is extracted from Plane-Wave Impulsive Approximation (PWIA) calculations with a relatively large theoretical
Search for neutrino oscillations in the MINOS experiment by using quasi-elastic interactions
Piteira, Rodolphe
2005-09-29
The enthusiasm of the scientific community for studying oscillations of neutrinos is equaled only by the mass of their detectors. The MINOS experiment determines and compares the near spectrum of muonic neutrinos from the NUMI beam to the far one, in order to measure two oscillation parameters: Δm$2\\atop{23}$ and sin^{2} (2θ_{23}). The spectra are obtained by analyzing the charged current interactions which difficulty lies in identifying the interactions products (e.g. muons). An alternative method identifying the traces of muons, bent by the magnetic field of the detectors, and determining their energies is presented in this manuscript. The sensitivity of the detectors is optimal for the quasi-elastic interactions, for which a selection method is proposed, to study their oscillation. Even though it reduces the statistics, such a study introduces fewer systematic errors, constituting the ideal method on the long range.
Local orbitals in electron scattering calculations*
NASA Astrophysics Data System (ADS)
Winstead, Carl L.; McKoy, Vincent
2016-05-01
We examine the use of local orbitals to improve the scaling of calculations that incorporate target polarization in a description of low-energy electron-molecule scattering. After discussing the improved scaling that results, we consider the results of a test calculation that treats scattering from a two-molecule system using both local and delocalized orbitals. Initial results are promising. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.
Pygmy Resonances Probed with Electron Scattering
Bertulani, Carlos A
2007-05-01
Pygmy resonances in light nuclei excited in electron scattering are discussed. These collective modes will be explored in future electron-ion colliders such as ELISe/FAIR (spokesperson: Haik Simon - GSI). Response functions for direct breakup are explored with few-body and hydrodynamical models, including the dependence upon final-state interactions.
Rotational rainbows in electron-molecule scattering
Ziegler, G.; Raedle, M.; Puetz, O.; Jung, K.; Ehrhardt, H.; Bergmann, K.
1987-06-22
We report the measurement of state-to-state differential cross sections for rotationally inelastic electron-Na/sub 2/ collisions for impact energies from 150 to 300 eV. The data demonstrate for the first time large rotational transitions (0less than or equal to..delta..jless than or equal to30) for backward scattering. The most surprising result is the observation of pronounced rotational rainbows. These structures are expected to be general features in high-energy electron-molecule scattering.
Distorted Coulomb field of the scattered electron
Thomsen, H. D.; Esberg, J.; Andersen, K. K.; Lund, M. D.; Knudsen, H.; Uggerhoej, U. I.; Sona, P.; Mangiarotti, A.; Ketel, T. J.; Dizdar, A.; Ballestrero, S.; Connell, S. H.
2010-03-01
Experimental results for the radiation emission from ultrarelativistic electrons in targets of 0.03%-5% radiation length is presented. For the thinnest targets, the radiation emission is in accordance with the Bethe-Heitler formulation of bremsstrahlung, the target acting as a single scatterer. In this regime, the radiation intensity is proportional to the thickness. As the thickness increases, the distorted Coulomb field of the electron that is the result of the first scattering events, leads to a suppressed radiation emission per interaction, upon subsequent scattering events. In that case, the radiation intensity becomes proportional to a logarithmic function of the thickness, due to the suppression. Eventually, once the target becomes sufficiently thick, the entire radiation process becomes influenced by multiple scattering and the radiation intensity is again proportional to the thickness, but with a different constant of proportionality. The observed logarithmic thickness dependence of radiation intensity at intermediate values of the thickness can be directly interpreted as a manifestation of the distortion of the electron Coulomb field resulting from a scattering event. The Landau-Pomeranchuk-Migdal effect is explored with high primary energy using materials with low nuclear charge (Z). Also, targets that should give rise to the claimed interference effect in high-energy radiation emission from a structured target of thin foils are investigated.
Elastic electron scattering by ethyl vinyl ether
NASA Astrophysics Data System (ADS)
Khakoo, M. A.; Hong, L.; Kim, B.; Winstead, C.; McKoy, V.
2010-02-01
We report measured and calculated results for elastic scattering of low-energy electrons by ethyl vinyl ether (ethoxyethene), a prototype system for studying indirect dissociative attachment processes that may play a role in DNA damage. The integral cross section displays the expected π* shape resonance. The agreement between the calculated and measured cross sections is generally good.
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.
Mayer, Nathan Samuel
2011-12-05
The Main Injector Neutrino Oscillation Search (MINOS) is a two detector, long baseline neutrino oscillation experiment. The MINOS near detector is an ironscintillator tracking/sampling calorimeter and has recorded the world’s largest data set of neutrino interactions in the 0-5 GeV region. This high statistics data set is used to make precision measurements of neutrino interaction cross-sections on iron. The Q^{2} dependence in charged current quasi-elastic (CCQE) scattering probes the axial and vector structure (form factor) of the nucleon/nuclear target, and nuclear effects in neutrino scattering. Presented here is a study of the MINOS Data that will introduce a method that improves the existing MINOS CCQE analysis. This analysis uses an additional CCQE dominated sub-sample from a different kinematic region to reduce correlations between fit parameters in the existing MINOS CCQE analysis. The measured value of the axial-vector mass is M^{QE} _{A} = 1.312^{+0.037} _{-0.038}(fit)^{+0.123} _{-0.265}(syst.) GeV.
Multiple electron scattering routines for PEREGRINE
White, J A
1999-08-23
The Monte Carlo electron scattering routines solve multiple elastic scatters in a condensed history approach. The Goudsmit-Saunderson scattering model is used and its implementation is taken from Kawrakow and Bielajew[l]. The subroutines produce an exit angle representing a likely scattering angle of a single incident electron after scattering elastically over a given step size. Two input parameters, {lambda} and {eta}, that depend on the atomic species and incident energy must first be specified. The mapping from species and energy to 77 and {lambda} already existed in the PEREGRINE code and was not redone or modified in any way. The software has been validated by comparisons to Moliere and Goudsmit-Saunderson models of D.W.O. Rogers[2]. As required by licensing considerations, no public domain or copyrighted software has been used in any phase of the preparation of any of these sub-routines or data files. Apart from needing to have {eta} and {lambda} specified through PEREGRINE, the code provided is completely self-contained. Everything is written in the FORTRAN 77 language to simplify inclusion in the existing PEREGRINE package.
Zamrun, Muhammad; Usman, Ida; Variani, Viska Inda; Kassim, Hasan Abu
2014-03-05
We study the heavy-ion collision at sub-barrier energies of {sub 16}O+{sub 144}Sm system using full order coupled-channels formalism. We especially investigate the sensitivity of fusion and quasi-elastic barrier distributions for this system on the coupling radius parameter. We found that the coupled-channels calculations of the fusion and the quasi-elastic barrier distributions are sensitive to the coupling radius for this reaction in contrast to the fusion and quasi-elastic cross section. Our study indicates that the larger coupling radius, i.e., r{sub coup}=1.20, is required by the experimental quasi-elastic barrier distribution. However, the experimental fusion barrier distribution compulsory the small value, i.e., r{sub coup}=1.06.
Nonlinear wave scattering and electron beam relaxation
NASA Technical Reports Server (NTRS)
Muschietti, L.; Dum, C. T.
1991-01-01
The role played by nonlinear scattering during the relaxation of a warm electron beam is investigated through a numerical code based on kinetic equations. The code encompasses the quasi-linear wave-electron interaction and wave-wave scattering off ion clouds. Ions with velocities 2 nu sub i (nu sub i being the ion thermal velocity) are found to be the most efficient for scattering the Langmuir waves off their polarization clouds. The transfer rate of the spectrum out of resonance with the beam is larger by a factor 3 compared to usual estimates. The changes produced in the dispersion relation by the presence of the beam electrons dramatically alter the characteristics of the secondary spectrum. In a late phase the classic condensate K of about 0 is depleted, with the formation of a new condensate in resonance with the flat-topped beam distribution, which follows from the fact that the mere presence of the beam electrons creates a minimum in the frequency-wave-number relation. For strong and slow beams, the predictions of the code are found to be in excellent agreement with the results of the particle simulation if a dispersion relation that includes the beam is used.
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.
Electron multiple, plural, and single scattering
Devaney, J.J.
1985-03-01
The angular distribution of a beam of electrons penetrating in infinite slab is studied with a view to providing simple accurate formulae for use in electron transport codes. We report success, but a highly disappointing success, for although the literature is vast, (over 150 papers), the experiments are limited, sparse, and often poorly described. The theory suffers from complexity, from incomplete, erroneous, or even absent comparisons with other theories and with experiment. Consequently, we cannot say with any assurance what the best theory is, nor to any great accuracy, especially in limiting cases, how good the theory we recommend is. We do give comparisons with the experiments known to us. With that caveat, we recommend the theory of Moliere as given by Bethe and by Hanson et al. Formulas are given. We expect accuracies of a few percent for multiple scattering. For the (in the cases studied) less dominant concomitant plural and single scattering the theory cannot do better than 10 to 30%. Because of the complexity of the functions, either series or tables must be employed. A bright spot in this somewhat gloomy state of affairs is the calculation of the 1/e width which can be done accurately (less than or equal to 2%) by a simple approximation due to Hanson et al. Using theories of Hanson et al. and variants thereof, an approximate Gaussian gives a good (7 to 20% error) simple description of the multiple scattering. Approximate single scattering formulas are also offered. 25 references, 6 tables.
Inelastic Scattering Of Electrons By Protons
DOE R&D Accomplishments Database
Cone, A. A.; Chen, K. W.; Dunning, J. R. Jr.; Hartwig, G.; Ramsey, N. F.; Walker, J. K.; Wilson, R.
1966-12-01
The inelastic scattering of electrons by protons has been measured at incident electron energies up to 5 BeV/c and momentum transfers q{sup 2}=4(BeV/c){sup 2}. Excitation of known nucleon resonances at M=1238, 1512, 1688 and possibly 1920 MeV have been observed. The calculations for the resonance at M=1238 MeV have been compared with calculations by Adler based on the dispersion theory of Chew, Goldberger, Low and Nambu. The agreement is good. Qualitative models are discussed for the other resonances.
Electron Scattering by Highly Polar Molecules.
NASA Astrophysics Data System (ADS)
Tino, Allen Joseph
I have investigated the scattering of 3.0 - 22. 5 eV electrons by CsBr, CsCl, Kl, RbBr, and RbCl. These measurements were taken using a high resolution crossed -beams apparatus recently designed and built at the New York University Atomic Beams Laboratory, and described in this thesis. This apparatus employs the molecular beam recoil technique, in which observation of the scattering is made on the recoiled molecule, rather than on the scattered electron. Unlike other scattering techniques, this allows one to perform absolute cross section measurements, requiring no normalization. These measurements, performed in the scattering -out mode, represent the absolute determination of an "effective cross section" for molecules recoiled out of the detector, Q' = (h/I(,e)) ((S-S')/S), where h is the height of the interaction region, I(,e) the electron current (e('-)/sec), and S' and S are the detector signals with the electron gun on and off respectively. This effective cross section can be related to a theoretical cross section, (sigma)((theta),E), by Q' = 2(pi) (INT) dv/v f(v) (INT) (GAMMA)((theta),E,v) (sigma)((theta),E) sin (theta) d(theta), where f(v) is the normalized velocity distribution in the molecular beam and (GAMMA)((theta),E,v) is the apparatus function which includes angular and energy resolution of the electron and molecular beams and the beam overlap geometry. The apparatus function is described in detail, enabling any theoretical cross section to be compared with the results of these experiments. I have compared these measurements with values for effective cross sections calculated using a rotating point-dipole model in the first Born approximation (RPDFBA), and an improved model proposed by Dickinson which combines the first Born approximation with classical perturbation theory. Based on these comparisons I conclude that, while our measurements approach either the RPDFBA or Dickinson results in certain cases, neither the RPDFBA or the Dickinson model
Proton radius from electron scattering data
NASA Astrophysics Data System (ADS)
Higinbotham, Douglas W.; Kabir, Al Amin; Lin, Vincent; Meekins, David; Norum, Blaine; Sawatzky, Brad
2016-05-01
Background: The proton charge radius extracted from recent muonic hydrogen Lamb shift measurements is significantly smaller than that extracted from atomic hydrogen and electron scattering measurements. The discrepancy has become known as the proton radius puzzle. Purpose: In an attempt to understand the discrepancy, we review high-precision electron scattering results from Mainz, Jefferson Lab, Saskatoon, and Stanford. Methods: We make use of stepwise regression techniques using the F test as well as the Akaike information criterion to systematically determine the predictive variables to use for a given set and range of electron scattering data as well as to provide multivariate error estimates. Results: Starting with the precision, low four-momentum transfer (Q2) data from Mainz (1980) and Saskatoon (1974), we find that a stepwise regression of the Maclaurin series using the F test as well as the Akaike information criterion justify using a linear extrapolation which yields a value for the proton radius that is consistent with the result obtained from muonic hydrogen measurements. Applying the same Maclaurin series and statistical criteria to the 2014 Rosenbluth results on GE from Mainz, we again find that the stepwise regression tends to favor a radius consistent with the muonic hydrogen radius but produces results that are extremely sensitive to the range of data included in the fit. Making use of the high-Q2 data on GE to select functions which extrapolate to high Q2, we find that a Padé (N =M =1 ) statistical model works remarkably well, as does a dipole function with a 0.84 fm radius, GE(Q2) =(1+Q2/0.66 GeV2) -2 . Conclusions: Rigorous applications of stepwise regression techniques and multivariate error estimates result in the extraction of a proton charge radius that is consistent with the muonic hydrogen result of 0.84 fm; either from linear extrapolation of the extremely-low-Q2 data or by use of the Padé approximant for extrapolation using a larger
Future of Electron Scattering and Diffraction
Hall, Ernest; Stemmer, Susanne; Zheng, Haimei; Zhu, Yimei; Maracas, George
2014-02-25
The ability to correlate the atomic- and nanoscale-structure of condensed matter with physical properties (e.g., mechanical, electrical, catalytic, and optical) and functionality forms the core of many disciplines. Directing and controlling materials at the quantum-, atomic-, and molecular-levels creates enormous challenges and opportunities across a wide spectrum of critical technologies, including those involving the generation and use of energy. The workshop identified next generation electron scattering and diffraction instruments that are uniquely positioned to address these grand challenges. The workshop participants identified four key areas where the next generation of such instrumentation would have major impact: A – Multidimensional Visualization of Real Materials B – Atomic-scale Molecular Processes C – Photonic Control of Emergence in Quantum Materials D – Evolving Interfaces, Nucleation, and Mass Transport Real materials are comprised of complex three-dimensional arrangements of atoms and defects that directly determine their potential for energy applications. Understanding real materials requires new capabilities for three-dimensional atomic scale tomography and spectroscopy of atomic and electronic structures with unprecedented sensitivity, and with simultaneous spatial and energy resolution. Many molecules are able to selectively and efficiently convert sunlight into other forms of energy, like heat and electric current, or store it in altered chemical bonds. Understanding and controlling such process at the atomic scale require unprecedented time resolution. One of the grand challenges in condensed matter physics is to understand, and ultimately control, emergent phenomena in novel quantum materials that necessitate developing a new generation of instruments that probe the interplay among spin, charge, orbital, and lattice degrees of freedom with intrinsic time- and length-scale resolutions. Molecules and soft matter require imaging and
Electron scattering and transport in liquid argon
Boyle, G. J.; Cocks, D. G.; White, R. D.; McEachran, R. P.
2015-04-21
The transport of excess electrons in liquid argon driven out of equilibrium by an applied electric field is revisited using a multi-term solution of Boltzmann’s equation together with ab initio liquid phase cross-sections calculated using the Dirac-Fock scattering equations. The calculation of liquid phase cross-sections extends previous treatments to consider multipole polarisabilities and a non-local treatment of exchange, while the accuracy of the electron-argon potential is validated through comparison of the calculated gas phase cross-sections with experiment. The results presented highlight the inadequacy of local treatments of exchange that are commonly used in liquid and cluster phase cross-section calculations. The multi-term Boltzmann equation framework accounting for coherent scattering enables the inclusion of the full anisotropy in the differential cross-section arising from the interaction and the structure factor, without an a priori assumption of quasi-isotropy in the velocity distribution function. The model, which contains no free parameters and accounts for both coherent scattering and liquid phase screening effects, was found to reproduce well the experimental drift velocities and characteristic energies.
SciNOvA: A Measurement of Neutrino-Nucleus Scattering in a Narrow-Band Beam
Paley, J.; Djurcic, Z.; Harris, D.; Tesarek, R.; Feldman, G.; Corwin, L.; Messier, M.D.; Mayer, N.; Musser, J.; Paley, J.; Tayloe, R.; /Indiana U. /Iowa State U. /Minnesota U. /South Carolina U. /Wichita State U. /William-Mary Coll.
2010-10-15
We propose to construct and deploy a fine-grained detector in the Fermilab NOvA 2 GeV narrow-band neutrino beam. In this beam, the detector can make unique contributions to the measurement of quasi-elastic scattering, neutral-current elastic scattering, neutral-current {pi}{sup 0} production, and enhance the NOvA measurements of electron neutrino appearance. To minimize cost and risks, the proposed detector is a copy of the SciBar detector originally built for the K2K long baseline experiment and used recently in the SciBooNE experiment.
New Results from MiniBooNE Charged-Current Quasi-Elastic Anti-Neutrino Data
Grange, Joseph
2011-07-01
MiniBooNE anti-neutrino charged-current quasi-elastic (CCQE) data is compared to model predictions. The main background of neutrino-induced events is examined first, where three independent techniques are employed. Results indicate the neutrino flux is consistent with a uniform reduction of {approx}20% relative to the largely uncertain prediction. After background subtraction, the Q{sup 2} shape of {bar v}{sub {mu}} CCQE events is consistent with the model parameter MA = 1.35 GeV determined from MiniBooNE v{sub {mu}} CCQE data, while the normalization is {approx} 20% high compared to the same prediction.
Electron-helium scattering in Debye plasmas
Zammit, Mark C.; Fursa, Dmitry V.; Bray, Igor; Janev, R. K.
2011-11-15
Electron-helium scattering in weakly coupled hot-dense (Debye) plasma has been investigated using the convergent close-coupling method. The Yukawa-type Debye-Hueckel potential has been used to describe plasma Coulomb screening effects. Benchmark results are presented for momentum transfer cross sections, excitation, ionization, and total cross sections for scattering from the ground and metastable states of helium. Calculations cover the entire energy range up to 1000 eV for the no screening case and various Debye lengths (5-100 a{sub 0}). We find that as the screening interaction increases, the excitation and total cross sections decrease, while the total ionization cross sections increase.
Advances in positron and electron scattering*
NASA Astrophysics Data System (ADS)
Limão-Vieira, Paulo; García, Gustavo; Krishnakumar, E.; Petrović, Zoran; Sullivan, James; Tanuma, Hajime
2016-10-01
The topical issue on Advances in Positron and Electron Scattering" combines contributions from POSMOL 2015 together with others devoted to celebrate the unprecedented scientific careers of our loyal colleagues and trusted friends Steve Buckman (Australian National University, Australia) and Michael Allan (University of Fribourg, Switzerland) on the occasion of their retirements. POSMOL 2015, the XVIII International Workshop on Low-Energy Positron and Positronium Physics and the XIX International Symposium on Electron-Molecule Collisions and Swarms, was held at Universidade NOVA de Lisboa, Lisboa, Portugal, from 17-20 July 2015. The international workshop and symposium allowed to achieve a very privileged forum of sharing and developing our scientific expertise on current aspects of positron, positronium and antiproton interactions with electrons, atoms, molecules and solid surfaces, and related topics, as well as electron interactions with molecules in both gaseous and condensed phases. Particular topics include studies of electron interactions with biomolecules, electron induced surface chemistry and the study of plasma processes. Recent developments in the study of swarms are also fully addressed.
P-Wave Electron-Hydrogen Scattering
NASA Technical Reports Server (NTRS)
Bhtia, Anand
2012-01-01
A variational wave function incorporating short range correlations via Hylleraas type functions plus long-range polarization terms of the polarized orbital type but with smooth cut-off factors has been used to calculate P-wave phase shifts for electron-hydrogen scattering. This approach gives the direct r(exp -4) potential and a non-local optical potential which is definite. The resulting phase shifts have rigorous lower bounds and the convergence is much faster than those obtained without the modification of the target function. Final results will be presented at the conference.
Scattering of electrons from neon atoms
NASA Technical Reports Server (NTRS)
Dasgupta, A.; Bhatia, A. K.
1984-01-01
Scattering of electrons from neon atoms is investigated by the polarized-orbital method. The perturbed orbitals calculated with use of the Sternheimer approximation lead to the polarizability 2.803 a(0)-cube in fairly good agreement with the experimental value 2.66 a(0)-cube. Phase shifts for various partial waves are calculated in the exchange, exchange-adiabatic, and polarized-orbital approximations. They are compared with the previous results. The calculated elastic differential, total, and momentum-transfer cross sections are compared with the experimental results. The polarized-orbital approximation yields results which show general improvement over the exchange-adiabatic approximation.
Inelastic electron scattering from a moving nucleon
Kuhn, S.E.; Griffioen, K.
1994-04-01
The authors propose to measure inelastically scattered electrons in coincidence with spectator protons emitted backwards relative to the virtual photon direction in the reaction d(e, e{prime}p{sub s})X. In a simple spectator model, the backward proton has equal and opposite momentum to the neutron before it is struck, allowing the authors to study the dependence on kinematics and off-shell behaviour of the electron-nucleon inelastic cross section. If the photon couples to a quark in a 6-quark bag, a different dependence of the cross section on the kinematic variables (x, Q{sup 2}, and p{sub s}) can be observed. This proposed experiment requires large acceptance and beam energies above 6 GeV. It is ideally suited for the CEBAF Large Acceptance Spectrometer (CLAS).
Hurtado Anampa, Kenyi Paolo
2016-01-01
The MINERvA Experiment (Main Injector Experiment v ₋ A interaction) [1] is a highly segmented detector of neutrinos, able to record events with high precision (over than thirteen million event in a four year run), using the NuMI Beam (Neutrino Main Injector) at the Fermi National Accelerator Laboratory [2]. This thesis presents a measurement of the Charged Current Quasi-Elastic Like1 vμ interaction on polystyrene scintillator (CH) in the MINERvA experiment with neutrino energies between 1.5 and 10 GeV. We use data taken between2 March 2010 and April 2012. The interactions were selected by requiring a negative muon, a reconstructed and identified proton, no michel electrons in the final state (in order to get rid of soft pions decaying) and a low calorimetric recoil energy away from the interaction vertex. The analysis is performed on 66,214 quasi-elastic like event candidates in the detectors tracker region with an estimated purity of 74%. The final measurement reported is a double differential cross sections in terms of the muon longitudinal and transversal momentum observables.
Imaging ultrafast electronic motion by x-ray scattering
NASA Astrophysics Data System (ADS)
Dixit, Gopal; Santra, Robin
2014-04-01
Time-resolved ultrafast x-ray scattering is an emerging approach to probe the temporally evolving electronic charge distribution in real-space and in real-time. In this contribution, time-resolved ultrafast x-ray scattering from an electronic wave packet is presented. It is shown that the spatial and temporal correlations are imprinted in the scattering patterns, obtained by ultrafast x-ray scattering from an electronic wave packet, which deviate drastically from the notion that the instantaneous electronic density is the key quantity being probed. Furthermore, a detailed analysis of ultrafast x-ray scattering from a sample containing a mixture of non-stationary and stationary electrons along with the role of scattering interference between a non-stationary and several stationary electrons to the total scattering signal is discussed.
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.
Future studies on electron scattering; a renaissance
NASA Astrophysics Data System (ADS)
Mason, Nigel J.
2014-12-01
2014 is the centenary of the first announcement of the Franck-Hertz experiment [1], now regarded as one of the pivotal experiments of modern physics. The Franck-Hertz experiment is widely regarded as an experiment that provided validation of the Bohr theory of atomic structure, itself only published in 2013, however it should also be viewed as the first quantitative experiment in electron scattering and the birth of scientific study of atomic and molecular phenomena by collisions. Today we recognize that electron-atom and electron- molecule collisions are prevalent across nature, describing disparate phenomena whilst the exploitation of such collisions underpins many of the technologies upon which modern society relies. The centenary of the Franck-Hertz experiment is thus a suitable opportunity to review both our current knowledge of electron interactions and to consider the directions of future research. In this article I therefore aim to both review our current state of knowledge and look forward, proposing that recent advances are providing something of a renaissance to the field and are vital for emerging technologies as well as answering some of the greatest scientific challenges of the 21st century.
Quark-Hadron Duality in Electron Scattering
Wally Melnitchouk; Rolf Ent; Cynthia Keppel
2004-08-01
The duality between partonic and hadronic descriptions of physical phenomena is one of the most remarkable features of strong interaction physics. A classic example of this is in electron-nucleon scattering, in which low-energy cross sections, when averaged over appropriate energy intervals, are found to exhibit the scaling behavior expected from perturbative QCD. We present a comprehensive review of data on structure functions in the resonance region, from which the global and local aspects of duality are quantified, including its flavor, spin and nuclear medium dependence. To interpret the experimental findings, we discuss various theoretical approaches which have been developed to understand the microscopic origins of quark-hadron duality in QCD. Examples from other reactions are used to place duality in a broader context, and future experimental and theoretical challenges are identified.
A Measurement of the Exclusive 3He(e,e'p) Reaction Below the Quasi-Elastic Peak
Kozlov, A; Sarty, A J; Aniol, K A; Bartsch, P; Baumann, D; Bertozzi, W; Bohinc, K; Bahm, R; Chen, J P; Dale, D; Dennis, L; Derber, S; Ding, M; Distler, M O; Dragovitsch, P; Ewald, I; Fissum, K G; Friedrich, J; Friedrich, J M; Geiges, R; Gilad, S; Jennewein, P; Kahrau, M; Kohl, M; Krygier, K W; Liesenfeld, A; Margaziotis, D J; Merkel, H; Merle, P; Moeller, U; Neuhausen, R; Pospischil, T; Potokar, M; Riccardi, G; Rochoe, R; Rosner, G; Rowntree, D; Schmieden, H; irca, S; Templon, J A; Thompson, M N; Wagner, A; Walcher, Th; Weis, M; Zhao, J; Zhou, Z -L; Golak, J; Glaeckle, W; Wita, H
2004-09-01
New, high-precision measurements of the 3He(e,e'p) reaction using the A1 collaboration spectrometers at the Mainz microtron MAMI are presented. These were performed in antiparallel kinematics at energy transfers below the quasi-elastic peak, and at a central momentum transfer of 685 MeV/c. Cross sections and distorted momentum distributions were extracted and compared to theoretical predictions and existing data. The longitudinal and transverse behavior of the cross section was also studied. Sizable differences in the cross-section behavior from theoretical predictions based on Plane Wave Impulse Approximation were observed in both the two- and three-body breakup channels. Full Faddeev-type calculations account for some of the observed excess cross section, but significant differences remain.
Fingerprints of Multiple Electron Scatterings in Single-Layer Graphene
Jung, Minbok; Sohn, So-Dam; Park, Jonghyun; Lee, Keun-U; Shin, Hyung-Joon
2016-01-01
The electrons in graphene exhibit unusual behaviours, which can be described by massless Dirac quasiparticles. Understanding electron scattering in graphene has been of significant importance for its future application in electronic devices because electron scattering determines electrical properties such as resistivity and electron transport. There are two types of electron scatterings in graphene: intervalley scattering and intravalley scattering. In single-layer graphene, to date, it has been difficult to observe intravalley scattering because of the suppression of backscattering resulting from the chiral nature of the electrons in graphene. Here, we report the multiple electron scattering behaviours in single-layer graphene on a metallic substrate. By applying one- and two-dimensional Fourier transforms to maps of the local density of states, we can distinguish individual scattering processes from complex interference patterns. These techniques enable us to provide direct evidence of intravalley scattering, revealing a linear dispersion relation with a Fermi velocity of ~7.4 × 105 m/s. PMID:26936521
NASA Astrophysics Data System (ADS)
Żywicka, B.; Możejko, P.
2013-10-01
Cross section for electron impact ionization of carboplatin, C6H12N2O4Pt, and oxaliplatin, C8H14N2O4Pt, have been calculated within binary-encounter-Bethe model for energies from the ionization threshold up to 5000 eV. Cross section for elastic electron scattering from carboplatin and oxaliplatin molecules have also been derived using independent atom method (IAM) and additivity rule for collision energies ranging from 50 eV to 3000 eV. Obtained cross sections have been compared with relevant cross sections for cisplatin molecules.
Nonasymptotic analysis of relativistic electron scattering in the Coulomb field
NASA Astrophysics Data System (ADS)
Feranchuk, I. D.; Skoromnik, O. D.
2010-11-01
It is shown that the conventional Born series for relativistic electron scattering in the Coulomb field cannot be used for calculating the scattering characteristics. The differential cross section at small scattering angles is found on the basis of the Furry-Sommerfeld-Maue solution of the Dirac equation. Propagation of the electron wave packet is considered in order to separate the incident and scattered fluxes. It is shown that the total scattering cross section proves to be finite but depends on the distance r between the scattering center and the observation point. It is also shown that the polarization characteristics of the scattered beam are changed due to the long-range character of the Coulomb potential. The results can be important because Coulomb scattering is often used for normalization of experimental data in high-energy physics.
Electron Scattering Studies in MAGNESIUM-24.
NASA Astrophysics Data System (ADS)
Zarek, Chaim Harry
1981-11-01
Experimental and theoretical results based on high resolution electron scattering experiments carried out in ('24)Mg are reported. Experiments were carried out at the MIT-Bates Linear Accelerator with beam energies in the range of 98 MeV to 285 MeV corresponding to a momentum transfer range of 1.0 fm('-1) to 2.2 fm('-1). Three themes are developed in the present work. The low-lying positive parity collective states were studied and compared with the predictions of two large scale calculations: the empirical interaction Shell Model of Chung and Wildenthal and the Projected Hartree-Fock Model (PHF) of Cusson and Lee. The experiments showed that the first 4+ state has an anomalous form factor. Though the Shell Model was capable of predicting the form factors for other positive parity states, it failed for the first 4+ state. The PHF successfully predicted the form factors for all the states studied. The Shell Model required an "effective charge" normalization to reproduce the transition strengths. The PHF did not require such parametrization and thus provides a more fundamental description of nuclear excited states. New features were found that were strongly excited in electron scattering. These states occur at high excitation energy though below the neutron emission threshold. The states were found to have simple particle-hole configurations on the basis of Open Shell Random Phase Approximation calculations. States identified were; 6- T = 1 (15.13 MeV), 5- T = 1, (13.94) MeV and a tentative 4- T = 1 (15.54 MeV). Negative parity states identified with collective bands were studied and compared to the OSRPA. The 3- states of the K = 0- and K = 3- bands were shown to have entirely different structures both experimentally and on the basis of the OSRPA calculations. A 5- state was identified with the K = 0- band. The OSRPA has been capable of describing the negative parity particle-hole states in ('24)Mg. This has been the first example of a comprehensive OSRPA
Electron Scattering by biomass molecular fragments
NASA Astrophysics Data System (ADS)
Lima, Marco
2015-09-01
The replacement of fossil fuels by biofuels from renewable sources may not be a definite answer for greenhouse gas emissions problems, but it is a good step towards a sustainable energy strategy. Few per cent of ethanol is being mixed to gasoline in many countries and in some of them, like Brazil, a very aggressive program has been developed, using, in large scale, flex fuel engines that can run with any mixture of gasoline and ethanol, including 100% ethanol. Important points are how to produce ethanol in a sustainable way and with which technology? Biomass is a good candidate to enhance the first generation (produced from Corn in USA and from sugarcane in Brazil) production towards the so-called second-generation ethanol, since it has cellulose and hemicellulose as source of sugars. In order to liberate these sugars for fermentation, it is important to learn how to separate the main components. Chemical routes (acid treatment) and biological routes (enzymatic hydrolysis) are combined and used for these purposes. Atmospheric plasmas can be useful for attacking the biomass in a controlled manner and low energy electrons may have an important role in the process. Recently, we have been studying the interaction of electrons with lignin subunits (phenol, guaiacol, p-coumaryl alcohol), cellulose components, β-D-glucose and cellobiose (β(1-4) linked glucose dimer) and hemicellulose components [2] (β-D-xylose). We also obtained results for the amylose subunits α-D-glucose and maltose (α(1-4) linked glucose dimer). Altogether, the resonance spectra of lignin, cellulose and hemicellulose components establish a physical-chemical basis for electron-induced biomass pretreatment that could be applied to biofuel production. In order to describe a more realistic system (where molecules are ``wet''), we have obtained the shape resonance spectra of phenol-water clusters, as obtained previously from elastic electron scattering calculations. Our results, obtained in a simple
Electron Elastic-Scattering Cross-Section Database
National Institute of Standards and Technology Data Gateway
SRD 64 NIST Electron Elastic-Scattering Cross-Section Database (PC database, no charge) This database provides values of differential elastic-scattering cross sections, corresponding total elastic-scattering cross sections, phase shifts, and transport cross sections for elements with atomic numbers from 1 to 96 and for electron energies between 50 eV and 20,000 eV (in steps of 1 eV).
Polarized electron scattering, new physics and dark parity violation
Marciano, William J.
2013-11-07
'New Physics' sensitivities of polarized electron scattering asymmetries, atomic parity violation, m{sub W} and sin{sup 2} θ{sub W} (Z pole measurements) are compared. The utility of low Q{sup 2} polarized electron scattering for probing parity violating 'dark boson' effects is discussed. A possible determination of the weak charge Q{sub w}({sup 12}C) to about ±0.3% via elastic e-Carbon scattering is advocated.
Variational calculation of electron elastic scattering by atomic helium
NASA Astrophysics Data System (ADS)
Chernek, P. J.
1982-12-01
The elastic-scattering of electrons from atomic helium in the ground state is investigated. It is shown that for low energy incident electrons the scattering problem reduced to solving an ordinary integro-differential equation for the scattering wave-function. A method is discussed to obtain approximate solutions to the integro-differential equation by variational principles. The extremum condition of the variational method is formulated into a general N x N matrix equation which reduces to a 2 x 2 eigen-value matrix problem for the phase-shift of the scattering electron. An algorithm is presented to obtain the collisional cross-section for elastic scattering as a function of incident electron energy.
Precision electroweak studies using parity violation in electron scattering
Paschke, Kent D,
2013-11-01
The nature of new neutral-current interactions can be revealed at the low-energy precision frontier, where studies of parity-violation in electron scattering will complement the energy-frontier studies at the LHC. Measurements of the parity-violating observable APV - the cross-section asymmetry in the scattering of longitudinally polarized electrons from an unpolarized target - are sensitive to possible contact interactions from new physics at multi-TeV mass scales. The 12 GeV upgrade at JLab and a new, high-intensity beam at Mainz offer opportunities for significant improvements in measurements of electron-electron and electron-quark parity-violating interactions.
A new dispersion relation for electron-atom scattering
NASA Technical Reports Server (NTRS)
Temkin, A.; Bhatia, A. K.; Kim, Y. S.
1986-01-01
A new forward-angle dispersion relation (DR) for electron-atom scattering is proposed. It is based on a subtraction of the static-exchange amplitude from the exact elastic scattering amplitude. Arguments are advanced to explain why this should obviate the difficulties associated with the Gerjuoy-Krall DR, specifically with the exchange Born amplitude. The new DR is tested in the elastic energy range for e-H scattering and compared with the GKDR.
Watabe, Masaki
2010-05-01
MINOS (Main Injector Neutrino Oscillation Search) experiment has been designed to search for a change in the avor composition of a beam of muon neutrinos as they travel between the Near Detector at Fermi National Accelerator Laboratory and the Far Detector in the Soudan mine in Minnesota, 735 km from the target. The MINOS oscillation analysis is mainly performed with the charged current (CC) events and sensitive to constrain high- Δm^{2} values. However, the quasi-elastic (QEL) charged current interaction is dominant in the energy region important to access low- m^{2} values. For further improvement, the QEL oscillation analysis is performed in this dissertation. A data sample based on a total of 2.50 x 10^{20} POT is used for this analysis. In summary, 55 QEL-like events are observed at the Far detector while 87.06 ± 13.17 (syst:) events are expected with null oscillation hypothesis. These data are consistent with disappearance via oscillation with m^{2} = 2:10 0.37 (stat:) ± 0.24 (syst:) eV^{2} and the maximal mixing angle.
Generalized pseudopotential approach for electron-atom scattering.
NASA Technical Reports Server (NTRS)
Zarlingo, D. G.; Ishihara, T.; Poe, R. T.
1972-01-01
A generalized many-electron pseudopotential approach is presented for electron-neutral-atom scattering problems. A calculation based on this formulation is carried out for the singlet s-wave and p-wave electron-hydrogen phase shifts with excellent results. We compare the method with other approaches as well as discuss its applications for inelastic and rearrangement collision problems.
Effect of multiple scattering on Cerenkov radiation from energetic electrons
Zheng Jian
2013-01-15
Cerenkov radiation can be used as a diagnostic tool to study energetic electrons generated in ultra-intense laser matter interactions. However, electrons suffer scattering with nuclei as they move in a medium. In this article, we theoretically study the effect of multiple scattering on Cerenkov radiation, and obtain analytical formulas under some circumstances. The results show that when the speed of an energetic electron is not close to the light speed in the medium, Cerenkov radiation is just slightly decreased due to multiple scattering. In the case that the electron speed is very close to the light speed in the medium, the effect of multiple scattering becomes significant, and the radiation is dominated by bremsstrahlung.
Hottes, M. Muench, F.; Rauber, M.; Stegmann, C.; Ensinger, W.; Dassinger, F.; Schlaak, H. F.
2015-02-02
In this Letter, we describe the electrodeposition of capped, micro-sized Pt nanowire arrays in ion-track etched polymer templates and measure their collective mechanical response to an external force. By using an aperture mask during the irradiation process, it was possible to restrict the creation of pores in the templates to defined areas, allowing the fabrication of small nanowire arrays in different geometries and sizes. The simultaneous and highly reliable formation of many nanowire arrays was achieved using a pulsed electrodeposition technique. After deposition, the polymer matrix was removed using a gentle, dry oxygen plasma treatment, resulting in an excellent preservation of the array nanostructure as confirmed by scanning electron microscopy. A force measuring station was set up to perform mechanical characterization series on free-standing arrays. The nanowire arrays show a high robustness and respond sensitively to the applied force, making them attractive as spring elements in miniaturized inertial sensors, for example.
Multiple scattering of electrons in the reflex triode
Creedon, J.M. )
1990-12-01
Analytical theories and Monte Carlo calculations are used to treat the scattering and energy loss of electrons in the anode of a reflex triode. The solution of this scattering problem is combined with the equations for particle flow in vacuum to give a quantitative theory of triode operation. It is now possible to calculate several important properties of this device. These include the operating voltage in the constant voltage mode, the ratio of ion-to-electron current and the ion transit time.
NASA Astrophysics Data System (ADS)
Xu, Chun Kai; Liu, Wen Jie; Zhang, Pan Ke; Li, Meng; Zhang, Han Jun; Xu, Ke Zun; Luo, Yi; Chen, Xiang Jun
2014-10-01
Electron energy-loss spectroscopy is a powerful tool for identifying the chemical composition of materials. It relies mostly on the measurement of inelastic electrons, which carry specific atomic or molecular information. Inelastic electron scattering, however, has a very low intensity, often orders of magnitude weaker than that of elastically scattered electrons. Here, we report the observation of enhanced inelastic electron scattering from silver nanostructures, the intensity of which can reach up to 60% of its elastic counterpart. A home-made scanning probe electron energy-loss spectrometer was used to produce highly localized plasmonic excitations, significantly enhancing the strength of the local electric field of silver nanostructures. The intensity of inelastic electron scattering was found to increase nonlinearly with respect to the electric field generated by the tip-sample bias, providing direct evidence of nonlinear electron scattering processes.
Parity Violation in Forward Angle Elastic Electron Proton Scattering
Krishna Kumar
1999-07-01
HAPPEX is a new experiment to probe the strange structure of the nucleon with parity violating electron scattering. We describe the physics motivation, provide an experimental overview and report on the results from the first data run. The asymmetry for the elastic scattering of 3.3 GeV electrons off target protons at a scattering angle of 12.5 degrees was measured to a precision of 15% of itself. The contribution from strange quark form factors was found to be zero within the experimental and theoretical uncertainties.
Effects of Auger electron elastic scattering in quantitative AES
NASA Astrophysics Data System (ADS)
Jablonski, Aleksander
1987-09-01
The Monte Carlo algorithm was developed for simulating the trajectories of electrons elastically scattered in the solid. The distribution of scattering angles was determined using the partial wave expansion method. This algorithm was used to establish the influence of Auger electron elastic collisions on the results of quantitative AES analysis. The calculations were performed for the most pronounced KLL, L 3 MM and M 5NN Auger transitions. It turned out that due to the elastic collisions the Auger electron signal is decreased by up to 10%. The corresponding decreased of the escape depth of Auger electrons reaches 30% as compared with the value derived from the inelastic mean free path. The values of the inelastic mean free path resulting from the overalyer method may be strongly affected by elastic scattering of Auger electrons.
Path integral approach to electron scattering in classical electromagnetic potential
NASA Astrophysics Data System (ADS)
Chuang, Xu; Feng, Feng; Ying-Jun, Li
2016-05-01
As is known to all, the electron scattering in classical electromagnetic potential is one of the most widespread applications of quantum theory. Nevertheless, many discussions about electron scattering are based upon single-particle Schrodinger equation or Dirac equation in quantum mechanics rather than the method of quantum field theory. In this paper, by using the path integral approach of quantum field theory, we perturbatively evaluate the scattering amplitude up to the second order for the electron scattering by the classical electromagnetic potential. The results we derive are convenient to apply to all sorts of potential forms. Furthermore, by means of the obtained results, we give explicit calculations for the one-dimensional electric potential. Project supported by the National Natural Science Foundation of China (Grant Nos. 11374360, 11405266, and 11505285) and the National Basic Research Program of China (Grant No. 2013CBA01504).
Surface roughness scattering of electrons in bulk mosfets
Zuverink, Amanda Renee
2015-11-01
Surface-roughness scattering of electrons at the Si-SiO_{2} interface is a very important consideration when analyzing Si metal-oxide-semiconductor field-effect transistors (MOSFETs). Scattering reduces the mobility of the electrons and degrades the device performance. 250-nm and 50-nm bulk MOSFETs were simulated with varying device parameters and mesh sizes in order to compare the effects of surface-roughness scattering in multiple devices. The simulation framework includes the ensemble Monte Carlo method used to solve the Boltzmann transport equation coupled with a successive over-relaxation method used to solve the two-dimensional Poisson's equation. Four methods for simulating the surface-roughness scattering of electrons were implemented on both devices and compared: the constant specularity parameter, the momentum-dependent specularity parameter, and the real-space-roughness method with both uniform and varying electric fields. The specularity parameter is the probability of an electron scattering speculariy from a rough surface. It can be chosen as a constant, characterizing partially diffuse scattering of all electrons from the surface the same way, or it can be momentum dependent, where the size of rms roughness and the normal component of the electron wave number determine the probability of electron-momentum randomization. The real-space rough surface method uses the rms roughness height and correlation length of an actual MOSFET to simulate a rough interface. Due to their charge, electrons scatter from the electric field and not directly from the surface. If the electric field is kept uniform, the electrons do not perceive the roughness and scatter as if from a at surface. However, if the field is allowed to vary, the electrons scatter from the varying electric field as they would in a MOSFET. These methods were implemented for both the 50-nm and 250-nm MOSFETs, and using the rms roughness heights and correlation lengths for real devices. The
Elastic scattering of electrons from Rb, Cs and Fr atoms
NASA Astrophysics Data System (ADS)
Gangwar, R. K.; Tripathi, A. N.; Sharma, L.; Srivastava, R.
2010-04-01
Differential, integrated elastic, momentum-transfer and total cross sections as well as differential S, T and U spin parameters for scattering of electrons from rubidium, caesium and francium atoms in the incident energy range up to 300 eV are calculated using a relativistic Dirac equation. The projectile electron-target atom interaction is represented by both real and complex parameter-free optical potentials for obtaining the solution of a Dirac equation for scattered electrons. The Dirac-Fock wavefunctions have been used to represent the Rb, Cs and Fr target atoms. The results of differential cross sections and spin asymmetry parameter S for e-Rb and e-Cs have been compared with the available experimental and theoretical results. Detailed results are reported for the elastic scattering of electrons from the ground states of a francium atom for the first time in the wide range of incident electron energies. The results of electron-Fr elastic scattering show the similar features to those obtained in the case of e-Rb and e-Cs elastic scattering.
Mettille, M.J.; Hester, R.D.
1988-05-01
Characterization of polymer molecular weight is an extremely important aspect of polymer research, and a vast number of analytical techniques has been used to determine molecular weights. One method is dynamic light scattering (DLS). DLS is also referred to as photon correlation spectroscopy (PCS), quasi-elastic light scattering (QLS), and may other appellations. The phenomenon that gives rise to the DLS technique was first observed in the early 1930's. In the mid 1950's, measurement techniques similar to modern dynamic light scattering were developed. Two major technical developments have greatly enhanced the use of DLS. The first was the development of the laser. This provided a light source with very high intensity at a single frequency. Also, major advances in digital electronics have allowed better data acquisition and faster data analysis than were previously available.
Electron scattering at NIKHEF with polarized beam and targets
M. Ferro-Luzzi; Ricardo Alarcon; N. van Bakel; T. Bauer; D. Boersma; Tancredi Botto; Maurice Bouwhuis; J.F.J. van den Brand; L. van Buuren; H.-J. Bulten; Rolf Ent; D. Geurts; Mark Harvey; Peter Heimberg; Douglas Higinbotham; Cornelis De Jager; S. Klous; Hauke Kolster; Julia Lange; B. Militsyn; Blaine Norum; I. Passchier; H.R. Poolman; M.C. Simani; E. Six; J.J.M. Steijger; D. Szczerba; H. de Vries; Zilu Zhou
1998-08-01
We present the Internal Target Facility of the NIKHEF 900 MeV polarized electron storage ring. We give some results which illustrate the presently unique opportunity offered by this facility to study the spin structure of the nucleon, 2-body and 3-body system by the measurement of spin-dependent electron scattering observables.
Mott scattering of polarized electrons in a strong laser field
Manaut, B.; Taj, S.; Attaourti, Y.
2005-04-01
We present analytical and numerical results of the relativistic calculation of the transition matrix element S{sub fi} and differential cross sections for Mott scattering of initially polarized Dirac particles (electrons) in the presence of a strong laser field with linear polarization. We use exact Dirac-Volkov wave functions to describe the dressed electrons and the collision process is treated in the first Born approximation. The influence of the laser field on the degree of polarization of the scattered electron is reported.
Electronic Structure of Dense Plasmas by X-Ray Scattering
Gregori, G; Glenzer, S H; Rogers, F J; Pollaine, S M; Froula, D H; Blancard, C; Faussurier, G; Renaudin, P; Kuhlbrodt, S; Redmer, R; Landen, O L
2003-10-07
We present an improved analytical expression for the x-ray dynamic structure factor from a dense plasma which includes the effects of weakly bound electrons. This result can be applied to describe scattering from low to moderate Z plasmas, and it covers the entire range of plasma conditions that can be found in inertial confinement fusion experiments, from ideal to degenerate up to moderately coupled systems. We use our theory to interpret x-ray scattering experiments from solid density carbon plasma and to extract accurate measurements of electron temperature, electron density and charge state. We use our experimental results to validate various equation-of-state models for carbon plasmas.
Electron-H P-Wave Elastic Scattering
NASA Technical Reports Server (NTRS)
Bhatia, A. K.
2004-01-01
In previous papers [Bhatia and Temkin, Phys. Rev. A 64, 032709-1 (2001), Phys. Rev. A 66, 064702 (2002)], electron-hydrogen and electron-He(+) S-wave scattering phase shifts were calculated using the optical potential approach. This method is now extended to the singlet and triplet electron-H P-wave scattering in the elastic region. Phase shifts are calculated using Hylleraas-type correlation functions with up to 220 terms. Results are rigorous lower bounds to the exact phase shifts and they are compared to phase shifts obtained from previous calculations.
Neutrino-electron scattering. Progress report
White, D.H.
1982-01-01
We present here a progress report on an experiment to measure the cross section for nu/sub ..mu../e scattering at the Brookhaven AGS. A wide band focussing horn is used with a neutrino beam energy centered at 1.5 GeV. We have in hand measurements with nu/sub ..mu../ and anti nu/sub ..mu../ beams but we present preliminary data on the nu/sub ..mu../ beam running only. We also measure the reactions: nu/sub ..mu../ + n ..-->.. ..mu../sup -/ + p and nu/sub e/ + n ..-->.. e/sup -/ + p which will be used in normalization and in background estimation.
Alonso, M. P.; Figueiredo, A. C. A.; Berni, L. A.; Machida, M.
2010-10-15
We present the first simultaneous measurements of the Thomson scattering and electron cyclotron emission radiometer diagnostics performed at TCABR tokamak with Alfven wave heating. The Thomson scattering diagnostic is an upgraded version of the one previously installed at the ISTTOK tokamak, while the electron cyclotron emission radiometer employs a heterodyne sweeping radiometer. For purely Ohmic discharges, the electron temperature measurements from both diagnostics are in good agreement. Additional Alfven wave heating does not affect the capability of the Thomson scattering diagnostic to measure the instantaneous electron temperature, whereas measurements from the electron cyclotron emission radiometer become underestimates of the actual temperature values.
