Secondary-electron-emission spectroscopy of tungsten: Angular dependence and phenomenology
Willis, Roy F.; Christensen, Niels Egede
1978-01-01
Angle-resolved energy-distribution measurements of secondary-electron emission (SEE) from metals reveal spectral fine structure that relates directly to the density distribution of the one-electron states throughout E-K→ space located above the vacuum level Ev. The angular dependence of the SEE...... have been carried out in both "reduced" and "extended" K→ space in order to assess the relative contribution of elastic umklapp scattering to the density distribution of contributing states profiles. The results indicate that the overall secondary-electron yield may be represented as the sum of....... Bulk and surface band-structure effects are concurrently manifest in the SEE spectra via the wave-matching conditions imposed at the solid-vacuum interface. The results are discussed within the general conceptual framework provided by "the (time-reversed) incoming final-state wave-function" approach to...
Lu, Wanglin; Ma, Xiaomeng; Fei, Zhen; Zhou, Jianguang; Zhang, Zhiyong; Jin, Chuanhong; Zhang, Ze
2015-07-01
In this study, we correlated the angular dependence of the Raman response of black phosphorus to its crystallographic orientation by using transmission electron microscopy and Raman spectroscopy. It was found that the intensity of the Ag 2 mode reached a maximum when the polarization direction of the incident light was parallel to the zigzag crystallographic orientation. Notably, it was further confirmed that the zigzag crystallographic direction exhibited superior conductance and carrier mobility. Because of the lattice extension along the armchair direction, an intensification