Complete Solution of Electronic Excitation and Ionization in Electron-Hydrogen Molecule Scattering.
Zammit, Mark C; Savage, Jeremy S; Fursa, Dmitry V; Bray, Igor
2016-06-10
The convergent close-coupling method has been used to solve the electron-hydrogen molecule scattering problem in the fixed-nuclei approximation. Excellent agreement with experiment is found for the grand total, elastic, electronic-excitation, and total ionization cross sections from the very low to the very high energies. This shows that for the electronic degrees of freedom the method provides a complete treatment of electron scattering on molecules as it does for atoms. PMID:27341229
Complete Solution of Electronic Excitation and Ionization in Electron-Hydrogen Molecule Scattering
NASA Astrophysics Data System (ADS)
Zammit, Mark C.; Savage, Jeremy S.; Fursa, Dmitry V.; Bray, Igor
2016-06-01
The convergent close-coupling method has been used to solve the electron-hydrogen molecule scattering problem in the fixed-nuclei approximation. Excellent agreement with experiment is found for the grand total, elastic, electronic-excitation, and total ionization cross sections from the very low to the very high energies. This shows that for the electronic degrees of freedom the method provides a complete treatment of electron scattering on molecules as it does for atoms.
Complete solution of electronic excitation and ionization in electron-hydrogen molecule scattering
Zammit, Mark C.; Savage, Jeremy S.; Fursa, Dmitry V.; Bray, Igor
2016-06-08
The convergent close-coupling method has been used to solve the electron-hydrogen molecule scattering problem in the fixed-nuclei approximation. Excellent agreement with experiment is found for the grand total, elastic, electronic-excitation, and total ionization cross sections from the very low to the very high energies. This shows that for the electronic degrees of freedom the method provides a complete treatment of electron scattering on molecules as it does for atoms.
Energy distribution of elastically scattered electrons from double layer samples
NASA Astrophysics Data System (ADS)
Tőkési, K.; Varga, D.
2016-02-01
We present a theoretical description of the spectra of electrons elastically scattered from thin double layered Au-C samples. The analysis is based on the Monte Carlo simulation of the recoil and Doppler effects in reflection and transmission geometries of the scattering at a fixed angle of 44.3 ° and a primary energy of 40 keV. The relativistic correction is taken into account. Besides the experimentally measurable energy distributions the simulations give many partial distributions separately, depending on the number of elastic scatterings (single, and multiple scatterings of different types). Furthermore, we present detailed analytical calculations for the main parameters of the single scattering, taking into account both the ideal scattering geometry, i.e. infinitesimally small angular range, and the effect of the real, finite angular range used in the measurements. We show our results for intensity ratios, peak shifts and broadenings for four cases of measurement geometries and layer thicknesses. While in the peak intensity ratios of gold and carbon for transmission geometries were found to be in good agreement with the results of the single scattering model, especially large deviations were obtained in reflection geometries. The separation of the peaks, depending on the geometry and the thickness, generally smaller, and the peak width generally larger than it can be expected from the nominal values of the primary energy, scattering angle, and mean kinetic energy of the atoms. We also show that the peaks are asymmetric even for the case of the single scattering due to the finite solid angle. Finally, we present a qualitative comparison with the experimental data. We find our resulting energy distribution of elastically scattered electrons to be in good agreement with recent measurements.
Low-energy scattering of electrons and positrons in liquids
NASA Technical Reports Server (NTRS)
Schrader, D. M.
1990-01-01
The scattering of low energy electrons and positrons is described for the liquid phase and compared and contrasted with that for the gas phase. Similarities as well as differences are noted. The loci of scattering sites, called spurs in the liquid phase, are considered in detail. In particular, their temporal and spatial evolution is considered from the point of view of scattering. Two emphases are made: one upon the stochastic calculation of the distribution of distances required for slowing down to thermal velocities, and the other upon the calculation of cross sections for energy loss by means of quantum mechanics.
Scattering of electrons by vacuum fluctuations of plasma waves
NASA Astrophysics Data System (ADS)
Veklenko, B. A.; Afanas'ev, V. P.; Lubenchenko, A. V.
2014-04-01
Interaction between a probe electron beam and longitudinal electromagnetic oscillations of the Fermi plasma in metals (plasmons) is investigated by the methods of quantum electrodynamics. The quantum description of plasmons allows one to construct a consistent theory of the scattering process and point out the applicability limits of the existing semiclassical theories. The quantum description of plasmons leads to the concept of electromagnetic vacuum of longitudinal waves, which is the subject of the present study. The vacuum of longitudinal waves significantly deforms the shape of plasma dielectric permittivity, thus leading to the broadening of Langmuir peaks of scattered electrons, which has so far resisted theoretical analysis. The presence of the electromagnetic vacuum of longitudinal plasma waves has a considerable effect on the integral scattering probability of electrons by plasmons.
Electron- and positron-proton elastic scattering in CLAS
L.B. Weinstein
2009-08-01
There is a significant disagreement between measurements of the proton electric form factor, G{sup p}{sub E}, using Rosenbluth separations and polarization transfer. This disagreement, if not explained, could pose a fundamental challenge to our understanding of electron scattering or proton structure. Two-photon exchange (TPE) processes, although not fully calculable, are the most likely explanation of this disagreement. We will definitively test this assertion by comparing the electron-proton and positron-proton elastic scattering cross section in the Jefferson Lab CLAS. We will make a mixed identical electron and positron tertiary beam by passing a 5.5 GeV primary electron beam through a radiator to make a photon beam and then passing the photon beam through a converter to make electron-positron pairs. Measuring the elastic cross sections simultaneously using identical lepton beams should significantly reduce systematic uncertainties.
Precision electroweak studies using parity violation in electron scattering
Paschke, K. D.
2013-11-07
The nature of new neutral-current interactions can be revealed at the low-energy precision frontier, where studies of parity-violation in electron scattering will complement the energy-frontier studies at the LHC. Measurements of the parity-violating observable A{sub PV} - the cross-section asymmetry in the scattering of longitudinally polarized electrons from an unpolarized target - are sensitive to possible contact interactions from new physics at multi-TeV mass scales. The 12 GeV upgrade at JLab and a new, high-intensity beam at Mainz offer opportunities for significant improvements in measurements of electron-electron and electron-quark parity-violating interactions.
Hybrid Theory of Electron-Hydrogenic Systems Elastic Scattering
NASA Technical Reports Server (NTRS)
Bhatia, A. K.
2007-01-01
Accurate electron-hydrogen and electron-hydrogenic cross sections are required to interpret fusion experiments, laboratory plasma physics and properties of the solar and astrophysical plasmas. We have developed a method in which the short-range and long-range correlations can be included at the same time in the scattering equations. The phase shifts have rigorous lower bounds and the scattering lengths have rigorous upper bounds. The phase shifts in the resonance region can be used to calculate very accurately the resonance parameters.
Glauber exchange amplitudes. [electron scattering from H atoms
NASA Technical Reports Server (NTRS)
Madan, R. N.
1975-01-01
The extrapolation method of Ochkur, valid for intermediate energies (about 50 eV), is applied to the exchange form of the Glauber amplitudes. In the case of elastic scattering of electrons from hydrogen atoms at 54.4 Ev the 'post' and 'prior' forms of the exchange amplitude are equivalent, whereas for the case of inelastic scattering there is a minute discrepancy between the two forms of the amplitude. The results are compared with the close-coupling calculation. The investigation is expected to be useful for optically forbidden exchange-allowed transitions due to electron impact at intermediate energies.
Laser-modified electron scattering from a slowly ionising atom
NASA Technical Reports Server (NTRS)
Fiordilino, E.; Mittleman, M. H.
1983-01-01
When an electron scatters from an atom in the presence of a laser field which is resonant with an atomic transition, off-shell effects enter into the cross section. These only become significant at higher laser intensities where the atom may also be ionised by the laser. Cross-sections are obtained for electron-atom scattering in which these off-shell effects appear and in which the slow ionisation of the atom by the laser is included. Experiments are suggested in which simplifications can occur and which still retain these 'exotic' effects.
Partial Wave Dispersion Relations: Application to Electron-Atom Scattering
NASA Technical Reports Server (NTRS)
Temkin, A.; Drachman, Richard J.
1999-01-01
In this Letter we propose the use of partial wave dispersion relations (DR's) as the way of solving the long-standing problem of correctly incorporating exchange in a valid DR for electron-atom scattering. In particular a method is given for effectively calculating the contribution of the discontinuity and/or poles of the partial wave amplitude which occur in the negative E plane. The method is successfully tested in three cases: (i) the analytically solvable exponential potential, (ii) the Hartree potential, and (iii) the S-wave exchange approximation for electron-hydrogen scattering.
Impurity entanglement through electron scattering in a magnetic field
NASA Astrophysics Data System (ADS)
Metavitsiadis, Alexandros; Dillenschneider, Raoul; Eggert, Sebastian
2014-04-01
We study the entanglement of magnetic impurities in an environment of electrons through successive scattering while an external magnetic field is applied. We show that the dynamics of the problem can be approximately described by a reduced model of three interacting spins, which reveals an intuitive view on how spins can be entangled by controlled electron scattering. The role of the magnetic field is rather crucial. Depending on the initial state configuration, the magnetic field can either increase or decrease the resulting entanglement but more importantly it can allow the impurities to be maximally entangled.
Electron Scattering in Hot/Warm Plasmas
Rozsnyai, B F
2008-01-18
Electrical and thermal conductivities are presented for aluminum, iron and copper plasmas at various temperatures, and for gold between 15000 and 30000 Kelvin. The calculations are based on the continuum wave functions computed in the potential of the temperature and density dependent self-consistent 'average atom' (AA) model of the plasma. The cross sections are calculated by using the phase shifts of the continuum electron wave functions and also in the Born approximation. We show the combined effect of the thermal and radiative transport on the effective Rosseland mean opacities at temperatures from 1 to 1000 eV. Comparisons with low temperature experimental data are also presented.
Linden, Steven K.
2011-01-01
Charged current single pion production (CCπ^{+}) and charged current quasi-elastic scattering (CCQE) are the most abundant interaction types for neutrinos at energies around 1 GeV, a region of great interest to oscillation experiments. The cross-sections for these processes, however, are not well understood in this energy range. This dissertation presents a measurement of the ratio of CCπ^{+} to CCQE cross-sections for muon neutrinos on mineral oil (CH_{2}) in the MiniBooNE experiment. The measurement is presented here both with and without corrections for hadronic re-interactions in the target nucleus and is given as a function of neutrino energy in the range 0.4 GeV < E_{ν} < 2.4 GeV. With more than 46,000 CCπ^{+} events collected in MiniBooNE, and with a fractional uncertainty of roughly 11% in the region of highest statistics, this measurement represents a dramatic improvement in statistics and precision over previous CCπ^{+} and CCQE measurements.
Modeling Electron Pitch-Angle Scattering Rates by EMIC Waves
NASA Astrophysics Data System (ADS)
Usanova, Maria; Shprits, Yuri; Drozdov, Alexander
2016-07-01
The response of electron fluxes to different geomagnetic activity is determined by competing electron acceleration and loss processes. Interaction with EMIC waves is believed to be an important loss mechanism for the radiation belt electrons, which can undergo cyclotron resonance with EMIC waves and consequent pitch-angle scattering into the atmosphere. The recent study by Usanova et al. [2014] reported the first definitive proof of EMIC waves scattering electrons into the atmosphere. These new results are particularly interesting and significant as EMIC is the only wave mode that can scatter ultra-relativistic electrons much faster and more efficient than other wave modes (e.g., chorus and hiss) and therefore, is supposed to be a dominant internal loss mechanism for ˜>2 MeV energy electrons. In this talk we will focus on numerical modeling of EMIC-related electron losses. We compute bounce-averaged pitch-angle diffusion coefficients of electrons due to EMIC waves using a quasi-linear approach and use these coefficients as further input to the Versatile Electron Radiation Belt (VERB) diffusion code to simulate the evolution of electron phase space density during selected events. We will present a comparison of the simulation results and observed pitch angle distributions on the Van Allen Probes during selected events. We will also address the following questions: Where and under which conditions signatures of EMIC-related electron loss are typically observed? What are the EMIC wave and background plasma parameters required for this interaction? Can we reproduce observed losses of radiation belt electrons using numerical modeling?
Energy measurement of electron beams by Compton scattering
NASA Technical Reports Server (NTRS)
Keppel, Cynthia
1995-01-01
A method has been proposed to utilize the well-known Compton scattering process as a tool to measure the centroid energy of a high energy electron beam at the 0.01% level. It is suggested to use the Compton scattering of an infrared laser off the electron beam, and then to measure the energy of the scattered gamma-rays very precisely using solid-state detectors. The technique proposed is applicable for electron beams with energies from 200 MeV to 16 GeV using presently available lasers. This technique was judged to be the most viable of all those proposed for beam energy measurements at the nearby Continuous Electron Beam Accelerator Facility (CEBAF). Plans for a prototype test of the technique are underway, where the main issues are the possible photon backgrounds associated with an electron accelerator and the electron and laser beam stabilities and diagnostics. The bulk of my ASEE summer research has been spent utilizing the expertise of the staff at the Aerospace Electronics Systems Division at LaRC to assist in the design of the test. Investigations were made regarding window and mirror transmission and radiation damage issues, remote movement of elements in ultra-high vacuum conditions, etc. The prototype test of the proposed laser backscattering method is planned for this December.
Induced Compton Scattering by Relativistic Electrons in Magnetized Astrophysical Plasmas.
NASA Astrophysics Data System (ADS)
Sincell, Mark William
1994-01-01
The effects of stimulated scattering on high brightness temperature radiation are studied in two important contexts. In the first case, we assume that the radiation is confined to a collimated beam traversing a relativistically streaming magnetized plasma. When the plasma is cold in the bulk frame, stimulated scattering is only significant if the angle between the photon motion and the plasma velocity is less than gamma^{-1} , where gamma is the bulk Lorentz factor. Under the assumption that the center of the photon beam is parallel to the bulk motion, we calculate the scattering rate as a function of the angular spread of the beam and gamma. Magnetization changes the photon recoil, without which stimulated scattering has no effect. It also introduces a strong dependence on frequency and polarization: if the photon frequency matches the electron cyclotron frequency, the scattering rate of photons polarized perpendicular to the magnetic field can be substantially enhanced relative to Thomson, and if the photon frequency is much less than the cyclotron frequency the scattering is suppressed. Applying these calculations to pulsars, we find that stimulated scattering of the radio beam in the magnetized wind believed to exist outside the light cylinder can substantially alter the spectrum and polarization state of the radio signal. We suggest that the scattering rate is so high in some pulsars that the ability of the radio signal to penetrate the pulsar magnetosphere requires modification of either the conventional model of the magnetosphere or assumptions about the effects of stimulated scattering upon a beam. In the second case, we present a model of the radio emission from synchrotron self-absorbed sources, including the effects of induced Compton scattering by the relativistic electrons in the source. Order of magnitude estimates show that stimulated scattering becomes the dominant absorption process when (kTB/m ec^2)tau_{T }_sp{~}> 0.1. Numerical simulations
Controlling electron-phonon scattering with metamaterial plasmonic structures
NASA Astrophysics Data System (ADS)
Kempa, Krzysztof; Wu, Xueyuan; Kong, Jiantao; Broido, David
Electron-plasmon scattering can be faster than electron-phonon scattering. While in metals plasmons occur in the UV range, phonons dominate behavior at much lower frequencies (far IR range), and this typically decouples these phenomena. In metamaterial plasmonic structures, however, plasma effects can be tuned down to the far IR range, allowing for their interference with phonons. It was recently shown, that such interference can protect hot electron energy induced in a solar cell, from dissipation into heat. In this work we explore the possibility of using such an effect to control the electron-phonon interaction and transport in semiconductors. We demonstrate, that this could lead to a novel path to enhancing the electrical and thermal conductivities and the thermoelectric figure of merit.
Electron scattering in HCl: An improved nonlocal resonance model
Fedor, J.; Winstead, C.; McKoy, V.; Cizek, M.; Houfek, K.; Kolorenc, P.; Horacek, J.
2010-04-15
We present an improved nonlocal resonance model for electron-HCl collisions. The short-range part of the model is fitted to ab initio electron-scattering eigenphase sums calculated using the Schwinger multichannel method, while the long-range part is based on the ab initio potential-energy curve of the bound anion HCl{sup -}. This model significantly improves the agreement of nonlocal resonance calculations with recent absolute experimental data on dissociative electron attachment cross sections for HCl and DCl. It also partly resolves an inconsistency in the temperature effect in dissociative electron attachment to HCl present in the literature. Finally, the present model reproduces all qualitative structures observed previously in elastic scattering and vibrational-excitation cross sections.
Modified effective range analysis of electron scattering from krypton
NASA Astrophysics Data System (ADS)
Fedus, Kamil
2014-10-01
The elastic cross sections for electron scattering on krypton from zero energy up to 10 eV have been analyzed by the modified effective range method. A simple model based on the analytical solution of the Schrödinger equation with the polarization potential using explicitly determined scattering phase shifts for the three lowest partial waves describes the elastic differential, integral and momentum transfer cross sections up to the energy threshold of the first inelastic process well. In detail, the contribution of the long-range polarization potential to the scattering phase shift is exactly expressed, while the contribution of the short-range effects is modelled by simple quadratic expressions (the effective range expansions). The effective range parameters are determined empirically by comparison with the latest experimental differential cross sections. Presently, the calculated integral and momentum transfer cross sections are validated against numerous electron scattering experiments and the most recent quantum-mechanical theories. To complete the picture, the two-term Boltzmann analysis is employed to determine the electron transport coefficients; the agreement with the electron swarm experimental data is found to be very good.
Scaling in electron scattering from a relativistic Fermi gas
W. M. Alberico; A. Molinari; T. William Donnelly; E. L. Kronenberg; Wally Van Orden
1988-10-01
Within the context of the relativistic Fermi gas model, the concept of ''y scaling'' for inclusive electron scattering from nuclei is investigated. Specific kinematic shifts of the single-nucleon response in the nuclear medium can be incorporated with this model. Suggested generalizations beyond the strict Fermi gas model, including treatments of separated longitudinal and transverse responses, are also explored.
Applying a Trochoidal Electron Monochromator in Dissociative Electron Attachment Scattering
NASA Astrophysics Data System (ADS)
Arreola, Esmeralda
2016-03-01
Since the pioneering work of Boudiaffa et al., it has been understood that electrons, even with energies near or below the ionization threshold, are capable of initiating strand-breaks in human DNA. This discovery raised important questions for cancer treatments, since sub-ionizing electrons are known to be the most copiously produced secondary product of radiation therapy. But even to date these factors are largely excluded from dosimetry calculations. This lack of inclusion is, at least in part, certainly due to the dearth of fundamental data describing low-energy electron interactions with nucleotide molecules that form the basis of DNA. Understanding of how such slow electrons are able to damage DNA remains incomplete, but the strongly peaked nature of Boudiaffa et al.'s data gives strong hints at resonantly driven collision processes. DNA damage is therefore most likely driven by ``dissociative electron attachment'' (DEA). DEA is a rather complicated process to model due to the coupling of electronic and nuclear degrees of freedom in the molecule. At the California State University Fullerton, we are currently commissioning a new spectrometer to study dissociation channels, reaction rates and orientation effects in DEA collisions between slow electrons and nucleotide molecules. At the meeting we will present design parameters and commissioning data for this new apparatus.
Polarization of photons scattered by electrons in any spectral distribution
Chang, Zhe; Lin, Hai-Nan; Jiang, Yunguo
2014-01-01
On the basis of the quantum electrodynamics, we present a generic formalism of the polarization for beamed monochromatic photons scattered by electrons in any spectral distribution. The formulae reduce to the components of the Fano matrix when electrons are at rest. We mainly investigate the polarization in three scenarios, i.e., electrons at rest, isotropic electrons with a power-law spectrum, and thermal electrons. If the incident beam is polarized, the polarization is reduced significantly by isotropic electrons at large viewing angles; the degree of polarization caused by thermal electrons is about half of that caused by power-law electrons. If the incident bean is unpolarized, soft γ-rays can lead to about 15% polarization at viewing angles around π/4. For isotropic electrons, one remarkable feature is that the polarization as a function of the incident photon energy always peaks roughly at 1 MeV; this is valid for both the thermal and power-law cases. This feature can be used to distinguish the model of the inverse Compton scattering from that of the synchrotron radiation.
Electron scattering by magnetosonic waves in the inner magnetosphere
NASA Astrophysics Data System (ADS)
Ma, Qianli; Li, Wen; Thorne, Richard M.; Bortnik, Jacob; Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.
2016-01-01
We investigate the importance of electron scattering by magnetosonic waves in the Earth's inner magnetosphere. A statistical survey of the magnetosonic wave amplitude and wave frequency spectrum, as a function of geomagnetic activity, is performed using the Van Allen Probes wave measurements and is found to be generally consistent with the wave distribution obtained from previous spacecraft missions. Outside the plasmapause the statistical frequency distribution of magnetosonic waves follows the variation of the lower hybrid resonance frequency, but this trend is not observed inside the plasmasphere. Drift and bounce averaged electron diffusion rates due to magnetosonic waves are calculated using a recently developed analytical formula. The resulting timescale of electron energization during disturbed conditions (when AE* > 300 nT) is more than 10 days. We perform a 2-D simulation of the electron phase space density evolution due to magnetosonic wave scattering during disturbed conditions. Outside the plasmapause, the waves accelerate electrons with pitch angles between 50° and 70° and form butterfly pitch angle distributions at energies from ~100 keV to a few MeV over a timescale of several days; whereas inside the plasmapause, the electron acceleration is very weak. Our study suggests that intense magnetosonic waves may cause the butterfly distribution of radiation belt electrons especially outside the plasmapause, but electron acceleration due to magnetosonic waves is generally not as effective as chorus wave acceleration.
Goeppert-Mayer Award Recipient: Electron Scattering and Nucleon Structure
NASA Astrophysics Data System (ADS)
Beise, Elizabeth
1998-04-01
Electron scattering from hydrogen and light nuclear targets has long been recognized as one of the best tools for understanding the electromagnetic structure of protons, neutrons and few-nucleon systems. In the last decade, considerable progress has been made in the field through advances in polarized beams and polarized targets. Improvements in polarized electron sources has made it feasible to also study the structure of the nucleon through parity-violating electron scattering, where the nucleon's neutral weak structure is probed. In this talk, a summary of the present experimental status of the nucleon's electroweak structure will be presented, with an emphasis on recent results from the MIT-Bates and Jefferson Laboratories.
Vector analyzing power in elastic electron-proton scattering
Diaconescu, L.; Ramsey-Musolf, M.J.
2004-11-01
We compute the vector analyzing power (VAP) for the elastic scattering of transversely polarized electrons from protons at low energies using an effective theory of electrons, protons, and photons. We study all contributions through second order in E/M, where E and M are the electron energy and nucleon mass, respectively. The leading-order VAP arises from the imaginary part of the interference of one- and two-photon exchange amplitudes. Subleading contributions are generated by the nucleon magnetic moment and charge radius as well as recoil corrections to the leading-order amplitude. Working to O(E/M){sup 2}, we obtain a prediction for A{sub n} that is free of unknown parameters and that agrees with the recent measurement of the VAP in backward angle ep scattering.
Vector analyzing power in elastic electron-proton scattering
NASA Astrophysics Data System (ADS)
Diaconescu, L.; Ramsey-Musolf, M. J.
2004-11-01
We compute the vector analyzing power (VAP) for the elastic scattering of transversely polarized electrons from protons at low energies using an effective theory of electrons, protons, and photons. We study all contributions through second order in E/M , where E and M are the electron energy and nucleon mass, respectively. The leading-order VAP arises from the imaginary part of the interference of one- and two-photon exchange amplitudes. Subleading contributions are generated by the nucleon magnetic moment and charge radius as well as recoil corrections to the leading-order amplitude. Working to O (E/M)2 , we obtain a prediction for An that is free of unknown parameters and that agrees with the recent measurement of the VAP in backward angle ep scattering.
Nonlinear single Compton scattering of an electron wave packet
NASA Astrophysics Data System (ADS)
Angioi, A.; Mackenroth, F.; Di Piazza, A.
2016-05-01
Nonlinear single Compton scattering has been thoroughly investigated in the literature under the assumption that the electron initially has a definite momentum. Here, we study a more general initial state and consider the electron as a wave packet. In particular, we investigate the energy spectrum of the emitted radiation and show that, in typical experimental situations, some features of the spectra shown in previous works are almost completely washed out. Moreover, we show that, at comparable relative uncertainties, the one in the momentum of the incoming electron has a larger impact on the photon spectra at a fixed observation direction than the one on the laser frequency.
Resonance electronic Raman scattering in rare earth crystals
Williams, G.M.
1988-11-10
The intensities of Raman scattering transitions between electronic energy levels of trivalent rare earth ions doped into transparent crystals were measured and compared to theory. A particle emphasis was placed on the examination of the effect of intermediate state resonances on the Raman scattering intensities. Two specific systems were studied: Ce/sup 3 +/(4f/sup 1/) in single crystals of LuPO/sub 4/ and Er/sup 3 +/(4f/sup 11/) in single crystals of ErPO/sub 4/. 134 refs., 92 figs., 33 tabs.
Electron scattering by laser-excited barium atoms
NASA Technical Reports Server (NTRS)
Register, D. F.; Trajmar, S.; Jensen, S. W.; Poe, R. T.
1978-01-01
Inelastic and superelastic scattering of 30- and 100-eV electrons by laser-excited 6s 6p 1P and subsequent cascade-populated 6s 6p 3P, 6s 5d 1D, and 6s 5d 3D Ba atoms have been observed. Absolute differential cross sections for the singlet and relative scattering intensities for the triplet species have been determined in the 5 to 20 deg angular region. Under the present conditions excitations dominate over deexcitations.
Study of the (e,e'p) quasi-elastic reaction in complex nuclei: theory and experiment
Herraiz, Joaquin Lopez
2010-03-01
Experimental coincidence cross section and transverse-longitudinal asymmetry _{ATL} have been obtained for the quasielastic (e,e'p) reaction in ^{16}O, ^{12}C, and {sup 208}Pb in constant q-ω kinematics in the missing momentum range -350 < p_{miss} < 350 MeV/c. In these experiments, performed in experimental Hall A of the Thomas Jefferson National Accelerator Facility (JLAB), the beam energy and the momentum and angle of the scattered electrons were kept fixed, while the angle between the proton momentum and the momentum transfer q was varied in order to map out the missing momentum distribution. The experimental cross section and A_{TL} asymmetry have been compared with Monte Carlo simulations based on Distorted Wave Impulse Approximation (DWIA) calculations with both relativistic and non-relativistic spinor structure. The spectroscopic factors obtained for both models are in agreement with previous experimental values, while A_{TL} measurements favor the relativistic DWIA calculation. This thesis describes the details of the experimental setup, the calibration of the spectrometers, the techniques used in the data analysis to derive the final cross sections and the A_{TL}, the ingredients of the theoretical calculations employed and the comparison of the results with the simulations based on these theoretical models.
Resonant Inelastic X-ray Scattering in Correlated Electron Systems
NASA Astrophysics Data System (ADS)
Kim, Young-June
2006-03-01
Extremely bright photons generated at the new generation of synchrotron light sources have made a huge impact on various scientific disciplines ranging from biology to materials science. One of the exciting new developments is the use of x-rays in the field of solid-state spectroscopy. Inelastic x-ray scattering, analogous to the well-known inelastic neutron scattering, is a powerful tool for studying momentum-dependent electronic excitations and phonons. In particular, resonant inelastic x-ray scattering in the hard x-ray regime has been widely utilized to study the momentum dependence of various electronic excitations in strongly correlated electron systems. For example, by tuning the incident photon energy to the Cu K-edge, one can gain a large intensity enhancement as well as element specific knowledge of the electronic excitations in various copper oxide compounds. Most of the work to date has been focused on the charge-transfer excitation between the bonding and antibonding molecular orbitals, the excitation across the Mott gap, and crystal field excitations between the d-orbitals. Recent improvements in instrumentation have allowed us to observe a new mode in the mid-infrared frequency region. We will discuss the momentum dependence of these excitations in prototypical cuprate superconductors, La2-xSrxCuO4, and also examine the evolution of such excitations as charge carriers are doped into the system.
Kinetic Enhancement of Raman Backscatter, and Electron Acoustic Thomson Scatter
Strozzi, D J; Williams, E A; Langdon, A B; Bers, A
2006-09-01
1-D Eulerian Vlasov-Maxwell simulations are presented which show kinetic enhancement of stimulated Raman backscatter (SRBS) due to electron trapping in regimes of heavy linear Landau damping. The conventional Raman Langmuir wave is transformed into a set of beam acoustic modes [L. Yin et al., Phys. Rev. E 73, 025401 (2006)]. For the first time, a low phase velocity electron acoustic wave (EAW) is seen developing from the self-consistent Raman physics. Backscatter of the pump laser off the EAW fluctuations is reported and referred to as electron acoustic Thomson scatter. This light is similar in wavelength to, although much lower in amplitude than, the reflected light between the pump and SRBS wavelengths observed in single hot spot experiments, and previously interpreted as stimulated electron acoustic scatter [D. S. Montgomery et al., Phys. Rev. Lett. 87, 155001 (2001)]. The EAW observed in our simulations is strongest well below the phase-matched frequency for electron acoustic scatter, and therefore the EAW is not produced by it. The beating of different beam acoustic modes is proposed as the EAW excitation mechanism, and is called beam acoustic decay. Supporting evidence for this process, including bispectral analysis, is presented. The linear electrostatic modes, found by projecting the numerical distribution function onto a Gauss-Hermite basis, include beam acoustic modes (some of which are unstable even without parametric coupling to light waves) and a strongly-damped EAW similar to the observed one. This linear EAW results from non-Maxwellian features in the electron distribution, rather than nonlinearity due to electron trapping.
Quasielastic electron-deuteron scattering in the weak binding approximation
Ethier, Jacob J.; Doshi, Nidhi P.; Malace, Simona P.; Melnitchouk, Wally
2014-06-01
We perform a global analysis of all available electron-deuteron quasielastic scattering data using Q^2-dependent smearing functions that describe inclusive inelastic e-d scattering within the weak binding approximation. We study the dependence of the cross sections on the deuteron wave function and the off-shell extrapolation of the elastic electron-nucleon cross section, which show particular sensitivity at x >> 1. The excellent overall agreement with data over a large range of Q^2 and x suggest a limited need for effects beyond the impulse approximation, with the exception of the very high-x or very low-Q^2 regions, where short-distance effects in the deuteron become more relevant.
Elastic Electron Scattering from Tritium and Helium-3
DOE R&D Accomplishments Database
Collard, H.; Hofstadter, R.; Hughes, E. B.; Johansson, A.; Yearian, M. R.; Day, R. B.; Wagner, R. T.
1964-10-01
The mirror nuclei of tritium and helium-3 have been studied by the method of elastic electron scattering. Absolute cross sections have been measured for incident electron energies in the range 110 - 690 MeV at scattering angles lying between 40 degrees and 135 degrees in this energy range. The data have been interpreted in a straightforward manner and form factors are given for the distributions of charge and magnetic moment in the two nuclei over a range of four-momentum transfer squared 1.0 - 8.0 F{sup -2}. Model-independent radii of the charge and magnetic moment distributions are given and an attempt is made to deduce form factors describing the spatial distribution of the protons in tritium and helium-3.
Measurement of neutrino flux from neutrino-electron elastic scattering
NASA Astrophysics Data System (ADS)
Park, J.; Aliaga, L.; Altinok, O.; Bellantoni, L.; Bercellie, A.; Betancourt, M.; Bodek, A.; Bravar, A.; Budd, H.; Cai, T.; Carneiro, M. F.; Christy, M. E.; Chvojka, J.; da Motta, H.; Dytman, S. A.; Díaz, G. A.; Eberly, B.; Felix, J.; Fields, L.; Fine, R.; Gago, A. M.; Galindo, R.; Ghosh, A.; Golan, T.; Gran, R.; Harris, D. A.; Higuera, A.; Kleykamp, J.; Kordosky, M.; Le, T.; Maher, E.; Manly, S.; Mann, W. A.; Marshall, C. M.; Martinez Caicedo, D. A.; McFarland, K. S.; McGivern, C. L.; McGowan, A. M.; Messerly, B.; Miller, J.; Mislivec, A.; Morfín, J. G.; Mousseau, J.; Naples, D.; Nelson, J. K.; Norrick, A.; Nuruzzaman; Osta, J.; Paolone, V.; Patrick, C. E.; Perdue, G. N.; Rakotondravohitra, L.; Ramirez, M. A.; Ray, H.; Ren, L.; Rimal, D.; Rodrigues, P. A.; Ruterbories, D.; Schellman, H.; Solano Salinas, C. J.; Tagg, N.; Tice, B. G.; Valencia, E.; Walton, T.; Wolcott, J.; Wospakrik, M.; Zavala, G.; Zhang, D.; Miner ν A Collaboration
2016-06-01
Muon-neutrino elastic scattering on electrons is an observable neutrino process whose cross section is precisely known. Consequently a measurement of this process in an accelerator-based νμ beam can improve the knowledge of the absolute neutrino flux impinging upon the detector; typically this knowledge is limited to ˜10 % due to uncertainties in hadron production and focusing. We have isolated a sample of 135 ±17 neutrino-electron elastic scattering candidates in the segmented scintillator detector of MINERvA, after subtracting backgrounds and correcting for efficiency. We show how this sample can be used to reduce the total uncertainty on the NuMI νμ flux from 9% to 6%. Our measurement provides a flux constraint that is useful to other experiments using the NuMI beam, and this technique is applicable to future neutrino beams operating at multi-GeV energies.
Theory of high-energy electron scattering by composite targets
Coester, F.
1988-01-01
The emphasis of these expository lectures is on the role of relativistic invariance and the unity of the theory for medium and high energies. Sec. 2 introduces the kinematic notation and provides an elementary derivation of the general cross section. The relevant properties of the Poincare group and the transformation properties of current operators and target states are described in Sec 3. In Sec. 4 representations of target states with kinematic light-front symmetry are briefly discussed. The focus is on two applications. An impulse approximation of inclusive electron nucleus scattering at both medium and high energies. A parton model of the proton applied to deep inelastic scattering of polarized electrons by polarized protons. 19 refs.
Measurement of neutrino flux from neutrino-electron elastic scattering
Park, J.; Aliaga, L.; Altinok, O.; Bellantoni, L.; Bercellie, A.; Betancourt, M.; Bodek, A.; Bravar, A.; Budd, H.; Cai, T.; et al
2016-06-10
In muon-neutrino elastic scattering on electrons is an observable neutrino process whose cross section is precisely known. Consequently a measurement of this process in an accelerator-based νμ beam can improve the knowledge of the absolute neutrino flux impinging upon the detector; typically this knowledge is limited to ~10% due to uncertainties in hadron production and focusing. We also isolated a sample of 135±17 neutrino-electron elastic scattering candidates in the segmented scintillator detector of MINERvA, after subtracting backgrounds and correcting for efficiency. We show how this sample can be used to reduce the total uncertainty on the NuMI νμ flux frommore » 9% to 6%. Finally, our measurement provides a flux constraint that is useful to other experiments using the NuMI beam, and this technique is applicable to future neutrino beams operating at multi-GeV energies.« less
Calculation of electron scattering from the ground state of ytterbium
Bostock, Christopher J.; Fursa, Dmitry V.; Bray, Igor
2011-05-15
We report on the application of the convergent close-coupling method, in both relativistic and nonrelativistic formulations, to electron scattering from ytterbium. Angle-differential and integrated cross sections are presented for elastic scattering and excitation of the states (6s6p){sup 3}P{sub 0,1,2}, (6s6p){sup 1}P{sub 1}{sup o}, (6s7p){sup 1}P{sub 1}{sup o}, and (6s5d){sup 1}D{sub 2}{sup e} for a range of incident electron energies. We also present calculations of the total cross section, and angle-differential Stokes parameters for excitation of the (6s6p){sup 3}P{sub 1}{sup o} state from the ground state. A comparison is made with the relativistic distorted-wave method and experiments.
Electron Scattering at Surfaces and Interfaces of Transition Metals
NASA Astrophysics Data System (ADS)
Zheng, Pengyuan
The effect of surfaces on the electron transport at reduced scales is attracting continuous interest due to its broad impact on both the understanding of materials properties and their application for nanoelectronics. The size dependence of for conductor's electrical resistivity rho due to electron surface scattering is most commonly described within the framework of Fuchs and Sondheimer (FS) and their various extensions, which uses a phenomenological scattering parameter p to define the probability of electrons being elastically (i.e. specularly) scattered by the surface without causing an increase of rho at reduced size. However, a basic understanding of what surface chemistry and structure parameters determine the specularity p is still lacking. In addition, the assumption of a spherical Fermi surface in the FS model is too simple for transition metals to give accurate account of the actual surface scattering effect. The goal of this study is to develop an understanding of the physics governing electron surface/interface scattering in transition metals and to study the significance of their Fermi surface shape on surface scattering. The advancement of the scientific knowledge in electron surface and interface scattering of transition metals can provide insights into how to design high-conductivity nanowires that will facilitate the viable development of advanced integrated circuits, thermoelectric power generation and spintronics. Sequential in situ and ex situ transport measurements as a function of surface chemistry demonstrate that electron surface/interface scattering can be engineered by surface doping, causing a decrease in the rho. For instance, the rho of 9.3-nm-thick epitaxial and polycrystalline Cu is reduced by 11--13% when coated with 0.75 nm Ni. This is due to electron surface scattering which exhibits a specularity p = 0.7 for the Cu-vacuum interface that transitions to completely diffuse (p = 0) when exposed to air. In contrast, Ni-coated surfaces
Short Range Correlations, Inclusive Electron-Nucleus Scattering, and Scaling
Day, Donal
2008-10-13
The presence of high momentum components in the nuclear wavefunction has been of great interest for many years. Unfortunately high momentum components, associated with the short range correlations (SRC), have been difficult to isolate unambiquously. Inclusive electron scattering cross sections in the quasielastic region have been measured over a wide range of energy and momentum transfers from very light to very heavy nuclei and the scaling analyses of these data can provide useful information on the presence of SRCs and more.
Two-photon exchange and elastic electron-proton scattering
Peter Blunden; Wally Melnitchouk; John Tjon
2003-06-01
Two-photon exchange contributions to elastic electron-proton scattering cross sections are evaluated in a simple hadronic model including the finite size of the proton. The corrections are found to be small, but with a strong angular dependence at fixed Q{sup 2}. This is significant for the Rosenbluth technique for determining the ratio of electric and magnetic form factors of the proton, and partly reconciles the apparent discrepancy with the results of the polarization transfer technique.
Electron Scattering on a Magnetic Skyrmion in the Nonadiabatic Approximation.
Denisov, K S; Rozhansky, I V; Averkiev, N S; Lähderanta, E
2016-07-01
We present a theory of electron scattering on a magnetic Skyrmion for the case when the exchange interaction is moderate so that the adiabatic approximation and the Berry phase approach are not applicable. The theory explains the appearance of a topological Hall current in the systems with magnetic Skyrmions, the special importance of which is its applicability to dilute magnetic semiconductors with a weak exchange interaction. PMID:27447521
NASA Astrophysics Data System (ADS)
Fu, H.; Scales, W. A.; Bernhardt, P. A.; Samimi, A.; Mahmoudian, A.; Briczinski, S. J.; McCarrick, M. J.
2013-09-01
Results of secondary radiation, Stimulated Electromagnetic Emission (SEE), produced during ionospheric modification experiments using ground-based high-power radio waves are reported. These results obtained at the High Frequency Active Auroral Research Program (HAARP) facility specifically considered the generation of Magnetized Stimulated Brillouin Scatter (MSBS) and Stimulated Ion Bernstein Scatter (SIBS) lines in the SEE spectrum when the transmitter frequency is near harmonics of the electron gyrofrequency. The heater antenna beam angle effect was investigated on MSBS in detail and shows a new spectral line postulated to be generated near the upper hybrid resonance region due to ion acoustic wave interaction. Frequency sweeping experiments near the electron gyroharmonics show for the first time the transition from MSBS to SIBS lines as the heater pump frequency approaches the gyroharmonic. Significantly far from the gyroharmonic, MSBS lines dominate, while close to the gyroharmonic, SIBS lines strengthen while MSBS lines weaken. New possibilities for diagnostic information are discussed in light of these new observations.
Low-Energy Elastic Electron Scattering by Atomic Oxygen
NASA Technical Reports Server (NTRS)
Zatsarinny O.; Bartschat, K.; Tayal, S. S.
2006-01-01
The B-spline R-matrix method is employed to investigate the low-energy elastic electron scattering by atomic oxygen. Flexible non-orthogonal sets of radial functions are used to construct the target description and to represent the scattering functions. A detailed investigation regarding the dependence of the predicted partial and total cross sections on the scattering model and the accuracy of the target description is presented. The predicted angle-integrated elastic cross sections are in good agreement with experiment, whereas significant discrepancies are found in the angle-differential elastic cross sections near the forward direction. .The near-threshold results are found to strongly depend on the treatment of inner-core short-range correlation effects in the target description, as well as on a proper account of the target polarizability. A sharp increase in the elastic cross sections below 1 eV found in some earlier calculations is judged to be an artifact of an unbalanced description of correlation in the N-electron target structure and the (N+l)-electron-collision problems.
Total cross section of electron scattering by fluorocarbon molecules
NASA Astrophysics Data System (ADS)
Yamada, T.; Ushiroda, S.; Kondo, Y.
2008-12-01
A compact linear electron transmission apparatus was used for the measurement of the total electron scattering cross section at 4-500 eV. Total cross sections of chlorofluorocarbon (CCl2F2), hydrochlorofluorocarbon (CHClF2), perfluoropropane (C3F8), perfluoro-n-pentane (C5F12), perfluoro-n-hexane (C6F14) and perfluoro-n-octane (C8F18) were obtained experimentally and compared with the values obtained from a theoretical calculation and semi-empirical model calculation.
Technology Transfer Automated Retrieval System (TEKTRAN)
The need to increase the use of low valued co-products derived from the processing of sugar beets has prompted the investigation of the structure of the pectin extracted from sugar beet pulp. The characterization of sugar beet pectin is essential as it has the potential to be used in the production ...
Beye, M; Hennies, F; Deppe, M; Suljoti, E; Nagasono, M; Wurth, W; Föhlisch, A
2009-12-01
Experimentally, we observe angular-momentum transfer in electron-phonon scattering, although it is commonly agreed that phonons transfer mostly linear momentum. Therefore, the incorporation of angular momentum to describe phonons is necessary already for simple semiconductors and bears significant implications for the formation of new quasiparticles in correlated functional materials. Separation of linear and angular-momentum transfer in electron-phonon scattering is achieved by highly selective excitations on the femtosecond time scale of resonant inelastic x-ray scattering.
Return Current Electron Beams and Their Generation of "Raman" Scattering
NASA Astrophysics Data System (ADS)
Simon, A.
1998-11-01
For some years, we(A. Simon and R. W. Short, Phys. Rev. Lett. 53), 1912 (1984). have proposed that the only reasonable explanation for many of the observations of "Raman" scattering is the presence of an electron beam in the plasma. (The beam creates a bump-on-tail instability.) Two major objections to this picture have been observation of Raman when no n_c/4 surface was present, with no likely source for the electron beam, and the necessity for the initially outward directed beam to bounce once to create the proper waves. Now new observations on LLE's OMEGA(R. Petrasso et al), this conference. and at LULI(C. Labaune et al)., Phys. Plasma 5, 234 (1998). have suggested a new origin for the electron beam. This new scenario answers the previous objections, maintains electron beams as the explanation of the older experiments, and may clear up puzzling observations that have remained unexplained. The new scenario is based on two assumptions: (1) High positive potentials develop in target plasmas during their creation. (2) A high-intensity laser beam initiates spark discharges from nearby surfaces to the target plasma. The resulting return current of electrons should be much more delta-like, is initially inwardly directed, and no longer requires the continued presence of a n_c/4 surface. Scattering of the interaction beam from the BOT waves yields the observed Raman signal. Experimental observations that support this picture will be cited. ``Pulsation'' of the scattering and broadband ``flashes'' are a natural part of this scenario. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460.
Optimization of Plasmon Decay Through Scattering and Hot Electron Transfer
NASA Astrophysics Data System (ADS)
DeJarnette, Drew
Light incident on metal nanoparticles induce localized surface oscillations of conductive electrons, called plasmons, which is a means to control and manipulate light. Excited plasmons decay as either thermal energy as absorbed phonons or electromagnetic energy as scattered photons. An additional decay pathway for plasmons can exist for gold nanoparticles situated on graphene. Excited plasmons can decay directly to the graphene as through hot electron transfer. This dissertation begins by computational analysis of plasmon resonance energy and bandwidth as a function of particle size, shape, and dielectric environment in addition to diffractive coupled in lattices creating a Fano resonance. With this knowledge, plasmon resonance was probed with incident electrons using electron energy loss spectroscopy in a transmission electron microscope. Nanoparticles were fabricated using electron beam lithography on 50 nanometer thick silicon nitride with some particles fabricated with a graphene layer between the silicon nitride and metal structure. Plasmon resonance was compared between ellipses on and off graphene to characterize hot electron transfer as a means of plasmon decay. It was observed that the presence of graphene caused plasmon energy to decrease by as much as 9.8% and bandwidth to increase by 25%. Assuming the increased bandwidth was solely from electron transfer as an additional plasmon decay route, a 20% efficiency of plasmon decay to graphene was calculated for the particular ellipses analyzed.
Elastic scattering of slow electrons by n-pentanol alcohol
NASA Astrophysics Data System (ADS)
de Oliveira, Eliane M.; Varella, Márcio T. do N.; Bettega, Márcio H. F.; Lima, Marco A. P.
2014-03-01
We report elastic integral (ICS), differential (DCS) and momentum transfer cross sections (MTCS) for low-energy electron scattering by n-pentanol alcohol in the gas phase. The Schwinger multichannel method implemented with pseudopotentials was employed in the calculations. The DCSs were computed for energies from 1 to 50 eV and the ICS and MTCS from 1 to 100 eV. Due to the significant value of the electric dipole moment, the DCSs are dominated by strong forward scattering. Despite this fact, the DCS around 10 eV displays a behavior related to a f-wave scattering pattern at intermediate angles which may be associated with shape resonances. This result is consistent with the ICS and the MTCS since they show a pronounced peak near this energy. For energies below 1 eV, the MTCS obtained in the static-exchange plus polarization approximation does not increase, as expected for polar molecules, suggesting that a Ramsauer-Townsend minimum could be present. This finding motivated us to revisit the previously studied methanol, ethanol, n-propanol and n-butanol molecules and to perform new calculations for impact energies below 1 eV (not addressed before). With the inclusion of polarization effects, the MTCS for the five alcohols suggest a Ramsauer-Townsend minimum coming from the negative to the positive scattering energies. To the best of our knowledge, there are neither experimental nor calculated cross sections for comparison with the present results.
Electron scattering from HeII ions at intermediate energies
NASA Astrophysics Data System (ADS)
McLaughlin, B. M.; Scott, M. P.; Burke, P. G.; Dahler, J. S.
1997-04-01
Electron collisional excitation cross sections and rate coefficients of HeII ions are of extreme interest in the modelling of astrophysical plasmas. They are required for reliable determination of the excitation and ionization in the solar corona, impulsive heating events in the solar transitions region, shock waves in the interstellar medium and in stellar atmospheres. Emission lines of HeII have been observed in a variety of solar and astrophysical objects at wavelengths below 350 ÅThe Extreme Ultra Violet Explorer (EUVE) spectra of Capella (HD 3402, G8 III + G0 III), the bright RS CVn binary system, is dominated by HeII (λ 303 Åand high ionization stages of iron. Accurate knowledge of the electron collisional excitation rates for the n = 2 and n = 3 levels of HeII are required in the modelling of the electron-ion equilibration in non-radiative shocks associated with SN 1006. Recently attention has focused on scattering at intermediate energies with emphasis on the n = 2 levels using the CCC formalism and the 2D-Rmatrix propagator method. In our work we have used the IERM approach of Burke, Scott and co-workers to obtain accurate cross sections for levels up to n = 3, as this has proved successful in dealing with electron - atomic hydrogen scattering at intermediate energies. A comprehensive set of results will be presented at the meeting.
y scaling in quasielastic electron scattering from nuclei
Kim, K. S.; Wright, L. E.
2007-10-15
A relativistic single-particle model is used to calculate the inclusive (e,e{sup '}) reaction from A=12, 40, 56, 197, and 208 nuclei in the quasielastic region. We have shown that this model provides a very good description of the available experimental cross sections when they are dominated by the quasielastic process. In this paper, we use this model to investigate the dependence of y scaling on electron kinematics, particularly the electron scattering angle, for a range of squared four-momentum transfer of 0.20-0.80 (GeV/c){sup 2}. In this kinematic domain, Coulomb distortion of the electron does not significantly affect scaling, but final state interactions of the knocked out nucleon do affect scaling, particularly when the nucleons have lower energies. In general, we find that scaling works for this reaction, but at lower values of the four-momentum transfer, the scaling function does have some dependence on the electron scattering angle. We also consider a modification of y scaling to include small binding energy effects as a function of Z and A and show that there is some improvement in scaling.
A Guide to Electronic Multipoles in Photon Scattering and Absorption
NASA Astrophysics Data System (ADS)
Lovesey, Stephen William; Balcar, Ewald
2013-02-01
The practice of replacing matrix elements in atomic calculations by those of convenient operators with strong physical appeal has a long history, and in condensed matter physics it is perhaps best known through use of operator equivalents in electron resonance by Elliott and Stevens. Likewise, electronic multipoles, created with irreducible spherical-tensors, to represent charge-like and magnetic-like quantities are widespread in modern physics. Examples in recent headlines include a magnetic charge (a monopole), an anapole (a dipole) and a triakontadipole (a magnetic-like atomic multipole of rank 5). In this communication, we aim to guide the reader through use of atomic, spherical multipoles in photon scattering, and resonant Bragg diffraction and dichroic signals in particular. Applications to copper oxide CuO and neptunium dioxide (NpO2) are described. In keeping with it being a simple guide, there is sparse use in the communication of algebra and expressions are gathered from the published literature and not derived, even when central to the exposition. An exception is a thorough grounding, contained in an Appendix, for an appropriate version of the photon scattering length based on quantum electrodynamics. A theme of the guide is application of symmetry in scattering, in particular constraints imposed on results by symmetry in crystals. To this end, a second Appendix catalogues constraints on multipoles imposed by symmetry in crystal point-groups.
Electron Scattering from MERCURY-198 and Mercury -204.
NASA Astrophysics Data System (ADS)
Laksanaboonsong, Jarungsaeng
This experiment is the first electron scattering study on mercury isotopes. Electron scattering from ^{198}Hg and ^{204 }Hg has been performed at the NIKHEF-K Medium Energy Accelerator. Measured cross sections cover an effective momentum transfer range from 0.4 to 2.9 fm^ {-1}. Elastic cross sections were determined for scattering from both isotopes. Cross section for inelastic excitations in ^{198}Hg below 3 MeV were also determined. Measured cross sections were fit using DWBA phase shift codes to determine coefficients for Fourier-Bessel expansions of ground state and transition charge densities. Differences between the ground state charge densities of the two isotopes reveal the effect of the polarization of the proton core in response to the addition of neutrons. Spin and parity of several excited states of ^{198}Hg were determined. Extracted transition densities of these states show their predominantly collective nature. Charge densities for members of the ground state rotational band were compared with axially symmetric Hartree-Fock and geometrical model predictions.
How Geometric Distortions Scatter Electronic Excitations in Conjugated Macromolecules.
Shi, Tian; Li, Hao; Tretiak, Sergei; Chernyak, Vladimir Y
2014-11-20
Effects of disorder and exciton-phonon interactions are the major factors controlling photoinduced dynamics and energy-transfer processes in conjugated organic semiconductors, thus defining their electronic functionality. All-atom quantum-chemical simulations are potentially capable of describing such phenomena in complex "soft" organic structures, yet they are frequently computationally restrictive. Here we efficiently characterize how electronic excitations in branched conjugated molecules interact with molecular distortions using the exciton scattering (ES) approach as a fundamental principle combined with effective tight-binding models. Molecule geometry deformations are incorporated to the ES view of electronic excitations by identifying the dependence of the Frenkel-type exciton Hamiltonian parameters on the characteristic geometry parameters. We illustrate our methodology using two examples of intermolecular distortions, bond length alternation and single bond rotation, which constitute vibrational degrees of freedom strongly coupled to the electronic system in a variety of conjugated systems. The effect on excited-state electronic structures has been attributed to localized variation of exciton on-site energies and couplings. As a result, modifications of the entire electronic spectra due to geometric distortions can be efficiently and accurately accounted for with negligible numerical cost. The presented approach can be potentially extended to model electronic structures and photoinduced processes in bulk amorphous polymer materials. PMID:26276475
How Geometric Distortions Scatter Electronic Excitations in Conjugated Macromolecules.
Shi, Tian; Li, Hao; Tretiak, Sergei; Chernyak, Vladimir Y
2014-11-20
Effects of disorder and exciton-phonon interactions are the major factors controlling photoinduced dynamics and energy-transfer processes in conjugated organic semiconductors, thus defining their electronic functionality. All-atom quantum-chemical simulations are potentially capable of describing such phenomena in complex "soft" organic structures, yet they are frequently computationally restrictive. Here we efficiently characterize how electronic excitations in branched conjugated molecules interact with molecular distortions using the exciton scattering (ES) approach as a fundamental principle combined with effective tight-binding models. Molecule geometry deformations are incorporated to the ES view of electronic excitations by identifying the dependence of the Frenkel-type exciton Hamiltonian parameters on the characteristic geometry parameters. We illustrate our methodology using two examples of intermolecular distortions, bond length alternation and single bond rotation, which constitute vibrational degrees of freedom strongly coupled to the electronic system in a variety of conjugated systems. The effect on excited-state electronic structures has been attributed to localized variation of exciton on-site energies and couplings. As a result, modifications of the entire electronic spectra due to geometric distortions can be efficiently and accurately accounted for with negligible numerical cost. The presented approach can be potentially extended to model electronic structures and photoinduced processes in bulk amorphous polymer materials.
Wave packet spreading and localization in electron-nuclear scattering
NASA Astrophysics Data System (ADS)
Grabowski, Paul E.; Markmann, Andreas; Morozov, Igor V.; Valuev, Ilya A.; Fichtl, Christopher A.; Richards, David F.; Batista, Victor S.; Graziani, Frank R.; Murillo, Michael S.
2013-06-01
The wave packet molecular dynamics (WPMD) method provides a variational approximation to the solution of the time-dependent Schrödinger equation. Its application in the field of high-temperature dense plasmas has yielded diverging electron width (spreading), which results in diminishing electron-nuclear interactions. Electron spreading has previously been ascribed to a shortcoming of the WPMD method and has been counteracted by various heuristic additions to the models used. We employ more accurate methods to determine if spreading continues to be predicted by them and how WPMD can be improved. A scattering process involving a single dynamic electron interacting with a periodic array of statically screened protons is used as a model problem for comparison. We compare the numerically exact split operator Fourier transform method, the Wigner trajectory method, and the time-dependent variational principle (TDVP). Within the framework of the TDVP, we use the standard variational form of WPMD, the single Gaussian wave packet (WP), as well as a sum of Gaussian WPs, as in the split WP method. Wave packet spreading is predicted by all methods, so it is not the source of the unphysical diminishing of electron-nuclear interactions in WPMD at high temperatures. Instead, the Gaussian WP's inability to correctly reproduce breakup of the electron's probability density into localized density near the protons is responsible for the deviation from more accurate predictions. Extensions of WPMD must include a mechanism for breakup to occur in order to yield dynamics that lead to accurate electron densities.
Electron scattering times in ZnO based polar heterostructures
Falson, J.; Kozuka, Y.; Smet, J. H.; Arima, T.; Tsukazaki, A.; Kawasaki, M.
2015-08-24
The remarkable historic advances experienced in condensed matter physics have been enabled through the continued exploration and proliferation of increasingly richer and cleaner material systems. In this work, we report on the scattering times of charge carriers confined in state-of-the-art MgZnO/ZnO heterostructures displaying electron mobilities in excess of 10{sup 6} cm{sup 2}/V s. Through an examination of low field quantum oscillations, we obtain the effective mass of charge carriers, along with the transport and quantum scattering times. These times compare favorably with high mobility AlGaAs/GaAs heterostructures, suggesting the quality of MgZnO/ZnO heterostructures now rivals that of traditional semiconductors.
J.C. Cornejo, J.L. Herraiz, A. Camsonne, A. Saha, J.M. Udias, G. Urciuoli, J.R. Vignote, K.A. Aniol
2012-09-01
Quasi elastic cross sections were measured for the first time for both negative and positive missing momenta for the {sup 209}Bi(e,e'p){sup 208}Pb reaction leading to the ground state and hole states of (208)Pb. Experimental cross sections obtained between -0.3 GeV/c to 0.3 GeV/c agree with theoretical calculations using RDWIA techniques both in shape and magnitude for the ground state. The data for the ground state production of {sup 208}Pb are consistent with a theoretical model assuming a single proton(1.06 +- 0.10) in the 1h9/2 orbit in {sup 209}Bi.
Practical correction procedures for elastic electron scattering effects in ARXPS
NASA Astrophysics Data System (ADS)
Lassen, T. S.; Tougaard, S.; Jablonski, A.
2001-06-01
Angle-resolved XPS and AES (ARXPS and ARAES) are widely used for determination of the in-depth distribution of elements in the surface region of solids. It is well known that elastic electron scattering has a significant effect on the intensity as a function of emission angle and that this has a great influence on the determined overlayer thicknesses by this method. However the applied procedures for ARXPS and ARAES generally neglect this because no simple and practical procedure for correction has been available. However recently, new algorithms have been suggested. In this paper, we have studied the efficiency of these algorithms to correct for elastic scattering effects in the interpretation of ARXPS and ARAES. This is done by first calculating electron distributions by Monte Carlo simulations for well-defined overlayer/substrate systems and then to apply the different algorithms. We have found that an analytical formula based on a solution of the Boltzmann transport equation provides a good account for elastic scattering effects. However this procedure is computationally very slow and the underlying algorithm is complicated. Another much simpler algorithm, proposed by Nefedov and coworkers, was also tested. Three different ways of handling the scattering parameters within this model were tested and it was found that this algorithm also gives a good description for elastic scattering effects provided that it is slightly modified so that it takes into account the differences in the transport properties of the substrate and the overlayer. This procedure is fairly simple and is described in detail. The model gives a much more accurate description compared to the traditional straight-line approximation (SLA). However it is also found that when attenuation lengths instead of inelastic mean free paths are used in the simple SLA formalism, the effects of elastic scattering are also reasonably well accounted for. Specifically, from a systematic study of several
Electron Scattering at Surfaces and Interfaces of Transition Metals
NASA Astrophysics Data System (ADS)
Zheng, Pengyuan
The effect of surfaces on the electron transport at reduced scales is attracting continuous interest due to its broad impact on both the understanding of materials properties and their application for nanoelectronics. The size dependence of for conductor's electrical resistivity rho due to electron surface scattering is most commonly described within the framework of Fuchs and Sondheimer (FS) and their various extensions, which uses a phenomenological scattering parameter p to define the probability of electrons being elastically (i.e. specularly) scattered by the surface without causing an increase of rho at reduced size. However, a basic understanding of what surface chemistry and structure parameters determine the specularity p is still lacking. In addition, the assumption of a spherical Fermi surface in the FS model is too simple for transition metals to give accurate account of the actual surface scattering effect. The goal of this study is to develop an understanding of the physics governing electron surface/interface scattering in transition metals and to study the significance of their Fermi surface shape on surface scattering. The advancement of the scientific knowledge in electron surface and interface scattering of transition metals can provide insights into how to design high-conductivity nanowires that will facilitate the viable development of advanced integrated circuits, thermoelectric power generation and spintronics. Sequential in situ and ex situ transport measurements as a function of surface chemistry demonstrate that electron surface/interface scattering can be engineered by surface doping, causing a decrease in the rho. For instance, the rho of 9.3-nm-thick epitaxial and polycrystalline Cu is reduced by 11--13% when coated with 0.75 nm Ni. This is due to electron surface scattering which exhibits a specularity p = 0.7 for the Cu-vacuum interface that transitions to completely diffuse (p = 0) when exposed to air. In contrast, Ni-coated surfaces
NASA Technical Reports Server (NTRS)
Kumar, Vijay; Subramanian, K. P.; Krishnakumar, E.
1987-01-01
Absolute electron-helium and electron-neon scattering cross sections have been measured at low electron energies using the powerful technique of photoelectron spectroscopy. The measurements have been carried out at 17 electron energies varying from 0.7 to 10 eV with an accuracy of + or - 2.7 percent. The results obtained in the present work have been compared with other recent measurement and calculations.
Scattering of positrons and electrons by alkali atoms
NASA Technical Reports Server (NTRS)
Stein, T. S.; Kauppila, W. E.; Kwan, C. K.; Lukaszew, R. A.; Parikh, S. P.; Wan, Y. J.; Zhou, S.; Dababneh, M. S.
1990-01-01
Absolute total scattering cross sections (Q sub T's) were measured for positrons and electrons colliding with sodium, potassium, and rubidium in the 1 to 102 eV range, using the same apparatus and experimental approach (a beam transmission technique) for both projectiles. The present results for positron-sodium and -rubidium collisions represent the first Q sub T measurements reported for these collision systems. Features which distinguish the present comparisons between positron- and electron-alkali atom Q sub T's from those for other atoms and molecules (room-temperature gases) which have been used as targets for positrons and electrons are the proximity of the corresponding positron- and electron-alkali atom Q sub T's over the entire energy range of overlap, with an indication of a merging or near-merging of the corresponding positron and electron Q sub T's near (and above) the relatively low energy of about 40 eV, and a general tendency for the positron-alkali atom Q sub T's to be higher than the corresponding electron values as the projectile energy is decreased below about 40 eV.
Measurement of parity violation in electron-quark scattering.
2014-02-01
Symmetry permeates nature and is fundamental to all laws of physics. One example is parity (mirror) symmetry, which implies that flipping left and right does not change the laws of physics. Laws for electromagnetism, gravity and the subatomic strong force respect parity symmetry, but the subatomic weak force does not. Historically, parity violation in electron scattering has been important in establishing (and now testing) the standard model of particle physics. One particular set of quantities accessible through measurements of parity-violating electron scattering are the effective weak couplings C2q, sensitive to the quarks' chirality preference when participating in the weak force, which have been measured directly only once in the past 40 years. Here we report a measurement of the parity-violating asymmetry in electron-quark scattering, which yields a determination of 2C2u - C2d (where u and d denote up and down quarks, respectively) with a precision increased by a factor of five relative to the earlier result. These results provide evidence with greater than 95 per cent confidence that the C2q couplings are non-zero, as predicted by the electroweak theory. They lead to constraints on new parity-violating interactions beyond the standard model, particularly those due to quark chirality. Whereas contemporary particle physics research is focused on high-energy colliders such as the Large Hadron Collider, our results provide specific chirality information on electroweak theory that is difficult to obtain at high energies. Our measurement is relatively free of ambiguity in its interpretation, and opens the door to even more precise measurements in the future.
Measurement of parity violation in electron-quark scattering
NASA Astrophysics Data System (ADS)
The Jefferson Lab Pvdis Collaboration; Wang, D.; Pan, K.; Subedi, R.; Deng, X.; Ahmed, Z.; Allada, K.; Aniol, K. A.; Armstrong, D. S.; Arrington, J.; Bellini, V.; Beminiwattha, R.; Benesch, J.; Benmokhtar, F.; Bertozzi, W.; Camsonne, A.; Canan, M.; Cates, G. D.; Chen, J.-P.; Chudakov, E.; Cisbani, E.; Dalton, M. M.; de Jager, C. W.; de Leo, R.; Deconinck, W.; Deur, A.; Dutta, C.; El Fassi, L.; Erler, J.; Flay, D.; Franklin, G. B.; Friend, M.; Frullani, S.; Garibaldi, F.; Gilad, S.; Giusa, A.; Glamazdin, A.; Golge, S.; Grimm, K.; Hafidi, K.; Hansen, J.-O.; Higinbotham, D. W.; Holmes, R.; Holmstrom, T.; Holt, R. J.; Huang, J.; Hyde, C. E.; Jen, C. M.; Jones, D.; Kang, Hoyoung; King, P. M.; Kowalski, S.; Kumar, K. S.; Lee, J. H.; Lerose, J. J.; Liyanage, N.; Long, E.; McNulty, D.; Margaziotis, D. J.; Meddi, F.; Meekins, D. G.; Mercado, L.; Meziani, Z.-E.; Michaels, R.; Mihovilovic, M.; Muangma, N.; Myers, K. E.; Nanda, S.; Narayan, A.; Nelyubin, V.; Nuruzzaman; Oh, Y.; Parno, D.; Paschke, K. D.; Phillips, S. K.; Qian, X.; Qiang, Y.; Quinn, B.; Rakhman, A.; Reimer, P. E.; Rider, K.; Riordan, S.; Roche, J.; Rubin, J.; Russo, G.; Saenboonruang, K.; Saha, A.; Sawatzky, B.; Shahinyan, A.; Silwal, R.; Sirca, S.; Souder, P. A.; Suleiman, R.; Sulkosky, V.; Sutera, C. M.; Tobias, W. A.; Urciuoli, G. M.; Waidyawansa, B.; Wojtsekhowski, B.; Ye, L.; Zhao, B.; Zheng, X.
2014-02-01
Symmetry permeates nature and is fundamental to all laws of physics. One example is parity (mirror) symmetry, which implies that flipping left and right does not change the laws of physics. Laws for electromagnetism, gravity and the subatomic strong force respect parity symmetry, but the subatomic weak force does not. Historically, parity violation in electron scattering has been important in establishing (and now testing) the standard model of particle physics. One particular set of quantities accessible through measurements of parity-violating electron scattering are the effective weak couplings C2q, sensitive to the quarks' chirality preference when participating in the weak force, which have been measured directly only once in the past 40years. Here we report a measurement of the parity-violating asymmetry in electron-quark scattering, which yields a determination of 2C2u-C2d (where u and d denote up and down quarks, respectively) with a precision increased by a factor of five relative to the earlier result. These results provide evidence with greater than 95 per cent confidence that the C2q couplings are non-zero, as predicted by the electroweak theory. They lead to constraints on new parity-violating interactions beyond the standard model, particularly those due to quark chirality. Whereas contemporary particle physics research is focused on high-energy colliders such as the Large Hadron Collider, our results provide specific chirality information on electroweak theory that is difficult to obtain at high energies. Our measurement is relatively free of ambiguity in its interpretation, and opens the door to even more precise measurements in the future.
Measurement of parity violation in electron-quark scattering.
2014-02-01
Symmetry permeates nature and is fundamental to all laws of physics. One example is parity (mirror) symmetry, which implies that flipping left and right does not change the laws of physics. Laws for electromagnetism, gravity and the subatomic strong force respect parity symmetry, but the subatomic weak force does not. Historically, parity violation in electron scattering has been important in establishing (and now testing) the standard model of particle physics. One particular set of quantities accessible through measurements of parity-violating electron scattering are the effective weak couplings C2q, sensitive to the quarks' chirality preference when participating in the weak force, which have been measured directly only once in the past 40 years. Here we report a measurement of the parity-violating asymmetry in electron-quark scattering, which yields a determination of 2C2u - C2d (where u and d denote up and down quarks, respectively) with a precision increased by a factor of five relative to the earlier result. These results provide evidence with greater than 95 per cent confidence that the C2q couplings are non-zero, as predicted by the electroweak theory. They lead to constraints on new parity-violating interactions beyond the standard model, particularly those due to quark chirality. Whereas contemporary particle physics research is focused on high-energy colliders such as the Large Hadron Collider, our results provide specific chirality information on electroweak theory that is difficult to obtain at high energies. Our measurement is relatively free of ambiguity in its interpretation, and opens the door to even more precise measurements in the future. PMID:24499917
Elastic Scattering of Low-Energy Electrons byTetrahydrofuran
Trevisan, Cynthia S.; Orel, Ann E.; Rescigno, Thomas N.
2006-05-09
We present the results of ab initio calculations for elasticelectron scattering by tetrahydrofuran (THF) using the complex Kohnvariational method. We carried out fixed-nuclei calculations at theequilibrium geometry of the target molecule for incident electronenergies up to 20 eV. The calculated momentum transfer cross sectionsclearly reveal the presence of broad shape resonance behavior in the 8-10eV energy range, in agreement with recent experiments. The calculateddifferential cross sections at 20 eV, which include the effects of thelong-range electron-dipole interaction, are alsofound to be in agreementwith the most recent experimental findings.
NASA Astrophysics Data System (ADS)
Livins, Peteris; Aton, T.; Schnatterly, S. E.
1988-09-01
Electron-energy-loss measurements for an amorphous chemical-vapor-deposited silicon nitride film and evaporated sapphire in the broad energy range 1-200 eV are investigated. A method, not requiring the zero-loss peak, to remove the multiple scattering is discussed, applied, and the optical constants obtained. An Elliot-type model used with aluminum oxide gives a valence-exciton binding energy of 1.36+/-0.2 eV with a band gap of 9.8+/-0.2 eV. The unexpected strength of the nitrogen 2s transition is noted in silicon nitride.
NASA Astrophysics Data System (ADS)
Signorini, C.; Mazzocco, M.; Molini, P.; Pierroutsakou, D.; Boiano, C.; Manea, C.; Strano, E.; Torresi, D.; Di Meo, P.; Nicoletto, M.; Boiano, A.; Glodariu, T.; Grebosz, J.; Guglielmetti, A.; La Commara, M.; Parascandolo, C.; Parascandolo, L.; Sandoli, M.; Soramel, F.; Stroe, L.; Toniolo, N.; Veronese, F.
2013-03-01
The quasi elastic scattering of a 17O projectile from a 58Ni target has been studied at beam energies ranging from 42.5 to 55.0 MeV in 2.5 MeV steps. The total reaction cross sections were derived from the measured angular distributions by using an optical model fit within the coupled-channel code FRESCO. These cross sections are very similar to those measured for 17F (loosely bound by 0.6 MeV), mirror nucleus of 17O (tightly bound by 4.14 MeV). This outcome points out that, in this energy range, the small binding energy of the 17F valence proton has negligible influence onto the reactivity of such a loosely bound projectile, contrary to simple expectations, and to what observed for other loosely bound nuclei. The reaction dynamics seems to be influenced mainly by the Coulomb interaction which is similar for both mirror projectiles.
Resonant electronic Raman scattering: A BCS-like system
NASA Astrophysics Data System (ADS)
Rodrigues, Leonarde N.; Arantes, A.; Schüller, C.; Bell, M. J. V.; Anjos, V.
2016-05-01
In this paper we investigate the resonant intersubband Raman scattering of two-dimensional electron systems in GaAs-AlGaAs single quantum wells. Self-consistent calculations of the polarized and depolarized Raman cross sections show that the appearance of excitations at the unrenormalized single-particle energy are related to three factors: the extreme resonance regime, the existence of degeneracy in intersubband excitations of the electron gas, and, finally, degeneracy in the interactions between pairs of excitations. It is demonstrated that the physics that governs the problem is similar to the one that gives rise to the formation of the superconducting state in the BCS theory of normal metals. Comparison between experiment and theory shows an excellent agreement.
Review of two-photon exchange in electron scattering
J. Arrington, P. G. Blunden, W. Melnitchouk
2011-10-01
We review the role of two-photon exchange (TPE) in electron-hadron scattering, focusing in particular on hadronic frameworks suitable for describing the low and moderate Q^2 region relevant to most experimental studies. We discuss the effects of TPE on the extraction of nucleon form factors and their role in the resolution of the proton electric to magnetic form factor ratio puzzle. The implications of TPE on various other observables, including neutron form factors, electroproduction of resonances and pions, and nuclear form factors, are summarized. Measurements seeking to directly identify TPE effects, such as through the angular dependence of polarization measurements, nonlinear epsilon contributions to the cross sections, and via e+p to e-p cross section ratios, are also outlined. In the weak sector, we describe the role of TPE and gamma-Z interference in parity-violating electron scattering, and assess their impact on the extraction of the strange form factors of the nucleon and the weak charge of the proton.
Total Electron Scattering and Electronic State Excitations Cross Sections for O_2, CO, and CH_4
NASA Technical Reports Server (NTRS)
Kanik, I.; Trajmar, S.; Nickel, J. C.
1993-01-01
Available electron collision cross section data concerning total and elastic scattering, vibrationalexcitation, and ionization for O_2, CO, and CH_4 have been critically reviewed, and a set of crosssections for modeling of planetary atmospheric behavior is recommended. Utilizing theserecommended cross sections, we derived total electronic state excitation cross sections and upperlimits for dissociation cross sections, which in the case of CH_4 should very closely equal the actualdissociation cross section.
Total electron scattering and electronic state excitations cross sections for O2, CO, and CH4
NASA Technical Reports Server (NTRS)
Kanik, I.; Trajmar, S.; Nickel, J. C.
1993-01-01
Available electron collision cross section data concerning total and elastic scattering, vibrational excitation, and ionization for O2, CO, and CH4 have been critically reviewed, and a set of cross sections for modeling of planetary atmospheric behavior is recommended. Utilizing these recommended cross sections, we derived total electronic state excitation cross sections and upper limits for dissociation cross sections, which in the case of CH4 should very closely equal the actual dissociation cross section.
NASA Astrophysics Data System (ADS)
Buhmann, H.; Predel, H.; Molenkamp, L. W.; Gurzhi, R. N.; Kalinenko, A. N.; Kopeliovich, A. I.; Yanovsky, A. V.
2001-10-01
Experimentally electron-beam injection and detection via quantum point-contacts is used to investigate the scattering of a non-equilibrium electron distribution in a two-dimensional electron gas (2DEG) of a GaAs/(Ga,Al)As heterostructure. The energy dependence of electron-electron scattering processes has been studied in a weak magnetic field by investigating the detector signal. Assuming electron beams with a narrow opening angle a magnetic field B perpendicular to the 2DEG plane causes only electrons which are scattered in a point O at an angle α to reach the detector. Thus, it is possible to measure directly the energy dependence of the angular electron distribution after scattering. The experimental data give a clear evidence for the importance of small angle scattering processes in two-dimensional systems, as predicted theoretically.
Compton scattering of electrons from optical pulses for quantum nondemolition measurements
Friberg, S.R. ); Hawkins, R.J. )
1995-01-01
Compton scattering of electrons from photons destroys neither electrons nor photons, permitting quantum nondemolition measurements of the photon number. Here we consider a Compton scattering quantum nondemolition measurement of the photon number of an optical pulse traveling in a prepared optical fiber. A beam of electrons is directed through the evanescent field associated with the optical pulse, causing the electrons to scatter through an angle proportional to the pulse's photon number.
Lee, Young S.
2015-02-12
The research accomplishments during the award involved experimental studies of correlated electron systems and quantum magnetism. The techniques of crystal growth, neutron scattering, x-ray scattering, and thermodynamic & transport measurements were employed, and graduate students and postdoctoral research associates were trained in these techniques.
Low-Energy Electron Scattering by Sugarcane Lignocellulosic Biomass Molecules
NASA Astrophysics Data System (ADS)
Oliveira, Eliane; Sanchez, Sergio; Bettega, Marcio; Lima, Marco; Varella, Marcio
2012-06-01
The use of second generation (SG) bioethanol instead of fossil fuels could be a good strategy to reduce greenhouse gas emissions. However, the efficient production of SG bioethanol has being a challenge to researchers around the world. The main barrier one must overcome is the pretreatment, a very important step in SG bioethanol aimed at breaking down the biomass and facilitates the extraction of sugars from the biomass. Plasma-based treatment, which can generate reactive species, could be an interesting possibility since involves low-cost atmospheric-pressure plasma. In order to offer theoretical support to this technique, the interaction of low-energy electrons from the plasma with biomass is investigated. This study was motived by several works developed by Sanche et al., in which they understood that DNA damage arises from dissociative electron attachment, a mechanism in which electrons are resonantly trapped by DNA subunits. We will present elastic cross sections for low-energy electron scattering by sugarcane biomass molecules, obtained with the Schwinger multichannel method. Our calculations indicate the formation of π* shape resonances in the lignin subunits, while a series of broad and overlapping σ* resonances are found in cellulose and hemicellulose subunits. The presence of π* and σ* resonances could give rise to direct and indirect dissociation pathways in biomass. Then, theoretical resonance energies can be useful to guide the plasma-based pretreatment to break down specific linkages of interest in biomass.
Relativistic electron beam acceleration by Compton scattering of extraordinary waves
Sugaya, R.
2006-05-15
Relativistic transport equations, which demonstrate that relativistic and nonrelativistic particle acceleration along and across a magnetic field and the generation of an electric field transverse to the magnetic field, are induced by nonlinear wave-particle scattering (nonlinear Landau and cyclotron damping) of almost perpendicularly propagating electromagnetic waves in a relativistic magnetized plasma were derived from the relativistic Vlasov-Maxwell equations. The relativistic transport equations show that electromagnetic waves can accelerate particles in the k{sup ''} direction (k{sup ''}=k-k{sup '}). Simultaneously, an intense cross-field electric field, E{sub 0}=B{sub 0}xv{sub d}/c, is generated via the dynamo effect owing to perpendicular particle drift to satisfy the generalized Ohm's law, which means that this cross-field particle drift is identical to the ExB drift. On the basis of these equations, acceleration and heating of a relativistic electron beam due to nonlinear wave-particle scattering of electromagnetic waves in a magnetized plasma were investigated theoretically and numerically. Two electromagnetic waves interact nonlinearly with the relativistic electron beam, satisfying the resonance condition of {omega}{sub k}-{omega}{sub k{sup '}}-(k{sub perpendicular}-k{sub perpendicula=} r{sup '})v{sub d}-(k{sub parallel}-k{sub parallel}{sup '})v{sub b}{approx_equal}m{omega}{sub ce}, where v{sub b} and v{sub d} are the parallel and perpendicular velocities of the relativistic electron beam, respectively, and {omega}{sub ce} is the relativistic electron cyclotron frequency. The relativistic transport equations using the relativistic drifted Maxwellian momentum distribution function of the relativistic electron beam were derived and analyzed. It was verified numerically that extraordinary waves can accelerate the highly relativistic electron beam efficiently with {beta}m{sub e}c{sup 2} < or approx. 1 GeV, where {beta}=(1-v{sub b}{sup 2}/c{sup 2}){sup -1/2}.
Klosowski, Lukasz; Piwinski, Mariusz; Dziczek, Dariusz; Pleskacz, Katarzyna; Chwirot, Stanislaw
2009-12-15
Electron impact coherence parameters for inelastic e-He scattering have been measured for the excitation to the 2 {sup 1}P{sub 1} state at collision energy of 100 eV. The experiment was conducted using angular correlation electron-photon coincidence technique with a magnetic angle changer allowing measurements in full range of scattering angles. The results are compared with other experimental data and theoretical predictions available for this collisional system.
Wave packet spreading and localization in electron-nuclear scattering
NASA Astrophysics Data System (ADS)
Markmann, Andreas; Grabowski*, P. E.; Morozov, I. V.; Valuev, I. A.; Fichtl, C. A.; Batista, V. S.; Graziani, F. R.; Murillo, M. S.; Cimarron Collaboration
2013-10-01
The wave packet molecular dynamics (WPMD) method solves the time-dependent Schrödinger equation via a variational approximation. Application to high-temperature dense plasmas has yielded diverging electron width (spreading) with diminished electron-nuclear interaction. This was previously ascribed to a shortcoming of WPMD and has been counteracted by heuristic additions to the model. We employ various methods to determine if spreading continues to be predicted. Single electron scattering on a periodic array of statically screened protons is used as a model problem for comparison via the numerically exact split operator Fourier transform method, the Wigner trajectory method, and the time-dependent variational principle (TDVP). Within the TDVP, we use as ansätze the standard form of WPMD, a single Gaussian wave packet (WP), as well as the split WP method, a linear combination of Gaussian WPs. Spreading is predicted by all methods, so is not the cause of unphysical diminishing interactions in WPMD. Instead, the Gaussian WP's inability to reproduce breakup of the density into fragments localized near ions is responsible for the deviation between methods. Hence, extensions of WPMD must include a mechanism for breakup. Authors contributed equally.
Signals of strong electronic correlation in ion scattering processes
NASA Astrophysics Data System (ADS)
Bonetto, F.; Gonzalez, C.; Goldberg, E. C.
2016-05-01
Previous measurements of neutral atom fractions for S r+ scattered by gold polycrystalline surfaces show a singular dependence with the target temperature. There is still not a theoretical model that can properly describe the magnitude and the temperature dependence of the neutralization probabilities found. Here, we applied a first-principles quantum-mechanical theoretical formalism to describe the time-dependent scattering process. Three different electronic correlation approaches consistent with the system analyzed are used: (i) the spinless approach, where two charge channels are considered (S r0 and S r+ ) and the spin degeneration is neglected; (ii) the infinite-U approach, with the same charge channels (S r0 and S r+ ) but considering the spin degeneration; and (iii) the finite-U approach, where the first ionization and second ionization energy levels are considered very, but finitely, separated. Neutral fraction magnitudes and temperature dependence are better described by the finite-U approach, indicating that e -correlation plays a significant role in charge-transfer processes. However, none of them is able to explain the nonmonotonous temperature dependence experimentally obtained. Here, we suggest that small changes in the surface work function introduced by the target heating, and possibly not detected by experimental standard methods, could be responsible for that singular behavior. Additionally, we apply the same theoretical model using the infinite-U approximation for the Mg-Au system, obtaining an excellent description of the experimental neutral fractions measured.
Polarization of circumstellar bow shocks due to electron scattering
NASA Astrophysics Data System (ADS)
Shrestha, Manisha; Hoffman, J. L.; Neilson, H.; Ignace, R.
2014-01-01
Circumstellar material (CSM) provides a link between interacting supernovae and their massive progenitor stars. This CSM arises from stellar winds, outflows, or eruptions from a massive star before it explodes and can be detected around stars or supernovae with polarimetric observations. We use a Monte Carlo based radiative transfer code (SLIP) to investigate the polarization created by different models for the CSM surrounding a central source such as supernovae or massive stars. We vary parameters such as the shape, optical depth, temperature, and brightness of the CSM and compare the simulated flux and polarization behavior with observational data. We present results from new simulations that assume a bow shock shape for the CSM. Bow shocks are commonly observed around massive stars; this shape forms when a star moving more quickly than the speed of sound in the local interstellar medium emits a stellar wind that drives a shock wave into the ISM. Since a bow shock projects an aspherical shape onto the sky, light from the central source that scatters in the shock region becomes polarized. We present electron-scattering polarization maps for this geometry and discuss the behavior of observed polarization with viewing angle in the unresolved case.
Low energy elastic electron scattering from CF3Br molecules.
Hargreaves, L R; Brunton, J R; Maddern, T M; Brunger, M J
2015-03-28
CF3Br is a potentially valuable precursor molecule for generating beams of gas phase Br radicals suitable for electron collisions studies. However, the utility of CF3Br for this purpose depends critically on the availability of sound scattering cross sections to allow the contribution of the precursor to be isolated within the total scattering signal. To this end, here we present elastic differential cross section (DCS) measurements for CF3Br at incident energies between 15 and 50 eV. Comparison of these DCSs to those from the only other available experimental study [Sunohara et al., J. Phys. B: At., Mol. Opt. Phys. 36, 1843 (2003)] and a Schwinger multichannel with pseudo potentials (SMCPPs) calculation [Bettega et al., J. Phys. B: At., Mol. Opt. Phys. 36, 1263 (2003)] shows generally a very good accord. Integral elastic and momentum transfer cross sections, derived from our DCSs, are also found to be in quite good agreement with the SMCPP results. PMID:25833582
Elastic electron-deuteron scattering within a relativistic potential model
Khokhlov, N. A. Vakulyuk, A. A.
2015-01-15
Elastic electron-deuteron scattering was considered in the point form of relativistic quantum mechanics. Observables of this process and the dependence of the deuteron form factors on the 4-momentum transfer Q up to 8 fm{sup −1} were calculated. The nucleon-nucleon potentials used in the calculations included the Nijmegen potentials NijmI and NijmII, the Bonn potential CD-Bonn, and the Moscow potential involving forbidden states. A parametrization of the nucleon form factors that complies with present-day experimental results was used as input data. The results of the calculations that employ all of the above potential types describe experimental data at least up to Q ≈ 5 fm{sup −}1.
Parity Violating Electron Scattering and Strangeness in the Nucleon
Maas, Frank E.
2008-10-13
A measurement of the weak form factor of the proton allows a flavor separation of the strangeness contribution to the electromagnetic form factors. The weak form factor is accessed experimentally by the measurement of a parity violating (PV) asymmetry in the scattering of polarized electrons on unpolarized protons. An extended experimental program to measure these parity violating asymmetries has been performed and is going on at different accelerators. After the first round of experiments allowing a separation of the strangeness form factors G{sub E}{sup s} and G{sub M}{sup s} at a Q{sup 2}-value of 0.1 (GeV/c){sup 2}, new, preliminary results have been achieved at 0.23 (GeV/c){sup 2}.
Superelastic electron scattering from laser-excited cesium atoms
Slaughter, D. S.; Karaganov, V.; Brunger, M. J.; Teubner, P. J. O.; Bray, I.; Bartschat, K.
2007-06-15
We present results from a joint experimental and theoretical investigation of superelastic electron scattering from laser-excited Cs atoms in the (6p){sup 2}P{sub 3/2} state. Comparison of the measured pseudo-Stokes parameters P{sub 1}, P{sub 2}, and P{sub 3} and the total degree of polarization P{sup +} for incident energies of 5.5 eV and 13.5 eV, respectively, with theoretical predictions based upon a nonrelativistic convergent close-coupling method and a 24-state semirelativistic Breit-Pauli R-matrix approach indicates that driving channel coupling to convergence for these observables is more important than accounting for relativistic effects.
The Empowerment of Plasma Modeling by Fundamental Electron Scattering Data
NASA Astrophysics Data System (ADS)
Kushner, Mark J.
2015-09-01
Modeling of low temperature plasmas addresses at least 3 goals - investigation of fundamental processes, analysis and optimization of current technologies, and prediction of performance of as yet unbuilt systems for new applications. The former modeling may be performed on somewhat idealized systems in simple gases, while the latter will likely address geometrically and electromagnetically intricate systems with complex gas mixtures, and now gases in contact with liquids. The variety of fundamental electron and ion scattering data (FSD) required for these activities increases from the former to the latter, while the accuracy required of that data probably decreases. In each case, the fidelity, depth and impact of the modeling depends on the availability of FSD. Modeling is, in fact, empowered by the availability and robustness of FSD. In this talk, examples of the impact of and requirements for FSD in plasma modeling will be discussed from each of these three perspectives using results from multidimensional and global models. The fundamental studies will focus on modeling of inductively coupled plasmas sustained in Ar/Cl2 where the electron scattering from feed gases and their fragments ultimately determine gas temperatures. Examples of the optimization of current technologies will focus on modeling of remote plasma etching of Si and Si3N4 in Ar/NF3/N2/O2 mixtures. Modeling of systems as yet unbuilt will address the interaction of atmospheric pressure plasmas with liquids Work was supported by the US Dept. of Energy (DE-SC0001939), National Science Foundation (CHE-124752), and the Semiconductor Research Corp.
Lee, E.Y.; Turner, B.R.; Schowalter, L.J.
1993-07-01
Ballistic-electron-emission microscopy (BEEM) of Au/Si(001) n type was done to study whether elastic scattering in the Au overlayer is dominant. It was found that there is no dependence of the BEEM current on the relative gradient of the Au surface with respect to the Si interface, and this demonstrates that significant elastic scattering must occur in the Au overlayer. Ballistic-electron-emission spectroscopy (BEES) was also done, and, rather than using the conventional direct-current BEES, alternating-current (ac) BEES was done on Au/Si and also on Au/PtSi/Si(001) n type. The technique of ac BEES was found to give linear threshold for the Schottky barrier, and it also clearly showed the onset of electron-hole pair creation and other inelastic scattering events. The study of device quality PtSi in Au/PtSi/Si(001) yielded an attenuation length of 4 nm for electrons of energy 1 eV above the PtSi Fermi energy. 20 refs., 5 figs.
Neutral particle effects on the spin-dependent electron scattering in dense plasmas
Lee, Gyeong Won; Jung, Young-Dae
2014-09-15
The influence of neutral particle collisions on the spin-channel preference for spin-asymmetry scattering is investigated in dense plasmas. The effective electron-electron interaction potential taking into account the electron-neutral collision effects is employed to obtain the scattering cross sections for the spin-triplet and singlet states and spin-asymmetry scattering parameter. It is found that the electron-neutral collision effect enhances the spin-asymmetry scattering parameter as well as the preference for the spin-singlet scattering channel. It is also shown that the preference for the spin-singlet scattering channel increases with an increase of the thermal energy. In addition, it is found that the angular averaged spin-asymmetry parameter decreases with increasing collision frequency and thermal energy. The variations of the spin-singlet and spin-triplet scattering channels are also discussed.
Phase-operation for conduction electron by atomic-scale scattering via single point-defect
Nagaoka, Katsumi Yaginuma, Shin; Nakayama, Tomonobu
2014-03-17
In order to propose a phase-operation technique for conduction electrons in solid, we have investigated, using scanning tunneling microscopy, an atomic-scale electron-scattering phenomenon on a 2D subband state formed in Si. Particularly, we have noticed a single surface point-defect around which a standing-wave pattern created, and a dispersion of scattering phase-shifts by the defect-potential against electron-energy has been measured. The behavior is well-explained with appropriate scattering parameters: the potential height and radius. This result experimentally proves that the atomic-scale potential scattering via the point defect enables phase-operation for conduction electrons.
Scattering of spin-polarized electron in an Aharonov-Bohm potential
Khalilov, V.R.; Ho, C.-L.
2008-05-15
The scattering of spin-polarized electrons in an Aharonov-Bohm vector potential is considered. We solve the Pauli equation in 3 + 1 dimensions taking into account explicitly the interaction between the three-dimensional spin magnetic moment of electron and magnetic field. Expressions for the scattering amplitude and the cross section are obtained for spin-polarized electron scattered off a flux tube of small radius. It is also shown that bound electron states cannot occur in this quantum system. The scattering problem for the model of a flux tube of zero radius in the Born approximation is briefly discussed.
Electron-He(+) P-wave Elastic Scattering and Photoabsorption in Two-electron Systems
NASA Technical Reports Server (NTRS)
Bhatia, A. K.
2006-01-01
In a previous paper [Bhatia, Phys. Rev. A 69,032714 (2004)], electron-hydrogen P-wave scattering phase shifts were calculated using the optical potential approach based on the Feshbach projection operator formalism. This method is now extended to the singlet and triplet electron-He(+) P-wave scattering in the elastic region. Phase shifts are calculated using Hylleraas-type correlation functions with up to 220 terms. Results are rigorous lower bounds to the exact phase shifts and they are compared to phase shifts obtained from the method of polarized orbitals and close-coupling calculations. The continuum functions calculated here are used to calculate photoabsorption cross sections. Photoionization cross sections of He and photodetachment cross sections of H(-) are calculated in the elastic region, i.e. leaving He(+) and H in their respective ground states, and compared with previous calculations. Radiative attachment rates are also calculated.
Zhang, Yawei
2013-10-01
A measurement of the inclusive target single-spin asymmetry has been performed using the quasi-elastic {sup 3}He{up_arrow}(e,e') reaction with a vertically polarized {sup 3}He target at Q{sup 2} values of 0.13, 0.46 and 0.97 GeV{sup 2}. This asymmetry vanishes under the one photon exchange assumption. But the interference between two-photon exchange and one-photon exchange gives rise to an imaginary amplitude, so that a non-zero A{sub y} is allowed. The experiment, conducted in Hall A of Jefferson Laboratory in 2009, used two independent spectrometers to simultaneously measure the target single-spin asymmetry. Using the effective polarization approximation, the neutron single-spin asymmetries were extracted from the measured {sup 3}He asymmetries. The measurement is to establish a non-vanishing A{sub y}. Non-zero asymmetries were observed at all Q{sup 2} points, and the overall precision is an order of magnitude improved over the existing proton data. The data provide new constraints on Generalized Parton Distribution (GPD) models and new information on the dynamics of the two-photon exchange process.
Mihovilovic, Miha
2012-01-01
This thesis is dedicated to a study of a spin-isospin structure of the polarized ^{3}He. First, an introduction to the spin structure of ^{3}He is given, followed by a brief overview of past experiments. The main focus of the thesis is the E05-102 experiment at Jefferson Lab, in which the reactions ${}^3\\vec{He}(\\vec{e},e' d)$ and ${}^3\\vec{He}(\\vec{e},e' p)$ in the quasi-elastic region were studied. The purpose of this experiment was to better understand the effects of the S'- and D-state contributions to the ^{3}He ground-state wave-functions by a precise measurement of beam-target asymmetries A_{x} and A_{z} in the range of recoil momenta from 0 to about 300 MeV/c. The experimental equipment utilized in these measurements is described, with special attention devoted to the calibration of the hadron spectrometer, BigBite. Results on the measured asymmetries are presented, together with first attempts at their comparison to the state-of-the art Faddeev calculations. The remaining open problems and challenges for future work are also discussed.
Katz, J.; Boni, R.; Sorce, C.; Follett, R.; Shoup, M. J. III; Froula, D. H.
2012-10-15
A reflective optical transport system has been designed for the OMEGA Thomson-scattering diagnostic. A Schwarzschild objective that uses two concentric spherical mirrors coupled to a Pfund objective provides diffraction-limited imaging across all reflected wavelengths. This enables the operator to perform Thomson-scattering measurements of ultraviolet (0.263 {mu}m) light scattered from electron plasma waves.
NASA Astrophysics Data System (ADS)
Jones, D. B.; da Costa, R. F.; Varella, M. T. do N.; Bettega, M. H. F.; Lima, M. A. P.; Blanco, F.; García, G.; Brunger, M. J.
2016-04-01
We report absolute experimental integral cross sections (ICSs) for electron impact excitation of bands of electronic-states in furfural, for incident electron energies in the range 20-250 eV. Wherever possible, those results are compared to corresponding excitation cross sections in the structurally similar species furan, as previously reported by da Costa et al. [Phys. Rev. A 85, 062706 (2012)] and Regeta and Allan [Phys. Rev. A 91, 012707 (2015)]. Generally, very good agreement is found. In addition, ICSs calculated with our independent atom model (IAM) with screening corrected additivity rule (SCAR) formalism, extended to account for interference (I) terms that arise due to the multi-centre nature of the scattering problem, are also reported. The sum of those ICSs gives the IAM-SCAR+I total cross section for electron-furfural scattering. Where possible, those calculated IAM-SCAR+I ICS results are compared against corresponding results from the present measurements with an acceptable level of accord being obtained. Similarly, but only for the band I and band II excited electronic states, we also present results from our Schwinger multichannel method with pseudopotentials calculations. Those results are found to be in good qualitative accord with the present experimental ICSs. Finally, with a view to assembling a complete cross section data base for furfural, some binary-encounter-Bethe-level total ionization cross sections for this collision system are presented.
NASA Astrophysics Data System (ADS)
Fransson, J.
2015-09-01
Inelastic scattering off magnetic impurities in a spin-chiral two-dimensional electron gas, e.g., the Rashba system, is shown to generate topological changes in the spin texture of the electron waves emanating from the scattering center. While elastic scattering gives rise to a purely in-plane spin texture for an in-plane magnetic scattering potential, out-of-plane components emerge upon activation of inelastic scattering processes. This property leads to a possibility to make controlled transitions between trivial and nontrivial topologies of the spin texture.
NASA Technical Reports Server (NTRS)
Register, D. F.; Trajmar, S.; Fineman, M. A.; Poe, R. T.; Csanak, G.; Jensen, S. W.
1983-01-01
Differential (in angle) electron scattering experiments on laser-excited Ba-138 1P were carried out at 30- and 100-eV impact energies. The laser light was linearly polarized and located in the scattering plane. The superelastic scattering signal was measured as a function of polarization direction of the laser light with respect to the scattering plane. It was found at low electron scattering angles that the superelastic scattering signal was asymmetric to reflection of the polarization vector with respect to the scattering plane. This is in contradiction with theoretical predictions. An attempt was made to pinpoint the reason for this observation, and a detailed investigation of the influence of experimental conditions on the superelastic scattering was undertaken. No explanation for the asymmetry has as yet been found.
NASA Technical Reports Server (NTRS)
Robinson, P. A.; Newman, D. L.
1990-01-01
Strong turbulence and transit-time scattering theory are applied here to calculate the statistical distribution of intense Langmuir fields and the consequent beam scattering in plasma turbulence driven by an electron beam. The experimentally observed electric-field distributions are compared with predictions of strong-turbulence theory, concentrating on the wave levels, the Gaussian tail of the high-field distribution observed in one experiment, the arrest scale of collapse, and the fractional volume occupied by the highest fields. The Guassian form of the tail is confirmed, and the results imply that the collapse is arrested at a scale where the peak electrostatic energy density is of the same order as the thermal energy density. The theory of transit-time interactions is generalized to include relativistic particle dynamics and is applied to predict the scattering of the beam electrons in energy and angle as they pass through strong Langmuir turbulence. The results support the validity of the recently developed scaling theory of strong turbulence.
Study of Low Energy Electron Inelastic Scattering Mechanisms Using Spin Sensitive Techniques
NASA Astrophysics Data System (ADS)
Hsu, Hongbing
1995-01-01
Spin sensitive electron spectroscopies were used to study low energy electron inelastic scattering from metal surfaces and thin films. In these experiments, a beam of spin polarized electrons from a GaAs source is directed on the sample surface, and the spin polarization and intensity are measured as a function of energy loss and scattering angle by a Mott electron polarimeter coupled with a concentric hemispherical energy analyzer. Systematic studies of the angular dependence of inelastically scattered electrons were conducted on a Cu(100) surface, and Mo/Cu(100), non-magnetized Fe/Cu(100), and Co/Cu(100) films. The polarization and intensity of scattered electrons were measured as function of energy loss and scattering angle. Further studies were also conducted on Ag(100) surface and amorphous Cu/Ag(100) films. From the experimental results, the angular distributions of dipole and impact scattered electrons can be determined individually and both are found to peak in the specular scattering direction. Preliminary studies were conducted on magnetized Co/Cu(100) films. The spin dependent scattering intensity asymmetry was measured, with a clearly observable peak at energy loss of ~1 eV, which coincides with the band splitting. The polarizations of secondary electrons produced by an unpolarized primary beam were also measured. The polarizations can be related to the band polarization of magnetized cobalt films.
Electron Scattering From High-Momentum Neutrons in Deuterium
A.V. Klimenko; S.E. Kuhn
2005-10-12
We report results from an experiment measuring the semi-inclusive reaction D(e,e'p{sub s}) where the proton p{sub s} is moving at a large angle relative to the momentum transfer. If we assume that the proton was a spectator to the reaction taking place on the neutron in deuterium, the initial state of that neutron can be inferred. This method, known as spectator tagging, can be used to study electron scattering from high-momentum (off-shell) neutrons in deuterium. The data were taken with a 5.765 GeV electron beam on a deuterium target in Jefferson Laboratory's Hall B, using the CLAS detector. A reduced cross section was extracted for different values of final-state missing mass W*, backward proton momentum {rvec p}{sub s} and momentum transfer Q{sup 2}. The data are compared to a simple PWIA spectator model. A strong enhancement in the data observed at transverse kinematics is not reproduced by the PWIA model. This enhancement can likely be associated with the contribution of final state interactions (FSI) that were not incorporated into the model. A ''bound neutron structure function'' F{sub 2n}{sup eff} was extracted as a function of W* and the scaling variable x* at extreme backward kinematics, where effects of FSI appear to be smaller. For p{sub s} > 400 MeV/c, where the neutron is far off-shell, the model overestimates the value of F{sub 2n}{sup eff} in the region of x* between 0.25 and 0.6. A modification of the bound neutron structure function is one of possible effects that can cause the observed deviation.
Brodusch, N; Demers, H; Gauvin, R
2013-04-01
A charge-coupled device camera of an electron backscattered diffraction system in a scanning electron microscope was positioned below a thin specimen and transmission Kikuchi patterns were collected. Contrary to electron backscattered diffraction, transmission electron forward scatter diffraction provides phase identification and orientation mapping at the nanoscale. The minimum Pd particle size for which a Kikuchi diffraction pattern was detected and indexed reliably was 5.6 nm. An orientation mapping resolution of 5 nm was measured at 30 kV. The resolution obtained with transmission electron forward scatter diffraction was of the same order of magnitude than that reported in electron nanodiffraction in the transmission electron microscope. An energy dispersive spectrometer X-ray map and a transmission electron forward scatter diffraction orientation map were acquired simultaneously. The high-resolution chemical, phase and orientation maps provided at once information on the chemical form, orientation and coherency of precipitates in an aluminium-lithium 2099 alloy.
Irradiation effects in close binaries in an electron scattering medium
NASA Astrophysics Data System (ADS)
Varghese, B. A.; Srinivasa Rao, M.
2016-03-01
In a close binary system, the effects of irradiation are studied from an extended surface of the secondary component on the atmosphere of the primary. Primary and the secondary components are assumed to have equal radii and the thickness of the atmosphere is assumed to be twice that of the stellar radius of the primary component. Self radiation of the primary component (Ss) is calculated through a numerical solution of line transfer equation in the comoving frame with Compton broadening due to electron scattering. The solution is developed through discrete space theory to deal with different velocities in a spherically expanding medium. The irradiation from the secondary (SI) is calculated using one dimensional rod model. It is assumed to be one, five and ten times the self radiation. The total source function (S=Ss+SI) is the sum of the source functions due to self radiation and that due to irradiation. The line fluxes are computed along the line of sight by using the above source functions. Line profiles are also computed for different line center optical depths along the line of sight of the observer at infinity.
Electron scattering disintegration processes on light nuclei in covariant approach
NASA Astrophysics Data System (ADS)
Kuznietsov, P. E.; Kasatkin, Yu. A.; Klepikov, V. F.
2016-07-01
We provide general analysis of electro-break up process of compound scalar system. We use covariant approach with conserved EM current, which gives the ability to include strong interaction into QED. Therefore, we receive the ability to describe disintegration processes on nonlocal matter fields applying standard Feynman rules of QED. Inclusion of phase exponent into wave function receives a physical sense while we deal with the dominance of strong interaction in the process. We apply Green's function (GF) formalism to describe disintegration processes. Generalized gauge invariant electro-break up process amplitude is considered. One is a sum of traditional pole series and the regular part. We explore the deposits of regular part of amplitude, and its physical sense. A transition from virtual to real photon considered in photon point limit. The general analysis for electro-break up process of component scalar system is given. Precisely conserved nuclear electromagnetic currents at arbitrary square of transited momentum are received. The only undefined quantity in theory is vertex function. Therefore, we have the opportunity to describe electron scattering processes taking into account minimal necessary set of parameters.
NASA Technical Reports Server (NTRS)
Parkins, G. R.; Lawrence, W. E.; Christy, R. W.
1981-01-01
The frequency and temperature dependence of the intraband optical conductivity of the noble metals Cu, Ag and Au is measured and contributions of electron-electron scattering are assessed. Optical measurements were performed at temperatures of 77, 295 and 425 K to obtain values of the Drude electron scattering rate with a linear dependence on temperature which may be attributed to electron-phonon scattering, and a quadratic dependence on photon energy, which is suggestive of electron-electron scattering but is a factor of two to three times greater than would be expected. Comparison of the optical data with dc electrical and thermal resistivity data which also show behavior attributed to electron-electron scattering reveals discrepancies of up to an order of magnitude. Other possible mechanisms for the frequency dependence, including absorptance, electron-surface plasmon interactions, a two-carrier model, and a structure dependence are considered, and it is concluded that the frequency dependence in the Drude scattering rates of the noble metals is not yet quantitatively understood
Ma, C.; Liescheski, P.B.; Bonham, R.A. )
1989-12-01
In this article we describe an experimental technique to measure the total electron-impact cross section by measurement of the attenuation of an electron beam passing through a gas at constant pressure with the unwanted forward scattering contribution removed. The technique is based on the different spatial propagation properties of scattered and unscattered electrons. The correction is accomplished by measuring the electron beam attenuation dependence on both the target gas pressure (number density) and transmission length. Two extended forms of the Beer--Lambert law which approximately include the contributions for forward scattering and for forward scattering plus multiple scattering from the gas outside the electron beam were developed. It is argued that the dependence of the forward scattering on the path length through the gas is approximately independent of the model used to describe it. The proposed methods were used to determine the total cross section and forward scattering contribution from argon (Ar) with 300-eV electrons. Our results are compared with those in the literature and the predictions of theory and experiment for the forward scattering and multiple scattering contributions. In addition, Monte Carlo simulations were performed as a further test of the method.
Fine structure of inelastic electron scattering cross-section spectra for MN
NASA Astrophysics Data System (ADS)
Parshin, A. S.; Igumenov, A. Yu; Mikhlin, Yu L.; Pchelyakov, O. P.; Zhigalov, V. S.
2016-04-01
The comparative analysis of the reflection electron energy loss spectra and the inelastic electron scattering cross-section spectra for Mn was carried out. It is shown that inelastic electron scattering cross-section spectra have certain advantages in the study of the interaction of electrons with the substance as compared to the electron energy loss spectra. The inelastic electron scattering cross section spectra fine structure was analysed by fitting the experimental spectra using the 3 parameters Lorentzian-type formula of Tougaard. This method was used for the quantitative analysis of the contributions of various loss processes in the inelastic electron scattering cross section spectra, determination of the loss peaks energies and origin.
Bose condensate in superfluid sup 4 He and momentum distributions by deep inelastic scattering
Silver, R.N. ); Sokol, P.E. . Dept. of Physics)
1989-01-01
There are several reasons for the high interest in the recent experimental and theoretical progress in understanding deep inelastic neutron scattering from liquid {sup 4}He: it tests the fundamental London hypothesis of a connection between superfluidity and Bose condensation; it provides a quantitative test of ab-initio calculational methods for all systems with strong correlations which are the focus of current quantum many-body research; and it establishes the range of validity of deep inelastic scattering as a method for measuring momentum distributions. In this paper we introduce the concepts of impulse approximation in more detail, we describe recent progress in the theory for final state corrections to the impulse approximation, we present quantitative predictions for neutron scattering experiments, we compare with recent high energy pulsed neutron source experiments on liquid {sup 4}He by P. Sokol and colleagues as well as other attempts to extract the Bose condensate fraction from the neutron scattering data, and we discuss the implications of this progress for future momentum distribution experiments in other systems such as liquid {sup 3}He and quasi-elastic electron nucleus scattering. 42 refs., 23 figs.
NASA Astrophysics Data System (ADS)
Follett, R. K.; Delettrez, J. A.; Edgell, D. H.; Henchen, R. J.; Katz, J.; Myatt, J. F.; Froula, D. H.
2016-11-01
Collective Thomson scattering is a technique for measuring the plasma conditions in laser-plasma experiments. Simultaneous measurements of ion-acoustic and electron plasma-wave spectra were obtained using a 263.25-nm Thomson-scattering probe beam. A fully reflective collection system was used to record light scattered from electron plasma waves at electron densities greater than 1021 cm-3, which produced scattering peaks near 200 nm. An accurate analysis of the experimental Thomson-scattering spectra required accounting for plasma gradients, instrument sensitivity, optical effects, and background radiation. Practical techniques for including these effects when fitting Thomson-scattering spectra are presented and applied to the measured spectra to show the improvements in plasma characterization.
An electron beam polarimeter based on scattering from a windowless, polarized hydrogen gas target
NASA Astrophysics Data System (ADS)
Bernauer, Jan; Milner, Richard
2013-11-01
Here we present the idea to develop a precision polarimeter for low energy, intense polarized electron beams using a windowless polarized hydrogen gas cell fed by an atomic beam source. This technique would use proven technology used successfully in both the electron scattering experiments: HERMES with 27 GeV electron and positron beams at DESY, and BLAST with 850 MeV electron beams at MIT-Bates. At 100 MeV beam energy, both spin-dependent Mo/ller and elastic electron-proton scattering processes have a high cross section and sizable spin asymmetries. The concept is described and estimates for realistic rates for elastic electron-proton scattering and Mo/ller scattering are presented. A number of important issues which affect the ultimate systematic uncertainty are identified.
Time-resolved internal-electron-scattering effect of H2 + in enhanced ionization regions
NASA Astrophysics Data System (ADS)
Li, Yang; Zhou, Yueming; He, Mingrui; Li, Min; Lan, Pengfei; Lu, Peixiang
2016-07-01
We theoretically investigate the electron interference dynamics of H2 + in an intense infrared laser field. At intermediate internuclear distances, an interference fringe appears in the electron momentum distribution. By tracing the time evolution of the electron density, we identify an internal scattering channel of the electrons. The observed fringe is attributed to the interference between the internal scattered and direct photoelectrons. Our results reveal that the electron behaviors inside a molecule can be mapped onto the experimentally accessible photoelectron momentum spectra, suggesting a time-resolved way of probing the complex laser-driven electron dynamics on an attosecond time scale.
Gamma-ray burst spectra from photon-deficient Compton scattering by nonthermal electrons
NASA Technical Reports Server (NTRS)
Zdziarski, Andrzej A.; Lamb, Don Q.
1986-01-01
Consideration is given to a model of gamma-ray burst sources based on repeated Compton scatterings of soft photons by relativistic nonthermal electrons. Relativistic electrons which are continuously produced in the source radiate the total power L supplied to them. Higher order Compton scatterings, which occur when L(soft) is much less than L make the model distinct. The spectrum having an X-ray energy index of about one results from the superposition of the spectral components from several orders of Compton scattering; the change of the slope at several hundred keV arises from the Klein-Nishina decline of the scattering cross section.
NASA Astrophysics Data System (ADS)
Ma, Y.; Kim, Y.; Kalugin, N. G.; Lombardo, A.; Ferrari, A. C.; Kono, J.; Imambekov, A.; Smirnov, D.
2014-03-01
We report the observation of strongly temperature (T)-dependent spectral lines in electronic Raman-scattering spectra of graphite in a high magnetic field up to 45 T applied along the c axis. The magnetic field quantizes the in-plane motion, while the out-of-plane motion remains free, effectively reducing the system dimension from 3 to 1. Optically created electron-hole pairs interact with, or shake up, the one-dimensional Fermi sea in the lowest Landau subbands. Based on the Tomonaga-Luttinger liquid theory, we show that interaction effects modify the spectral line shape from (ω-Δ)-1/2 to (ω-Δ)2α-1/2 at T = 0. At finite T, we predict a thermal broadening factor that increases linearly with T. Our model reproduces the observed T-dependent line shape, determining the electron-electron interaction parameter α to be ˜0.05 at 40 T.
Low-energy electron elastic scattering from Os atom: New electron affinity
NASA Astrophysics Data System (ADS)
Felfli, Z.; Kiros, F.; Msezane, A. Z.
2013-05-01
Bilodeau and Haugan measured the binding energies (BEs) of the ground state and the excited state of the Os- ion to be 1.07780(12) eV and 0.553(3) eV, respectively. These values are consistent with those calculated in. Here our investigation, using the recent complex angular momentum methodology wherein is embedded the crucial electron-electron correlations and the vital core polarization interaction, has found that the near threshold electron-Os elastic scattering total cross section (TCS) is characterized by three stable bound states of the Os- ion formed as resonances during the slow electron collision, with BEs of 1.910 eV, 1.230 eV and 0.224 eV. The new extracted electron affinity (EA) value from the TCS of 1.910 eV for the Os atom is significantly different from that measured in. Our calculated elastic differential cross sections (DCSs) also yield the relevant BEs for the ground and the two excited states of the Os- ion. The complex characteristic resonance structure in the TCS for the Os atom is ideal for catalysis, but makes it difficult to execute the Wigner threshold law in describing the threshold detachment behavior of complex atoms and extracting the reliable attendant EAs. Supported by U.S. DOE, AFOSR and CAU CFNM, NSF-CREST Program.
Artemyev, A. V.; Mourenas, D.; Krasnoselskikh, V. V.
2015-06-15
In this paper, we study relativistic electron scattering by fast magnetosonic waves. We compare results of test particle simulations and the quasi-linear theory for different spectra of waves to investigate how a fine structure of the wave emission can influence electron resonant scattering. We show that for a realistically wide distribution of wave normal angles θ (i.e., when the dispersion δθ≥0.5{sup °}), relativistic electron scattering is similar for a wide wave spectrum and for a spectrum consisting in well-separated ion cyclotron harmonics. Comparisons of test particle simulations with quasi-linear theory show that for δθ>0.5{sup °}, the quasi-linear approximation describes resonant scattering correctly for a large enough plasma frequency. For a very narrow θ distribution (when δθ∼0.05{sup °}), however, the effect of a fine structure in the wave spectrum becomes important. In this case, quasi-linear theory clearly fails in describing accurately electron scattering by fast magnetosonic waves. We also study the effect of high wave amplitudes on relativistic electron scattering. For typical conditions in the earth's radiation belts, the quasi-linear approximation cannot accurately describe electron scattering for waves with averaged amplitudes >300 pT. We discuss various applications of the obtained results for modeling electron dynamics in the radiation belts and in the Earth's magnetotail.
Electron elastic scattering off A @C60 : The role of atomic polarization under confinement
NASA Astrophysics Data System (ADS)
Dolmatov, V. K.; Amusia, M. Ya.; Chernysheva, L. V.
2015-10-01
The present paper explores possible features of electron elastic scattering off endohedral fullerenes A @C60 . It focuses on how dynamical polarization of the encapsulated atom A by an incident electron might alter scattering off A @C60 compared to the static-atom-A case, as well as how the C60 confinement modifies the impact of atomic polarization on electron scattering compared to the free-atom case. The aim is to provide researchers with a "relative frame of reference" for understanding which part of the scattering processes could be due to electron scattering off the encapsulated atom and which could be due to scattering off the C60 cage. To meet the goal, the C60 cage is modeled by an attractive spherical potential of a certain inner radius, thickness, and depth which is a model used frequently in a great variety of fullerene studies to date. Then, the Dyson equation for the self-energy part of the Green's function of an incident electron moving in the combined field of an encapsulated atom A and C60 is solved in order to account for the impact of dynamical polarization of the encaged atom upon e +A @C60 scattering. The Ba@C60 endohedral is chosen as the case study. The impact is found to be significant, and its utterly different role compared to that in e +Ba scattering is unraveled.
Electron scattering by native defects in III-V nitrides and their alloys
Hsu, L.; Walukiewicz, W.
1996-03-01
We have calculated the electron mobilities in GaN and InN taking into consideration scattering by short range potentials, in addition to all standard scattering mechanisms. These potentials are produced by the native defects which are responsible for the high electron concentrations in nominally undoped nitrides. Comparison of the calculated mobilities with experimental data shows that scattering by short range potentials is the dominant mechanism limiting the electron mobilities in unintentionally doped nitrides with large electron concentrations. In the case of Al{sub x}Ga{sub 1-x}N alloys, the reduction in the electron concentration due to the upward shift of the conduction band relative to the native defect level can account for the experimentally measured mobilities. Resonant scattering is shown to be important when the defect and Fermi levels are close in energy.
Relativistic electron scattering from a freely movable proton in a strong laser field
NASA Astrophysics Data System (ADS)
Liu, Ai-Hua; Li, Shu-Min
2014-11-01
We study the electron scattering from the freely movable spin-1/2 proton in the presence of a linearly polarized laser field in the first Born approximation. The dressed state of the electron is described by a time-dependent wave function derived from a perturbation treatment (in a laser field). With the aid of numerical results we explore the dependencies of the differential cross section (DCS) on the electron-impact energy. Due to the mobility of the target, the DCS of this process is modified compared to the Mott scattering, especially in large scattering angles.
Review of the progress in model theoretical studies of e + A @C60 electron scattering
NASA Astrophysics Data System (ADS)
Dolmatov, V.; Amusia, M.; Chernysheva, L.
2016-05-01
A series of recent semi-empirical theoretical studies of electron scattering off endohedral atoms A@ C60 have identified interesting measurements as well as more rigorous calculations of e + A @C60 scattering to perform. This report provides the interested researchers with a review of the most significant findings of works on e + A @C60 scattering. First, we demonstrate features of e + A @C60 elastic scattering of slow electrons and low-frequency bremsstrahlung when both the atom A and the cage C60 are ``frozen''. Then, we ``unfrozen'' the atom A but keep the C60 cage ``frozen'' and demonstrate novel effects of dynamical polarization of the atom A under the ``frozen'' C60 confinement on e + A @C60 scattering. Finally, we demonstrate the combined effect of both the dynamical polarization of the encapsulated atom and the static polarization of C60 on the scattering process. Supported by the NSF grant PHY-1305085.
A model study of np tensor correlation effects on the electron scattering response functions
NASA Astrophysics Data System (ADS)
Leidemann, W.; Orlandini, G.
1990-01-01
The role played by np tensor correlations in the longitudinal and transverse response functions is investigated in the quasi-free region. A model is proposed where the response in plane-wave impulse approximation is modified by introducing responses of strongly correlated deuteron-like pairs. Various pair correlations are studied. The introduction of the pair responses does not lead to a violation of the Coulomb- and the f-sum rules. The results show that tensor correlations shift the strength from the quasi-elastic peak towards higher energy. The additional contributions of meson exchange and isobar currents in the transverse channel can compensate the quenching due to correlations.
LA phonons scattering of surface electrons in Bi2Se3
NASA Astrophysics Data System (ADS)
Huang, Lang-Tao; Zhu, Bang-Fen
2013-03-01
Within the Boltzmann equation formalism we evaluate the transport relaxation time of Dirac surface states (SSs) in the typical topological insulator(TI) Bi2Se3 due to the phonon scattering. We find that although the back-scattering of the SSs in TIs is strictly forbidden, the in-plane scattering between SSs in 3-dimensional TIs is allowed, maximum around the right-angle scattering. Thus the topological property of the SSs only reduces the scattering rate to its one half approximately. Besides, the larger LA deformation potential and lower sound velocity of Bi2Se3 enhance the scattering rate significantly. Compared with the Dirac electrons in graphene, we find the scattering rate of SSs in Bi2Se3 are two orders of magnitudes larger, which agree with the recent transport experiments. This work was supported by the NSFC (Grant No. 11074143), and the Program of Basic Research Development of China (Grant No. 2011CB921901).
LA phonons scattering of surface electrons in Bi2Se3
NASA Astrophysics Data System (ADS)
Huang, Lang-Tao; Zhu, Bang-Fen
2013-12-01
Within the Boltzmann equation formalism we evaluate the transport relaxation time of Dirac surface states (SSs) in the typical topological insulator(TI) Bi2Se3 due to the phonon scattering. We find that although the back-scattering of the SSs in TIs is strictly forbidden, the in-plane scattering between SSs in 3-dimensional TIs is allowed, maximum around the right-angle scattering. Thus the topological property of the SSs only reduces the scattering rate to its one half approximately. Besides, the larger LA deformation potential and lower sound velocity of Bi2Se3 enhance the scattering rate significantly. Compared with the Dirac electrons in graphene, we find the scattering rate of SSs in Bi2Se3 are two orders of magnitudes larger, which agree with the recent transport experiments.
The electron-furfural scattering dynamics for 63 energetically open electronic states
NASA Astrophysics Data System (ADS)
da Costa, Romarly F.; do N. Varella, Márcio T.; Bettega, Márcio H. F.; Neves, Rafael F. C.; Lopes, Maria Cristina A.; Blanco, Francisco; García, Gustavo; Jones, Darryl B.; Brunger, Michael J.; Lima, Marco A. P.
2016-03-01
We report on integral-, momentum transfer- and differential cross sections for elastic and electronically inelastic electron collisions with furfural (C5H4O2). The calculations were performed with two different theoretical methodologies, the Schwinger multichannel method with pseudopotentials (SMCPP) and the independent atom method with screening corrected additivity rule (IAM-SCAR) that now incorporates a further interference (I) term. The SMCPP with N energetically open electronic states (Nopen) at either the static-exchange (Nopen ch-SE) or the static-exchange-plus-polarisation (Nopen ch-SEP) approximation was employed to calculate the scattering amplitudes at impact energies lying between 5 eV and 50 eV, using a channel coupling scheme that ranges from the 1ch-SEP up to the 63ch-SE level of approximation depending on the energy considered. For elastic scattering, we found very good overall agreement at higher energies among our SMCPP cross sections, our IAM-SCAR+I cross sections and the experimental data for furan (a molecule that differs from furfural only by the substitution of a hydrogen atom in furan with an aldehyde functional group). This is a good indication that our elastic cross sections are converged with respect to the multichannel coupling effect for most of the investigated intermediate energies. However, although the present application represents the most sophisticated calculation performed with the SMCPP method thus far, the inelastic cross sections, even for the low lying energy states, are still not completely converged for intermediate and higher energies. We discuss possible reasons leading to this discrepancy and point out what further steps need to be undertaken in order to improve the agreement between the calculated and measured cross sections.
The electron-furfural scattering dynamics for 63 energetically open electronic states.
da Costa, Romarly F; do N Varella, Márcio T; Bettega, Márcio H F; Neves, Rafael F C; Lopes, Maria Cristina A; Blanco, Francisco; García, Gustavo; Jones, Darryl B; Brunger, Michael J; Lima, Marco A P
2016-03-28
We report on integral-, momentum transfer- and differential cross sections for elastic and electronically inelastic electron collisions with furfural (C5H4O2). The calculations were performed with two different theoretical methodologies, the Schwinger multichannel method with pseudopotentials (SMCPP) and the independent atom method with screening corrected additivity rule (IAM-SCAR) that now incorporates a further interference (I) term. The SMCPP with N energetically open electronic states (N(open)) at either the static-exchange (N(open) ch-SE) or the static-exchange-plus-polarisation (N(open) ch-SEP) approximation was employed to calculate the scattering amplitudes at impact energies lying between 5 eV and 50 eV, using a channel coupling scheme that ranges from the 1ch-SEP up to the 63ch-SE level of approximation depending on the energy considered. For elastic scattering, we found very good overall agreement at higher energies among our SMCPP cross sections, our IAM-SCAR+I cross sections and the experimental data for furan (a molecule that differs from furfural only by the substitution of a hydrogen atom in furan with an aldehyde functional group). This is a good indication that our elastic cross sections are converged with respect to the multichannel coupling effect for most of the investigated intermediate energies. However, although the present application represents the most sophisticated calculation performed with the SMCPP method thus far, the inelastic cross sections, even for the low lying energy states, are still not completely converged for intermediate and higher energies. We discuss possible reasons leading to this discrepancy and point out what further steps need to be undertaken in order to improve the agreement between the calculated and measured cross sections. PMID:27036451
NASA Technical Reports Server (NTRS)
Weatherford, Charles A.
1993-01-01
One version of the multichannel theory for electron-target scattering based on the Schwinger variational principle, the SMC method, requires the introduction of a projection parameter. The role of the projection parameter a is investigated and it is shown that the principal-value operator in the SMC equation is Hermitian regardless of the value of a as long as it is real and nonzero. In a basis that is properly orthonormalizable, the matrix representation of this operator is also Hermitian. The use of such basis is consistent with the Schwinger variational principle because the Lippmann-Schwinger equation automatically builds in the correct boundary conditions. Otherwise, an auxiliary condition needs to be introduced, and Takatsuka and McKoy's original value of a is one of the three possible ways to achieve Hermiticity. In all cases but one, a can be uncoupled from the Hermiticity condition and becomes a free parameter. An equation for a based on the variational stability of the scattering amplitude is derived; its solution has an interesting property that the scattering amplitude from a converged SMC calculation is independent of the choice of a even though the SMC operator itself is a-dependent. This property provides a sensitive test of the convergence of the calculation. For a static-exchange calculation, the convergence requirement only depends on the completeness of the one-electron basis, but for a general multichannel case, the a-invariance in the scattering amplitude requires both the one-electron basis and the N plus 1-electron basis to be complete. The role of a in the SMC equation and the convergence property are illustrated using two examples: e-CO elastic scattering in the static-exchange approximation, and a two-state treatment of the e-H2 Chi(sup 1)Sigma(sub g)(+) yields b(sup 3)Sigma(sub u)(+) excitation.
Determination of Rest Mass Energy of the Electron by a Compton Scattering Experiment
ERIC Educational Resources Information Center
Prasannakumar, S.; Krishnaveni, S.; Umesh, T. K.
2012-01-01
We report here a simple Compton scattering experiment which may be carried out in graduate and undergraduate laboratories to determine the rest mass energy of the electron. In the present experiment, we have measured the energies of the Compton scattered gamma rays with a NaI(Tl) gamma ray spectrometer coupled to a 1 K multichannel analyzer at…
Zang Qing; Zhao Junyu; Gao Xiang; Shi Lingwei; Zhang Tao; Xi Xiaoqi; Yang Li; Hu Qingsheng; Sajjad, S.
2007-11-15
A multipulse neodym doped yttrium aluminum garnet laser Thomson scattering system calibrated by the anti-Stokes rotational Raman scattering from nitrogen gas had been developed in the HT-7 superconducting Tokmak. By virtue of this system, measured electron density results of the plasma were obtained. The results showed good repeatability and its total uncertainty was estimated to be {+-}18%.
NASA Astrophysics Data System (ADS)
Wang, Yuan-Cheng; Zhou, Ya-Jun; Cheng, Yong-Jun; Ma, Jia
2009-08-01
Coupled-channels optical calculations for total and resonance excitation integral cross sections for electron scattering on the metastable level 21,3 S of helium are presented. The results are in agreement with other theoretical and experimental data.
Electron scattering studies of DMS, DMDS and DMSO homologous series
NASA Astrophysics Data System (ADS)
Kaur, Jaspreet; Singh, Suvam; Antony, Bobby
2015-12-01
The present paper reports ionisation, elastic and total cross section for the first three members of dimethyl sulphide, dimethyl disulphide and dimethyl sulphoxide family of molecules. The multi-scattering centre spherical complex optical potential formalism is applied for integral elastic and inelastic cross section calculations. From the inelastic part, ionisation cross section is derived using complex scattering potential-ionisation contribution method. The total cross section is then obtained from the sum of elastic and inelastic contributions. A reasonably good agreement is obtained for elastic cross section, wherever comparison is available. The ionisation and total cross section calculation for the complete set of molecules has been performed for the first time.
Quantum correlations of magnetic impurities by a multiple electron scattering in carbon nanotubes
NASA Astrophysics Data System (ADS)
Gamboa Angulo, Didier; Cordourier Maruri, Guillermo; de Coss Gómez, Romeo
In this work we analyze the quantum correlations and polarizations states of magnetic impurities spins, when a multiple electron scattering was taken place. A sequence of non-correlated electrons interacts through scattering producing quantum correlation which will have an impact on the electronic transmission. We consider a short range Heisenberg interaction between ballistic electron and static impurities. We analyze the cases when the electron scattering is produce by one and two impurities, obtaining the electronic transmission rates. Concurrence and fidelity calculations are performed to obtain the level of quantum entanglement and polarization correlations. We also discuss the possible application of this model to metallic and semiconductor carbon nanotubes, which could have important implications on spintronics and quantum information devices.
On the importance of electron-electron scattering for hot-carrier degradation
NASA Astrophysics Data System (ADS)
Tyaginov, Stanislav; Bina, Markus; Franco, Jacopo; Wimmer, Yannick; Kaczer, Ben; Grasser, Tibor
2015-04-01
Using our physics based model for hot-carrier degradation (HCD) we analyze the importance of the effect of electron-electron scattering (EES) on HCD in transistors with different channel lengths. The model is based on a thorough treatment of carrier transport and is implemented into the deterministic Boltzmann transport equation solver ViennaSHE. Two competing mechanism of Si-H bond-breakage are captured by the model: the one triggered by the multiple vibrational excitation of the bond and another which is due to excitation of one of the bonding electrons to an antibonding state by a solitary hot carrier. These processes are considered self-consistently as competing pathways of the same dissociation reaction. To analyze the importance of the EES process we use a series of nMOSFETs with identical architecture but different gate lengths. The gate length varies in the wide range of 44-300 nm to cover short-channel MOSFETs as well as their longer counterparts. According to previous findings, EES starts to become important at a channel length of 180 nm. This situation is captured in the targeted gate length interval. Our results show that the channel length alone is not a sufficient criterion on the importance of EES and that the applied bias conditions have to be taken into account as well.
A measurement of two-photon exchange in unpolarized elastic electron-proton scattering
NASA Astrophysics Data System (ADS)
Yurov, Mikhail
2016-03-01
Jefferson Lab experiment E05-017 was designed to study 2-photon exchange contributions to elastic electron-proton scattering over a wide kinematic range. By detecting the scattered proton instead of the electron these measurements will be very sensitive to the ɛ dependence of the cross section and consequently the ratio GE/GM. The goals of the experiment, the experimental technique and the kinematic range will be presented. The analysis sequence and results of the early steps will be outlined.
Soliton-like solutions in scattering of electrons by an ion in magnetized plasma
NASA Astrophysics Data System (ADS)
Novak, O.; Kholodov, R.
2015-04-01
Scattering of an electron on positive and negative ions has been studied. The transverse electron motion is assumed to be suppressed by a strong magnetic field. Transferred energy is greater for scattering on a negative ion and shows a sharp peak for the impact parameter equal to the distance of the closest approach. It has been found that the motion equations have a soliton-like solution in this case.
Electron recombination, photoionization, and scattering via many-electron compound resonances
NASA Astrophysics Data System (ADS)
Dzuba, V. A.; Flambaum, V. V.; Gribakin, G. F.; Harabati, C.; Kozlov, M. G.
2013-12-01
Highly excited eigenstates of atoms and ions with open f shell are chaotic superpositions of thousands, or even millions, of Hartree-Fock determinant states. The interaction between dielectronic and multielectronic configurations leads to the broadening of dielectronic recombination resonances and relative enhancement of photon emission due to opening of thousands of radiative decay channels. The radiative yield is close to 100% for electron energy ≲1 eV and rapidly decreases for higher energies due to opening of many autoionization channels. The same mechanism predicts suppression of photoionization and relative enhancement of the Raman scattering. Results of our calculations of the recombination rate are in agreement with the experimental data for W20+ and Au25+.
Smith, D. R.; Mazzucato, E.; Lee, W.; Park, H. K.; Domier, C. W.; Luhmann, Jr., N. C.
2009-02-13
A collective scattering system has been installed on the National Spherical Torus Experiment (NSTX) to measure electron gyroscale fluctuations in NSTX plasmas. Up to five distinct wavenumbers are measured simultaneously, and the large toroidal curvature of NSTX plasmas provides enhanced spatial localization. Steerable optics can position the scattering volume throughout the plasma from the magnetic axis to the outboard edge. Initial measurements indicate rich turbulent dynamics on the electron gyroscale. The system will be a valuable tool for investigating the connection between electron temperature gradient turbulence and electron thermal transport in NSTX plasmas.
NASA Astrophysics Data System (ADS)
Carey, Ralph; Lucchese, Robert R.; Gianturco, F. A.
2013-05-01
We present scattering calculations of electron collisions with the platinum-containing compound cis-diamminedichloroplatinum (CDDP), commonly known as cisplatin, between 0.5 eV and 6 eV, and the corresponding isolated Pt atom from 0.1 eV to 10 eV. We find evidence of resonances in e--CDDP scattering, using an ab initio description of the target. We computed scattering matrix elements from equations incorporating exchange and polarization effects through the use of the static-exchange plus density functional correlation potential. Additionally, we made use of a purely local adiabatic model potential that allows Siegert eigenstates to be calculated, thereby allowing inspection of the possible resonant scattering wave functions. The total cross section for electron scattering from (5d10) 1S Pt displays a large magnitude, monotonic decay from the initial collision energies, with no apparent resonance scattering features in any scattering symmetry. By contrast, the e--CDDP scattering cross section shows a small feature near 3.8 eV, which results from a narrow, well localized resonance of b2 symmetry. These findings are then related to the possible electron-mediated mechanism of the action of CDDP on DNA replication as suggested by recent experiments.
Spin-dependent electron scattering at graphene edges on Ni(111).
Garcia-Lekue, A; Balashov, T; Olle, M; Ceballos, G; Arnau, A; Gambardella, P; Sanchez-Portal, D; Mugarza, A
2014-02-14
We investigate the scattering of surface electrons by the edges of graphene islands grown on Ni(111). By combining local tunneling spectroscopy and ab initio electronic structure calculations we find that the hybridization between graphene and Ni states results in strongly reflecting graphene edges. Quantum interference patterns formed around the islands reveal a spin-dependent scattering of the Shockley bands of Ni, which we attribute to their distinct coupling to bulk states. Moreover, we find a strong dependence of the scattering amplitude on the atomic structure of the edges, depending on the orbital character and energy of the surface states.
Electron-cyclotron wave scattering by edge density fluctuations in ITER
Tsironis, Christos; Peeters, Arthur G.; Isliker, Heinz; Chatziantonaki, Ioanna; Vlahos, Loukas; Strintzi, Dafni
2009-11-15
The effect of edge turbulence on the electron-cyclotron wave propagation in ITER is investigated with emphasis on wave scattering, beam broadening, and its influence on localized heating and current drive. A wave used for electron-cyclotron current drive (ECCD) must cross the edge of the plasma, where density fluctuations can be large enough to bring on wave scattering. The scattering angle due to the density fluctuations is small, but the beam propagates over a distance of several meters up to the resonance layer and even small angle scattering leads to a deviation of several centimeters at the deposition location. Since the localization of ECCD is crucial for the control of neoclassical tearing modes, this issue is of great importance to the ITER design. The wave scattering process is described on the basis of a Fokker-Planck equation, where the diffusion coefficient is calculated analytically as well as computed numerically using a ray tracing code.
Evaluation of angular scattering models for electron-neutral collisions in Monte Carlo simulations
NASA Astrophysics Data System (ADS)
Janssen, J. F. J.; Pitchford, L. C.; Hagelaar, G. J. M.; van Dijk, J.
2016-10-01
In Monte Carlo simulations of electron transport through a neutral background gas, simplifying assumptions related to the shape of the angular distribution of electron-neutral scattering cross sections are usually made. This is mainly because full sets of differential scattering cross sections are rarely available. In this work simple models for angular scattering are compared to results from the recent quantum calculations of Zatsarinny and Bartschat for differential scattering cross sections (DCS’s) from zero to 200 eV in argon. These simple models represent in various ways an approach to forward scattering with increasing electron energy. The simple models are then used in Monte Carlo simulations of range, straggling, and backscatter of electrons emitted from a surface into a volume filled with a neutral gas. It is shown that the assumptions of isotropic elastic scattering and of forward scattering for the inelastic collision process yield results within a few percent of those calculated using the DCS’s of Zatsarinny and Bartschat. The quantities which were held constant in these comparisons are the elastic momentum transfer and total inelastic cross sections.
Elastic scattering of vortex electrons provides direct access to the Coulomb phase
NASA Astrophysics Data System (ADS)
Ivanov, I. P.; Seipt, D.; Surzhykov, A.; Fritzsche, S.
2016-10-01
Vortex electron beams are freely propagating electron waves carrying adjustable orbital angular momentum with respect to the propagation direction. Such beams were experimentally realized just a few years ago and are now used to probe various electromagnetic processes. So far, these experiments used the single vortex electron beams, either propagating in external fields or impacting a target. Here, we investigate the elastic scattering of two such aligned vortex electron beams and demonstrate that this process allows one to experimentally measure features which are impossible to detect in the usual plane-wave scattering. The scattering amplitude of this process is well approximated by two plane-wave scattering amplitudes with different momentum transfers, which interfere and give direct experimental access to the Coulomb phase. This phase (shift) affects the scattering of all charged particles and has thus received significant theoretical attention but was never probed experimentally. We show that a properly defined azimuthal asymmetry, which has no counterpart in plane-wave scattering, allows one to directly measure the Coulomb phase as function of the scattering angle.
Scattering of intense laser radiation by a single-electron wave packet
Corson, John P.; Peatross, Justin; Mueller, Carsten; Hatsagortsyan, Karen Z.
2011-11-15
A quantum theoretical description of photoemission by a single laser-driven electron wave packet is presented. Energy-momentum conservation ensures that the partial emissions from individual momentum components of the electron wave packet do not interfere when the driving field is unidirectional. In other words, light scattering by an electron packet is independent of the phases of the pure momentum states comprising the packet; the size of the electron wave packet does not matter. This result holds also in the case of high-intensity multiphoton scattering. Our analysis is first presented in the QED framework. Since QED permits the second-quantized entangled electron-photon final state to be projected onto pure plane-wave states, the Born probability interpretation requires these projections to be first squared and then summed to find an overall probability of a scattering event. The QED treatment indicates how a semiclassical framework can be developed to recover the key features of the correct result.
Spin-dependent intravalley and intervalley electron-phonon scatterings in germanium
NASA Astrophysics Data System (ADS)
Liu, Z.; Nestoklon, M. O.; Cheng, J. L.; Ivchenko, E. L.; Wu, M. W.
2013-08-01
The spin-dependent electron-phonon scattering in the L and Γ valleys of germanium crystals has been investigated theoretically. For this purpose, the 16 × 16 k · p Hamiltonian correctly describing the electron dispersion in the vicinity of the L point of the Brillouin zone in germanium in the lowest conduction bands and the highest valence bands has been constructed. This Hamiltonian facilitates the analysis of the spin-dependent properties of conduction electrons. Then, the electron scatterings by phonons in the L and Γ valleys, i.e., intra- L valley, intra-Γ valley, inter- L-Γ valley, and inter- L-L valley scatterings, have been considered successively. The scattering matrix expanded in powers of the electron wave vectors counted from the centers of the valleys has been constructed using the invariant method for each type of processes. The numerical coefficients in these matrices have been found by the pseudopotential method. The partial contributions of the Elliott and Yafet mechanisms to the spin-dependent electron scattering have been analyzed. The obtained results can be used in studying the optical orientation and relaxation of hot electrons in germanium.
Brooks, R.D.; Pietrzyk, Z.A.
1985-08-01
High energy electrons in plasmas have been attributed to various causes including trapping by electron plasma waves created by stimulated Raman scattering. A theory, consistent with experimental results, based on the acceleration of trapped electrons by such electron plasma waves as they propagate in the presence of a density gradient away from the region where they are created is presented. Single particle simulations show accelerating voltages as high as 20 GV/m.
Optical modeling of plasma-deposited ZnO films: Electron scattering at different length scales
Knoops, Harm C. M. Loo, Bas W. H. van de; Smit, Sjoerd; Ponomarev, Mikhail V.; Weber, Jan-Willem; Sharma, Kashish; Kessels, Wilhelmus M. M.; Creatore, Mariadriana
2015-03-15
In this work, an optical modeling study on electron scattering mechanisms in plasma-deposited ZnO layers is presented. Because various applications of ZnO films pose a limit on the electron carrier density due to its effect on the film transmittance, higher electron mobility values are generally preferred instead. Hence, insights into the electron scattering contributions affecting the carrier mobility are required. In optical models, the Drude oscillator is adopted to represent the free-electron contribution and the obtained optical mobility can be then correlated with the macroscopic material properties. However, the influence of scattering phenomena on the optical mobility depends on the considered range of photon energy. For example, the grain-boundary scattering is generally not probed by means of optical measurements and the ionized-impurity scattering contribution decreases toward higher photon energies. To understand this frequency dependence and quantify contributions from different scattering phenomena to the mobility, several case studies were analyzed in this work by means of spectroscopic ellipsometry and Fourier transform infrared (IR) spectroscopy. The obtained electrical parameters were compared to the results inferred by Hall measurements. For intrinsic ZnO (i-ZnO), the in-grain mobility was obtained by fitting reflection data with a normal Drude model in the IR range. For Al-doped ZnO (Al:ZnO), besides a normal Drude fit in the IR range, an Extended Drude fit in the UV-vis range could be used to obtain the in-grain mobility. Scattering mechanisms for a thickness series of Al:ZnO films were discerned using the more intuitive parameter “scattering frequency” instead of the parameter “mobility”. The interaction distance concept was introduced to give a physical interpretation to the frequency dependence of the scattering frequency. This physical interpretation furthermore allows the prediction of which Drude models can be used in a specific
Thomson scattering from near-solid density plasmas using soft x-ray free electron lasers
Holl, A; Bornath, T; Cao, L; Doppner, T; Dusterer, S; Forster, E; Fortmann, C; Glenzer, S H; Gregori, G; Laarmann, T; Meiwes-Broer, K H; Przystawik, A; Radcliffe, P; Redmer, R; Reinholz, H; Ropke, G; Thiele, R; Tiggesbaumker, J; Toleikis, S; Truong, N X; Tschentscher, T; Uschmann, I; Zastrau, U
2006-11-21
We propose a collective Thomson scattering experiment at the VUV free electron laser facility at DESY (FLASH) which aims to diagnose warm dense matter at near-solid density. The plasma region of interest marks the transition from an ideal plasma to a correlated and degenerate many-particle system and is of current interest, e.g. in ICF experiments or laboratory astrophysics. Plasma diagnostic of such plasmas is a longstanding issue. The collective electron plasma mode (plasmon) is revealed in a pump-probe scattering experiment using the high-brilliant radiation to probe the plasma. The distinctive scattering features allow to infer basic plasma properties. For plasmas in thermal equilibrium the electron density and temperature is determined from scattering off the plasmon mode.
NASA Astrophysics Data System (ADS)
Sargsian, Misak; Cosyn, Wim; Weiss, Christian
2015-10-01
For the past several years there have been an intensive research and development for the possible electron-ion collider that will be able to probe deep inelastic processes at unprecedentedly high energies in eA channel. One of the important advantages of the collider kinematics in DIS processes is the possibility for an unambiguous separation of hadrons emerging from DIS and hadrons fragmenting from the target nucleus. This creates a unique possibility for tagging the interacting nucleon with the recoil slow fragments in the DIS process. The situation is most clean for the deuteron target in which case the recoil particle is a nucleon. In addition, the possibility of having polarized deuteron beams will create unprecedented opportunities in probing polarization degrees of freedom for parton distributions in the interacting bound nucleon. In this work we develop a theoretical framework for the polarized electron-polarized deuteron deep inelastic scattering in which the recoil nucleon is detected in the target fragmentation region. Two main contributions for which theoretical models are developed are the plane-wave impulse approximation, in which no reinteractions are taking place between the final state products of DIS and the recoil nucleon.
A Measurement of Inclusive Quasielastic Electron Cross Sections at X > 1 and High Q{sup 2}
Thomas Petitjean
2002-07-01
Experiment E89-008 measured inclusive electron scattering cross sections from different nuclei in Hall C at Jefferson Laboratory. Cross sections on the low energy loss side of the quasi-elastic peak (x{sub Bj} > 1) are extracted for carbon, aluminum, iron and gold. The data cover four-momentum transfers squared of 0:97 to 5:73 GeV 2 =c 2 . The measured cross sections are compared to cross sections calculated using a microscopic spectral function. The cross section results are also analyzed in terms of the two scaling functions F (y) and f( psi ). For both the data is found to be independent of the momentum transfer (scaling of the first kind). For f( psi ) the data is in addition independent of the mass number A (scaling of the second kind) and thus exhibits superscaling properties.
NASA Astrophysics Data System (ADS)
Parshin, A. S.; Igumenov, A. Yu.; Mikhlin, Yu. L.; Pchelyakov, O. P.; Zhigalov, V. S.
2016-05-01
The inelastic electron scattering cross section spectra of Fe have been calculated based on experimental spectra of characteristic reflection electron energy loss as dependences of the product of the inelastic mean free path by the differential inelastic electron scattering cross section on the electron energy loss. It has been shown that the inelastic electron scattering cross-section spectra have certain advantages over the electron energy loss spectra in the analysis of the interaction of electrons with substance. The peaks of energy loss in the spectra of characteristic electron energy loss and inelastic electron scattering cross sections have been determined from the integral and differential spectra. It has been shown that the energy of the bulk plasmon is practically independent of the energy of primary electrons in the characteristic electron energy loss spectra and monotonically increases with increasing energy of primary electrons in the inelastic electron scattering cross-section spectra. The variation in the maximum energy of the inelastic electron scattering cross-section spectra is caused by the redistribution of intensities over the peaks of losses due to various excitations. The inelastic electron scattering cross-section spectra have been analyzed using the decomposition of the spectra into peaks of the energy loss. This method has been used for the quantitative estimation of the contributions from different energy loss processes to the inelastic electron scattering cross-section spectra of Fe and for the determination of the nature of the energy loss peaks.
NASA Astrophysics Data System (ADS)
Sobków, W.; Błaut, A.
2016-05-01
In this paper, we analyze the theoretically possible scenario beyond the standard model in order to show how the presence of the exotic scalar, tensor, {V}+{A} weak interactions in addition to the standard vector-axial ({V}-{A}) ones may help to distinguish the Dirac from Majorana neutrinos in the elastic scattering of an (anti)neutrino beam off the unpolarized electrons in the relativistic limit. We assume that the incoming (anti)neutrino beam comes from the polarized muon decay at rest and is the left-right chiral superposition with assigned direction of the transversal spin polarization with respect to the production plane. Our analysis is carried out for the flavour (current) neutrino eigenstates. It means that the transverse neutrino polarization estimates are the same both for the Dirac and Majorana cases. We display that the azimuthal asymmetry in the angular distribution of recoil electrons is generated by the interference terms between the standard and exotic couplings, which are proportional to the transversal (anti)neutrino spin polarization and independent of the neutrino mass. This asymmetry for the Majorana neutrinos is larger than for the Dirac ones. We also indicate the possibility of utilizing the azimuthal asymmetry measurements to search for the new CP-violating phases. Our study is based on the assumption that the possible detector (running for 1 year) has the shape of a flat circular ring, while the intense neutrino source is located in the centre of the ring and polarized perpendicularly to the ring. In addition, the large low-threshold, real-time detector is able to measure with a high resolution both the polar angle and the azimuthal angle of outgoing electron momentum. Our analysis is model-independent and consistent with the current upper limits on the non-standard couplings.
Use of single scatter electron monte carlo transport for medical radiation sciences
Svatos, Michelle M.
2001-01-01
The single scatter Monte Carlo code CREEP models precise microscopic interactions of electrons with matter to enhance physical understanding of radiation sciences. It is designed to simulate electrons in any medium, including materials important for biological studies. It simulates each interaction individually by sampling from a library which contains accurate information over a broad range of energies.
Electron diffraction patterns with thermal diffuse scattering maxima around Kikuchi lines
NASA Astrophysics Data System (ADS)
Karakhanyan, R. K.; Karakhanyan, K. R.
2011-01-01
Transmission electron diffraction patterns of silicon with thermal diffuse maxima around Kikuchi lines, which are analogs of the maxima of thermal diffuse electron scattering around point reflections, have been recorded. Diffuse maxima are observed only around Kikuchi lines with indices that are forbidden for the silicon structure. The diffraction conditions for forming these maxima are discussed.
What Causes Scatter-free Transport of Non-relativistic Solar Electrons?
NASA Astrophysics Data System (ADS)
Tan, Lun C.; Reames, Donald V.; Ng, Chee K.; Shao, Xi; Wang, Linghua
2011-02-01
We have examined the cause of the scatter-free transport of non-relativistic solar electrons. Electron scatter-free transport events are compared with the diffusive transport event. The emphasis of our examination is on the energy dependence of electron angular distributions and the steepening of interplanetary magnetic field (IMF) power spectral densities (PSDs). Near and above the proton gyrofrequency, the effects of both R-mode (whistler) and L-mode (electromagnetic ion cyclotron, EMIC) waves need to be taken into account separately. The PSD spectral steepening due to the EMIC wave damping by solar-wind thermal ions becomes essential. In a fast-rise-fast-decay impulsive electron event we have observed such steepening, which significantly reduces PSD levels at frequencies above the proton gyrofrequency. The spectral steepening thus produced favors the occurrence of scatter-free transport of low-energy electrons. Consequently, within the Wind/3D Plasma and Energetic Particle Instrument/Silicon Semiconductor Telescope measured energy range (~25-500 keV), there appears to be an electron energy window, across which the scatter-free transport of lower energy electrons would change to the diffusive transport of higher energy electrons. We have observed such a change and found it is correlated with the occurrence of broken power-law spectra of electrons. Thus the connection between the transition from diffusive to scatter-free electron transport and the concurrent transition from high to low IMF PSD levels with corresponding breaks in the electron power-law energy spectrum and PSD spectrum has been recognized.
Double electron ionization in Compton scattering of high energy photons by helium atoms
Amusia, M.Y.; Mikhailov, A.I.
1995-08-01
The cross section for double-electron ionization of two-electron atoms and ions in Compton scattering of high energy photons is calculated. It is demonstrated that its dependence on the incoming photon frequency is the same as that for single-electron ionization. The ratio of {open_quotes}double-to-single{close_quotes} ionization in Compton scattering was found to be energy independent and almost identical with the corresponding value for photoionization. For the He atom it is 1.68%. This surprising result deserves experimental verification.
Electron muon scattering in the exotic Z(0)' pole
Diaz, H.; Ravinez, O.; Romero, D.; Reyes, J.
2009-04-30
The search for new physics in the future Internacional Linear Collider ILC, implies the existence of new particles, among them, the Z(0)' particle. In this regard, we calculate the e{sup +}+e{sup -}{yields}{mu}{sup +}+{mu}{sup -} scattering cross section near the Z(0)' pole, whitin the contex of the SU(3){sub L}xU(1){sub Y} weak model, which contains exotic leptons, quarks, and bosons (E,J,U,V) with the finality of obtain constraints in the parameters of the model.
Visualizing One-Dimensional Electronic States and their Scattering in Semi-conducting Nanowires
NASA Astrophysics Data System (ADS)
Beidenkopf, Haim; Reiner, Jonathan; Norris, Andrew; Nayak, Abhay Kumar; Avraham, Nurit; Shtrikman, Hadas
One-dimensional electronic systems constitute a fascinating playground for the emergence of exotic electronic effects and phases, within and beyond the Tomonaga-Luttinger liquid paradigm. More recently topological superconductivity and Majorana modes were added to that long list of phenomena. We report scanning tunneling microscopy and spectroscopy measurements conducted on pristine, epitaxialy grown InAs nanowires. We resolve the 1D electronic band structure manifested both via Van-Hove singularities in the local density-of-states, as well as by the quasi-particle interference patterns, induced by scattering from surface impurities. By studying the scattering of the one-dimensional electronic states off various scatterers, including crystallographic defects and the nanowire end, we identify new one-dimensional relaxation regimes and yet unexplored effects of interactions. Some of these may bear implications on the topological superconducting state and Majorana modes therein. The authors acknowledge support from the Israeli Science Foundation (ISF).
NASA Astrophysics Data System (ADS)
Sauer, Stephan P. A.; Paidarová, Ivana; Čársky, Petr; Čurík, Roman
2016-05-01
In this paper we present calculations of the static polarizability and its derivatives for the adamantane molecule carried out at the density functional theory level using the B3LYP exchange-correlation functional and Sadlej's polarized valence triple zeta basis set. It is shown that the polarizability tensor is necessary to correct long-range behavior of DFT functionals used in electron-molecule scattering calculations. The impact of such a long-range correction is demonstrated on elastic and vibrationally inelastic electron collisions with adamantane, a molecule representing a large polyatomic target for electron scattering calculations. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.
Chutjian, A
1979-03-01
Geometries and focal properties are given for two types of electron-lens systems commonly needed in electron scattering. One is an electron gun which focuses electrons from a thermionic emitter onto a fixed point (target) over a wide range of final energies. The other is an electron analyzer system which focuses scattered electrons of variable energy onto a fixed position (e.g., the entrance plane of an analyzer) at fixed energy with a zero final beam angle. Analyzer-system focusing properties are given for superelastic, elastic, and inelastically-scattered electrons. Computer calculations using recent, accurate tube-lens focal properties are used to compute lens voltages, locations and diameters of all pupils and windows, and filling factors and asymptotic rays throughout each lens system. Focus voltages as a function of electron energy and energy change are given, and limits of operation of each system discussed. Both lens systems have been in routine use for several years, and good agreement has been consistently found between calculated and operating lens voltages.
Precision Determination of Electron Scattering Angle by Differential Nuclear Recoil Energy Method
Liyanage, Nilanga; Saenboonruang, Kiadtisak
2015-09-01
The accurate determination of the scattered electron angle is crucial to electron scattering experiments, both with open-geometry large-acceptance spectrometers and ones with dipole-type magnetic spectrometers for electron detection. In particular, for small central-angle experiments using dipole-type magnetic spectrometers, in which surveys are used to measure the spectrometer angle with respect to the primary electron beam, the importance of the scattering angle determination is emphasized. However, given the complexities of large experiments and spectrometers, the accuracy of such surveys is limited and insufficient to meet demands of some experiments. In this article, we present a new technique for determination of the electron scattering angle based on an accurate measurement of the primary beam energy and the principle of differential nuclear recoil. This technique was used to determine the scattering angle for several experiments carried out at the Experimental Hall A, Jefferson Lab. Results have shown that the new technique greatly improved the accuracy of the angle determination compared to surveys.
Electron-nucleus scattering at small angles in the field of a pulsed laser wave
NASA Astrophysics Data System (ADS)
Lebed', A. A.
2016-04-01
We study scattering of an electron by a screened potential of a nucleus in the field of a pulsed laser wave at small scattering angles. The interaction of an electron with the field of a nucleus is considered in the first Born approximation. An external field of a pulsed laser is accounted accurately as a quasimonochromatic wave. Analytical expressions are obtained for the transition amplitude and the cross section of the considered process. Scattering kinematics is defined at the minimal value of a transferred momentum. In this case the cross section contains a peak near the preferred scattering direction. It is shown that the maximum value of the cross section is determined by both the initial-electron energy and the energy of an external-field photon. Thus, the cross section of electron-nucleus scattering in a pulsed laser field can exceed in two orders of magnitude the cross section in absence of an external field in the case of ultrarelativistic energies and external field of a free-electron laser with keV-order photon energy.
Precision determination of electron scattering angle by differential nuclear recoil energy method
Liyanage, N.; Saenboonruang, K.
2015-12-01
The accurate determination of the scattered electron angle is crucial to electron scattering experiments, both with open-geometry large-acceptance spectrometers and ones with dipole-type magnetic spectrometers for electron detection. In particular, for small central-angle experiments using dipole-type magnetic spectrometers, in which surveys are used to measure the spectrometer angle with respect to the primary electron beam, the importance of the scattering angle determination is emphasized. However, given the complexities of large experiments and spectrometers, the accuracy of such surveys is limited and insufficient to meet demands of some experiments. In this article, we present a new technique for determination of the electron scattering angle based on an accurate measurement of the primary beam energy and the principle of differential nuclear recoil. This technique was used to determine the scattering angle for several experiments carried out at the Experimental Hall A, Jefferson Lab. Results have shown that the new technique greatly improved the accuracy of the angle determination compared to surveys.
Effect of the third π ∗ resonance on the angular distributions for electron-pyrimidine scattering
NASA Astrophysics Data System (ADS)
Mašín, Zdeněk; Gorfinkiel, Jimena D.
2016-07-01
We present a detailed analysis of the effect of the well known third π∗ resonance on the angular behaviour of the elastic cross section in electron scattering from pyrimidine. This resonance, occurring approximately at 4.7 eV, is of mixed shape and core-excited character. Experimental and theoretical results show the presence of a peak/dip behaviour in this energy range, that is absent for other resonances. Our investigations show that the cause of the peak/dip is an interference of background p-wave to p-wave scattering amplitudes with the amplitudes for resonant scattering. The equivalent resonance in pyrazine shows the same behaviour and the effect is therefore likely to appear in other benzene-like molecules. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.
Elastic electron scattering in krypton in the energy range from 5 to 10 eV
Linert, Ireneusz; Mielewska, Brygida; Zubek, Mariusz; King, George C.
2010-01-15
Differential cross sections for elastic electron scattering in krypton have been measured at the energies of 5,7.5, and 10 eV over the scattering angle range from 30 deg. to 180 deg. The measurements for backward scattering employed the magnetic angle-changing technique. These differential cross sections have been integrated to yield the elastic integral and momentum transfer cross sections at the above energies. These new results are compared with the most recent measurements and calculations of the respective cross sections in krypton. The dependence of the differential cross sections on atomic polarizability of the heavier rare gas atoms argon, krypton, and xenon has also been investigated over the electron energy range 5-30 eV and for forward, backward, and intermediate scattering angles.
Alignment creaction by elastic electron scattering by ions in a plasma
Csanak, G. Y.; Kilcrease, D. P.; Bray, I; Fursa, D. V.
2004-01-01
Alignment creation by elastic hcavy particle scattering has been studied for many years by Oniont, by Dyakonov and Perel, and by Petrashen, Rebane, and Rebane. The technique has been adapted for arbitrary perturbers (including electrons) by Fujimoto et al. and by Fujimoto and Kazantsev. In the case of heavy particle perturbers (e.g. ions) there was an argument by Petrashen, Rebane, and Rebane that under certain conditions (namely only elastic scattering is possible and the semi-classical straight-line trajectory assumption holds) in the case of an isolated level, alignment can not be created by elastic scattering. This contention has been questioned by Dashevskaya and Nikitin who argued that the above conclusion of Petrashen et al. is due to an extra symmetry introduced into the problem by the straight-line trajectory approximation (which introduces detailed balance for magnetic sublevel to magnetic sublevel transitions) and if a more accurate approximation is made alignment creation can be obtained by elastic scattering. See the discussion in Fujimoto et al. In the case of inelastic scattering Kazantsev et al. gave a quantum-mechanical definition of the alignment creation cross section. In carlier works, Trdjrnaf et al. and Csanak et al. adopted the inelastic alignment creation cross section definition of Kazantsev et al. for elastic electron scattering and reported results for Ba and O V ions based on that formula. (Apparently Dashevskaya and Nikitin used the same formula.) However, a closer inspection of the semi-classical formula of Fujimoto et al. and Fujimoto and Kazantsev 1141 as well as the quantum-mechanical rate equations of Ben-Reuven and Nienhuis and Bommier and Sahal-Brechot also indicated that the inelastic scattering fomiula might not hold for elastic scattering. The present work reinvestigates this problem, and shows that indeed the alignment creation cross section formula is different for elastic scattering, as compared to the inelastic Scattering
Thermal Photon and Residual Gas Scattering of the Electrons in the ILC RTML
Seletskiy, S.M.; /SLAC
2006-08-16
The scattering of the primary beam electrons off of thermal photons and residual gas molecules in the projected International Linear Collider (ILC) is a potential source of beam haloes which must be collimated downstream of the linac. In this report we give the analytic estimations of the individual input that each of the main scattering processes makes in the production of off-energy and large amplitude particles in the Damping Ring to Main Linac region (RTML).
Laser-assisted inelastic scattering of electrons by helium atoms
NASA Astrophysics Data System (ADS)
Agueny, H.; Makhoute, A.; Dubois, A.; Ajana, I.; Rahali, G.
2015-07-01
The differential cross section for electron-impact excitation of helium atoms in the presence of a linearly polarized laser field is calculated. The interaction of the laser field with both the projectile electron and the target atom is treated in a fully nonperturbative way, while the electron-atom interaction is treated within the first Born approximation. We are interested in studying two cases where the photon energy of the laser field is chosen to be far from resonance and when it matches with 2 1S ⟶2 1P and 3 1S ⟶3 1P transition frequencies. The agreement between perturbative and nonperturbative results is good, except close to the resonance where the perturbative cross sections diverge while the nonperturbative ones predict no maximum of the cross sections. Another interesting effect is the presence of an avoided crossing of the Floquet pseudoenergies at resonance.
Pauli blocking and final-state interaction in electron-nucleus quasielastic scattering
Liu, Lon-chang
2008-01-01
The nucleon final-state interaction in electron-nucleus quasielastic scattering is studied. Based on the unitarity equation satisfied by the scattering-wave operators, a doorway model is developed to implement the Pauli-blocking of nucleon knockout. The model is complementary to the commonly used nuclear Fermi gas model which can not be applied with confidence to light- and medium-mass nuclei. Pauli blocking in these latter nuclei is illustrated with the case of Coulomb interaction. Significant effects are noted for beam energies below {approx} 350 MeV/c. Extension of the model to high-energy hadron-nucleus quasielastic scatterings is discussed.
Gorelik, Tatiana E; Schmidt, Martin U; Kolb, Ute; Billinge, Simon J L
2015-04-01
This paper shows that pair-distribution function (PDF) analyses can be carried out on organic and organometallic compounds from powder electron diffraction data. Different experimental setups are demonstrated, including selected area electron diffraction and nanodiffraction in transmission electron microscopy or nanodiffraction in scanning transmission electron microscopy modes. The methods were demonstrated on organometallic complexes (chlorinated and unchlorinated copper phthalocyanine) and on purely organic compounds (quinacridone). The PDF curves from powder electron diffraction data, called ePDF, are in good agreement with PDF curves determined from X-ray powder data demonstrating that the problems of obtaining kinematical scattering data and avoiding beam damage of the sample are possible to resolve.
Measurements of ultra-low-energy electron scattering cross sections of atoms and molecules
Kitajima, M.; Shigemura, K.; Kurokawa, M.; Odagiri, T.; Kato, H.; Hoshino, M.; Tanaka, H.; Ito, K.
2014-03-05
A new experimental technique for the total cross section measurements of ultra-low energy electron collisions with atoms and molecules utilizing the synchrotron radiation is presented. The technique employs a combination of the penetrating field technique and the threshold photoionization of rare gas atoms using the synchrotron radiation as an electron source in order to produce a high resolution electron beam at very low energy. Absolute total cross sections for electron scattering from He, Ne, Ar, Kr, and Xe in the energy region from extremely low electron energy to 20 eV are presented.
NASA Astrophysics Data System (ADS)
Mayer, A.; Vigneron, J.-P.
1999-07-01
Electronic projection imaging is described in the framework of a multiple-scattering theory, by using a combination of transfer-matrix and Green's-function formalisms. The transfer-matrix methodology is used to compute the wave propagation within the tip and object scattering region, while the Green's-function formalism is used to describe the electron projection from the scatterers towards a distant imaging screen. This full-order theory is needed to overcome the limits of the first Born approximation and deal with three-dimensional effects. In particular, this approach is able to account for sucking-in and standing-wave effects taking place close to or inside the object. The simulation of the electronic diffraction by a model nanoscopic carbon rod, eventually containing inhomogeneities, is considered in detail.
Two-stage electron acceleration by simultaneous stimulated Raman backward and forward scattering
Bertrand, P.; Ghizzo, A.; Karttunen, S.J.; Paettikangas, T.J.H.; Salomaa, R.R.E.; Shoucri, M.
1995-08-01
The coexistence of stimulated Raman forward and backward scattering of intense electromagnetic radiation, which can occur, for instance, in laser fusion plasmas, is investigated. The simultaneous Raman forward and backward scattering is shown to create an electrostatic field structure which is exceptionally efficient in producing highly relativistic electrons. The mechanism of the electron acceleration is analyzed both by Vlasov--Maxwell simulations with self-consistent fields and by test particle calculations with prescribed electrostatic fields. The Vlasov--Maxwell simulations reveal that the two plasma waves generated by the backward and forward scattering are spatially separated, and thus form a two-stage electron ``accelerator.`` {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
Scattering-induced quantum correlation in electronic waveguides with static magnetic impurities
NASA Astrophysics Data System (ADS)
Ghanbari-Adivi, E.; Soltani, M.; Alami, Z.; Sheikhali, M.
2016-07-01
Entanglement generation due to low-energy scattering of the transporting electrons in an electronic waveguide by a quantum dot magnetic impurity is theoretically investigated. The transverse confining potential of the waveguide is considered as a two-dimensional harmonic potential, and the interaction of the electron with the impurity is described by a zero-range pseudopotential modulated by an Ising or a Heisenberg spin interaction. Our calculation shows that the scattering process leads to creation of a considerable amount of entanglement in the state of the reflected and transmitted electrons. The situation is extended to the scattering of the electrons by two well-separated magnetic impurities localized on the nanowire axis. It is shown that the scattering process causes the magnetic impurities embedded in the nanowire to share their quantum information; subsequently, they can be entangled by spin interaction with the injected electron. The created entanglement between the impurities is calculated and discussed. It is shown that the exact three-dimensional problem can be approximated as a one-dimensional problem under certain circumstances. The approximate results are compared to exact calculations and discussed.
NASA Astrophysics Data System (ADS)
Lavraud, B.; Zhang, Y. C.; Vernisse, Y.; Gershman, D. J.; Dorelli, J.; Cassak, P. A.; Dargent, J.; Pollock, C.; Giles, B.; Aunai, N.; Argall, M.; Avanov, L.; Barrie, A.; Burch, J.; Chandler, M.; Chen, L.-J.; Clark, G.; Cohen, I.; Coffey, V.; Eastwood, J. P.; Egedal, J.; Eriksson, S.; Ergun, R.; Farrugia, C. J.; Fuselier, S. A.; Génot, V.; Graham, D.; Grigorenko, E.; Hasegawa, H.; Jacquey, C.; Kacem, I.; Khotyaintsev, Y.; MacDonald, E.; Magnes, W.; Marchaudon, A.; Mauk, B.; Moore, T. E.; Mukai, T.; Nakamura, R.; Paterson, W.; Penou, E.; Phan, T. D.; Rager, A.; Retino, A.; Rong, Z. J.; Russell, C. T.; Saito, Y.; Sauvaud, J.-A.; Schwartz, S. J.; Shen, C.; Smith, S.; Strangeway, R.; Toledo-Redondo, S.; Torbert, R.; Turner, D. L.; Wang, S.; Yokota, S.
2016-04-01
Based on high-resolution measurements from NASA's Magnetospheric Multiscale mission, we present the dynamics of electrons associated with current systems observed near the diffusion region of magnetic reconnection at Earth's magnetopause. Using pitch angle distributions (PAD) and magnetic curvature analysis, we demonstrate the occurrence of electron scattering in the curved magnetic field of the diffusion region down to energies of 20 eV. We show that scattering occurs closer to the current sheet as the electron energy decreases. The scattering of inflowing electrons, associated with field-aligned electrostatic potentials and Hall currents, produces a new population of scattered electrons with broader PAD which bounce back and forth in the exhaust. Except at the center of the diffusion region the two populations are collocated and appear to behave adiabatically: the inflowing electron PAD focuses inward (toward lower magnetic field), while the bouncing population PAD gradually peaks at 90° away from the center (where it mirrors owing to higher magnetic field and probable field-aligned potentials).
Scattering-induced quantum correlation in electronic waveguides with static magnetic impurities
NASA Astrophysics Data System (ADS)
Ghanbari-Adivi, E.; Soltani, M.; Alami, Z.; Sheikhali, M.
2016-10-01
Entanglement generation due to low-energy scattering of the transporting electrons in an electronic waveguide by a quantum dot magnetic impurity is theoretically investigated. The transverse confining potential of the waveguide is considered as a two-dimensional harmonic potential, and the interaction of the electron with the impurity is described by a zero-range pseudopotential modulated by an Ising or a Heisenberg spin interaction. Our calculation shows that the scattering process leads to creation of a considerable amount of entanglement in the state of the reflected and transmitted electrons. The situation is extended to the scattering of the electrons by two well-separated magnetic impurities localized on the nanowire axis. It is shown that the scattering process causes the magnetic impurities embedded in the nanowire to share their quantum information; subsequently, they can be entangled by spin interaction with the injected electron. The created entanglement between the impurities is calculated and discussed. It is shown that the exact three-dimensional problem can be approximated as a one-dimensional problem under certain circumstances. The approximate results are compared to exact calculations and discussed.
A split-electrode for clearing scattered electrons in the RHIC e-lens
Gu X.; Pikin, A.; Thieberger, P.; Fischer, W.; Hock, J.; Hamdi, K.; Gassner,D.; Luo, Y.; Montag, C.; Okamura, M.
2012-05-20
We are designing two electron lenses that will be installed at RHIC IR10 to compensate for the head-on beam-beam effect. To clear accumulated scattered electrons from 100 GeV proton-electron head-on collisions in the e-lens, a clearing split electrode may be constructed. The feasibility of this proposed electrode was demonstrated via the CST Particle Studio and Opera program simulations. By splitting one of the drift tubes in the e-lens and applying {approx} 380 V across the two parts, the scattered electrons can be cleared out within several hundred micro-seconds. At the same time we can restrict the unwanted shift of the primary electron-beam that already passed the 2-m interaction region in e-lens, to less than 15um.
Classical electron-ion scattering in strongly magnetized plasmas. I. A generalized Coulomb logarithm
Geller, D.K.; Weisheit, J.C.
1997-12-01
In a strongly magnetized plasma, where the electron cyclotron radius is less than the Debye length, the Rutherford scattering formula is expected to break down. In this paper, analytic expressions are developed for classical, small-angle scattering of electrons and ions in strong magnetic fields. Numerical evaluation of these expressions shows quantitatively how strong B fields can significantly inhibit electron deflections. The influence of the field on transport phenomena is then explored{emdash}in particular, a generalized Coulomb logarithm which includes the effects of a magnetic field is formulated and computed for a wide range of trajectory pitch angles. This generalized Coulomb logarithm is used to illustrate how a strong field influences the effective electron-ion cross section, the electron velocity diffusion coefficient, and the (parallel) electrical and thermal resistivity in a variety of astrophysical and terrestrial plasmas. {copyright} {ital 1997 American Institute of Physics.}
Entanglement of magnetic impurities through electron scattering in an electric field
NASA Astrophysics Data System (ADS)
Lazo-Arjona, Oscar; Cordourier-Maruri, Guillermo; de Coss, Romeo
2015-10-01
We show that the entanglement between two distant magnetic impurities, generated via electron scattering, can be easily modulated by controlling the magnitude of an applied external electric field. We assume that the two magnetic impurities are fixed and located on an one-dimensional quantum wire. A ballistic electron moving through the wire is scattered off by both impurities, so the electron spin can be seen as a mediator between the spins of the impurities. Heisenberg operators are used to describe the interactions between electron and impurities spins. We use a wave guide formalism to model the ballistic electron wave function. Entanglement control is shown to be possible for three different protocols of entanglement detection. The effect of detection protocols on the entanglement extraction is discussed.
A time-dependent approach to electron-atom scattering
NASA Astrophysics Data System (ADS)
Buffington, Gavin Douglas
1997-08-01
This time-dependent approach utilizes a fully correlated two electron wave function developed by Bottcher, Schultz and Madison. A finite element spline basis is employed with the principle of collocation in order to express the wave function and Hamiltonian numerically. An initial state, composed of a wavepacket for the projectile and an isolated atomic wave function, is evolved in time according to the time-dependent Schrodinger equation. Probabilities for excitation and ionization are computed as a function of time by taking projections onto states and pseudostates of the target atom. The wavepacket approach obviates the need for consideration of three- body boundary conditions and the asymptotic form of the wave function. Cross sections for electron impact excitation and ionization are obtained and compared with results from other theoretical methods.
Focusing effects in laser-electron Thomson scattering
NASA Astrophysics Data System (ADS)
Harvey, Chris; Marklund, Mattias; Holkundkar, Amol R.
2016-09-01
We study the effects of laser pulse focusing on the spectral properties of Thomson scattered radiation. Modeling the laser as a paraxial beam we find that, in all but the most extreme cases of focusing, the temporal envelope has a much bigger effect on the spectrum than the focusing itself. For the case of ultrashort pulses, where the paraxial model is no longer valid, we adopt a subcycle vector beam description of the field. It is found that the emission harmonics are blue shifted and broaden out in frequency space as the pulse becomes shorter. Additionally the carrier envelope phase becomes important, resulting in an angular asymmetry in the spectrum. We then use the same model to study the effects of focusing beyond the limit where the paraxial expansion is valid. It is found that fields focussed to subwavelength spot sizes produce spectra that are qualitatively similar to those from subcycle pulses due to the shortening of the pulse with focusing. Finally, we study high-intensity fields and find that, in general, the focusing makes negligible difference to the spectra in the regime of radiation reaction.
Hongguo Zhu
2000-08-01
The form factors of the neutron give information on fundamental properties of the nucleons and provide a critical testing ground for models based on QCD. In late 1998, Jefferson Lab (JLAB) experiment E93-026 measured the spin-dependent part of the exclusive (e, e'n) scattering cross section from a polarized deuterated ammonia ({sup 15}ND{sub 3}) target at a four momentum transfer squared of Q{sup 2} = 0.5 (GeV/c){sub 2}. A longitudinally polarized electron beam was scattered from the polarized target and the quasi-elastically scattered electron was detected in coincidence with the knocked-out neutron. The data have been analyzed in terms of the spin-correlation parameter, or the electron-deuteron vector asymmetry (A{sub ed}{sup V}), of (e, e'n) to determine the neutron electric form factor G{sub E}{sup n}. The result is consistent with data from existing experiments and shows a good agreement with the Galster parameterization of G{sub E}{sup n} within experimental uncertainty.
Electron beam final focus system for Thomson scattering at ELBE
NASA Astrophysics Data System (ADS)
Krämer, J. M.; Budde, M.; Bødker, F.; Irman, A.; Jochmann, A.; Kristensen, J. P.; Lehnert, U.; Michel, P.; Schramm, U.
2016-09-01
The design of an electron beam final focus system (FFS) aiming for high-flux laser-Thomson backscattering X-ray sources at ELBE is presented. A telescope system consisting of four permanent magnet based quadrupoles was found to have significantly less chromatic aberrations than a quadrupole doublet or triplet as commonly used. Focusing properties like the position of the focal plane and the spot size are retained for electron beam energies between 20 and 30 MeV by adjusting the position of the quadrupoles individually on a motorized stage. The desired ultra-short electron bunches require an increased relative energy spread up to a few percent and, thus, second order chromatic effects must be taken into account. We also present the design and test results of the permanent magnet quadrupoles. Adjustable shunts allow for correction of the field strength and compensation of deviations in the permanent magnet material. For a beam emittance of 13 mm mrad, we predict focal spot sizes of about 40 μm (rms) and divergences of about 10 mrad using the FFS.
NASA Astrophysics Data System (ADS)
Bogdanov, O. V.; Kazinski, P. O.
2015-02-01
The problem of scattering of ultrarelativistic electrons by a strong plane electromagnetic wave of a low (optical) frequency and linear polarization is solved in the semiclassical approximation, when the electron wave packet size is much smaller than the wavelength of electromagnetic wave. The exit momenta of ultrarelativistic electrons scattered are found using the exact solutions to the equations of motion with radiation reaction included (the Landau-Lifshitz equation). It is found that the momentum components of electrons traversed the electromagnetic wave depend weakly on the initial values of momenta. These electrons are mostly scattered at small angles to the propagation direction of the electromagnetic wave. The maximum Lorentz factor of electrons crossed the electromagnetic wave is proportional to the work done by the electromagnetic field and is independent of the initial momentum. The momentum component parallel to the electric field vector of the electromagnetic wave is determined solely by the laser beam diameter measured in the units of the classical electron radius. As for the reflected electrons, they for the most part lose the energy, but remain relativistic. A reflection law that relates the incident and reflection angles and is independent of any parameters is found.
Elastic scattering of low energy electrons in partially ionized dense semiclassical plasma
Dzhumagulova, K. N. Shalenov, E. O.; Ramazanov, T. S.
2015-08-15
Elastic scattering of electrons by hydrogen atoms in a dense semiclassical hydrogen plasma for low impact energies has been studied. Differential scattering cross sections were calculated within the effective model of electron-atom interaction taking into account the effect of screening as well as the quantum mechanical effect of diffraction. The calculations were carried out on the basis of the phase-function method. The influence of the diffraction effect on the Ramsauer–Townsend effect was studied on the basis of a comparison with results made within the effective polarization model of the Buckingham type.
Neutrino-Electron Scattering in MINERvA for Constraining the NuMI Neutrino Flux
Park, Jaewon
2013-01-01
Neutrino-electron elastic scattering is used as a reference process to constrain the neutrino flux at the Main Injector (NuMI) beam observed by the MINERvA experiment. Prediction of the neutrino flux at accelerator experiments from other methods has a large uncertainty, and this uncertainty degrades measurements of neutrino oscillations and neutrino cross-sections. Neutrino-electron elastic scattering is a rare process, but its cross-section is precisely known. With a sample corresponding to $3.5\\times10^{20}$ protons on target in the NuMI low-energy neutrino beam, a sample of $120$ $\
Electron and positron scattering on rubidium at 200 eV
Chin, J. H.; Ratnavelu, K.; Zhou, Y.
2014-03-05
The recent implementation of the coupled-channels-optical method (CCOM) [1,2], in the study of the electron and positron-Rubidium(Rb) scattering at intermediate energies [3,4], shows that the continuum effect remains important as the energy increases, even to 100 eV. Here, we study the effect of the continuum in electron and positron scattering on Rb at an even higher energy namely 200 eV. The total, elastic and inelastic integral and differential cross sections are therefore calculated and compared to the available experimental [5] and theoretical data [6,7].
Determination of the Proton's Weak Charge via Parity Violating Electron Scattering
Hoskins, Joshua Russell
2015-08-01
The Qweak experiment, which completed running in May of 2012 at Jefferson Laboratory, has measured the parity-violating asymmetry in elastic electron-proton scattering at four-momentum transfer Q^{2}=0.025 (GeV/c)^{2} in order to provide the first direct measurement of the proton's weak charge, Qpw. The Standard Model makes firm predictions for the weak charge; deviations from the predicted value would provide strong evidence of new physics beyond the Standard Model. Using an 89% polarized electron beam at 145 microA scattering from a 34.4 cm long liquid hydrogen target, scattered electrons were detected using an array of eight fused-silica detectors placed symmetric about the beam axis. The parity-violating asymmetry was then measured by reversing the helicity of the incoming electrons and measuring the normalized difference in rate seen in the detectors. The low Q^{2} enables a theoretically clean measurement; the higher order hadronic corrections are constrained using previous parity-violating electron scattering world data. The experimental method will be discussed, with recent results constituting 4% of our total data and projections of our proposed uncertainties on the full data set.
Vos, M; Moreh, R; Tokési, K
2011-07-14
The momentum distributions of C atoms in polycrystalline diamond (produced by chemical vapor deposition) and in highly oriented pyrolitic graphite (HOPG) are studied by scattering of 40 keV electrons at 135°. By measuring the Doppler broadening of the energy of the elastically scattered electrons, we resolve a Compton profile of the motion of the C atoms. The aim of the present work is to resolve long-standing disagreements between the calculated kinetic energies of carbon atoms in HOPG and in diamond films and the measured ones, obtained both by neutron Compton scattering (NCS) and by nuclear resonance photon scattering (NRPS). The anisotropy of the momentum distribution in HOPG was measured by rotating the HOPG sample relative to the electron beam. The obtained kinetic energies for the motion component along, and perpendicular to, the graphite planes were somewhat higher than those obtained from the most recent NCS data of HOPG. Monte Carlo simulations indicate that multiple scattering adds about 2% to the obtained kinetic energies. The presence of different isotopes in carbon affects the measurement at a 1% level. After correcting for these contributions, the kinetic energies are 3%-6% larger than the most recent NCS results for HOPG, but 15%-25% smaller than the NRPS results. For diamond, the corrected direction-averaged kinetic energy is ≈ 6% larger than the calculated value. This compares favorably to the ≈25% discrepancy between theory and both the NCS and NRPS results for diamond.
Electronic scattering of pseudo-magnetic field induced by local bump in graphene
NASA Astrophysics Data System (ADS)
Yang, Mou; Cui, Yan; Wang, Rui-Qiang; Zhao, Hong-Bo
2012-10-01
We investigated the electronic scattering properties of a local bump strain in graphene sheet in frame of Born approximation. The differential scattering cross section is a function of outgoing and incident angles and has the six-fold rotational symmetry with respect to both angles. The incident plane wave is scattered into two backward fan-waves in different directions in low energy limit and is split into two branches spanning the angle reversely proportional to the incident wavevector k in high energy limit. The total scattering cross section depends on incident wavevector by the form k5 in the former limit, while it is independent of k and sensitive to the incident orientation in the latter limit. We explained these features using the symmetry of the strain-induced pseudo-magnetic field.
Rotational excitation of physisorbed molecules by resonant electron scattering
NASA Astrophysics Data System (ADS)
Teillet-Billy, D.; Gauyacq, J. P.
2002-04-01
The resonant rotational excitation of physisorbed H 2 molecules by low energy electron impact is studied using the rotational sudden approximation. The rotational excitation efficiency is analysed as a function of the constraint imposed on the molecular rotation by the adsorption. This allows the description of the variation of the energy loss spectrum corresponding to rovibrational excitation as a function of the constraint on molecular rotation. This model study is then used to discuss the recent results by Svensson et al. [Phys. Rev. Lett. 83 (1999) 124] on the rovibrational excitation of H 2 molecules adsorbed at steps on Cu(5 1 0), in terms of quasi-2D rotor and of constrained 3D rotors.
Born Hartree Bethe approximation in the theory of inelastic electron molecule scattering
NASA Astrophysics Data System (ADS)
Kretinin, I. Yu; Krisilov, A. V.; Zon, B. A.
2008-11-01
We propose a new approximation in the theory of inelastic electron atom and electron molecule scattering. Taking into account the completeness property of atomic and molecular wavefunctions, considered in the Hartree approximation, and using Bethe's parametrization for electronic excitations during inelastic collisions via the mean excitation energy, we show that the calculation of the inelastic total integral cross-sections (TICS), in the framework of the first Born approximation, involves only the ground-state wavefunction. The final analytical formula obtained for the TICS, i.e. for the sum of elastic and inelastic ones, contains no adjusting parameters. Calculated TICS for electron scattering by light atoms and molecules (He, Ne, and H2) are in good agreement within the experimental data; results show asymptotic coincidence for heavier ones (Ar, Kr, Xe and N2).
Smith, D. R.; Mazzucato, E.; Lee, W.; Park, H. K.; Domier, C. W.; Luhmann, N. C. Jr.
2008-12-15
A collective scattering system has been installed on the National Spherical Torus Experiment (NSTX) to measure electron gyroscale fluctuations in NSTX plasmas. The system measures fluctuations with k{sub perpendicular}{rho}{sub e} < or approx. 0.6 and k{sub perpendicular} < or approx. 20 cm{sup -1}. Up to five distinct wavenumbers are measured simultaneously, and the large toroidal curvature of NSTX plasmas provides enhanced spatial localization. Steerable optics can position the scattering volume throughout the plasma from the magnetic axis to the outboard edge. Initial measurements indicate rich turbulent dynamics on the electron gyroscale. The system will be a valuable tool for investigating the connection between electron temperature gradient turbulence and electron thermal transport in NSTX plasmas.
Singh, Suvam; Naghma, Rahla; Kaur, Jaspreet; Antony, Bobby
2016-07-21
The total and ionization cross sections for electron scattering by benzene, halobenzenes, toluene, aniline, and phenol are reported over a wide energy domain. The multi-scattering centre spherical complex optical potential method has been employed to find the total elastic and inelastic cross sections. The total ionization cross section is estimated from total inelastic cross section using the complex scattering potential-ionization contribution method. In the present article, the first theoretical calculations for electron impact total and ionization cross section have been performed for most of the targets having numerous practical applications. A reasonable agreement is obtained compared to existing experimental observations for all the targets reported here, especially for the total cross section. PMID:27448889
NASA Astrophysics Data System (ADS)
Singh, Suvam; Naghma, Rahla; Kaur, Jaspreet; Antony, Bobby
2016-07-01
The total and ionization cross sections for electron scattering by benzene, halobenzenes, toluene, aniline, and phenol are reported over a wide energy domain. The multi-scattering centre spherical complex optical potential method has been employed to find the total elastic and inelastic cross sections. The total ionization cross section is estimated from total inelastic cross section using the complex scattering potential-ionization contribution method. In the present article, the first theoretical calculations for electron impact total and ionization cross section have been performed for most of the targets having numerous practical applications. A reasonable agreement is obtained compared to existing experimental observations for all the targets reported here, especially for the total cross section.
Ab initio electron scattering cross-sections and transport in liquid xenon
NASA Astrophysics Data System (ADS)
Boyle, G. J.; McEachran, R. P.; Cocks, D. G.; Brunger, M. J.; Buckman, S. J.; Dujko, S.; White, R. D.
2016-09-01
Ab initio fully differential cross-sections for electron scattering in liquid xenon are developed from a solution of the Dirac-Fock scattering equations, using a recently developed framework (Boyle et al 2015 J. Chem. Phys. 142 154507) which considers multipole polarizabilities, a non-local treatment of exchange, and screening and coherent scattering effects. A multi-term solution of Boltzmann’s equation accounting for the full anisotropic nature of the differential cross-section is used to calculate transport properties of excess electrons in liquid xenon. The results were found to agree to within 25% of the measured mobilities and characteristic energies over the reduced field range of 10-4-1 Td. The accuracies are comparable to those achieved in the gas phase. A simple model, informed by highly accurate gas-phase cross-sections, is presented to improve the liquid cross-sections, which was found to enhance the accuracy of the transport coefficient calculations.
Ab initio electron scattering cross-sections and transport in liquid xenon
NASA Astrophysics Data System (ADS)
Boyle, G. J.; McEachran, R. P.; Cocks, D. G.; Brunger, M. J.; Buckman, S. J.; Dujko, S.; White, R. D.
2016-09-01
Ab initio fully differential cross-sections for electron scattering in liquid xenon are developed from a solution of the Dirac–Fock scattering equations, using a recently developed framework (Boyle et al 2015 J. Chem. Phys. 142 154507) which considers multipole polarizabilities, a non-local treatment of exchange, and screening and coherent scattering effects. A multi-term solution of Boltzmann’s equation accounting for the full anisotropic nature of the differential cross-section is used to calculate transport properties of excess electrons in liquid xenon. The results were found to agree to within 25% of the measured mobilities and characteristic energies over the reduced field range of 10‑4–1 Td. The accuracies are comparable to those achieved in the gas phase. A simple model, informed by highly accurate gas-phase cross-sections, is presented to improve the liquid cross-sections, which was found to enhance the accuracy of the transport coefficient calculations.
Model independent extraction of the proton magnetic radius from electron scattering
NASA Astrophysics Data System (ADS)
Epstein, Zachary; Paz, Gil; Roy, Joydeep
2014-10-01
We combine constraints from analyticity with experimental electron-proton scattering data to determine the proton magnetic radius without model-dependent assumptions on the shape of the form factor. We also study the impact of including electron-neutron scattering data, and ππ→NN ¯ data. Using representative data sets we find for a cut of Q2≤0.5 GeV2, rMp=0.91-0.06+0.03±0.02 fm using just proton scattering data; rMp=0.87-0.05+0.04±0.01 fm adding neutron data; and rMp=0.87-0.02+0.02 fm adding ππ data. We also extract the neutron magnetic radius from these data sets obtaining rMn=0.89-0.03+0.03 fm from the combined proton, neutron, and ππ data.
Murguia, Gabriela; Moreno, Matias; Torres, Manuel
2009-04-20
A well known example in quantum electrodynamics (QED) shows that Coulomb scattering of unpolarized electrons, calculated to lowest order in perturbation theory, yields a results that exactly coincides (in the non-relativistic limit) with the Rutherford formula. We examine an analogous example, the classical and perturbative quantum scattering of an electron by a magnetic field confined in an infinite solenoid of finite radius. The results obtained for the classical and the quantum differential cross sections display marked differences. While this may not be a complete surprise, one should expect to recover the classical expression by applying the classical limit to the quantum result. This turn not to be the case. Surprisingly enough, it is shown that the classical result can not be recuperated even if higher order corrections are included. To recover the classic correspondence of the quantum scattering problem a suitable non-perturbative methodology should be applied.
Polarized Bhabha scattering and a precision measurement of the electron neutral current couplings
Abe, K.; Abt, I.; Ahn, C.J.; Akagi, T.; Ash, W.W.; Aston, D.; Bacchetta, N.; Baird, K.G.; Baltay, C.; Band, H.R.; Barakat, M.B.; Baranko, G.; Bardon, O.; Barklow, T.; Bazarko, A.O.; Ben-David, R.; Benvenuti, A.C.; Bienz, T.; Bilei, G.M.; Bisello, D.; Blaylock, G.; Bogart, J.R.; Bolton, T.; Bower, G.R.; Brau, J.E.; Breidenbach, M.; Bugg, W.M.; Burke, D.; Burnett, T.H.; Burrows, P.N.; Busza, W.; Calcaterra, A.; Caldwell, D.O.; Calloway, D.; Camanzi, B.; Carpinelli, M.; Cassell, R.; Castaldi, R.; Castro, A.; Cavalli-Sforza, M.; Church, E.; Cohn, H.O.; Coller, J.A.; Cook, V.; Cotton, R.; Cowan, R.F.; Coyne, D.G.; D`Oliveira, A.; Damerell, C.J.S.; Dasu, S.; De Sangro, R.; De Simone, P.; Dell`Orso, R.; Dima, M.; Du, P.Y.C.; Dubois, R.; Eisenstein, B.I.; Elia, R.; Falciai, D.; Fan, C.; Fero, M.J.; Frey, R.; Furuno, K.; Gillman, T.; Gladding, G.; Gonzalez, S.; Hallewell, G.D.; Hart, E.L.; Hasegawa, Y.; Hedges, S.; Hertzbach, S.S.; Hildreth, M.D.; Huber, J.; Huffer, M.E.; Hughes, E.W.; Hwang, H.; Iwasaki, Y.; Jacques, P.; Jaros, J.; Johnson, A.S.; Johnson, J.R.; Johnson, R.A.; Junk, T.; Kajikawa, R.; Kalelkar, M.; Karliner, I.; Kawahara, H.; Kendall, H.W.; Kim, Y.; King, M.E.; King, R.; Kofler, R.R.; Krishna, N.M.; Kroeger, R.S.; Labs, J.F.; Langston, M.; Lath, A.; Lauber, J.A.; Leith, D.W.G.; Liu, X.; Loreti, M.; Lu, A.; Lynch, H.L.; Ma, J.; Mancinelli, G.; Manly, S.; Mantovani, G.; Markiewicz, T.W.; Maruyama, T.; Massetti, R.; Masuda, H.; Mazzucato, E.; McKemey, A.K.; Meadows, B.T.; Messner, R.; Mockett, P.M.; Moffeit, K.C.; Mours, B.; Mueller, G.; Muller, D.; Nagamine, T.; Nauenberg, U.; Neal, H.; Nussbaum, M.; Ohnishi, Y.; Osborne, L.S.; Panvini, R.S.; Park, H.; Pavel, T.J.; Peruzzi, I.; Pescara, L.; Piccolo, M.; Piemontese, L.; Pieroni, E.; Pitts, K.T.; Plano, R.J.; Prepost, R.; Prescott, C.Y.; Punkar, G.D.; Quigley, J.; Ratcliff, B.N.; Reeves, T.W.; Rensing, P.E.; Rochester, L.S.; Rothberg, J.E.; Rowson, P.C.; Russell, J.J.; Saxton, O.H.; Schalk, T.; (SLD Collaborat...
1995-04-10
Bhabha scattering with polarized electrons at the {ital Z}{sup 0} resonance has been measured with the SLD experiment at the SLAC Linear Collider. The first measurement of the left-right asymmetry in Bhabha scattering is presented, yielding the effective weak mixing angle of sin{theta}{sup eff}{sub {ital W}}=0.2245{plus_minus}0.0049{plus_minus}0.0010. The effective electron couplings to the {ital Z}{sup 0} are extracted from a combined analysis of polarized Bhabha scattering and the left-right asymmetry previously published: {upsilon}{sub {ital e}}={minus}0.0414{plus_minus}0.0020 and {ital a}{sub {ital e}}={minus}0.4977{plus_minus}0.0045.
NASA Astrophysics Data System (ADS)
Gumbs, Godfrey; Iurov, Andrii; Huang, Danhong; Fekete, Paula; Zhemchuzhna, Liubov
2014-03-01
A two-dimensional periodic array of scatterers has been introduced to a single layer of graphene in the presence of an external magnetic field perpendicular to the graphene layer. The eigenvalue equation for such a system has been solved numerically to display the structure of split Landau subbands as functions of both wave number and magnetic flux. The effects of pseudo-spin coupling and Landau subbands mixing by a strong scattering potential have been demonstrated. Additionally, we investigated the square barrier tunneling problem when magnetic field is present, as well as demonstrate the crucial difference in the modulated band structure between graphene and the two-dimensional electron gas. The low-magnetic field regime is particularly interesting for Dirac fermions and has been discussed. Tunneling of Dirac electrons through a magnetic potential barrier has been investigated to complement the reported results on electrostatic potential scattering in the presence of an ambient magnetic field.
Entangled valence electron-hole dynamics revealed by stimulated attosecond x-ray Raman scattering
Healion, Daniel; Zhang, Yu; Biggs, Jason D.; Govind, Niranjan; Mukamel, Shaul
2012-09-06
We show that broadband x-ray pulses can create wavepackets of valence electrons and holes localized in the vicinity of a selected atom (nitrogen, oxygen or sulfur in cysteine) by resonant stimulated Raman scattering. The subsequent dynamics reveals highly correlated motions of entangled electrons and hole quasiparticles. This information goes beyond the time-dependent total charge density derived from x-ray diffraction.
Parity conservation in electron-phonon scattering in zigzag graphene nanoribbon
Chu, Yanbiao; Gautreau, Pierre; Basaran, Cemal
2014-09-15
In contrast with carbon nanotubes, the absence of translational symmetry (or periodical boundary condition) in the restricted direction of zigzag graphene nanoribbon removes the selection rule of subband number conservation. However, zigzag graphene nanoribbons with even dimers do have the inversion symmetry. We, therefore, propose a selection rule of parity conservation for electron-phonon interactions. The electron-phonon scattering matrix in zigzag graphene nanoribbons is developed using the tight-binging model within the deformation potential approximation.
TWO-PHOTON EXCHANGE IN ELECTRON-PROTON ELASTIC SCATTERING: THEORY UPDATE
Andrei Afanasev
2007-05-21
Recent theoretical developments in the studies of two-photon exchange effects in elastic electron-proton scattering are reviewed. Two-photon exchange mechanism is considered a likely source of discrepancy between polarized and unpolarized experimental measurements of the proton electric form factor at momentum transfers of several GeV$^2$. This mechanism predicts measurable effects that are currently studied experimentally.
Gerasimov, R. E. Fadin, V. S.
2015-01-15
An analysis of approximations used in calculations of radiative corrections to electron-proton scattering cross section is presented. We investigate the difference between the relatively recent Maximon and Tjon result and the Mo and Tsai result, which was used in the analysis of experimental data. We also discuss the proton form factors ratio dependence on the way we take into account radiative corrections.
Can neutrino-electron scattering tell us whether neutrinos are Dirac or Majorana particles
Kayser, B.
1988-04-01
There has recently been interest in the possibility that neutrino-electron scattering experiments could determine whether neutrinos are Dirac or Majorana particles by providing information on their electromagnetic structure. We try to explain why studies of neutrino electromagnetic structure actually cannot distinguish between Dirac and Majorana neutrinos. 9 refs.
Constrained {gamma}Z correction to parity-violating electron scattering
Hall, Nathan Luk; Blunden, Peter Gwithian; Melnitchouk, Wally; Thomas, Anthony W.; Young, Ross D.
2013-11-01
We update the calculation of {gamma}Z interference corrections to the weak charge of the proton. We show how constraints from parton distributions, together with new data on parity-violating electron scattering in the resonance region, significantly reduce the uncertainties on the corrections compared to previous estimates.
Constrained γZ correction to parity-violating electron scattering
Hall, N. L.; Thomas, A. W.; Young, R. D.; Blunden, P. G.; Melnitchouk, W.
2013-11-07
We update the calculation of γZ interference corrections to the weak charge of the proton. We show how constraints from parton distributions, together with new data on parity-violating electron scattering in the resonance region, significantly reduce the uncertainties on the corrections compared to previous estimates.
Refutation of a propensity rule in low-energy electron scattering by neon atoms
NASA Astrophysics Data System (ADS)
Hargreaves, Leigh; Campbell, Colin; Khakoo, Murtadha A.; Zatsarinny, Oleg; Bartschat, Klaus
2012-06-01
Since the work of Kohmoto and Fano [1] there has been considerable interest in the sign of the `orientation' parameter Lperp, which describes the angular momentum of an excited electronic state perpendicular to the scattering plane imparted by the projectile electron. In a polarization-correlation experiment, Lperp can be related to the measurable Stokes parameter P3 (Lperp = -P3), which describes the circular polarization of the photon emitted perpendicular to the scattering plane. Of particular interest is the empirical observation that, for S to P transitions, P3 universally trends to negative values for small scattering angles, regardless of the target or incident energy. A number of studies (e.g. [1-3]) have therefore considered the generality of this `propensity rule' and its theoretical basis. Here, a recent joint experimental and theoretical study of electronic excitation of the resonant transition in neon by 25eV electrons is presented. In both the theoretical and experimental data it is observed that P3 is positive at small scattering angles, demonstrating a refutation of this propensity rule, in disagreement with the classical arguments of Kohomoto and Fano [1]. [4pt] [1] M. Kohmoto and U. Fano, J. Phys. B 14, L447 (1981)[0pt] [2] D. H. Madison and K. H. Winters, Phys. Rev. Lett. 47, 1885 (1981)[0pt] [3] K. Bartschat, N. Andersen and D. Loveall, Phys. Rev. Lett. 83, 5254 (1999)
Identical particle states and operators and the case of two-electron scattering
NASA Astrophysics Data System (ADS)
Ferrell, W. R.; Ritchie, R. H.; Ferrell, T. L.
1984-10-01
A simplified notation is introduced for dealing with systems of indistinguishable fermions and bosons. The second-quantized form of system operators is obtained in a simpler manner than is offered ordinarily in textbooks. Details of the calculation of the nonrelativistic M≂ller cross section for scattering of two electrons are given as an example.
Measuring the Weak Charge of the Proton via Elastic Electron-Proton Scattering
Jones, Donald C.
2015-10-01
The Qweak experiment which ran in Hall C at Jefferson Lab in Newport News, VA, and completed data taking in May 2012, measured the weak charge of the proton Q^{p}_{W} via elastic electron-proton scattering. Longitudinally polarized electrons were scattered from an unpolarized liquid hydrogen target. The helicity of the electron beam was flipped at approximately 1 kHz between left and right spin states. The Standard Model predicts a small parity-violating asymmetry of scattering rates between right and left helicity states due to the weak interaction. An initial result using 4% of the data was published in October 2013 [1] with a measured parity-violating asymmetry of -279 ± 35(stat) ± 31 (syst) ppb. This asymmetry, along with other data from parity-violating electron scattering experiments, provided the world's first determination of the weak charge of the proton. The weak charge of the proton was found to be ^{p}_{W} = 0.064 ± 0.012, in good agreement with the Standard Model prediction of ^{p}_{W}(SM) = 0.0708 ± 0.0003[2].
Electron scattering in the Δ{sub 1} model of the conduction band of germanium single crystals
Luniov, S. V. Burban, O. V.; Nazarchuk, P. F.
2015-05-15
Electron scattering in the possible Δ{sub 1} models of the conduction band in germanium crystals formed by hydrostatic or uniaxial pressure is investigated. On the basis of the theory of anisotropic scattering, the temperature dependences of the anisotropy parameter of the relaxation times and electron mobility for these models under conditions of scattering at impurity ions, as well as at acoustic and intervalley phonons are obtained. Analysis of the temperature dependences indicates that, in the temperature range of 77–300 K, intervalley scattering becomes substantial. Only for the Δ{sub 1} model formed by uniaxial pressure along the crystallographic direction [100], the electron scattering at intervalley phonons, which correspond to the g transitions, is minor with respect to scattering at acoustic phonons (the intravalley scattering) and impurity ions.
Influence of the angular scattering of electrons on the runaway threshold in air
NASA Astrophysics Data System (ADS)
Chanrion, O.; Bonaventura, Z.; Bourdon, A.; Neubert, T.
2016-04-01
The runaway electron mechanism is of great importance for the understanding of the generation of x- and gamma rays in atmospheric discharges. In 1991, terrestrial gamma-ray flashes (TGFs) were discovered by the Compton Gamma-Ray Observatory. Those emissions are bremsstrahlung from high energy electrons that run away in electric fields associated with thunderstorms. In this paper, we discuss the runaway threshold definition with a particular interest in the influence of the angular scattering for electron energy close to the threshold. In order to understand the mechanism of runaway, we compare the outcome of different Fokker-Planck and Monte Carlo models with increasing complexity in the description of the scattering. The results show that the inclusion of the stochastic nature of collisions smooths the probability to run away around the threshold. Furthermore, we observe that a significant number of electrons diffuse out of the runaway regime when we take into account the diffusion in angle due to the scattering. Those results suggest using a runaway threshold energy based on the Fokker-Planck model assuming the angular equilibrium that is 1.6 to 1.8 times higher than the one proposed by [1, 2], depending on the magnitude of the ambient electric field. The threshold also is found to be 5 to 26 times higher than the one assuming forward scattering. We give a fitted formula for the threshold field valid over a large range of electric fields. Furthermore, we have shown that the assumption of forward scattering is not valid below 1 MeV where the runaway threshold usually is defined. These results are important for the thermal runaway and the runaway electron avalanche discharge mechanisms suggested to participate in the TGF generation.
NASA Astrophysics Data System (ADS)
Karimov, A. R.; Poponin, V. P.; Rukhadze, Anri A.; Shcheglov, V. A.
1999-05-01
The properties of stimulated coherent scattering of an electromagnetic wave by a relativistic electron beam were studied in the framework of a three-wave approximation for a noncollinear geometry, when the incident and the scattered waves can propagate at arbitrary angles relative to the electron beam direction. The dispersion equation was obtained, making it possible to investigate the modes of collective (Raman) and single-particle (Compton) scattering from a unified viewpoint and to include the effect of an external longitudinal magnetic field on the electron motion in the field of a combination wave. Formulas were obtained for the amplitude increments of the scattered and the combination waves for those scattering modes, which can be used to make estimates when selecting the optimal scheme of a free-electron laser with a noncollinear scattering geometry.
Multiband electron resonant Raman scattering in quantum wells in a magnetic field
NASA Astrophysics Data System (ADS)
López-Richard, V.; Hai, G.-Q.; Trallero-Giner, C.; Marques, G. E.
2003-04-01
A theoretical model has been developed for the electronic resonant Raman scattering processes in direct band zinc blende type semiconductor quantum wells in a magnetic field. In order to take into account the spin-flip transitions, anomalous behavior of the Landau levels and the Landè g factor, an 8×8 Kane-Weiler Hamiltonian model has been considered for the evaluation of the Raman scattering amplitude. Elements concerning the selection rules of resonant inelastic light scattering in quantum well systems are reported. The multiband model predicts conditions for resonant spin-flip Raman processes in several light scattering configurations for crossed and parallel polarization. Special emphasis is given to the effects of the interlevel coupling and mixing within the conduction subband and their relation to spin-flip and inter-Landau level transitions. Symmetry and electronic properties of the level structure in the first conduction subband as well as anomalous Landè factors are discussed in terms of complementary Raman scattering configurations, Fermi energy, and multiband parameters.
Vos, M.; Went, M. R.
2006-11-15
High-resolution measurements of 40-keV electrons scattered over 44.3 deg. from evaporated carbon films are presented. The observed width of the energy distribution of electrons scattered from carbon is significantly larger than the experimental energy resolution, and its position is shifted to lower energy. Measurements were done for transmission and reflection geometries for thin films with thicknesses varying from 90 A ring to 1400 A ring . The observed peak shape is largely independent of the thickness and measurement geometry. The peak shape deviates from Gaussian in all cases, in a way consistent with theories that describe these processes beyond the impulse approximation. The energy shift of the carbon peak is measured by evaporating a small amount of Au on these films. Separation of the Au and C peak is somewhat smaller than calculated assuming scattering from free C and Au atoms, but independent of measurement geometry. Finally spectra were measured from highly oriented pyrolytic graphite (HOPG) films. Now different widths are observed in reflection geometry and transmission geometry. This is attributed to the anisotropy of the motion of the C atoms in HOPG. Also the Au-C separation is slightly orientation dependent for HOPG. All observations agree at least semiquantitatively with neutron Compton scattering results, a related scattering experiment that studies neutron-atom collisions at similar momentum transfers.
Artemyev, A. V. Vasiliev, A. A.; Mourenas, D.; Krasnoselskikh, V. V.
2014-10-15
In this paper, we consider high-energy electron scattering and nonlinear trapping by oblique whistler waves via the Landau resonance. We use recent spacecraft observations in the radiation belts to construct the whistler wave model. The main purpose of the paper is to provide an estimate of the critical wave amplitude for which the nonlinear wave-particle resonant interaction becomes more important than particle scattering. To this aim, we derive an analytical expression describing the particle scattering by large amplitude whistler waves and compare the corresponding effect with the nonlinear particle acceleration due to trapping. The latter is much more rare but the corresponding change of energy is substantially larger than energy jumps due to scattering. We show that for reasonable wave amplitudes ∼10–100 mV/m of strong whistlers, the nonlinear effects are more important than the linear and nonlinear scattering for electrons with energies ∼10–50 keV. We test the dependencies of the critical wave amplitude on system parameters (background plasma density, wave frequency, etc.). We discuss the role of obtained results for the theoretical description of the nonlinear wave amplification in radiation belts.
Low-energy electron scattering from CO. 2: Ab-initio study using the frame-transformation theory
NASA Technical Reports Server (NTRS)
Chandra, N.
1976-01-01
The Wigner-Eisenbud R matrix method has been combined with the frame transformation theory to study electron scattering from molecular systems. The R matrix, calculated at the boundary point of the molecular core radius, has been transformed to the space frame in order to continue the solution of the scattering equations in the outer region where rotational motion of the nuclei is taken into account. This procedure has been applied to a model calculation of thermal energy electron scattering from CO.
Doubly excited states of ammonia by scattered electron-ion coincidence measurements
NASA Astrophysics Data System (ADS)
Yamamoto, Karin; Sakai, Yasuhiro
2012-03-01
To obtain information on the optically forbidden doubly excited states of ammonia (NH3), we performed scattered electron-ion coincidence measurements. First, we observed scattered electrons using electron energy-loss spectroscopy and determined the generalized oscillator strength distribution (GOSD) under 200 eV incident electron energy at a scattering angle of 8°. Ionic GOSDs were also determined by combination with the coincidence signal, which was observed by the time-of-flight mass spectrometer at each energy-loss value, for each ion. The total and partial ionic GOSDs were compared with the experimental results of both photon and fast electron impact. Moreover, the neutral GOSD determined by subtracting the total ionic GOSD from the total was compared with previous results. In addition to the optically forbidden doubly excited states, which were identified by Kato et al (2003 J. Phys. B: At. Mol. Opt. Phys. 36 3541) and Ishikawa et al (2008 J. Phys. B: At. Mol. Opt. Phys. 41 195204), we found a new optically forbidden doubly excited state at around 35 eV.
Electron mobility limited by scattering from threading dislocation lines within gallium nitride
NASA Astrophysics Data System (ADS)
Mohammad Alavi, Seyed; Bagani, Erfan
2016-03-01
Theoretical as well as experimental studies in the literature suggest that defect sites associated with the threading dislocation lines within n-type gallium nitride (GaN) act to trap free electrons from the bulk of this semiconductor material. As a result, the core of the threading dislocation lines become negatively charged. The charge accumulated along the core of a threading dislocation line should be screened by a charge of opposite polarity and equal in absolute value per unit length along the dislocation line. In the present work, we model this screened charge buildup along the threading dislocation lines by two concentric space-charge cylinders. Quantum mechanical theory of scattering in cylindrical coordinates is then employed in order to numerically compute the electron mobility limited by scattering from the charged threading dislocation lines. The dependence of the computed electron mobility on the dislocation line density and on the amount of charge accumulated per unit length along the core of the dislocation lines is also investigated in this work. Our computed electron mobility results are compared with results from existing calculations of the GaN dislocation scattering limited electron mobility in the literature.
Electron-phonon interaction and scattering in Si and Ge: Implications for phonon engineering
Tandon, Nandan; Albrecht, J. D.; Ram-Mohan, L. R.
2015-07-28
We report ab-initio results for electron-phonon (e-ph) coupling and display the existence of a large variation in the coupling parameter as a function of electron and phonon dispersion. This variation is observed for all phonon modes in Si and Ge, and we show this for representative cases where the initial electron states are at the band gap edges. Using these e-ph matrix elements, which include all possible phonon modes and electron bands within a relevant energy range, we evaluate the imaginary part of the electron self-energy in order to obtain the associated scattering rates. The temperature dependence is seen through calculations of the scattering rates at 0 K and 300 K. The results provide a basis for understanding the impacts of phonon scattering vs. orientation and geometry in the design of devices, and in analysis of transport phenomena. This provides an additional tool for engineering the transfer of energy from carriers to the lattice.
Design of a collective scattering system for electron gyroscale turbulence study in KSTAR
NASA Astrophysics Data System (ADS)
Lee, Woochang; Park, Hyeon; Lee, Dongjae; Leem, Juneeok; Nam, Yongun
2015-11-01
The design characteristics of a multi-channel collective (or coherent) scattering system for electron scale turbulence study in KSTAR, which is planned to be installed in 2016, are investigated. A few critical issues are discussed in depth such as effect of the Faraday rotation of the electric field polarization of probing and scattered, the probing wave frequency which is related to the optics for measurement of electron gyro scale turbulence, the wave polarization to minimize absorption of the probing power by electron cyclotron resonant layers, and the probing power. A proper and feasible optics with 300 GHz probing wave, which is based on these issues, provides a simultaneous measurement of electron density fluctuations at four discrete poloidal wave numbers up to 21 cm-1. The upper limit corresponds to the normalized wave number k⊥ρe of 0.2 in KSTAR plasmas. To detect scattered wave power and extract phase information, a quadrature detection system consisting of four-channel antenna/detector array and electronics will be employed. Work supported by NRF Korea under grant numbers NRF-2015M1A7A1A02002627 and NRF-2014M1A7A1A03029865.
NASA Astrophysics Data System (ADS)
Wang, Bin; Su, Zhenpeng; Zhang, Yan; Shi, Shengwei; Wang, Geng
2016-04-01
In response to solar wind disturbances, radiation belt (a few hundreds of keV to several MeV) electron fluxes can be depleted significantly over the entire equatorial pitch angle range. The frequently mentioned cyclotron resonant scattering is applicable only for electrons mirroring off the equator. Here we propose a new physical mechanism, nonlinear Landau resonance with oblique electromagnetic ion cyclotron (EMIC) waves, to effectively scatter the near equatorially mirroring electrons. Our test particle simulations show that the nonlinear Landau trapping can occur over a wide energy range and yield the net decrease in equatorial pitch angle Δαeq≈10° within several seconds. Our parametric studies further reveal that this nonlinear Landau-trapping process is favored by a low plasma density, an intense wave field, a high wave frequency close to ion gyrofrequencies, and a large wave normal angle.
Relativistic convergent close-coupling method applied to electron scattering from mercury
Bostock, Christopher J.; Fursa, Dmitry V.; Bray, Igor
2010-08-15
We report on the extension of the recently formulated relativistic convergent close-coupling (RCCC) method to accommodate two-electron and quasi-two-electron targets. We apply the theory to electron scattering from mercury and obtain differential and integrated cross sections for elastic and inelastic scattering. We compared with previous nonrelativistic convergent close-coupling (CCC) calculations and for a number of transitions obtained significantly better agreement with the experiment. The RCCC method is able to resolve structure in the integrated cross sections for the energy regime in the vicinity of the excitation thresholds for the (6s6p) {sup 3}P{sub 0,1,2} states. These cross sections are associated with the formation of negative ion (Hg{sup -}) resonances that could not be resolved with the nonrelativistic CCC method. The RCCC results are compared with the experiment and other relativistic theories.
Electronic Raman scattering as an ultra-sensitive probe of strain effects in semiconductors
Fluegel., Brian; Mialitsin, Aleksej V.; Beaton, Daniel A.; Reno, John L.; Mascarenhas, Angelo
2015-05-28
Semiconductor strain engineering has become a critical feature of high-performance electronics because of the significant device performance enhancements that it enables. These improvements, which emerge from strain-induced modifications to the electronic band structure, necessitate new ultra-sensitive tools to probe the strain in semiconductors. Here, we demonstrate that minute amounts of strain in thin semiconductor epilayers can be measured using electronic Raman scattering. We also applied this strain measurement technique to two different semiconductor alloy systems using coherently strained epitaxial thin films specifically designed to produce lattice-mismatch strains as small as 10-4. Thus, comparing our strain sensitivity and signal strength inmore » AlxGa 1-x As with those obtained using the industry-standard technique of phonon Raman scattering, we found that there was a sensitivity improvement of 200-fold and a signal enhancement of 4 × 103, thus obviating key constraints in semiconductor strain metrology.« less
Electron Accumulation Layers in InN Nanocolumns Studied by Raman Scattering
Gallardo, E.; Lazic, S.; Calleja, J. M.; Agullo-Rueda, F.; Grandal, J.; Sanchez-Garcia, M. A.; Calleja, E.
2010-01-04
Inelastic light scattering measurements on single crystal InN nanocolumns grown by plasma-assisted molecular beam epitaxy on both Si(001) and Si(111) substrates reveal the existence of a surface electron accumulation layer in the lateral non-polar sidewalls of the nanocolumns. Small and reversible electron density variations of this surface layer has been induced by chemical treatments of the nanocolumns, which can be accurately determined from the frequency of the LO phonon-plasmon coupled mode L{sub -}. The L{sub -} to E{sub 1}(LO) phonon intensity ratio dependence on the column diameter and the excitation wavelength is interpreted in terms of the inhomogeneous electron distribution in the nanocolumns volume and the presence of strong elastic light scattering by the nanocolumns. The TO modes fail to obey conventional selection rules, a fact that is also observed in GaN nanocolumns.
An investigation into electron scattering from pyrazine at intermediate and high energies
Sanz, A. G.; Fuss, M. C.; Blanco, F.; Gorfinkiel, J. D.; Almeida, D.; Ferreira da Silva, F.; Limão-Vieira, P.; Brunger, M. J.; García, G.
2013-11-14
Total electron scattering cross sections for pyrazine in the energy range 10–500 eV have been measured with a new magnetically confined electron transmission-beam apparatus. Theoretical differential and integral elastic, as well as integral inelastic, cross sections have been calculated by means of a screening-corrected form of the independent-atom representation (IAM-SCAR) from 10 to 1000 eV incident electron energies. The present experimental and theoretical total cross sections show a good level of agreement, to within 10%, in the overlapping energy range. Consistency of these results with previous calculations (i.e., the R-matrix and Schwinger Multichannel methods) and elastic scattering measurements at lower energies, below 10 eV, is also discussed.
Electronic Raman scattering as an ultra-sensitive probe of strain effects in semiconductors
Fluegel, Brian; Mialitsin, Aleksej V.; Beaton, Daniel A.; Reno, John L.; Mascarenhas, Angelo
2015-01-01
Semiconductor strain engineering has become a critical feature of high-performance electronics because of the significant device performance enhancements that it enables. These improvements, which emerge from strain-induced modifications to the electronic band structure, necessitate new ultra-sensitive tools to probe the strain in semiconductors. Here, we demonstrate that minute amounts of strain in thin semiconductor epilayers can be measured using electronic Raman scattering. We applied this strain measurement technique to two different semiconductor alloy systems using coherently strained epitaxial thin films specifically designed to produce lattice-mismatch strains as small as 10−4. Comparing our strain sensitivity and signal strength in AlxGa1−xAs with those obtained using the industry-standard technique of phonon Raman scattering, we found that there was a sensitivity improvement of 200-fold and a signal enhancement of 4 × 103, thus obviating key constraints in semiconductor strain metrology. PMID:26017853
Tkach, N. V. Seti, Ju.
2009-03-15
In the effective mass approximation in the model of rectangular potentials, the scattering cross section of electrons in an open spherical quantum dot is calculated for the first time. It is shown that, for such a nanosystem with a barrier of several monolayers, the experimental measurements of the scattering cross section allow adequate identification of the resonance energies and the widths of resonance states in the low-energy region of the quasi-stationary electron spectrum. It is also shown that, for an open spherical quantum dot with a low-strength potential barrier, the adequate spectral parameters of the quasi-stationary spectrum are the generalized resonance energies and widths determined via the probability of an electron being inside the quantum dot.
Inelastic electron scattering in the high-Tc compound YBa2Cu3O7-x
NASA Astrophysics Data System (ADS)
Tarrio, C.; Schnatterly, S. E.
1988-07-01
We have carried out inelastic electron scattering transmission measurements on the high-Tc compound YBa2Cu3O7-x in the energy range 1-100 eV. We have directly observed the free-electron plasma peak at 1.1 eV in addition to the bound electron plasmon at 25.5 eV. The interband threshold is at 2.1 eV, above which the material behaves as a typical oxide insulator.
Tsikata, S.; Pisarev, V.; Gresillon, D. M.; Lemoine, N.
2009-03-15
Kinetic models and numerical simulations of E-vectorxB-vector plasma discharges predict microfluctuations at the scales of the electron cyclotron drift radius and the ion plasma frequency. With the help of a specially designed collective scattering device, the first experimental observations of small-scale electron density fluctuations inside the plasma volume are obtained, and observed in the expected ranges of spatial and time scales. The anisotropy, dispersion relations, form factor, amplitude, and spatial distribution of these electron density fluctuations are described and compared to theoretical expectations.
NASA Astrophysics Data System (ADS)
Weber, Hannes; Maj, Omar; Poli, Emanuele
2015-03-01
The physics and first results of the new WKBeam code for electron cyclotron beams in tokamak plasmas are presented. This code is developed on the basis of a kinetic radiative transfer model which is general enough to account for the effects of diffraction and density fluctuations on the beam. Our preliminary numerical results show a significant broadening of the power deposition profile in ITER due to scattering from random density fluctuations at the plasma edge, while such scattering effects are found to be negligible in medium-size tokamaks like ASDEX upgrade.
{Delta} resonance contribution to two-photon exchange in electron-proton scattering
S. Kondratyuk; P. G. Blunden; W. Melnitchouk; J. A. Tjon
2005-06-01
We calculate the effects on the elastic electron-proton scattering cross section of the two-photon exchange contribution with an intermediate {Delta} resonance. The {Delta} two-photon exchange contribution is found to be smaller in magnitude than the previously evaluated nucleon contribution, with an opposite sign at backward scattering angles. The sum of the nucleon and {Delta} two-photon exchange corrections has the angular dependence compatible with both the polarization transfer and the Rosenbluth methods of measuring the nucleon electromagnetic form factors.
Inversion of Dynamical Scattering from Large-Angle Rocking-Beam Electron Diffraction Patterns
NASA Astrophysics Data System (ADS)
Wang, Feng; Pennington, Robert S.; Koch, Christoph T.
2016-07-01
A method for ab initio structure factor retrieval from large-angle rocking-beam electron diffraction data of thin crystals is described and tested with experimental and simulated data. No additional information, such as atomicity or information about chemical composition, has been made use of. Our numerical experiments show that the inversion of dynamical scattering works best, if the beam tilt range is large and the specimen not too thick, because for moderate multiple scattering, the large tilt amplitude effectively removes local minima in this global optimization problem.
NASA Astrophysics Data System (ADS)
Monturet, Serge; Saalfrank, Peter
2010-08-01
Some time ago, it has been observed that vibrationally highly excited NO(v) molecules (with typical vibrational quantum numbers v≈15 ) lose substantial amounts of vibrational energy when scattering off a Au(111) surface [H. Huang, C. Rettner, D. Auerbach, and A. Wodtke, Science 290, 111 (2000)10.1126/science.290.5489.111]. This has been interpreted as a sign for the breakdown of the Born-Oppenheimer approximation due to vibration-electron coupling. It has been argued that this process cannot be understood on the basis of single-quantum transitions which are typical for “electronic friction” models based on a perturbative treatment of weak vibration-electron couplings. Rather, multiple-quanta transitions characteristic for strong nonadiabatic effects are needed according to recent classical surface hopping calculations involving multiple potential-energy surfaces and model Hamiltonians [N. Shenvi, S. Roy, and J. C. Tully, Science 326, 829 (2009)10.1126/science.1179240]. Here we address the importance and magnitude of electronic friction for NO@Au(111) by using fully quantum-mechanical, parameter-free first-principles theories in reduced dimensions. Periodic density-functional theory calculations are performed to obtain a ground-state potential-energy surface along the desorption and NO-vibration coordinates, and coordinate-resolved, finite NO vibrational lifetimes due to vibration-electron coupling. Using this input, the scattering event is modeled by open-system density-matrix theory in the frame of the coupled-channel-density-matrix method, which allows for the inclusion of energy relaxation of the scattering NO molecules. It is found that within this model at least, electronic friction accounts for the observed vibrational deactivation of NO scattering from gold.
NASA Astrophysics Data System (ADS)
Hagelberg, Frank
2004-03-01
In this contribution, we address the problem how to determine accurately the nonadiabatic content of any given dynamic process involving molecular motion. More specifically, we generate a dynamic electronic wave function using Electron Nuclear Dynamics (END) theory^2 and cast this wave function into the language of electronic excitations. This is achieved by adiabatic transport of an electronic basis along the classical nuclear trajectories of the studied molecular system. This basis is chosen as the static UHF molecular ground state determinant of the system in conjunction with all determinants that arise from the ground state by single, double and triple substitutions. Projecting the dynamic wave function into this basis, we arrive at a natural distinction between adiabatic and nonadiabatic components of the motion considered. We will discuss this concept by the examples of various scattering problems, among them the interaction of proton projectiles with methylene targets. ^2E. Deumens et al., Rev. Mod. Phys. 1994, 66, 917.
NASA Astrophysics Data System (ADS)
Arenas, Claudio; Henriquez, Ricardo; Moraga, Luis; Muñoz, Enrique; Munoz, Raul C.
2015-02-01
We calculate the electrical resistivity of a metallic specimen, under the combined effects of electron scattering by impurities, grain boundaries, and rough surfaces limiting the film, using a quantum theory based upon the Kubo formalism. Grain boundaries are represented by a one-dimensional periodic array of Dirac delta functions separated by a distance "d" giving rise to a Kronig-Penney (KP) potential. We use the Green's function built from the wave functions that are solutions of this KP potential; disorder is included by incorporating into the theory the probability that an electron is transmitted through several successive grain boundaries. We apply this new theory to analyze the resistivity of samples S1, S2, S7 and S8 measured between 4 and 300 K reported in Appl. Surf. Science273, 315 (2013). Although both the classical and the quantum theories predict a resistivity that agrees with experimental data to within a few percent or better, the phenomena giving rise to the increase of resistivity over the bulk are remarkably different. Classically, each grain boundary contributes to the electrical resistance by reflecting a certain fraction of the incoming electrons. In the quantum description, there are states (in the allowed KP bands) that transmit electrons unhindered, without reflections, while the electrons in the forbidden KP bands are localized. A distinctive feature of the quantum theory is that it provides a description of the temperature dependence of the resistivity where the contribution to the resistivity originating on electron-grain boundary scattering can be identified by a certain unique grain boundary reflectivity R, and the resistivity arising from electron-impurity scattering can be identified by a certain unique ℓIMP mean free path attributable to impurity scattering. This is in contrast to the classical theory of Mayadas and Shatzkes (MS), that does not discriminate properly between a resistivity arising from electron-grain boundary
Elastic electron scattering from water vapor and ice at high momentum transfer.
Vos, M; Weigold, E; Moreh, R
2013-01-28
We compare the area, peak separation, and width of the H and O elastic peak for light and heavy water, as observed in spectra of keV electrons scattered over large angles. Peak separation is well reproduced by the theory, but the O:H area ratio is somewhat larger than expected and is equal to the O:D area ratio. Thus no anomalous scattering from H was observed. Only minor differences are observed for scattering from a gaseous or a solid target. The extracted mean kinetic energy of H and D agreed within 5% with the calculated ones for ice. For the more difficult vapor measurements agreement was on a 12% level. A preliminary attempt to extract the O kinetic energy in ice agreed within 10% with the calculated values.
Monte Carlo simulation of 1-10-keV electron scattering in an aluminum target
NASA Astrophysics Data System (ADS)
Kotera, Masatoshi; Murata, Kenji; Nagami, Koichi
1981-12-01
New Monte Carlo simulations of electron scattering based on the single scattering model have been performed in the low-energy region for an aluminum target, where two basic equations are required, namely the elastic scattering cross section and the energy-loss rate. We investigated the screened Rutherford equation and the Mott equation for two different atomic potentials for the former, and the Rao Sahib-Wittry equation (the modified Bethe equation) for the latter. The validity of each model is discussed in a comparison between Monte Carlo results and experimental results such as the electron range, electron backscattering, and electron transmission which have been reported by various authors. Consequently, it was found that a combination of the Mott cross section and the Rao Sahib-Wittry equation showed the best accuracy. However, the accuracy of a previous model with the screened Rutherford equation is not as bad as aniticipated because of the higher accuracy of the Born approximation for light elements such as Al, compared to Au.
Stimulated Brillouin scattering during electron gyro-harmonic heating at EISCAT
NASA Astrophysics Data System (ADS)
Fu, H. Y.; Scales, W. A.; Bernhardt, P. A.; Briczinski, S. J.; Kosch, M. J.; Senior, A.; Rietveld, M. T.; Yeoman, T. K.; Ruohoniemi, J. M.
2015-08-01
Observations of secondary radiation, stimulated electromagnetic emission (SEE), produced during ionospheric modification experiments using ground-based, high-power, high-frequency (HF) radio waves are considered. The High Frequency Active Auroral Research Program (HAARP) facility is capable of generating narrowband SEE in the form of stimulated Brillouin scatter (SBS) and stimulated ion Bernstein scatter (SIBS) in the SEE spectrum. Such narrowband SEE spectral lines have not been reported using the European Incoherent Scatter (EISCAT) heater facility before. This work reports the first EISCAT results of narrowband SEE spectra and compares them to SEE previously observed at HAARP during electron gyro-harmonic heating. An analysis of experimental SEE data shows observations of emission lines within 100 Hz of the pump frequency, interpreted as SBS, during the 2012 July EISCAT campaign. Experimental results indicate that SBS strengthens as the pump frequency approaches the third electron gyro-harmonic. Also, for different heater antenna beam angles, the CUTLASS radar backscatter induced by HF radio pumping is suppressed near electron gyro-harmonics, whereas electron temperature enhancement weakens as measured by EISCAT/UHF radar. The main features of these new narrowband EISCAT observations are generally consistent with previous SBS measurements at HAARP.
Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data
Adikaram, D.; Rimal, D.; Weinstein, L. B.; Raue, B.; Khetarpal, P.; Bennett, R.; Arrington, J.; Brooks, W.; Adhikari, K.; Afanasev, A.; et al
2015-02-10
There is a significant discrepancy between the values of the proton electric form factor, GpE, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of GpE from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (epsilon) and momentummore » transfer (Q2) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ε at Q2=1.45 GeV2. This measurement is consistent with the size of the form factor discrepancy at Q2≈1.75 GeV2 and with hadronic calculations including nucleon and Delta intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV2.« less
Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data
Adikaram, D.; Rimal, D.; Weinstein, L. B.; Raue, B.; Khetarpal, P.; Bennett, R.; Arrington, J.; Brooks, W.; Adhikari, K.; Afanasev, A.; Amaryan, M.; Anderson, M.; Anefalos Pereira, S.; Avakian, H.; Ball, J.; Battaglieri, M.; Bedlinskiy, I.; Biselli, A.; Bono, J.; Boiarinov, S.; Briscoe, W.; Burkert, V.; Carman, D.; Careccia, S.; Celentano, A.; Chandavar, S.; Charles, G.; Colaneri, L.; Cole, P.; Contalbrigo, M.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Dodge, G.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Filippi, A.; Fleming, J.; Fradi, A.; Garillon, B.; Gilfoyle, G.; Giovanetti, K.; Girod, F.; Goetz, J.; Gohn, W.; Golovatch, E.; Gothe, R.; Griffioen, K.; Guegan, B.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Harrison, N.; Hattawy, M.; Hicks, K.; Holtrop, M.; Hughes, S.; Hyde, C. E.; Ilieva, Y.; Ireland, D.; Ishkhanov, B.; Jenkins, D.; Jiang, H.; Jo, H.; Joo, K.; Joosten, S.; Kalantarians, N.; Keller, D.; Khandaker, M.; Kim, A.; Kim, W.; Klein, A.; Klein, F.; Koirala, S.; Kubarovsky, V.; Kuhn, S.; Livingston, K.; Lu, H.; MacGregor, I.; Markov, N.; Mattione, P.; Mayer, M.; McKinnon, B.; Mestayer, M.; Meyer, C.; Mirazita, M.; Mokeev, V.; Montgomery, R.; Moody, C.; Moutarde, H.; Movsisyan, A.; Camacho, C. Munoz; Nadel-Turonski, P.; Niccolai, S.; Niculescu, G.; Osipenko, M.; Ostrovidov, A.; Park, K.; Pasyuk, E.; Pisano, S.; Pogorelko, O.; Price, J.; Procureur, S.; Prok, Y.; Protopopescu, D.; Puckett, A.; Ripani, M.; Rizzo, A.; Rosner, G.; Rossi, P.; Roy, P.; Sabati, F.; Salgado, C.; Schott, D.; Schumacher, R.; Seder, E.; Sharabian, Y.; Simonyan, A.; Skorodumina, I.; Smith, E.; Smith, G.; Sober, D.; Sokhan, D.; Sparveris, N.; Stepanyan, S.; Stoler, P.; Strauch, S.; Sytnik, V.; Taiuti, M.; Tian, Ye; Trivedi, A.; Ungaro, M.; Voskanyan, H.; Voutier, E.; Walford, N.; Watts, D.; Wei, X.; Wood, M.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, Z.; Zonta, I.
2015-02-10
There is a significant discrepancy between the values of the proton electric form factor, GpE, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of GpE from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (epsilon) and momentum transfer (Q2) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ε at Q2=1.45 GeV2. This measurement is consistent with the size of the form factor discrepancy at Q2≈1.75 GeV2 and with hadronic calculations including nucleon and Delta intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV2.
Towards a resolution of the proton form factor problem: new electron and positron scattering data.
Adikaram, D; Rimal, D; Weinstein, L B; Raue, B; Khetarpal, P; Bennett, R P; Arrington, J; Brooks, W K; Adhikari, K P; Afanasev, A V; Amaryan, M J; Anderson, M D; Anefalos Pereira, S; Avakian, H; Ball, J; Battaglieri, M; Bedlinskiy, I; Biselli, A S; Bono, J; Boiarinov, S; Briscoe, W J; Burkert, V D; Carman, D S; Careccia, S; Celentano, A; Chandavar, S; Charles, G; Colaneri, L; Cole, P L; Contalbrigo, M; Crede, V; D'Angelo, A; Dashyan, N; De Vita, R; De Sanctis, E; Deur, A; Djalali, C; Dodge, G E; Dupre, R; Egiyan, H; El Alaoui, A; El Fassi, L; Elouadrhiri, L; Eugenio, P; Fedotov, G; Fegan, S; Filippi, A; Fleming, J A; Fradi, A; Garillon, B; Gilfoyle, G P; Giovanetti, K L; Girod, F X; Goetz, J T; Gohn, W; Golovatch, E; Gothe, R W; Griffioen, K A; Guegan, B; Guidal, M; Guo, L; Hafidi, K; Hakobyan, H; Hanretty, C; Harrison, N; Hattawy, M; Hicks, K; Holtrop, M; Hughes, S M; Hyde, C E; Ilieva, Y; Ireland, D G; Ishkhanov, B S; Jenkins, D; Jiang, H; Jo, H S; Joo, K; Joosten, S; Kalantarians, N; Keller, D; Khandaker, M; Kim, A; Kim, W; Klein, A; Klein, F J; Koirala, S; Kubarovsky, V; Kuhn, S E; Livingston, K; Lu, H Y; MacGregor, I J D; Markov, N; Mattione, P; Mayer, M; McKinnon, B; Mestayer, M D; Meyer, C A; Mirazita, M; Mokeev, V; Montgomery, R A; Moody, C I; Moutarde, H; Movsisyan, A; Camacho, C Munoz; Nadel-Turonski, P; Niccolai, S; Niculescu, G; Osipenko, M; Ostrovidov, A I; Park, K; Pasyuk, E; Peña, C; Pisano, S; Pogorelko, O; Price, J W; Procureur, S; Prok, Y; Protopopescu, D; Puckett, A J R; Ripani, M; Rizzo, A; Rosner, G; Rossi, P; Roy, P; Sabatié, F; Salgado, C; Schott, D; Schumacher, R A; Seder, E; Sharabian, Y G; Simonyan, A; Skorodumina, I; Smith, E S; Smith, G D; Sober, D I; Sokhan, D; Sparveris, N; Stepanyan, S; Stoler, P; Strauch, S; Sytnik, V; Taiuti, M; Tian, Ye; Trivedi, A; Ungaro, M; Voskanyan, H; Voutier, E; Walford, N K; Watts, D P; Wei, X; Wood, M H; Zachariou, N; Zana, L; Zhang, J; Zhao, Z W; Zonta, I
2015-02-13
There is a significant discrepancy between the values of the proton electric form factor, G(E)(p), extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of G(E)(p) from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (ϵ) and momentum transfer (Q(2)) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ϵ at Q(2)=1.45 GeV(2). This measurement is consistent with the size of the form factor discrepancy at Q(2)≈1.75 GeV(2) and with hadronic calculations including nucleon and Δ intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV(2).
NASA Astrophysics Data System (ADS)
Essert, Sven; Schneider, Hans Christian
2011-12-01
We theoretically investigate spin-dependent carrier dynamics due to the electron-phonon interaction after ultrafast optical excitation in ferromagnetic metals. We calculate the electron-phonon matrix elements including the spin-orbit interaction in the electronic wave functions and the interaction potential. Using the matrix elements in Boltzmann scattering integrals, the momentum-resolved carrier distributions are obtained by solving their equation of motion numerically. We find that the optical excitation with realistic laser intensities alone leads to a negligible magnetization change, and that the demagnetization due to electron-phonon interaction is mostly due to hole scattering. Importantly, the calculated demagnetization quenching due to this Elliot-Yafet-type depolarization mechanism is not large enough to explain the experimentally observed result. We argue that the ultrafast demagnetization of ferromagnets does not occur exclusively via an Elliott-Yafet type process, i.e., scattering in the presence of the spin-orbit interaction, but is influenced to a large degree by a dynamical change of the band structure, i.e., the exchange splitting.
Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data
Adikaram, D.; Rimal, D.; Weinstein, L. B.; Raue, B.; Khetarpal, P.; Bennett, R. P.; Arrington, J.; Brooks, W. K.; Adhikari, K. P.; Afanasev, A. V.; Dupre, R.; El Alaoui, A.; El Fassi, L.; Hafidi, K.; Moody, C. I.
2015-02-10
There is a significant discrepancy between the values of the proton electric form factor, G(E)(p), extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of G(E)(p). from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (epsilon) and momentum transfer (Q(2)) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing epsilon at Q(2) = 1.45 GeV2. This measurement is consistent with the size of the form factor discrepancy at Q(2) approximate to 1.75 GeV2 and with hadronic calculations including nucleon and Delta intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV2.
Electron scattering by biomass molecular fragments: useful data for plasma applications?*
NASA Astrophysics Data System (ADS)
Ridenti, Marco A.; Amorim Filho, Jayr; Brunger, Michael J.; da Costa, Romarly F.; Varella, Márcio T. do N.; Bettega, Márcio H. F.; Lima, Marco A. P.
2016-08-01
Recent data obtained for electron scattering by biomass molecular fragments, indicated that low-energy resonances may have an important role in the de-lignification of biomass through a plasma pre-treatment. To support these findings, we present new experimental evidence of the predicted dissociation pathways on plasma treatment of biomass. An important question is how accurate must the experimental and/or the theoretical data be in order to indicate that plasma modelings can be really useful in understanding plasma applications? In this paper, we initiate a discussion on the role of data accuracy of experimental and theoretical electron-molecule scattering cross sections in plasma modeling. First we review technological motivations for carrying out electron-molecule scattering studies. Then we point out the theoretical and experimental limitations that prevent us from obtaining more accurate cross sections. We present a few examples involving biomass molecular fragments, to illustrate theoretical inaccuracies on: resonances positions and widths, electronic excitation, superelastic cross sections from metastable states and due to multichannel effects on the momentum transfer cross sections. On the experimental side we briefly describe challenges in making absolute cross sections measurements with biomass species and radicals. And finally, through a simulation of a N2 plasma, we illustrate the impact on the simulation due to inaccuracies on the resonance positions and widths and due to multichannel effects on the momentum transfer cross sections. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.Supplementary material in the form of one pdf and two mp4 files available from the Journal web page at http://dx.doi.org/10.1140/epjd/e2016-70272-8
Esser, N.; Koepp, M.; Haier, P.
1993-07-01
Resonance Raman scattering (RRS) experiments have been performed to explore the electronic states via the vibrational modes of highly ordered (1 X 1) monolayers of Sb on InP(110) and GaAs(110) prepared by thermal annealing. In accordance to the C{sub s} symmetry of the two-atom unit cell of the monolayers three modes of A{prime} and one of A{double_prime} symmetry are observed by Raman scattering. The scattering intensities show pronounced resonances which are related to electronic transitions between the two-dimensional electronic surface bands. The resonances are found to be characteristic for each vibrational mode. This can be understood in terms of different electronic bands being involved in the scattering process. For Sb on GaAs(110), the resonance of the A{double_prime} mode yields a maximum between 2.2 and 2.3 eV. On InP(110), resonances at 2.55 eV for the 1A{prime}, 2.3-2.6 eV for the 2A{prime}, 1.9 eV for the 1A{double_prime} and{>=}3.0 eV for the 3A{prime} modes occur. For both Sb on GaAs and InP the transition energies observed by RRS coincide with features reported by several other techniques. The resonance behavior of the ideal monolayers can be understood as a fingerprint of the joint density of states at the interface. In contrast, resonance Raman spectra taken after deposition of 1.5 ML Sb without annealing reveal a different resonance behavior. In this case, where the monolayer is not ideally ordered, the resonances are smeared out over an energy range between 2.3 and 2.7 eV revealing the influence of imperfections on the electronic band structure. 41 refs., 3 figs., 1 tab.
NASA Astrophysics Data System (ADS)
Shprits, Yuri Y.; Runov, Andrei; Ni, Binbin
2013-02-01
In the current study, we perform statistical analysis of the magnetosonic (MS) waves (also often referred to as extremely low frequency (ELF) equatorial noise) in the range between the ion cyclotron frequency and the lower hybrid resonance frequency within 10° of the magnetic equator. Observations were made between 2 and 9 RE using THEMIS Filter Bank (FBK) data. ELF waves with spectral power exceeding 10-6 nT2/Hz are registered in ~3% of all samples in the inner magnetosphere. The survey has shown that, during the solar minimum, the average amplitude of equatorial ELF waves is less than 0.025 nT. Interpreting ELF events as MS waves, we have evaluated the corresponding wave-induced resonant scattering coefficients of radiation belt energetic electrons. We also study the effect of heavy ions on the scattering rates. The analysis reveals that the scattering by magnetosonic waves for various plasma compositions during geomagnetically quiet times is by up to two orders of magnitude slower than was previously reported and cannot significantly contribute to the long-term dynamics of the radiation belts. Computed electron scattering rates by magnetosonic waves extends to higher αeq when the fraction of H+ in the plasma decreases, while the range of pitch angles for which resonance occurs remains relatively insensitive to the plasma composition. While inclusion of multi-ion species into the wave dispersion relation produces noticeable changes in bounce-averaged scattering rates, the average rates are still significantly below typical scattering rates of chorus or hiss waves.
Gorelik, Tatiana E.; Billinge, Simon J. L.; Schmidt, Martin U.; Kolb, Ute
2015-04-01
This paper shows for the first time that pair-distribution function analyses can be carried out on organic and organo-metallic compounds from powder electron diffraction data. Different experimental setups are demonstrated, including selected area electron diffraction (SAED) and nanodiffraction in transmission electron microscopy (TEM) or nanodiffraction in scanning transmission electron microscopy (STEM) modes. The methods were demonstrated on organo-metallic complexes (chlorinated and unchlorinated copper-phthalocyanine) and on purely organic compounds (quinacridone). The PDF curves from powder electron diffraction data, called ePDF, are in good agreement with PDF curves determined from X-ray powder data demonstrating that the problems of obtaining kinematical scattering data and avoiding beam-damage of the sample are possible to resolve.
Gorelik, Tatiana E; Schmidt, Martin U; Kolb, Ute; Billinge, Simon J L
2015-04-01
This paper shows that pair-distribution function (PDF) analyses can be carried out on organic and organometallic compounds from powder electron diffraction data. Different experimental setups are demonstrated, including selected area electron diffraction and nanodiffraction in transmission electron microscopy or nanodiffraction in scanning transmission electron microscopy modes. The methods were demonstrated on organometallic complexes (chlorinated and unchlorinated copper phthalocyanine) and on purely organic compounds (quinacridone). The PDF curves from powder electron diffraction data, called ePDF, are in good agreement with PDF curves determined from X-ray powder data demonstrating that the problems of obtaining kinematical scattering data and avoiding beam damage of the sample are possible to resolve. PMID:25510245
Gorelik, Tatiana E.; Billinge, Simon J. L.; Schmidt, Martin U.; Kolb, Ute
2015-04-01
This paper shows for the first time that pair-distribution function analyses can be carried out on organic and organo-metallic compounds from powder electron diffraction data. Different experimental setups are demonstrated, including selected area electron diffraction (SAED) and nanodiffraction in transmission electron microscopy (TEM) or nanodiffraction in scanning transmission electron microscopy (STEM) modes. The methods were demonstrated on organo-metallic complexes (chlorinated and unchlorinated copper-phthalocyanine) and on purely organic compounds (quinacridone). The PDF curves from powder electron diffraction data, called ePDF, are in good agreement with PDF curves determined from X-ray powder data demonstrating that the problems of obtaining kinematical scattering datamore » and avoiding beam-damage of the sample are possible to resolve.« less
Inelastic electron and Raman scattering from the collective excitations in quantum wires
NASA Astrophysics Data System (ADS)
Kushwaha, Manvir
2014-03-01
The nanofabrication technology has taught us that an m-dimensional confining potential imposed upon an n-dimensional electron gas paves the way to a quasi-(n- m)-dimensional electron gas, with m <= n and 1 <= n , m <= 3 . This is the road to the (semiconducting) quasi- n dimensional electron gas systems we have been happily traversing on now for almost two decades. Achieving quasi-one dimensional electron gas (Q-1DEG) led us to some mixed moments in this journey: while the reduced phase space for the scattering led us believe in the route to the faster electron devices, the proximity to the 1D systems left us in the dilemma of describing it as a Fermi liquid or as a Luttinger liquid. No one had ever suspected the potential of the former, but it took quite a while for some to convince the others on the latter. A realistic Q-1DEG system at the low temperatures is best describable as a Fermi liquid rather than as a Luttinger liquid. This has motivated us to employ the Bohm-Pines' full RPA to develop a systematic methodology for the inelastic electron and light scattering from the collective (plasmon) excitations in Q-1DEG [or quantum wires]. We will discuss in detail the results published in AIP Advances 3, 042103 (2013).
Electron and Positron Scattering with a Few Alkyne Molecules - Theoretical Cross sections
NASA Astrophysics Data System (ADS)
Patel, U. R.; Joshipura, K. N.; Kothari, H. N.
2016-05-01
Electron molecule scattering processes play an important role in the understanding of the electron driven physiochemical phenomena in diverse environments such as biological media, planetary atmospheres, interstellar clouds and plasmas. In modeling and simulating effects induced by electrons traversing through matter, the relevant cross section data are required as an input. An alternative probe, positron has also been used for the similar study of atoms, molecules and matter in bulk. Interaction of positrons with atoms and molecules differs from electron interactions due to opposite sign of charge and absence of exchange potential. In the present paper, our aim is to apply an identical theoretical method1,2 to electrons as well as positrons interacting with alkyne molecules like acetylene (HC ≡ CH), 1- Butyne (HC ≡ C- CH2 CH3) and Propyne (HC ≡ C- CH3) . We have carried out calculations of total scattering cross sections by starting with complex potential approach followed by the solution of the Schrodinger equation using numerical method. Ionization cross sections are deduced as in1,2. Comparisons have been made with available theoretical and experimental results for both electron (e-) and positron (e+) . The study will be extended to alkanes and alkenes.
Inclusive electron scattering from nuclei at x greater than 1 and high 4-momentum
NASA Astrophysics Data System (ADS)
Arrington, John Robert
CEBAF experiment e89-008 measured inclusive electron scattering from nuclei in a Q2 range between 0.8 and 7.3 (GeV/c)2 for xBjorken/ ~>/ 1. The cross sections for scattering from D, C, Fe, and Au were measured. The C, Fe, and Au data have been analyzed in terms of F(y) to examine y-scaling of the quasielastic scattering, and to study the momentum distribution of the nucleons in the nucleus. The data have also been analyzed in terms of the structure function /nu W2 to examine scaling of the inelastic scattering in x and /xi, and to study the momentum distribution of the quarks. In the regions where quasielastic scattering dominates the cross section (low Q2 or large negative values of y), the data are shown to exhibit y-scaling. However, the y- scaling breaks down once the inelastic contributions become large. The data do not exhibit x-scaling, except at the lowest values of x, while the structure function does appear to scale in the Nachtmann variable, /xi.
Inclusive Electron Scattering From Nuclei at x >1 and High Q^2
John Arrington
1998-06-02
CEBAF experiment e89-008 measured inclusive electron scattering from nuclei in a Q{sup 2} range between 0.8 and 7.3 (GeV/c){sup 2} for x{sub Bjorken} approximately greater than 1. The cross sections for scattering from D C, Fe, and Au were measured. The C, Fe, and Au data have been analyzed in terms of F(y) to examine y-scaling of the quasielastic scattering, and to study the momentum distribution of the nucleons in the nucleus. The data have also been analyzed in terms of the structure function vW{sub 2} to examine scaling of the inelastic scattering in x and xi and to study the momentum distribution of the quarks. In the regions where quasielastic scattering dominates the cross section (low Q{sup 2} or large negative values of y), the data are shown to exhibit y-scaling. However, the y-scaling breaks down once the inelastic contributions become large. The data do not exhibit x-scaling, except at the lowest values of x, while the structure function does appear to scale in the Nachtmann variable, xi.
Intersubband scattering in modulation-doped Si two-dimensional electron gases
NASA Astrophysics Data System (ADS)
Su, Yi-Hsin; Li, Jiun-Yun; Rokhinson, Leonid; Sturm, James
A bilayer of modulation doped two-dimensional electron gas (2DEG) is of great interest to probe Coulomb drag. For bottom-doped Si 2DEGs, impurity scattering due to poor phosphorus (P) turn-off results in low carrier mobility. Here we demonstrate a record-high electron mobility of 470,000 cm2/V-s at 0.3 K in a bottom-doped 2DEG, comparable to that in top-doped structures. The power-law exponent of mobility vs. density was also evaluated for different P turn-off slopes. With fast turn-off, the power is 1.5, indicative of dominant remote doping scattering. The power decreases with slower P turn-off due to the enhanced scattering from the segregated P atoms. Further, for the first time, we report the second subband occupancy and intersubband scattering in a single Si quantum well, supported by the Shubnikov-de Haas oscillation data.
Kameda, Jun; Inoguchi, Ryoichi; Prior, David J; Kogure, Toshihiro
2007-12-01
We present a new method for the morphological analyses of minute faceted crystals by combining stereo-photogrammetric analysis of scanning electron microscope images and electron back-scattered diffraction. Two scanning electron microscope images of the same crystal, recorded at different tilt angles of the specimen stage, are used to determine the orientations of crystal edges in a specimen-fixed coordinate system. The edge orientations are converted to the indices [uvw] in the crystal system using the crystal orientation determined by electron back-scattered diffraction analysis. The Miller indices of crystal facets are derived from the indices of the edges surrounding the facets. The method is applicable to very small crystal facets. The angular error, as derived from tests using a calcite crystal of known morphology, is a few degrees. To demonstrate the applicability of the method, the morphology of boehmite (gamma-AlOOH) precipitated from solution during the dissolution of anorthite was analyzed. The micrometre-sized boehmite crystals are surrounded by two {010} basal facets and eight equivalent side facets that can be indexed equally well as {323}, {434} or {545}. We suggest that these side facets are in fact {111}, the morphology having been modified slightly (by a few degrees) by a small extension associated with opening along (010) microcleavage planes. Tiny {140} facets are also commonly observed.
Gupta, D. N. Yadav, Pinki; Avinash, K.; Jang, D. G.; Suk, H.; Hur, M. S.
2015-05-15
Stimulated Raman scattering of a laser in plasmas with energetic drifting electrons was investigated by analyzing the growth of interacting waves during the Raman scattering process. The Langmuir wave and scattered electromagnetic sideband wave grow initially and are dampened after attaining a maximum level that indicates a periodic exchange of energy between the pump wave and the daughter waves. The presence of energetic drifting electrons in the laser-produced plasma influences the stimulated Raman scattering process. The plasma wave generated by Raman scattering may be influenced by the energetic electrons, which enhance the growth rate of the instability. Our results show that the presence of energetic (hot) drifting electrons in a plasma has an important effect on the evolution of the interacting waves. This phenomenon is modeled via two-dimensional particle-in-cell simulations of the propagation and interaction of the laser under Raman instability.
Yoshikawa, M. Nagasu, K.; Shimamura, Y.; Shima, Y.; Kohagura, J.; Sakamoto, M.; Nakashima, Y.; Imai, T.; Ichimura, M.; Yasuhara, R.; Yamada, I.; Funaba, H.; Kawahata, K.; Minami, T.
2014-11-15
A multi-pass Thomson scattering (TS) has the advantage of enhancing scattered signals. We constructed a multi-pass TS system for a polarisation-based system and an image relaying system modelled on the GAMMA 10 TS system. We undertook Raman scattering experiments both for the multi-pass setting and for checking the optical components. Moreover, we applied the system to the electron temperature measurements in the GAMMA 10 plasma for the first time. The integrated scattering signal was magnified by approximately three times by using the multi-pass TS system with four passes. The electron temperature measurement accuracy is improved by using this multi-pass system.
A Clean Measurement of the Neutron Skin of 208Pb Through Parity Violating Electron Scattering
Riad Suleiman
2003-07-01
The difference between the neutron radius Rn of a heavy nucleus and the proton radius Rp is believed to be on the order of several percent. This qualitative feature of nuclei, which is essentially a neutron skin, has proven to be elusive to pin down experimentally in a rigorous fashion. A new Jefferson Lab experiment will measure the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from 208Pb. Since the Z-boson couples mainly to neutrons, this asymmetry provides a measure of the size of Rn that can be interpreted with as much confidence as the traditional electron scattering data. The projected experimental precision corresponds to a 1% determination of Rn, which will have a big impact on nuclear theory and its application to neutron rich matter such as neutron stars.
Scattering of emission lines in galaxy cluster cores: measuring electron temperature
NASA Astrophysics Data System (ADS)
Khedekar, S.; Churazov, E.; Sazonov, S.; Sunyaev, R.; Emsellem, E.
2014-06-01
The central galaxies of some clusters can be strong emitters in the Lyα and Hα lines. This emission may arise either from the cool/warm gas located in the cool core of the cluster or from the bright AGN within the central galaxy. The luminosities of such lines can be as high as 1042-1044 erg s-1. This emission originating from the core of the cluster will get Thomson scattered by hot electrons of the intra-cluster medium with an optical depth ˜0.01 giving rise to very broad (Δλ/λ ˜ 15 per cent) features in the scattered spectrum. We discuss the possibility of measuring the electron density and temperature using information on the flux and width of the highly broadened line features.
Transverse Beam Spin Asymmetries in Forward-Angle Elastic Electron-Proton Scattering
David Armstrong; Francois Arvieux; Razmik Asaturyan; Todd Averett; Stephanie Bailey; Guillaume Batigne; Douglas Beck; Elizabeth Beise; Jay Benesch; Louis Bimbot; James Birchall; Angela Biselli; Peter Bosted; Elodie Boukobza; Herbert Breuer; Roger Carlini; Robert Carr; Nicholas Chant; Yu-Chiu Chao; Swapan Chattopadhyay; Russell Clark; Silviu Covrig; Anthony Cowley; Daniel Dale; Charles Davis; Willie Falk; John Finn; Tony Forest; Gregg Franklin; Christophe Furget; David Gaskell; Joseph Grames; Keith Griffioen; Klaus Grimm; Benoit Guillon; Hayko Guler; Lars Hannelius; Richard HASTY; Alice Hawthorne Allen; Tanja Horn; Kathleen Johnston; Mark Jones; Peter Kammel; Reza Kazimi; Paul King; Ameya Kolarkar; Elie Korkmaz; Wolfgang Korsch; Serge Kox; Joachim Kuhn; Jeff Lachniet; Lawrence Lee; Jason Lenoble; Eric Liatard; Jianglai Liu; Berenice Loupias; Allison Lung; Dominique Marchand; Jeffery Martin; Kenneth McFarlane; David McKee; Robert McKeown; Fernand Merchez; Hamlet Mkrtchyan; Bryan Moffit; M. Morlet; Itaru Nakagawa; Kazutaka Nakahara; Retief Neveling; Silvia Niccolai; S. Ong; Shelley Page; Vassilios Papavassiliou; Stephen Pate; Sarah Phillips; Mark Pitt; Benard Poelker; Tracy Porcelli; Gilles Quemener; Brian Quinn; William Ramsay; Aamer Rauf; Jean-Sebastien Real; Julie Roche; Philip Roos; Gary Rutledge; Jeffery Secrest; Neven Simicevic; Gregory Smith; Damon Spayde; Samuel Stepanyan; Marcy Stutzman; Vince Sulkosky; Vincent Sulkosky; Vince Sulkosky; Vincent Sulkosky; Vardan Tadevosyan; Raphael Tieulent; Jacques Van de Wiele; Willem van Oers; Eric Voutier; William Vulcan; Glen Warren; Steven Wells; Steven Williamson; Stephen Wood; Chen Yan; Junho Yun; Valdis Zeps
2007-08-01
We have measured the beam-normal single-spin asymmetry in elastic scattering of transversely-polarized 3 GeV electrons from unpolarized protons at Q^2 values of 0.15 and 0.25 (GeV/c)^2 with results of A_n = -4.06 +- 0.99(stat) +- 0.63(syst) and A_n = -4.82 +- 1.87(stat) +- 0.98(syst) ppm. These results are inconsistent with calculations solely using the elastic nucleon intermediate state, and generally agree with calculations with significant inelastic hadronic intermediate state contributions. A_n provides a direct probe of the imaginary component of the two-photon exchange amplitude, the complete description of which is important in the interpretation of data from precision electron-scattering experiments.
Thakar, Aruna; Kumar, Ajai; Thomas, Jinto; Chavda, Chhaya
2008-09-01
An IR enhanced thermoelectrically cooled Si-avalanche photodiode (Si-APD) module is used for detection of scattered photons from plasma electrons. Present design of signal conditioning electronics for the APD has fast (50 MHz) and slow (500 kHz) channels to measure scattered and plasma background light, respectively. We report design analysis for different stages and their performance. The performance of fast channel is analyzed for two different group delays, speed, linearity, and its cross-talk with slow channel. Temperature dependence of APD's responsivity is studied in the wavelength range of 900-1060 nm. A minimum detection of approximately 25 photoelectrons (with SN=1) in the range of 5 to 25 degrees C is achieved at an APD gain of 75 in the present design.
Variational approach to the scattering of charged particles by a many-electron system
Nazarov, V.U.; Kim, C.S.; Nishigaki, S.; Pitarke, J. M.
2005-03-15
We report a variational approach to the nonlinearly screened interaction of charged particles with a many-electron system. This approach has been developed by introducing a modification of the Schwinger variational principle of scattering theory, which allows one to obtain nonperturbative scattering cross sections of moving projectiles from the knowledge of the linear and quadratic density-response functions of the target. Our theory is illustrated with a calculation of the energy loss per unit path length of slow antiprotons moving in a uniform electron gas, which shows good agreement with a fully nonlinear self-consistent Hartree calculation. Since available self-consistent calculations are restricted to low heavy-projectile velocities, we expect our theory to have applications to a variety of processes where nonlinear screening plays an important role.
Constrained gamma-Z interference corrections to parity-violating electron scattering
Hall, Nathan Luke; Blunden, Peter Gwithian; Melnitchouk, Wally; Thomas, Anthony W.; Young, Ross D.
2013-07-01
We present a comprehensive analysis of gamma-Z interference corrections to the weak charge of the proton measured in parity-violating electron scattering, including a survey of existing models and a critical analysis of their uncertainties. Constraints from parton distributions in the deep-inelastic region, together with new data on parity-violating electron scattering in the resonance region, result in significantly smaller uncertainties on the corrections compared to previous estimates. At the kinematics of the Qweak experiment, we determine the gamma-Z box correction to be Re\\box_{gamma-Z}^V = (5.61 +- 0.36) x 10^{-3}. The new constraints also allow precise predictions to be made for parity-violating deep-inelastic asymmetries on the deuteron.
Ueda, S.; Mizuguchi, M.; Kojima, T.; Takanashi, K.; Ishimaru, S.; Tsujikawa, M.; Shirai, M.
2014-03-31
We report ultrahigh-resolution spin-resolved hard X-ray photoemission (HAXPES) for a buried FeNi alloy film. By utilizing the forward Mott scattering in a Au layer on FeNi, our spin-resolved HAXPES method does not require a standard spin detector and allows us to use the multi-channel electron detection system for the high-efficient electron detection as used in conventional photoemission spectroscopy. A combination of the forward Mott scattering and multi-channel detection leads us to measure a clear spin polarization as well as spin-resolved majority and minority states in the Fe 2p core-level spectra without using the standard spin detector. This method enables us to measure spin-resolved core-level spectra for buried ferromagnetic materials.
Kubo, S; Nishiura, M; Tanaka, K; Shimozuma, T; Yoshimura, Y; Igami, H; Takahash, H; Mutoh, T; Tamura, N; Tatematsu, Y; Saito, T; Notake, T; Korsholm, S B; Meo, F; Nielsen, S K; Salewski, M; Stejner, M
2010-10-01
Collective Thomson scattering (CTS) system has been constructed at LHD making use of the high power electron cyclotron resonance heating (ECRH) system in Large Helical Device (LHD). The necessary features for CTS, high power probing beams and receiving beams, both with well defined Gaussian profile and with the fine controllability, are endowed in the ECRH system. The 32 channel radiometer with sharp notch filter at the front end is attached to the ECRH system transmission line as a CTS receiver. The validation of the CTS signal is performed by scanning the scattering volume. A new method to separate the CTS signal from background electron cyclotron emission is developed and applied to derive the bulk and high energy ion components for several combinations of neutral beam heated plasmas.
NASA Astrophysics Data System (ADS)
Carles, R.; Bayle, M.; Benzo, P.; Benassayag, G.; Bonafos, C.; Cacciato, G.; Privitera, V.
2015-11-01
Since the discovery of surface-enhanced Raman scattering (SERS) 40 years ago, the origin of the "background" that is systematically observed in SERS spectra has remained questionable. To deeply analyze this phenomenon, plasmon-resonant Raman scattering was recorded under specific experimental conditions on a panel of composite multilayer samples containing noble metal (Ag and Au) nanoparticles. Stokes, anti-Stokes, and wide, including very low, frequency ranges have been explored. The effects of temperature, size (in the nm range), embedding medium (SiO2, Si3N4, or TiO2) or ligands have been successively analyzed. Both lattice (Lamb modes and bulk phonons) and electron (plasmon mode and electron-hole excitations) dynamics have been investigated. This work confirms that in Ag-based nanoplasmonics composite layers, only Raman scattering by single-particle electronic excitations accounts for the background. This latter appears as an intrinsic phenomenon independently of the presence of molecules on the metallic surface. Its spectral shape is well described by revisiting a model developed in the 1990s for analyzing electron scattering in dirty metals, and used later in superconductors. The gs factor, that determines the effective mean-free path of free carriers, is evaluated, gsexpt=0.33 ±0.04 , in good agreement with a recent evaluation based on time-dependent local density approximation gstheor=0.32 . Confinement and interface roughness effects at the nanometer range thus appear crucial to understand and control SERS enhancement and more generally plasmon-enhanced processes on metallic surfaces.
NASA Astrophysics Data System (ADS)
Khakoo, Murtadha A.
2011-10-01
The near-threshold scattering of electrons from polyatomic molecules of fundamental interest, e.g. water, primary alcohols and ring molecules e.g. furan, benzene are important in plasma fuel processes, plasmas used in biological processes e.g. in the treatment of skin diseases, astrophysical plasmas, etc. The determination of cross-sections for such molecules has gathered impetus because of the increasing number of applications industrial plasma and biomedical processes and the need to understand and model these complex processes. It is now possible to determine accurate differential cross-sections for electron scattering from these polyatomic molecules. We will present recent normalized, absolute low energy electron scattering differential cross-sections for near-threshold elastic and inelastic scattering from water, primary alcohols, furan and benzene using a well-tested electron spectrometer apparatus. We will also compare our results with those of other experiments and available theoretical models, which show an encouragingly overall improved picture in terms of agreement between the different research groups. Funded by the National Science Foundation Research in an Undergraduate Institution Grant #s 0653452 and 1135203. This work was done collaboratively with Drs. V. Mckoy and C. Winstead, Caltech, USA (National Science Foundation Grant # 0653396 and Office of Basic Energy Sciences, US DOE Grant) and Dr. M. C. A. Lopes, U. Fed. de Juiz de Fora, Minas Gerais, Brazil; Dr. M. H. F. Bettega, U. Fed. do Parana, Curitiba, Brazil Drs. R. F. da Costa and M. A. P. Lima, Universidade Estadual de Campinas UNICAMP and CTBE, Campinas, Brazil (CNPq, FAPESP, FAPEMG, Finep, CENAPAD-SP and CAPES grants). Funded by US-NSF Grant #s 0653452 and 1135203.
Visualizing a protein quake with time resolved X-ray scattering at a free electron laser
Arnlund, David; Johansson, Linda C.; Wickstrand, Cecilia; Barty, Anton; Williams, Garth J.; Malmerberg, Erik; Davidsson, Jan; Milathianaki, Despina; DePonte, Daniel P.; Shoeman, Robert L.; Wang, Dingjie; James, Daniel; Katona, Gergely; Westenhoff, Sebastian; White, Thomas A.; Aquila, Andrew; Bari, Sadia; Berntsen, Peter; Bogan, Mike; van Driel, Tim Brandt; Doak, R. Bruce; Kjær, Kasper Skov; Frank, Matthias; Fromme, Raimund; Grotjohann, Ingo; Henning, Robert; Hunter, Mark S.; Kirian, Richard A.; Kosheleva, Irina; Kupitz, Christopher; Liang, Mengning; Martin, Andrew V.; Nielsen, Martin Meedom; Messerschmidt, Marc; Seibert, M. Marvin; Sjöhamn, Jennie; Stellato, Francesco; Weierstall, Uwe; Zatsepin, Nadia A.; Spence, John C. H.; Fromme, Petra; Schlichting, Ilme; Boutet, Sébastien; Groenhof, Gerrit; Chapman, Henry N.; Neutze, Richard
2014-01-01
A ‘protein quake’ describes the hypothesis that proteins rapidly dissipate energy through quake like structural motions. Here we measure ultrafast structural changes in the Blastochloris viridis photosynthetic reaction center following multi-photon excitation using time-resolved wide angle X-ray scattering at an X-ray free electron laser. A global conformational change arises within picoseconds, which precedes the propagation of heat through the protein. This motion is damped within a hundred picoseconds. PMID:25108686
Quasielastic electron scattering from methane, methane-d4, methane-d2, ethylene, and 2-methylpropane
NASA Astrophysics Data System (ADS)
Cooper, G.; Christensen, E.; Hitchcock, A. P.
2007-08-01
Quasielastic electron scattering from gaseous species at high momentum transfer was recently reported for the first time [Cooper et al., J. Electron Spectrosc. Relat. Phenom. 155, 28 (2007)]. The first results for CH4 and CD4 were well explained by a classical electron Compton scattering picture in which the electron scatters independently from each atom rather than the molecule as a whole. However, an alternative possible interpretation in terms of nondipole molecular vibrational excitation is suggested by previously published quantum mechanical calculations on high momentum transfer electron scattering from diatomic molecules [Bonham and de Souza, J. Chem. Phys. 79, 134 (1983)]. In order to determine which of these two interpretations best fits the experimental results, we have measured the quasielastic spectra of gaseous 2-methylpropane, ethylene, methane, and two isotopically substituted methanes, CH2D2 and CD4, at a momentum transfer of ˜20a.u. (2.25keV impact energy and 100° scattering angle). The experimental spectra are found to be composed of as many peaks as there are different atomic isotopes in the molecule (two for CH4, C2H4, 2-methylpropane, and CD4 and three for CH2D2). The peak positions are predicted accurately by the independent atom electron Compton scattering model, and the relative intensities are in reasonable agreement. The experimental results thus support classical electron Compton scattering as the origin of the signal.
Electron-electron correlations in fullerene C{sub 60} probed by incoherent scattering of x rays
Petrillo, C.; Sacchetti, F.; Orecchini, A.; De Renzi, R.; Ricco, M.
2006-08-15
The static structure factor of electrons in fullerene has been obtained by a properly designed x-ray diffraction experiment. Due to the intense diffuse scattering caused by the orientational disorder of the C{sub 60} molecules in fullerene, the experiment presented several difficulties. Nonetheless, the data were accurate enough to provide an estimate of the exchange-correlation energy and to make a valuable comparison of the static structure factors of fullerene and diamond. The observed value of the exchange-correlation energy, which is larger in fullerene than in diamond, suggests a clear link between carbon polymorphism and dynamic electron correlations. The experimental data of static structure factor of fullerene, together with the derived exchange-correlation contribution to the cohesion and the pair-correlation function, offer an interesting test on the validity of the local-density treatment of the electron correlations in solids.
Middendorf, H.D.; Miller, A.
1994-12-31
Energy-resolving neutron scattering techniques provide spatiotemporal data suitable for testing and refining analytical models or computer simulations of a variety of dynamical processes in biomolecular systems. This paper reviews experimental work on hydrated biopolymers at ISIS, the UK Pulsed Neutron Facility. Following an outline of basic concepts and a summary of the new instrumental capabilities, the progress made is illustrated by results from recent experiments in two areas: quasi- elastic scattering from highly hydrated polysaccharide gels (agarose and hyaluronate), and inelastic scattering from vibrational modes of slightly hydrated collagen fibers.
Absorptive potentials due to ionization and thermal diffuse scattering by fast electrons in crystals
Allen, L.J. ); Rossouw, C.J. )
1990-12-15
An expression for the Fourier coefficients of the absorptive potential due to electron-impact ionization in crystals is derived and the cross section is given in terms of these Fourier components. Absorptive potentials due to {ital K}-shell ionization and thermal diffuse scattering (TDS) are calculated with use of a hydrogenic model and an Einstein model, respectively. Inelastic potentials require integration over all states of the scattered electron and, for {ital K}-shell ionization, integration over all states of the ejected electron. These potentials are thus dependent on incident-beam energy, in contrast with the elastic potential. The projected spatial distribution of these potentials are plotted and compared with the elastic potential for CdTe, GaAs, Si, and diamond. The delocalization of the ionization absorptive potential is similar to that expected from classical impact-parameter arguments. The form of the TDS potential is substantially different from that due to elastic scattering, being extremely peaked on atomic positions with no absorption in the channels between atomic planes.
Proton form factors and two-photon exchange in elastic electron-proton scattering
Nikolenko, D. M.; Arrington, J.; Barkov, L. M.; Vries, H. de; Gauzshtein, V. V.; Golovin, R. A.; Gramolin, A. V.; Dmitriev, V. F.; Zhilich, V. N.; Zevakov, S. A.; Kaminsky, V. V.; Lazarenko, B. A.; Mishnev, S. I.; Muchnoi, N. Yu.; Neufeld, V. V.; Rachek, I. A.; Sadykov, R. Sh.; Stibunov, V. N.; Toporkov, D. K.; Holt, R. J.; and others
2015-05-15
Proton electromagnetic form factors are among the most important sources of information about the internal structure of the proton. Two different methods for measuring these form factors, the method proposed by Rosenbluth and the polarization-transfer method, yield contradictory results. It is assumed that this contradiction can be removed upon taking into account the hard part of the contribution of two-photon exchange to the cross section for elastic electron-proton scattering. This contribution can measured experimentally via a precision comparison of the cross sections for the elastic scattering of positrons and electrons on protons. Such a measurement, performed at the VEPP-3 storage ring in Novosibirsk at the beam energies of 1.6 and 1.0 GeV for positron (electron) scattering angles in the ranges of θ{sub e} = 15°–25° and 55°–75° in the first case and in the range of θ{sub e} = 65°–105° in the second case is described in the present article. Preliminary results of this experiment and their comparison with theoretical predictions are described.
NASA Astrophysics Data System (ADS)
Ziemkiewicz, M. P.; Zutz, A.; Nesbitt, D. J.
2012-06-01
Room temperature ionic liquids (RTIL’s) are a highly diverse class of materials with many potential technological applications. They are candidates for use in advanced electrolytes, green solvents, and supported liquid membranes for CO_2 sequestration. We present studies where inelastic scattering of high or low velocity nitric oxide provides insight into the microscopic structure of these complex surfaces. As an open shell diatomic, jet-cooled NO [^2π1/2(J = 0.5)] features both molecular and electronic collision dynamics as seen by probing scattered rotational and spin-orbit distributions respectively. These studies show substantial variation in degree of rotational and electronic excitation as ionic liquid identity is varied. Also, surface heating is found to have a strong effect on scattered spin-orbit branching, possibly due to the dependence of surface structure on temperature. This is discussed in terms of a picture where the electronic degree of freedom may serve as a sensitive measure of the cationic versus anionic nature of the top few layers of this material.
NASA Astrophysics Data System (ADS)
Roberts, B. M.; Dzuba, V. A.; Flambaum, V. V.; Pospelov, M.; Stadnik, Y. V.
2016-06-01
We revisit the WIMP-type dark matter scattering on electrons that results in atomic ionization and can manifest itself in a variety of existing direct-detection experiments. Unlike the WIMP-nucleon scattering, where current experiments probe typical interaction strengths much smaller than the Fermi constant, the scattering on electrons requires a much stronger interaction to be detectable, which in turn requires new light force carriers. We account for such new forces explicitly, by introducing a mediator particle with scalar or vector couplings to dark matter and to electrons. We then perform state-of-the-art numerical calculations of atomic ionization relevant to the existing experiments. Our goals are to consistently take into account the atomic physics aspect of the problem (e.g., the relativistic effects, which can be quite significant) and to scan the parameter space—the dark matter mass, the mediator mass, and the effective coupling strength—to see if there is any part of the parameter space that could potentially explain the DAMA modulation signal. While we find that the modulation fraction of all events with energy deposition above 2 keV in NaI can be quite significant, reaching ˜50 %, the relevant parts of the parameter space are excluded by the XENON10 and XENON100 experiments.
Critical binding and electron scattering by symmetric-top polar molecules
Garrett, W. R.
2014-10-28
Quantum treatments of electron interactions with polar symmetric-top rotor molecules show features not present in the treatment of the linear-polar-rotor model. For symmetric tops possessing non-zero angular momentum about the symmetry axis, a new critical dipole can be defined that guarantees an infinite set of dipole-bound states independent of the values of the components of the inertial tensor. Additionally, for this same class, the scattering cross section diverges for all nonzero values of dipole moments and inertial moments, similar to solutions for the fixed linear dipole. Additional predictions are presented for electron affinities and rotational resonances of these systems.
David Abbott; Abdellah Ahmidouch; Heinz Anklin; Francois Arvieux; Jacques Ball; S. Beedoe; Elizabeth Beise; Louis Bimbot; Werner Boeglin; Herbert Breuer; Roger Carlini; Nicholas Chant; Samuel Danagoulian; K. Dow; Jean-Eric Ducret; James Dunne; Lars Ewell; Laurent Eyraud; Christophe Furget; Michel Garcon; Ronald Gilman; Charles Glashausser; Paul Gueye; Kenneth Gustafsson; Kawtar Hafidi; Adrian Honegger; Juerg Jourdan; Serge Kox; Gerfried Kumbartzki; L. Lu; Allison Lung; David Mack; Pete Markowitz; Justin McIntyre; David Meekins; Fernand Merchez; Joseph Mitchell; R. Mohring; Sekazi Mtingwa; Hamlet Mkrtchyan; David Pitz; Liming Qin; Ronald Ransome; Jean-Sebastien Real; Philip Roos; Paul Rutt; Reyad Sawafta; Samuel Stepanyan; Raphael Tieulent; Egle Tomasi-Gustafsson; William Turchinetz; Kelley Vansyoc; Jochen Volmer; Eric Voutier; William Vulcan; Claude Williamson; Stephen Wood; Chen Yan; Jie Zhao; Wenxia Zhao
2000-05-01
Tensor polarization observables (t20, t21 and t22) have been measured in elastic electron-deuteron scattering for six values of momentum transfer between 0.66 and 1.7 (GeV/c){sup 2}. The experiment was performed at the Jefferson Laboratory in Hall C using the electron HMS Spectrometer, a specially designed deuteron magnetic channel and the recoil deuteron polarimeter POLDER. The new data determine to much larger Q{sup 2} the deuteron charge form factors G{sub C} and G{sub Q}. They are in good agreement with relativistic calculations and disagree with pQCD predictions.
Kohagen, Miriam; Mason, Philip E; Jungwirth, Pavel
2016-03-01
Modeled ions, described by nonpolarizable force fields, can suffer from unphysical ion pairing and clustering in aqueous solutions well below their solubility limit. The electronic continuum correction takes electronic polarization effects of the solvent into account in an effective way by scaling the charges on the ions, resulting in a much better description of the ionic behavior. Here, we present parameters for the sodium ion consistent with this effective polarizability approach and in agreement with experimental data from neutron scattering, which could be used for simulations of complex aqueous systems where polarization effects are important.
NASA Technical Reports Server (NTRS)
Nickel, J. C.; Zetner, P. W.; Shen, G.; Trajmar, S.
1989-01-01
Procedures and calibration techniques for measuring the absolute elastic and inelastic differential cross sections (DCS) for electron impact on molecular (atomic) species are described and illustrated by examples. The elastic DCS for the molecule under study is first determined by calibration against helium using the relative flow technique. The second step involves the production of energy-loss spectra for the instrument response function, the unfolding of overlapping inelastic structures and the normalization of inelastic intensities to the elastic cross sections. It is concluded that this method of determining absolute differential electron-molecule (atom) scattering cross sections is generally applicable and provides reliable results.
NASA Astrophysics Data System (ADS)
Belkacem, Ali; Slaughter, Daniel
2015-05-01
Understanding electron-driven chemical reactions is important for improving a variety of technological applications such as materials processing and the important role they play in the radiation damage in bulk matter. Furthermore, dissociative electron attachment often exhibits site-selective bond cleavage, which holds promise for prediction and precise control of electron-driven chemical reactions. Recent dynamical studies of these reactions have demonstrated that an understanding of anion dissociation dynamics beyond simple one-dimensional models is crucial in interpreting the measured fragment angular distributions. We combine ion fragment momentum imaging experiments with electron attachment entrance amplitude calculations to interrogate the non-Born-Oppenheimer dynamics of dissociative electron attachment in polyatomic molecules. We will report recent experimental developments in molecules of technological interest including methanol, methane and uracil. Work supported by Chemical Sciences, Geosciences and Biosciences division of BES/DOE.
Direct evidence for EMIC wave scattering of relativistic electrons in space
NASA Astrophysics Data System (ADS)
Zhang, X.-J.; Li, W.; Ma, Q.; Thorne, R. M.; Angelopoulos, V.; Bortnik, J.; Chen, L.; Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.; Baker, D. N.; Reeves, G. D.; Spence, H. E.; Blake, J. B.; Fennell, J. F.
2016-07-01
Electromagnetic ion cyclotron (EMIC) waves have been proposed to cause efficient losses of highly relativistic (>1 MeV) electrons via gyroresonant interactions. Simultaneous observations of EMIC waves and equatorial electron pitch angle distributions, which can be used to directly quantify the EMIC wave scattering effect, are still very limited, however. In the present study, we evaluate the effect of EMIC waves on pitch angle scattering of ultrarelativistic (>1 MeV) electrons during the main phase of a geomagnetic storm, when intense EMIC wave activity was observed in situ (in the plasma plume region with high plasma density) on both Van Allen Probes. EMIC waves captured by Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes and on the ground across the Canadian Array for Real-time Investigations of Magnetic Activity (CARISMA) are also used to infer their magnetic local time (MLT) coverage. From the observed EMIC wave spectra and local plasma parameters, we compute wave diffusion rates and model the evolution of electron pitch angle distributions. By comparing model results with local observations of pitch angle distributions, we show direct, quantitative evidence of EMIC wave-driven relativistic electron losses in the Earth's outer radiation belt.
Electronic Raman scattering in graphite and single-layer and few-layer graphene
NASA Astrophysics Data System (ADS)
Ponosov, Yu. S.; Ushakov, A. V.; Streltsov, S. V.
2015-05-01
We investigated polarization-resolved electronic Raman scattering in different graphitic structures, including bulk graphite and single-layer and few-layer graphene. For all investigated samples, the broad continua of interband electronic transitions were detected at an energy ˜0.35 eV, while they were expected to be at ˜6 eV [Phys. Rev. B 88, 085416 (2013), 10.1103/PhysRevB.88.085416]. The symmetry of the observed excitations corresponds to the A2 g irreducible representation. A quasilinear behavior of the Raman response is observed at low energies in all cases at room temperature, in agreement with performed tight-binding calculations. High-energy features at ˜0.8 eV are detected in the spectra of graphite and few-layer graphene. They are attributed to interband transitions in the vicinity of the K point, which involve electronic bands split by interlayer interaction. The effects of the substrate type, defect amount, and doping on the continuum line shape and symmetry are discovered. The silent layer-breathing mode is observed in a single-layer graphene. The results evidence that the electronic light scattering in graphitic structures without an external magnetic field is a powerful tool, which provides a variety of data on the structure and symmetry of low-energy electronic excitations.
Beausang, K V; Prunty, S L; Scannell, R; Beurskens, M N; Walsh, M J; de la Luna, E
2011-03-01
The present work is motivated by a long standing discrepancy between the electron temperature measurements of Thomson scattering (TS) and electron cyclotron emission (ECE) diagnostics for plasmas with strong auxiliary heating observed at both JET and TFTR above 6–7 keV, where in some cases the ECE electron temperature measurements can be 15%–20% higher than the TS measurements. Recent analysis based on ECE results at JET has shown evidence of distortions to the Maxwellian electron velocity distribution and a correlation with the TS and ECE discrepancies has been suggested. In this paper, a technique to determine the presence of non-Maxwellian behavior using TS diagnostics is outlined. The difficulties and limitations of modern TS system designs to determine the electron velocity distribution are also discussed. It is demonstrated that small deviations such as those suggested by previous ECE analysis could be potentially detected, depending on the spectral layout of the TS polychromators. The spectral layout of the JET high resolution Thomson scattering system is such that it could be used to determine these deviations between 1 and 6 keV, and the results presented here indicate that no evidence of non-Maxwellian behavior is observed in this range. In this paper, a modification to the current polychromator design is proposed, allowing non-Maxwellian distortions to be detected up to at least 10 keV. PMID:21585113
Correlated R-matrix theory of electron scattering: A coupled-cluster approach
NASA Astrophysics Data System (ADS)
Sur, Chiranjib; Pradhan, Anil; Sadayappan, P.
2007-06-01
Study of electron scattering from heavy atoms/ions not only demands high speed computing machines but also improved theoretical descriptions of the relativistic and correlation effects for the target atoms/ions as well. We will give an outline of the coupled-cluster R-matrix (CCRM) theory to incorporate the effect of electron correlation through coupled-cluster theory (CCT), the size extensive and one of the most accurate many body theories which is equivalant to an all-order many-body perturbation theory (MBPT). General theoretical formulation of CCRM and the computational implementation using the high level Mathematica style language compiler known as Tensor Contraction Engine (TCE) will be presented. Electronic structure calculations using CCT involve large collections of tensor contractions (generalized matrix multiplications). TCE searches for an optimal implementation of these tensor contraction expressions and generates high performance FORTRAN code for CCT. We will also comment on the interfacing of TCE generated code with the Breit-Pauli R-matrix code to make a next generation CCRM software package. This theoretical formulation and the new sets of codes can be used to study electron scattering / photoionization in heavy atomic systems where relativistic and electron correlation effects are very important.
Beausang, K V; Prunty, S L; Scannell, R; Beurskens, M N; Walsh, M J; de la Luna, E
2011-03-01
The present work is motivated by a long standing discrepancy between the electron temperature measurements of Thomson scattering (TS) and electron cyclotron emission (ECE) diagnostics for plasmas with strong auxiliary heating observed at both JET and TFTR above 6–7 keV, where in some cases the ECE electron temperature measurements can be 15%–20% higher than the TS measurements. Recent analysis based on ECE results at JET has shown evidence of distortions to the Maxwellian electron velocity distribution and a correlation with the TS and ECE discrepancies has been suggested. In this paper, a technique to determine the presence of non-Maxwellian behavior using TS diagnostics is outlined. The difficulties and limitations of modern TS system designs to determine the electron velocity distribution are also discussed. It is demonstrated that small deviations such as those suggested by previous ECE analysis could be potentially detected, depending on the spectral layout of the TS polychromators. The spectral layout of the JET high resolution Thomson scattering system is such that it could be used to determine these deviations between 1 and 6 keV, and the results presented here indicate that no evidence of non-Maxwellian behavior is observed in this range. In this paper, a modification to the current polychromator design is proposed, allowing non-Maxwellian distortions to be detected up to at least 10 keV.
Positron and electron scattering from alkane molecules. Normal- and cyclo-octane
NASA Astrophysics Data System (ADS)
Sueoka, O.; Makochekanwa, C.; Kimura, M.
2006-03-01
Total cross-sections (TCSs) for 0.2 1000 eV positrons and 0.4 1000 eV electrons colliding with normal-octane and cyclo-octane molecules have been studied using a relative measurement method. The TCS curves for positron and electron vary smoothly and compare well with other alkane molecules, in order of increasing carbon number. For positron scattering, weak humps at 1.5 2.5 eV for both normal- and cyclo-octane were observed. In the energy range lower than 2.2 eV, positron TCSs are roughly equal to or larger than electron TCSs. For electron scattering, a resonance peak at 8 eV and a shoulder at 25.0 eV were observed for both molecules. Over all the energy range, the TCS values for normal-octane are larger than those of cyclo-octane. The positron and electron TCS data for normal- and cyclo-octane molecules are briefly compared with those for normal- and cyclo-hexane.
Electron heating and confinemet measurements in EBT-S using Thomson scattering
Bighel, L.; Cobble, J.A.
1980-09-01
Thomson scattering of ruby laser light was used to measure electron temperatures and densities in the ELMO Bumpy Torus-Scale (EBT-S) at Oak Ridge National Laboratory. The measurements were made primarily during May 1980, although some were taken during January 1980. The scattering system, which was designed for very low electron density measurements, features a 14-J ruby laser, a high-throughput spectrometer, and 15% quantum efficiency photomultipliers. The measured electron densities lie in the range 5 X 10/sup 11/ cm/sup -3/ to 2.2 X 10/sup 12/ cm/sup -3/ with electron temperatures from 50 to 500 eV. The radial profiles of T/sub e/ and n/sub e/ are reasonably flat over an 8-cm region from the plasma center outward. The dependence of T/sub e/ and n/sub e/ on microwave power input and on background pressure is discussed. The electron data are used to derive approximate values of the energy confinement time.
NASA Technical Reports Server (NTRS)
Rich, A.; Van House, J.; Hegstrom, R. A.
1982-01-01
A dynamical calculation is presented of the helicity induced in an initially unpolarized electron beam after elastic scattering from an optically active medium, a process analogous to the circular polarization induced in unpolarized light following Rayleigh scattering from chiral targets. The calculation is based on the bound helical electron model of a chiral molecule, according to which the major contribution to the helicity is provided by the perturbation of the electron bound state by the spin-orbit interaction of the bound electrons moving in the electric field of the molecular core. The net helicity acquired is found to depend directly on a molecular asymmetry factor and the square of the atomic number of the heaviest atom in an asymmetric environment. For the case of carbon, the induced helicity is on the order of 0.00001, which would account for its lack of observation in a recent experiment. Results may have implications for the origin of optical activity in biological molecules by the differential ionization of D and L isomers by beta-decay electrons.
Van Compernolle, B; Bortnik, J; Pribyl, P; Gekelman, W; Nakamoto, M; Tao, X; Thorne, R M
2014-04-11
Resonant interactions between energetic electrons and whistler mode waves are an essential ingredient in the space environment, and in particular in controlling the dynamic variability of Earth's natural radiation belts, which is a topic of extreme interest at the moment. Although the theory describing resonant wave-particle interaction has been present for several decades, it has not been hitherto tested in a controlled laboratory setting. In the present Letter we report on the first laboratory experiment to directly detect resonant pitch angle scattering of energetic (∼keV) electrons due to whistler mode waves. We show that the whistler mode wave deflects energetic electrons at precisely the predicted resonant energy, and that varying both the maximum beam energy, and the wave frequency, alters the energetic electron beam very close to the resonant energy.
Khurgin, Jacob B.; Bajaj, Sanyam; Rajan, Siddharth
2015-12-28
Longitudinal optical (LO) phonons in GaN generated in the channel of high electron mobility transistors (HEMT) are shown to undergo nearly elastic scattering via collisions with hot electrons. The net result of these collisions is the diffusion of LO phonons in the Brillouin zone causing reduction of phonon and electron temperatures. This previously unexplored diffusion mechanism explicates how an increase in electron density causes reduction of the apparent lifetime of LO phonons, obtained from the time resolved Raman studies and microwave noise measurements, while the actual decay rate of the LO phonons remains unaffected by the carrier density. Therefore, the saturation velocity in GaN HEMT steadily declines with increased carrier density, in a qualitative agreement with experimental results.
Measurement of parity-violating asymmetry in electron-deuteron inelastic scattering
Wang, D.; Pan, K.; Subedi, R.; Ahmed, Z.; Allada, K.; Aniol, K. A.; Armstrong, D. S.; Arrington, J.; Bellini, V.; Beminiwattha, R.; et al
2015-04-01
The parity-violating asymmetries between a longitudinally-polarized electron beam and an unpolarized deuterium target have been measured recently. The measurement covered two kinematic points in the deep inelastic scattering region and five in the nucleon resonance region. We provide here details of the experimental setup, data analysis, and results on all asymmetry measurements including parity-violating electron asymmetries and those of inclusive pion production and beam-normal asymmetries. The parity-violating deep-inelastic asymmetries were used to extract the electron-quark weak effective couplings, and the resonance asymmetries provided the first evidence for quark-hadron duality in electroweak observables. These electron asymmetries and their interpretation were publishedmore » earlier, but are presented here in more detail.« less
Measurement of parity-violating asymmetry in electron-deuteron inelastic scattering
Wang, D.; Pan, K.; Subedi, R.; Ahmed, Z.; Allada, K.; Aniol, K. A.; Armstrong, D. S.; Arrington, J.; Bellini, V.; Beminiwattha, R.; Benesch, J.; Benmokhtar, F.; Bertozzi, W.; Camsonne, A.; Canan, M.; Cates, G. D.; Chen, J.-P.; Chudakov, E.; Cisbani, E.; Dalton, M. M.; de Jager, C. W.; De Leo, R.; Deconinck, W.; Deng, X.; Deur, A.; Dutta, C.; Fassi, L. El; Erler, J.; Flay, D.; Franklin, G. B.; Friend, M.; Frullani, S.; Garibaldi, F.; Gilad, S.; Giusa, A.; Glamazdin, A.; Golge, S.; Grimm, K.; Hafidi, K.; Hansen, J.-O.; Higinbotham, D. W.; Holmes, R.; Holmstrom, T.; Holt, R. J.; Huang, J.; Hyde, C. E.; Jen, C. M.; Jones, D.; Kang, Hoyoung; King, P. M.; Kowalski, S.; Kumar, K. S.; Lee, J. H.; LeRose, J. J.; Liyanage, N.; Long, E.; McNulty, D.; Margaziotis, D. J.; Meddi, F.; Meekins, D. G.; Mercado, L.; Meziani, Z.-E.; Michaels, R.; Mihovilovic, M.; Muangma, N.; Mesick, K. E.; Nanda, S.; Narayan, A.; Nelyubin, V.; Nuruzzaman, none; Oh, Y.; Parno, D.; Paschke, K. D.; Phillips, S. K.; Qian, X.; Qiang, Y.; Quinn, B.; Rakhman, A.; Reimer, P. E.; Rider, K.; Riordan, S.; Roche, J.; Rubin, J.; Russo, G.; Saenboonruang, K.; Saha, A.; Sawatzky, B.; Shahinyan, A.; Silwal, R.; Sirca, S.; Souder, P. A.; Suleiman, R.; Sulkosky, V.; Sutera, C. M.; Tobias, W. A.; Urciuoli, G. M.; Waidyawansa, B.; Wojtsekhowski, B.; Ye, L.; Zhao, B.; Zheng, X.
2015-04-01
The parity-violating asymmetries between a longitudinally-polarized electron beam and an unpolarized deuterium target have been measured recently. The measurement covered two kinematic points in the deep inelastic scattering region and five in the nucleon resonance region. We provide here details of the experimental setup, data analysis, and results on all asymmetry measurements including parity-violating electron asymmetries and those of inclusive pion production and beam-normal asymmetries. The parity-violating deep-inelastic asymmetries were used to extract the electron-quark weak effective couplings, and the resonance asymmetries provided the first evidence for quark-hadron duality in electroweak observables. These electron asymmetries and their interpretation were published earlier, but are presented here in more detail.
NASA Astrophysics Data System (ADS)
Khurgin, Jacob B.; Bajaj, Sanyam; Rajan, Siddharth
2015-12-01
Longitudinal optical (LO) phonons in GaN generated in the channel of high electron mobility transistors (HEMT) are shown to undergo nearly elastic scattering via collisions with hot electrons. The net result of these collisions is the diffusion of LO phonons in the Brillouin zone causing reduction of phonon and electron temperatures. This previously unexplored diffusion mechanism explicates how an increase in electron density causes reduction of the apparent lifetime of LO phonons, obtained from the time resolved Raman studies and microwave noise measurements, while the actual decay rate of the LO phonons remains unaffected by the carrier density. Therefore, the saturation velocity in GaN HEMT steadily declines with increased carrier density, in a qualitative agreement with experimental results.
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.
Neutrino Scattering on Atomic Electrons in Searches for the Neutrino Magnetic Moment
Voloshin, M. B.
2010-11-12
The scattering of a neutrino on atomic electrons is considered in the situation where the energy transferred to the electrons is comparable to the characteristic atomic energies, as relevant to the current experimental search for the neutrino magnetic moment. The process is induced by the standard electroweak interaction as well as by the possible neutrino magnetic moment. Quantum-mechanical sum rules are derived for the inclusive cross section at a fixed energy deposited in the atomic system, and it is shown that the differential over the energy transfer cross section is given, modulo very small corrections, by the same expression as for free electrons, once all possible final states of the electronic system are taken into account. Thus, the atomic effects effectively cancel in the inclusive process.
Cerkic, A.; Milosevic, D. B.
2006-03-15
Using the example of electron-atom scattering in a strong laser field, it is shown that the oscillatory structure of the scattered electron spectrum can be explained as a consequence of the interference of the real electron trajectories in terms of Feynman's path integral. While in previous work on quantum-orbit theory the complex solutions of the saddle-point equations were considered, we show here that for the electron-atom scattering with much simpler real solutions a satisfactory agreement with the strong-field-approximation results can be achieved. Real solutions are applicable both for the direct (low-energy) and the rescattering (high-energy) plateau in the scattered electron spectrum. In between the plateaus and beyond the rescattering cutoff good results can be obtained using the complex (quantum) solutions and the uniform approximation. The interference of real solutions is related to the recent attosecond double-slit experiment in time.
NASA Astrophysics Data System (ADS)
Zhidkov, A.; Masuda, S.; Bulanov, S. S.; Koga, J.; Hosokai, T.; Kodama, R.
2014-05-01
Nonlinear cascade scattering of intense, tightly focused laser pulses by relativistic electrons is studied numerically in the classical approximation including radiation damping for the quantum parameter ⟨ℏωxray⟩/ɛ <1 and an arbitrary radiation parameter χ. The electron's energy loss, along with its being scattered to the side by the ponderomotive force, makes scattering in the vicinity of a high laser field nearly impossible at high electron energies. The use of a second, copropagating laser pulse as a booster is shown to partially solve this problem.
FERM3D: A finite element R-matrix electron molecule scattering code
NASA Astrophysics Data System (ADS)
Tonzani, Stefano
2007-01-01
FERM3D is a three-dimensional finite element program, for the elastic scattering of a low energy electron from a general polyatomic molecule, which is converted to a potential scattering problem. The code is based on tricubic polynomials in spherical coordinates. The electron-molecule interaction is treated as a sum of three terms: electrostatic, exchange, and polarization. The electrostatic term can be extracted directly from ab initio codes ( GAUSSIAN 98 in the work described here), while the exchange term is approximated using a local density functional. A local polarization potential based on density functional theory [C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785] describes the long range attraction to the molecular target induced by the scattering electron. Photoionization calculations are also possible and illustrated in the present work. The generality and simplicity of the approach is important in extending electron-scattering calculations to more complex targets than it is possible with other methods. Program summaryTitle of program:FERM3D Catalogue identifier:ADYL_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADYL_v1_0 Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer for which the program is designed and others on which it has been tested:Intel Xeon, AMD Opteron 64 bit, Compaq Alpha Operating systems or monitors under which the program has been tested:HP Tru64 Unix v5.1, Red Hat Linux Enterprise 3 Programming language used:Fortran 90 Memory required to execute with typical data:900 MB (neutral CO 2), 2.3 GB (ionic CO 2), 1.4 GB (benzene) No. of bits in a word:32 No. of processors used:1 Has the code been vectorized?:No No. of lines in distributed program, including test data, etc.:58 383 No. of bytes in distributed program, including test data, etc.:561 653 Distribution format:tar.gzip file CPC Program library subprograms used:ADDA, ACDP Nature of physical problem:Scattering of an
Regeta, Khrystyna; Allan, Michael; Winstead, Carl; McKoy, Vincent; Mašín, Zdeněk; Gorfinkiel, Jimena D
2016-01-14
We measured differential cross sections for elastic (rotationally integrated) electron scattering on pyrimidine, both as a function of angle up to 180(∘) at electron energies of 1, 5, 10, and 20 eV and as a function of electron energy in the range 0.1-14 eV. The experimental results are compared to the results of the fixed-nuclei Schwinger variational and R-matrix theoretical methods, which reproduce satisfactorily the magnitudes and shapes of the experimental cross sections. The emphasis of the present work is on recording detailed excitation functions revealing resonances in the excitation process. Resonant structures are observed at 0.2, 0.7, and 4.35 eV and calculations for different symmetries confirm their assignment as the X̃(2)A2, Ã(2)B1, and B̃(2)B1 shape resonances. As a consequence of superposition of coherent resonant amplitudes with background scattering the B̃(2)B1 shape resonance appears as a peak, a dip, or a step function in the cross sections recorded as a function of energy at different scattering angles and this effect is satisfactorily reproduced by theory. The dip and peak contributions at different scattering angles partially compensate, making the resonance nearly invisible in the integral cross section. Vibrationally integrated cross sections were also measured at 1, 5, 10 and 20 eV and the question of whether the fixed-nuclei cross sections should be compared to vibrationally elastic or vibrationally integrated cross section is discussed.
Observations of the scatter-free solar-flare electrons in the energy range 20-1000 keV
NASA Technical Reports Server (NTRS)
Wang, J. R.; Fisk, L. A.; Lin, R. P.
1971-01-01
Observations of the scatter-free electron events from solar active region McMath No. 8905 are presented. The measurements were made on Explorer 33 satellite. The data show that more than 80% of the electrons from these events undergo no or little scattering and that these electrons travel only approximately 1.5 a.u. between the sun and the earth. The duration of these events cannot be accounted fully by velocity dispersion alone. It is suggested that these electrons could be continuously injected into interplanetary medium for a time interval of approximately 2 to 3 minutes. Energy spectra of these electrons are discussed.
Carrier density independent scattering rate in SrTiO₃-based electron liquids
Mikheev, Evgeny; Raghavan, Santosh; Zhang, Jack Y.; Marshall, Patrick B.; Kajdos, Adam P.; Balents, Leon; Stemmer, Susanne
2016-02-10
We examine the carrier density dependence of the scattering rate in two- and three-dimensional electron liquids in SrTiO3 in the regime where it scales with Tn (T is the temperature and n ≤ 2) in the cases when it is varied by electrostatic control and chemical doping, respectively. It is shown that the scattering rate is independent of the carrier density. This is contrary to the expectations from Landau Fermi liquid theory, where the scattering rate scales inversely with the Fermi energy (EF). We discuss that the behavior is very similar to systems traditionally identified as non-Fermi liquids (n
Effect of EMIC Wave Normal Angle Distribution on Relativistic Electron Scattering in Outer RB
NASA Technical Reports Server (NTRS)
Khazanov, G. V.; Gamayunov, K. V.
2007-01-01
We present the equatorial and bounce average pitch angle diffusion coefficients for scattering of relativistic electrons by the H+ mode of EMIC waves. Both the model (prescribed) and self consistent distributions over the wave normal angle are considered. The main results of our calculation can be summarized as follows: First, in comparison with field aligned waves, the intermediate and highly oblique waves reduce the pitch angle range subject to diffusion, and strongly suppress the scattering rate for low energy electrons (E less than 2 MeV). Second, for electron energies greater than 5 MeV, the |n| = 1 resonances operate only in a narrow region at large pitch-angles, and despite their greatest contribution in case of field aligned waves, cannot cause electron diffusion into the loss cone. For those energies, oblique waves at |n| greater than 1 resonances are more effective, extending the range of pitch angle diffusion down to the loss cone boundary, and increasing diffusion at small pitch angles by orders of magnitude.
Electronic Raman Scattering as an Ultra-Sensitive Probe of Strain Effects in Semiconductors
NASA Astrophysics Data System (ADS)
Mascarenhas, Angelo; Fluegel, Brian; Beaton, Dan
Semiconductor strain engineering has become a critical feature of high-performance electronics due to the significant device performance enhancements it enables. These improvements that emerge from strain induced modifications to the electronic band structure necessitate new ultra-sensitive tools for probing strain in semiconductors. Using electronic Raman scattering, we recently showed that it is possible to measure minute amounts of strain in thin semiconductor epilayers. We applied this strain measurement technique to two different semiconductor alloy systems, using coherently strained epitaxial thin films specifically designed to produce lattice-mismatch strains as small as 10-4. Comparing our strain sensitivity and signal strength in AlxGa1-xAs with those obtained using the industry-standard technique of phonon Raman scattering we found a sensitivity improvement of ×200, and a signal enhancement of 4 ×103 thus obviating key constraints in semiconductor strain metrology. The sensitivity of this approach rivals that of contemporary techniques and opens up a new realm for optically probing strain effects on electronic band structure. We acknowledge the financial support of the DOE Office of Science, BES under DE-AC36-80GO28308.
Thomson Scattering Observation of Non-Maxwellian EEDF and the Effect of Local Electron Heating
NASA Astrophysics Data System (ADS)
Kono, A.; Funahashi, H.
2001-10-01
Laser Thomson scattering measurements were carried out to study electron energy distribution function (EEDF) of inductively coupled plasmas using C_4F_8/Ar and CF_4/Ar mixture gases. The plasma was produced using a one-turn coil antenna immersed in the plasma at a total pressure of 25 mTorr. A specially designed triple-grating spectrometer was used, which produces Thomson spectra on the output focal plane with the interfering Rayleigh and stray components highly suppressed; an ICCD camera operated in the photon-counting mode was used for multichannel detection of the spectrum. At a RF (13.56 MHz) input power of 300 W in the case of pure Ar plasma, EEDF was Maxwellian with an enectron density >10^12 cm-3. Upon mixing of C_4F8 as well as CF_4, decrease in the electron density and upward bend of the plot of the Thomson spectrum (energy vs. logarithmic scattering intensity) at energies around 5 eV was observed. The mechanism for producing this bend was studied via Monte-Carlo particle simulation. The results indicate that electron heating in a uniform electric field does not lead to upward bend; electrons should be heated locally near the antenna surface where the RF electric field is strong and cooled in other part of the plasma by inelastic collisions.
Structure of acetylcholine receptor dimer determined by neutron scattering and electron microscopy
Wise, D.S.; Schoenborn, B.P.; Karlin, A.
1981-04-10
Previous work has shown that the predominant native form of the acetylcholine receptor from the electric tissue of Torpedo californica is a dimer of M/sub r/ = 500,000, cross-linked by a disulfide bond between the largest (delta) of the five chains (..cap alpha../sub 2/..beta gamma..delta) that comprise the monomer. Small-angle neutron scattering of purified receptor dimer in Triton X-100 solution containing 18% D/sub 2/O, in which the Triton X-100 is contrast-matched, yields a radius of gyration of the dimer of 66 A. Based on the assumptions that the dimer is symmetrical and that the radius of gyration of the monomer does not change in forming dimer, this value, together with the radius of gyration of the receptor monomer (46 A), determined previously, allows the calculation of the distance separating the centers of neutron scattering density of monomers in a dimer; the result is 96 A. Electron microscopy of negatively stained dimers permits an independent measurement of the distance between the apparent centers of mass of the monomers; the average is 96 A, in agreement with the result of the neutron scattering analysis. The electron micrographs of dimer also permit the location of the delta chains at the region of contact of the monomers. A model for the receptor dimer consistent with all available structural information is presented.
NASA Astrophysics Data System (ADS)
Kushwaha, Manvir S.
2013-04-01
The nanofabrication technology has taught us that an m-dimensional confining potential imposed upon an n-dimensional electron gas paves the way to a quasi-(n-m)-dimensional electron gas, with m ⩽ n and 1 ⩽ n, m ⩽ 3. This is the road to the (semiconducting) quasi-n dimensional electron gas systems we have been happily traversing on now for almost two decades. Achieving quasi-one dimensional electron gas (Q-1DEG) [or quantum wire(s) for more practical purposes] led us to some mixed moments in this journey: while the reduced phase space for the scattering led us believe in the route to the faster electron devices, the proximity to the 1D systems left us in the dilemma of describing it as a Fermi liquid or as a Luttinger liquid. No one had ever suspected the potential of the former, but it took quite a while for some to convince the others on the latter. A realistic Q-1DEG system at the low temperatures is best describable as a Fermi liquid rather than as a Luttinger liquid. In the language of condensed matter physics, a critical scrutiny of Q-1DEG systems has provided us with a host of exotic (electronic, optical, and transport) phenomena unseen in their higher- or lower-dimensional counterparts. This has motivated us to undertake a systematic investigation of the inelastic electron scattering (IES) and the inelastic light scattering (ILS) from the elementary electronic excitations in quantum wires. We begin with the Kubo's correlation functions to derive the generalized dielectric function, the inverse dielectric function, and the Dyson equation for the dynamic screened potential in the framework of Bohm-Pines' random-phase approximation. These fundamental tools then lead us to develop methodically the theory of IES and ILS for the Q-1DEG systems. As an application of the general formal results, which know no bounds regarding the subband occupancy, we compute the density of states, the Fermi energy, the full excitation spectrum [comprised of intrasubband and
Gao, H.; Arrington, J.; Beise, E.J.; Bray, B.; Carr, R.W.; Filippone, B.W.; Lung, A.; McKeown, R.D.; Mueller, B.; Pitt, M.L. ); Jones, C.E. ); DeSchepper, D.; Dodson, G.; Dow, K.; Ent, R.; Farkhondeh, M.; Hansen, J.; Korsch, W.; Kramer, L.H.; Lee, K.; Makins, N.; Milner, R.G.; Tieger, D.R.; Welch, T.P. ); Candell, E.; Napolitano, J.; Wojtsekhowski, B.B.; Tripp, C. ); Lorenzon, W. )
1994-08-01
We report a measurement of the asymmetry in spin-dependent quasielastic scattering of longitudinally polarized electrons from a polarized [sup 3]He target. The neutron magnetic form factor [ital G][sup [ital n
NASA Astrophysics Data System (ADS)
Dhal, Satyanarayan; Chatterjee, Shyamal; Samarin, Sergey; Williams, James F.; Giebels, Franz; Gollisch, Herbert; Feder, Roland
2015-02-01
The energy and azimuthal angle dependencies of the asymmetry of spin-polarized low-energy electrons ((00) beam) elastically scattered from a W(110) surface, have been studied before and after irradiated with slow Ar+ ions with energies of 200 eV, 500 eV and 1 keV at a fluence of 5 × 1015 ions/cm2. The energy dependence of the scattered electron asymmetries and intensities (for a fixed azimuthal angle of 55°, which is determined by the angle between the normal to the scattering plane and the [?] direction in the surface of the W(110) crystal) and the azimuthal angle dependence of the asymmetry for two different incident electron energies of 14 eV and 23 eV showed a significant change after irradiation. The low-energy ion irradiation influenced the spin-polarized electron scattering more than the higher energy ions. The reason for the change of spin-dependent electron scattering is a quenching of coherent elastic multiple scattering, mainly due to lattice defects induced by implanted ions. Thus, these modifications demonstrate a technological way to construct spin-active interface with required properties. The agreement between experimental results and theoretical ones with and without multiple scattering provides a consistent explanation of the observations.
Comparison of local exchange potentials of electron-N2 scattering
NASA Astrophysics Data System (ADS)
Rumble, J. R., Jr.; Truhlar, D. G.
1980-05-01
Vibrationally and electronically elastic electron scattering by N2 at 2-30 eV impact energy is considered. Static, static-exchange, and static-exchange-plus-polarization potentials, Cade-Sales-Wahl and INDO/1s wave functions, and semiclassical exchange and Hara free-electron-gas exchange potentials are examined. It is shown that the semiclassical exchange approximation is too attractive at low energy for N2. It is also shown quantitatively by consideration of partial and total integral cross sections how the effects of approximations to exchange become smaller as the incident energy is increased until the differences are about 8% for the total integral cross section at 30 eV.
Radial Electron Temperature and Density Measurements Using Thomson Scattering System in GAMMA 10/PDX
NASA Astrophysics Data System (ADS)
Yoshikawa, M.; Ohta, K.; Wang, X.; Chikatsu, M.; Kohagura, J.; Shima, Y.; Sakamoto, M.; Imai, T.; Nakashima, Y.; Yasuhara, R.; Yamada, I.; Funaba, H.; Minami, T.
2015-11-01
A Thomson scattering (TS) system in GAMMA 10/PDX has been developed for the measurement of radial profiles of electron temperature and density in a single plasma and laser shot. The TS system has a large solid angle optical collection system and high-sensitivity signal detection system. The TS signals are obtained using four-channel high-speed digital oscilloscopes controlled by a Windows PC. We designed the acquisition program for six oscilloscopes to obtain 10-Hz TS signals in a single plasma shot, following which the time-dependent electron temperatures and densities can be determined. Moreover, in order to obtain larger TS signal intensity in the edge region, we added a second collection mirror. The radial electron temperatures and densities at six radial positions in GAMMA 10/PDX were successfully obtained.
Cross sections for elastic electron scattering by tetramethylsilane in the intermediate-energy range
Sugohara, R. T.; Lee, M.-T.; Iga, I.; Souza, G. L. C. de; Homem, M. G. P.
2011-12-15
Organosilicon compounds are of current interest due to the numerous applications of these species in industries. Some of these applications require the knowledge of electron collision cross sections, which are scarce for such compounds. In this work, we report absolute values of differential, integral, and momentum-transfer cross sections for elastic electron scattering by tetramethylsilane (TMS) measured in the 100-1000 eV energy range. The relative-flow technique is used to normalize our data. In addition, the independent-atom-model (IAM) and the additivity rule (AR), widely used to model electron collisions with light hydrocarbons, are also applied for e{sup -}-TMS interaction. The comparison of our measured results of cross sections and the calculated data shows good agreement, particularly near the higher-end of incident energies.
Boullay, P; Lutterotti, L; Chateigner, D; Sicard, L
2014-09-01
The full quantitative characterization of nanopowders using transmission electron microscopy scattering patterns is shown. This study demonstrates the feasibility of the application of so-called combined analysis, a global approach for phase identification, structure refinement, characterization of anisotropic crystallite sizes and shapes, texture analysis and texture variations with the probed scale, using electron diffraction patterns of TiO2 and Mn3O4 nanocrystal aggregates and platinum films. Electron diffraction pattern misalignments, positioning, and slight changes from pattern to pattern are directly integrated and refined within this approach. The use of a newly developed full-pattern search-match methodology for phase identification of nanopowders and the incorporation of the two-wave dynamical correction for diffraction patterns are also reported and proved to be efficient. PMID:25176993
Wolcott, J.
2016-02-25
The first direct measurement of electron neutrino quasielastic and quasielasticlike scattering on hydrocarbon in the few-GeV region of incident neutrino energy has been carried out using the MINERvA detector in the NuMI beam at Fermilab. The flux-integrated differential cross sections in the electron production angle, electron energy, and Q2 are presented. The ratio of the quasielastic, flux-integrated differential cross section in Q2 for νe with that of similarly selected νμ-induced events from the same exposure is used to probe assumptions that underpin conventional treatments of charged-current νe interactions used by long-baseline neutrino oscillation experiments. Furthermore, the data are found tomore » be consistent with lepton universality and are well described by the predictions of the neutrino event generator GENIE.« less
Boullay, P; Lutterotti, L; Chateigner, D; Sicard, L
2014-09-01
The full quantitative characterization of nanopowders using transmission electron microscopy scattering patterns is shown. This study demonstrates the feasibility of the application of so-called combined analysis, a global approach for phase identification, structure refinement, characterization of anisotropic crystallite sizes and shapes, texture analysis and texture variations with the probed scale, using electron diffraction patterns of TiO2 and Mn3O4 nanocrystal aggregates and platinum films. Electron diffraction pattern misalignments, positioning, and slight changes from pattern to pattern are directly integrated and refined within this approach. The use of a newly developed full-pattern search-match methodology for phase identification of nanopowders and the incorporation of the two-wave dynamical correction for diffraction patterns are also reported and proved to be efficient.
High-energy Electron Scattering and the Charge Distributions of Selected Nuclei
DOE R&D Accomplishments Database
Hahn, B.; Ravenhall, D. G.; Hofstadter, R.
1955-10-01
Experimental results are presented of electron scattering by Ca, V, Co, In, Sb, Hf, Ta, W, Au, Bi, Th, and U, at 183 Mev and (for some of the elements) at 153 Mev. For those nuclei for which asphericity and inelastic scattering are absent or unimportant, i.e., Ca, V, Co, In, Sb, Au, and Bi, a partial wave analysis of the Dirac equation has been performed in which the nuclei are represented by static, spherically symmetric charge distributions. Smoothed uniform charge distributions have been assumed; these are characterized by a constant charge density in the central region of the nucleus, with a smoothed-our surface. Essentially two parameters can be determined, related to the radium and to the surface thickness. An examination of the Au experiments show that the functional forms of the surface are not important, and that the charge density in the central regions is probably fairly flat, although it cannot be determined very accurately.
Scattering and collapse of Langmuir waves driven by a weak electron beam
NASA Technical Reports Server (NTRS)
Hafizi, B.; Weatherall, J. C.; Goldman, M. V.; Nicholson, D. R.
1982-01-01
Wave-wave interactions are examined, particularly for significance in relation to Langmuir turbulence associated with type III solar radio emissions. The Zakharov equations are considered as two coupled nonlinear partial differential equations for the low-frequency density and the Langmuir envelope, and the electron and ion temperatures are regarded as equal. The Zhakharov equations are solved in one dimension, and display no collapse of a driven broadband pump, indicating that scattering instabilities are important in the saturation of a beam-plasma instability. A two-dimensional numerical simulation is developed to interpret the role of parametric instabilities, and it is concluded that the distortion of a wave packet is due to scattering instability, and not a change in the physics of direct collapse due to an artificial numerical damping. Further discussions are presented for comparisons of models of Langmuir turbulence in type III bursts.
NASA Astrophysics Data System (ADS)
Bakhlanov, S. V.; Bazlov, N. V.; Derbin, A. V.; Drachnev, I. S.; Kayunov, A. S.; Muratova, V. N.; Semenov, D. A.; Unzhakov, E. V.
2016-06-01
In this paper we present a method of scintillation detector energy calibration using the gamma-rays. The technique is based on the Compton scattering of gamma-rays in a scintillation detector and subsequent photoelectric absorption of the scattered photon in the Ge-detector. The novelty of this method is that the source of gamma rays, the germanium and scintillation detectors are immediately arranged adjacent to each other. The method presents an effective solution for the detectors consisting of a low atomic number materials, when the ratio between Compton effect and photoelectric absorption is large and the mean path of gamma-rays is comparable to the size of the detector. The technique can be used for the precision measurements of the scintillator light yield dependence on the electron energy.
NASA Astrophysics Data System (ADS)
Ominato, Yuya; Koshino, Mikito
2015-01-01
We theoretically study the quantum transport in a three-dimensional Weyl electron system in the presence of the charged impurity scattering using a self-consistent Born approximation. The scattering strength is characterized by the effective fine-structure constant α , which depends on the dielectric constant and the Fermi velocity of the linear band. We find that the Boltzmann theory fails at the band touching point, where the conductivity takes a nearly constant value almost independent of α , even though the density of states linearly increases with α . There the magnitude of the conductivity only depends on the impurity density. The qualitative behavior is quite different from the case of the Gaussian impurities, where the minimum conductivity vanishes below a certain critical impurity strength.
Magnetic liposomes and entrapping : time-resolved neutron scattering TR-SANS and electron microscopy
NASA Astrophysics Data System (ADS)
Nawroth, Thomas; Rusp, Monika; May, Roland P.
2004-07-01
Magnetic liposomes were prepared by a novel method from stabilized iron-complex solutions and biogenic phospholipids using a pH-jump procedure. During preparation Boron was entrapped inside the liposomes. This enables the later application in Neutron capture cancer therapy, a local radiation therapy, as well as rheological experiments with magnetic tweezers. The formation of the liposomes and the internal iron oxide structure was observed by time-resolved neutron scattering TR-SANS and electron microscopy using a stopped-flow mixing device. The liposome size was estimated by dynamic light scattering (DLS) also. Under selected conditions, the iron oxide was obtained as shell located at the inner surface of the lipid layer. Thus the internal volume was free for entrapping of other material, e.g. the Boron compounds for Neutron capture or drug targetting applications. The magnetic shell liposomes revealed a typical size of 100-400nm, as required for applications in vivo.
Comparative study of nuclear effects in polarized electron scattering from 3 He
Ethier, J. J.; Melnitchouk, W.
2013-11-01
We present a detailed analysis of nuclear effects in inclusive electron scattering from polarized 3He nuclei for polarization asymmetries, structure functions and their moments, both in the nucleon resonance and deep-inelastic regions. We compare the results of calculations within the weak binding approximation at finite Q2 with the effective polarization ansatz often used in experimental data analyses, and explore the impact of Δ components in the nuclear wave function and nucleon off-shell corrections on extractions of the free neutron structure. Using the same framework we also make predictions for the Q2 dependence of quasielastic scattering from polarized 3He, data onmore » which can be used to constrain the spin-dependent nuclear smearing functions in 3He.« less
J-matrix calculation of electron-helium S-wave scattering
Konovalov, D. A.; Fursa, D. V.; Bray, I.
2011-09-15
The J-matrix approach to electron-atom scattering is revised by merging it with the Fano's multiconfiguration interaction matrix elements [U. Fano, Phys. Rev. 140, A67 (1965)]. The revised method is then applied to the S-wave model of the e-He scattering problem demonstrating remarkable computational efficiency and accuracy. In particular, the method is in complete agreement with the convergent-close-coupling elastic, 2{sup 1,3}S excitation and single ionization cross sections for impact energies in the range 0.1-1000 eV. The S-wave resonance structures in the elastic and 2{sup 1,3}S excitation cross sections are highlighted.
Higher lying resonances in low-energy electron scattering with carbon monoxide*
NASA Astrophysics Data System (ADS)
Dora, Amar; Tennyson, Jonathan; Chakrabarti, Kalyan
2016-10-01
R-matrix calculations on electron collisions with CO are reported whose aim is to identify any higher-lying resonances above the well-reported and lowest 2Π resonance at about 1.6 eV. Extensive tests with respect to basis sets, target models and scattering models are performed. The final results are reported for the larger cc-pVTZ basis set using a 50 state close-coupling (CC) calculation. The Breit-Wigner eigenphase sum and the time-delay methods are used to detect and fit any resonances. Both these methods find a very narrow 2Σ+ symmetry Feshbach-type resonance very close to the target excitation threshold of the b 3Σ+ state which lies at 12.9 eV in the calculations. This resonance is seen in the CC calculation using cc-pVTZ basis set while a CC calculation using the cc-pVDZ basis set does not produce this feature. The electronic structure of CO- is analysed in the asymptotic region; 45 molecular states are found to correlate with states dissociating to an anion and an atom. Electronic structure calculations are used to study the behaviour of these states at large internuclear separation. Quantitative results for the total, elastic and electronic excitation cross sections are also presented. The significance of these results for models of the observed dissociative electron attachment of CO in the 10 eV region is discussed. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limão-Vieira, Gustavo García, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrović.
Electron Scattering Region of Quasars from Optical Polarization and Ultraviolet Observations
NASA Astrophysics Data System (ADS)
Zhang, Shuang-Nan; Liao, Jinyuan
For many quasars, there exists a correlation between the optical polarization and the radio structure axis from the optical polarization and radio observations. Antonucci et al. (1983) found that the polarization of type I quasars tend to be parallel to the radio axis, and that of type II quasars tend to be perpendicular to the radio axis. This can be interpreted naturally by two different electron scattering regions in the nuclei of quasars, i.e., polar scattering region and equatorial scattering region (Young 2000; Smith et al. 2002). However, some important relationship is still not clear so far, e.g., the relationship between the radio luminosity and the optical polarization. It is generally accepted that the spectrum of a quasar is dominated by the radiation from the accretion disk around the super-massive black hole in optical band. Therefore, the ratio between the luminosity of the polarized and the total (polarized + non-polarized) spectrum in optical band is usually treated as the optical polarization. However, it sometimes suffers from serious contamination (e.g., starlight, radiation of the hot dust). Here we compile 16 type I quasars with both optical polarization and ultraviolet (UV) observations. We obtain the true optical polarization of the accretion disk by jointly analyzing the optical polarization and UV observations with the model described in Hu & Zhang (2012). We find no correlation between their radio luminosity and optical polarization. However, an anti-correlation between the optical polarization and the dispersion of the polarization position angle (PA) is present in our work. If true, this anti-correlation cannot be interpreted by the two purported scattering regions and may be caused by an unknown scattering region with a moderate distance from the inner region accretion disk, which can be confirmed by future reverberation mapping of polarization observations of type I AGNs.
Jens-ole Hansen; Brian Anderson; Leonard Auerbach; Todd Averett; William Bertozzi; Tim Black; John Calarco; Lawrence Cardman; Gordon Cates; Zhengwei Chai; Jiang-Ping Chen; Seonho Choi; Eugene Chudakov; Steve Churchwell; G Corrado; Christopher Crawford; Daniel Dale; Alexandre Deur; Pibero Djawotho; Dipangkar Dutta; John Finn; Haiyan Gao; Ronald Gilman; Oleksandr Glamazdin; Charles Glashausser; Walter Gloeckle; Jacek Golak; Javier Gomez; Viktor Gorbenko; F. Hersman; Douglas Higinbotham; Richard Holmes; Calvin Howell; Emlyn Hughes; Thomas Humensky; Sebastien Incerti; Piotr Zolnierczuk; Cornelis De Jager; John Jensen; Xiaodong Jiang; Cathleen Jones; Mark Jones; R Kahl; H Kamada; A Kievsky; Ioannis Kominis; Wolfgang Korsch; Kevin Kramer; Gerfried Kumbartzki; Michael Kuss; Enkeleida Lakuriqi; Meihua Liang; Nilanga Liyanage; John LeRose; Sergey Malov; Demetrius Margaziotis; Jeffery Martin; Kathy McCormick; Robert McKeown; Kevin McIlhany; Zein-Eddine Meziani; Robert Michaels; Greg Miller; Joseph Mitchell; Sirish Nanda; Emanuele Pace; Tina Pavlin; Gerassimos Petratos; Roman Pomatsalyuk; David Pripstein; David Prout; Ronald Ransome; Yves Roblin; Marat Rvachev; Giovanni Salme; Michael Schnee; Charles Seely; Taeksu Shin; Karl Slifer; Paul Souder; Steffen Strauch; Riad Suleiman; Mark Sutter; Bryan Tipton; Luminita Todor; M Viviani; Branislav Vlahovic; John Watson; Claude Williamson; H Witala; Bogdan Wojtsekhowski; Feng Xiong; Wang Xu; Jen-chuan Yeh
2006-05-05
We have measured the transverse asymmetry A{sub T'} in the quasi-elastic {sup 3}/rvec He/(/rvec e/,e') process with high precision at Q{sup 2}-values from 0.1 to 0.6 (GeV/c){sup 2}. The neutron magnetic form factor G{sub M}{sup n} was extracted at Q{sup 2}-values of 0.1 and 0.2 (GeV/c){sup 2} using a non-relativistic Faddeev calculation which includes both final-state interactions (FSI) and meson-exchange currents (MEC). Theoretical uncertainties due to the FSI and MEC effects were constrained with a precision measurement of the spin-dependent asymmetry in the threshold region of {sup 3}/rvec He/(/rvec e/,e'). We also extracted the neutron magnetic form factor G{sub M}{sup n} at Q{sup 2}-values of 0.3 to 0.6 (GeV/c){sup 2} based on Plane Wave Impulse Approximation calculations.
NASA Astrophysics Data System (ADS)
Wilkinson, C.; Terri, R.; Andreopoulos, C.; Bercellie, A.; Bronner, C.; Cartwright, S.; de Perio, P.; Dobson, J.; Duffy, K.; Furmanski, A. P.; Haegel, L.; Hayato, Y.; Kaboth, A.; Mahn, K.; McFarland, K. S.; Nowak, J.; Redij, A.; Rodrigues, P.; Sánchez, F.; Schwehr, J. D.; Sinclair, P.; Sobczyk, J. T.; Stamoulis, P.; Stowell, P.; Tacik, R.; Thompson, L.; Tobayama, S.; Wascko, M. O.; Żmuda, J.
2016-04-01
There has been a great deal of theoretical work on sophisticated charged current quasi-elastic (CCQE) neutrino interaction models in recent years, prompted by a number of experimental results that measured unexpectedly large CCQE cross sections on nuclear targets. As the dominant interaction mode at T2K energies, and the signal process in oscillation analyses, it is important for the T2K experiment to include realistic CCQE cross section uncertainties in T2K analyses. To this end, T2K's Neutrino Interaction Working Group has implemented a number of recent models in NEUT, T2K's primary neutrino interaction event generator. In this paper, we give an overview of the models implemented and present fits to published νμ and ν¯ μ CCQE cross section measurements from the MiniBooNE and MINER ν A experiments. The results of the fits are used to select a default cross section model for future T2K analyses and to constrain the cross section uncertainties of the model. We find strong tension between datasets for all models investigated. Among the evaluated models, the combination of a modified relativistic Fermi gas with multinucleon CCQE-like interactions gives the most consistent description of the available data.
Parshin, A. S. Igumenov, A. Yu.; Mikhlin, Yu. L.; Pchelyakov, O. P.; Nikiforov, A. I.; Timofeev, V. A.
2015-04-15
Reflection electron-energy loss spectra are obtained for a series of Si samples with different crystallographic orientations, prepared under different technological conditions. Using the experimental spectra, the electron energy loss dependences of the product of the mean inelastic free path and differential inelastic electron scattering cross section are calculated. A new technique is suggested for analyzing the spectra of inelastic electron scattering cross section by simulating experimental spectra with the use of the three-parameter Tougaard universal cross section functions. The results of the simulation are used to determine the nature of loss peaks and to calculate the surface parameter.
Electronic Raman scattering as an ultra-sensitive probe of strain effects in semiconductors
Fluegel., Brian; Mialitsin, Aleksej V.; Beaton, Daniel A.; Reno, John L.; Mascarenhas, Angelo
2015-05-28
Semiconductor strain engineering has become a critical feature of high-performance electronics because of the significant device performance enhancements that it enables. These improvements, which emerge from strain-induced modifications to the electronic band structure, necessitate new ultra-sensitive tools to probe the strain in semiconductors. Here, we demonstrate that minute amounts of strain in thin semiconductor epilayers can be measured using electronic Raman scattering. We also applied this strain measurement technique to two different semiconductor alloy systems using coherently strained epitaxial thin films specifically designed to produce lattice-mismatch strains as small as 10^{-4}. Thus, comparing our strain sensitivity and signal strength in Al_{x}Ga _{1-x} As with those obtained using the industry-standard technique of phonon Raman scattering, we found that there was a sensitivity improvement of 200-fold and a signal enhancement of 4 × 10^{3}, thus obviating key constraints in semiconductor strain metrology.
NASA Astrophysics Data System (ADS)
Critchley, A. D. J.
2003-10-01
The main emphasis of the diode research project at the Atomic Weapons Establishment (AWE) UK is to produce small diameter radiographic spot sizes at high dose to improve the resolution of the transmission radiographs taken during hydrodynamic experiments. Experimental measurements of conditions within the diodes of Pulsed Power driven flash x-ray machines are vital to provide a benchmark for electromagnetic PIC codes such as LSP which are used to develop new diode designs. The potential use of inverse Compton scattering (ICS) as a diagnostic technique in the determination of electron energies within the diode has been investigated. The interaction of a laser beam with a beam of high-energy electrons will create an ICS spectrum of photons. Theoretically, one should be able to glean information on the energies and positions of the electrons from the energy spectrum and differential cross section of the scattered photons. The feasibility of fielding this technique on various diode designs has been explored, and an experimental setup with the greatest likelihood of success is proposed.
Scattered hard X-ray and γ-ray generation from a chromatic electron beam
Coleman, J. E.; Welch, D. R.; Miller, C. L.
2015-11-14
An array of photon diagnostics has been deployed on a high power relativistic electron beam diode. Electrons are extracted through a 17.8 cm diode from the surface discharge of a carbon fiber velvet cathode with a nominal diode voltage of 3.8 MV. <10% of the 100 ns electron pulse is composed of off energy electrons (1–3 MeV) accelerated during the rise and fall of the pulse that impact the stainless steel beam pipe and generate a Bremsstrahlung spectrum of 0.1–3 MeV photons with a total count of 10{sup 11}. The principal objective of these experiments is to quantify the electron beam dynamics and spatial dynamics of the hard X-ray and γ-ray flux generated in the diode region. A qualitative comparison of experimental and calculated results are presented, including time and energy resolved electron beam propagation and scattered photon measurements with X-ray PIN diodes and a photomultiplier tube indicating a dose dependence on the diode voltage >V{sup 4} and detected photon counts of nearly 10{sup 6} at a radial distance of 1 m which corresponds to dose ∼40 μrad at 1 m.
Electron Neutrino Charged-Current Quasielastic Scattering in the MINERvA Experiment
Wolcott, J.
2015-12-31
The electron-neutrino charged-current quasielastic (CCQE) cross section on nuclei is an important input parameter for electron neutrino appearance oscillation experiments. Current experiments typically begin with the muon neutrino cross section and apply theoretical corrections to obtain a prediction for the electron neutrino cross section. However, at present no experimental verification of the estimates for this channel at an energy scale appropriate to such experiments exists. We present the cross sections for a CCQE-like process determined using the MINERvA detector, which are the first measurements of any exclusive reaction in few-GeV electron neutrino interactions. The result is given as differential cross-sections vs. the electron energy, electron angle, and square of the four-momentum transferred to the nucleus, $Q^{2}$. We also compute the ratio to a muon neutrino cross-section in $Q^{2}$ from MINERvA. We find satisfactory agreement between these measurements and the predictions of the GENIE generator. We furthermore report on a photon-like background unpredicted by the generator which we interpret as neutral-coherent diffractive scattering from hydrogen.
Scattered hard X-ray and γ-ray generation from a chromatic electron beam
NASA Astrophysics Data System (ADS)
Coleman, J. E.; Welch, D. R.; Miller, C. L.
2015-11-01
An array of photon diagnostics has been deployed on a high power relativistic electron beam diode. Electrons are extracted through a 17.8 cm diode from the surface discharge of a carbon fiber velvet cathode with a nominal diode voltage of 3.8 MV. <10% of the 100 ns electron pulse is composed of off energy electrons (1-3 MeV) accelerated during the rise and fall of the pulse that impact the stainless steel beam pipe and generate a Bremsstrahlung spectrum of 0.1-3 MeV photons with a total count of 1011. The principal objective of these experiments is to quantify the electron beam dynamics and spatial dynamics of the hard X-ray and γ-ray flux generated in the diode region. A qualitative comparison of experimental and calculated results are presented, including time and energy resolved electron beam propagation and scattered photon measurements with X-ray PIN diodes and a photomultiplier tube indicating a dose dependence on the diode voltage >V4 and detected photon counts of nearly 106 at a radial distance of 1 m which corresponds to dose ˜40 μrad at 1 m.
NASA Astrophysics Data System (ADS)
Stefan, V. Alexander
2011-04-01
Stimulated Raman scattering in the electron cyclotron frequency range of the X-Mode and O-Mode driver with the ITER plasma leads to the ``tail heating'' via the generation of suprathermal electrons and energetic ions. The scattering off Trivelpiece-Gould (T-G) modes is studied for the gyrotron frequency of 170GHz; X-Mode and O-Mode power of 24 MW CW; on-axis B-field of 10T. The synergy between the two-plasmon decay and Raman scattering is analyzed in reference to the bulk plasma heating. Supported in part by Nikola TESLA Labs, La Jolla, CA
Chiari, L.; Jones, D. B.; Thorn, P. A.; Pettifer, Z.; Duque, H. V.; Silva, G. B. da; Limão-Vieira, P.; Duflot, D.; Hubin-Franskin, M.-J.; Delwiche, J.; Blanco, F.; García, G.; and others
2014-07-14
We report on measurements of differential cross sections (DCSs) for electron impact excitation of a series of Rydberg electronic-states in α-tetrahydrofurfuryl alcohol (THFA). The energy range of these experiments was 20–50 eV, while the scattered electron was detected in the 10°–90° angular range. There are currently no other experimental data or theoretical computations against which we can directly compare the present measured results. Nonetheless, we are able to compare our THFA DCSs with earlier cross section measurements for Rydberg-state electronic excitation for tetrahydrofuran, a similar cyclic ether, from Do et al. [J. Chem. Phys. 134, 144302 (2011)]. In addition, “rotationally averaged” elastic DCSs, calculated using our independent atom model with screened additivity rule correction approach are also reported. Those latter results give integral cross sections consistent with the optical theorem, and supercede those from the only previous study of Milosavljević et al. [Eur. Phys. J. D 40, 107 (2006)].
Allen, G.R.; Parke Davis, H.; Brandenburg, J.E.
1983-01-01
The electron density (n/sub e/) and temperature (T/sub e/) of the plasma channel created by the propagation of a relativistic electron beam in air have been measured by a ruby laser Thomson scattering diagnostic. The measurements were made at the MIMI electron beam accelerator (1.6 MV, 21 kA, 70 ns) at various times during the plasma channel development, with 25 ns temporal resolution and 2 mm radial resolution. For example, in 5 Torr air, at the time of maximum electron beam current, the results are n/sub e/ = 1.86 x 10/sup 15/ cm/sup -3/ (+- 12%), T/sub e/ = 4.24 eV (+- 20%). These results, as well as those with other timing, are in good agreement with the theoretical results of the Air Propagation Code: n/sub e/ = 1.65 x 10/sup 15/ cm/sup -3/, T/sub e/ = 2.59 eV. Signal-to-noise is very good (10:1), limited by x-ray fluorescence of the fiber optics at the spectrometer. In fielding the diagnostic on higher energy accelerators, however, the dominant noise is expected to be the background light from the plasma and hot gas, or the fluorescence of the collecting optics. Improvements to the diagnostic and an ongoing experiment in 80 Torr of air, 4 MV, 50 kA to address these issues is presented.
NASA Technical Reports Server (NTRS)
Gamayunov, K. V.; Khazanov, G. V.
2007-01-01
We consider the effect of oblique EMIC waves on relativistic electron scattering in the outer radiation belt using simultaneous observations of plasma and wave parameters from CRRES. The main findings can be s ummarized as follows: 1. In 1comparison with field-aligned waves, int ermediate and highly oblique distributions decrease the range of pitc h-angles subject to diffusion, and reduce the local scattering rate b y an order of magnitude at pitch-angles where the principle absolute value of n = 1 resonances operate. Oblique waves allow the absolute va lue of n > 1 resonances to operate, extending the range of local pitc h-angle diffusion down to the loss cone, and increasing the diffusion at lower pitch angles by orders of magnitude; 2. The local diffusion coefficients derived from CRRES data are qualitatively similar to the local results obtained for prescribed plasma/wave parameters. Conseq uently, it is likely that the bounce-averaged diffusion coefficients, if estimated from concurrent data, will exhibit the dependencies similar to those we found for model calculations; 3. In comparison with f ield-aligned waves, intermediate and highly oblique waves decrease th e bounce-averaged scattering rate near the edge of the equatorial lo ss cone by orders of magnitude if the electron energy does not excee d a threshold (approximately equal to 2 - 5 MeV) depending on specified plasma and/or wave parameters; 4. For greater electron energies_ ob lique waves operating the absolute value of n > 1 resonances are more effective and provide the same bounce_averaged diffusion rate near the loss cone as fiel_aligned waves do.
COOLING RATES FOR RELATIVISTIC ELECTRONS UNDERGOING COMPTON SCATTERING IN STRONG MAGNETIC FIELDS
Baring, Matthew G.; Wadiasingh, Zorawar; Gonthier, Peter L. E-mail: zw1@rice.edu
2011-05-20
For inner magnetospheric models of hard X-ray and gamma-ray emission in high-field pulsars and magnetars, resonant Compton upscattering is anticipated to be the most efficient process for generating continuum radiation. This is in part due to the proximity of a hot soft photon bath from the stellar surface to putative radiation dissipation regions in the inner magnetosphere. Moreover, because the scattering process becomes resonant at the cyclotron frequency, the effective cross section exceeds the classical Thomson value by over two orders of magnitude, thereby enhancing the efficiency of continuum production and the cooling of relativistic electrons. This paper presents computations of the electron cooling rates for this process, which are needed for resonant Compton models of non-thermal radiation from such highly magnetized pulsars. The computed rates extend previous calculations of magnetic Thomson cooling to the domain of relativistic quantum effects, sampled near and above the quantum critical magnetic field of 44.13 TG. This is the first exposition of fully relativistic, quantum magnetic Compton cooling rates for electrons, and it employs both the traditional Johnson and Lippmann cross section and a newer Sokolov and Ternov (ST) formulation of Compton scattering in strong magnetic fields. Such ST formalism is formally correct for treating spin-dependent effects that are important in the cyclotron resonance and has not been addressed before in the context of cooling by Compton scattering. The QED effects are observed to profoundly lower the rates below extrapolations of the familiar magnetic Thomson results, as expected, when recoil and Klein-Nishina reductions become important.
Tsytovich, Vadim; Gusein-zade, Namik; Ignatov, Alexander
2015-07-15
Dust structuring is a natural and universal process in complex plasmas. The scattering of electromagnetic waves by dust structures is governed by the factor of coherency, i.e., the total number of coherent electrons in a single structure. In the present paper, we consider how the factor of coherency changes due to additional pulse electron heating and show that it obeys a hysteresis. After the end of the pulse heating, the scattering intensity differs substantially from that before heating. There are three necessary conditions for scattering hysteresis: first, the radiation wavelength should be larger than the pattern (structure) size; second, the total number of coherent electrons confined by the structure should be large; and third, the heating pulse duration should be shorter than the characteristic time of dust structure formation. We present the results of numerical calculations using existing models of self-consistent dust structures with either positively or negatively charged dust grains. It is shown that, depending on the grain charge and the ionization rate, two types of hysteresis are possible: one with a final increase of the scattering and the other with a final decrease of the scattering. It is suggested that the hysteresis of coherent scattering can be used as a tool in laboratory experiments and that it can be a basic mechanism explaining the observed hysteresis in radar scattering by noctilucent clouds during active experiments on electron heating in mesosphere.
Recent Results in Parity-Violating Electron Scattering at Jefferson Lab: PREX and HAPPEX-III
NASA Astrophysics Data System (ADS)
Jen, Chun-Min; PREx Collaboration
2011-10-01
The parity-violating asymmetry APV in electron scattering from the 208Pb nucleus is cleanly sensitive to the neutron radius Rn. A precision measurement of Rn would have important implications for the understanding of nuclear structure, and be a powerful constraint on the symmetry energy Sν(n) of neutron-rich nuclear matter, including neutron stars. The PREX collaboration has completed a first run, measuring Rn to a precision of ~2.5% and providing the first electroweak evidence for the neutron skin of a heavy nucleus. Results from this measurement, and prospects for more precise future measurements, will be discussed.
A low-temperature sample mount for an inelastic electron scattering spectrometer
NASA Astrophysics Data System (ADS)
Tarrio, C.; Schnatterly, S. E.; Benitez, E. L.
1990-10-01
A continuously operable low-temperature (10-20 K) sample mount for a solid-state inelastic electron scattering spectrometer is described. The cooling is achieved by a closed-cycle gas phase He refrigerator. Because the entire sample chamber is at a potential of 300 kV, it must be isolated from ground, requiring computer automation for positioning, and insulating plumbing for the helium. The motion control has a detachable coupling that allows for complete thermal isolation from room temperature. Details and problems encountered in the design are described.
Parity-Violating Electron Deuteron Scattering and the Proton's Neutral Weak Axial Vector Form Factor
Ito, Takeyasu; Averett, Todd; Barkhuff, David; Batigne, Guillaume; Beck, Douglas; Beise, Elizabeth; Blake, A.; Breuer, Herbert; Carr, Robert; Clasie, Benjamin; Covrig, Silviu; Danagoulian, Areg; Dodson, George; Dow, Karen; Dutta, Dipangkar; Farkhondeh, Manouchehr; Filippone, Bradley; FRANKLIN, W.; Furget, Christophe; Gao, Haiyan; Gao, Juncai; Gustafsson, Kenneth; Hannelius, Lars; Hasty, R.; Allen, Alice; Herda, M.C.; Jones, CE; King, Paul; Korsch, Wolfgang; Kowalski, Stanley; Kox, Serge; Kramer, Kevin; Lee, P.; Liu, Jinghua; Martin, Jeffery; McKeown, Robert; Mueller, B.; Pitt, Mark; Plaster, Bradley; Quemener, Gilles; Real, Jean-Sebastien; Ritter, J.; Roche, Julie; Savu, V.; Schiavilla, Rocco; Seely, Charles; Spayde, Damon; Suleiman, Riad; Taylor, S.; Tieulent, Raphael; Tipton, Bryan; Tsentalovich, E.; Wells, Steven; Yang, Bin; Yuan, Jing; Yun, Junho; Zwart, Townsend
2004-03-01
We report on a new measurement of the parity-violating asymmetry in quasielastic electron scattering from the deuteron at backward angles at Q2 = 0.038 (GeV/c)2. This quantity provides a determination of the neutral weak axial vector form factor of the nucleon, which can potentially receive large electroweak corrections. The measured asymmetry A = z3.51Â±0.57 (stat)Â±0.58 (syst) ppm is consistent with theoretical predictions. We also report on updated results of the previous experiment at Q2 = 0.091 (GeV/c)2, which are also consistent with theoretical predictions.
Transverse inelastic electron scattering from the deuteron at high momentum transfers
Bosted, P.E.; Arnold, R.G.; Benton, D.; Clogher, L.; DeChambrier, G.; Katramatou, A.T.; Lambert, J.; Lung, A.; Petratos, G.G.; Rahbar, A.; and others
1988-11-20
Cross sections for 180/sup 0/ inelastic electron scattering from the deuteron were measured from the break-up threshold to beyond the quasielastic peak for incident beam energies between 0.7 and 1.3 GeV, corresponding to 0.75less than or equal toQ/sup 2/less than or equal to2.75 (GeV/c)/sup 2/. The data are in reasonable agreement with nonrelativistic models that include final-state interactions are meson exchange currents.
Armstrong, David S.; McKeown, Robert
2012-11-01
Measurement of the neutral weak vector form factors of the nucleon provides unique access to the strange quark content of the nucleon. These form factors can be studied using parity-violating electron scattering. A comprehensive program of experiments has been performed at three accelerator laboratories to determine the role of strange quarks in the electromagnetic form factors of the nucleon. This article reviews the remarkable technical progress associated with this program, describes the various methods used in the different experiments, and summarizes the physics results along with recent theoretical calculations.
Endstation for ultrafast magnetic scattering experiments at the free-electron laser in Hamburg
Mueller, L.; Gutt, C.; Streit-Nierobisch, S.; Walther, M.; Gruebel, G.; Schaffert, S.; Pfau, B.; Flewett, S.; Geilhufe, J.; Eisebitt, S.; Buettner, F.; Guenther, C. M.; Kobs, A.; Hille, M.; Stickler, D.; Froemter, R.; Oepen, H. P.; Luening, J.
2013-01-15
An endstation for pump-probe small-angle X-ray scattering (SAXS) experiments at the free-electron laser in Hamburg (FLASH) is presented. The endstation houses a solid-state absorber, optical incoupling for pump-probe experiments, time zero measurement, sample chamber, and detection unit. It can be used at all FLASH beamlines in the whole photon energy range offered by FLASH. The capabilities of the setup are demonstrated by showing the results of resonant magnetic SAXS measurements on cobalt-platinum multilayer samples grown on freestanding Si{sub 3}N{sub 4} membranes and pump-laser-induced grid structures in multilayer samples.
Measurement of the Neutron Radius of 208Pb Through Parity-Violation in Electron Scattering
Abrahamyan, Sergey; Albataineh, Hisham; Aniol, Konrad; Armstrong, David; Armstrong, Whitney; Averett, Todd; Babineau, Benjamin; Barbieri, A.; Bellini, Vincenzo; Beminiwattha, Rakitha; et al
2012-03-15
We report the first measurement of the parity-violating asymmetry APV in the elastic scattering of polarized electrons from 208Pb. APV is sensitive to the radius of the neutron distribution (Rn). The result APV = 0.656 ± 0.060 (stat) ± 0.013 (syst) corresponds to a difference between the radii of the neutron and proton distributions Rn-Rp = 0.33-0.18+0.16 fm and provides the first electroweak observation of the neutron skin which is expected in a heavy, neutron-rich nucleus.
Inelastic electron scattering to negative parity states of /sup 24/Mg
Zarek, H.; Yen, S.; Pich, B.O.; Drake, T.E.; Williamson, C.F.; Kowalski, S.; Sargent, C.P.
1984-05-01
The electromagnetic form factors for the stronger transitions to negative parity states in /sup 24/Mg were measured for electron energies 90--280 MeV and scattering angles of 90/sup 0/ and 160/sup 0/. The isoscalar K/sup ..pi../ = 0/sup -/ and 3/sup -/ bands show form factors in agreement with open-shell random-phase approximation calculations, even though the parentages of these two bands are radically different. For the isovector negative parity states, a quenching of magnetic strength is observed; its origins are discussed.
Time evolution analysis of the electron distribution in Thomson/Compton back-scattering
Petrillo, V.; Bacci, A.; Curatolo, C.; Maroli, C.; Serafini, L.; Rossi, A. R.
2013-07-28
We present the time evolution of the energy distribution of a relativistic electron beam after the Compton back-scattering with a counter-propagating laser field, performed in the framework of the Quantum Electrodynamics, by means of the code CAIN. As the correct angular distribution of the spontaneous emission is accounted, the main effect is the formation of few stripes, followed by the diffusion of the more energetic particles toward lower values in the longitudinal phase space. The Chapman-Kolmogorov master equation gives results in striking agreement with the numerical ones. An experiment on the Thomson source at SPARC-LAB is proposed.
Rose, Harvey; Daughton, W; Yin, L
2009-01-01
The onset of Stimulated Raman scatter from an intense laser speckle is the simplest experimentally realizable laser-plasma-interaction environment. Despite this data and recent 3D particle simulations, the controlling mechanism at the onset of backscatter in the kinetic regime when strong electron trapping in the daughter Langmuir wave is a dominant nonlinearity is not understood. This paper explores the consequences of assuming that onset is controlled by large thermal fluctuations. A super exponential dependence of mean reflectivity on speckle intensity in the onset regime is predicted.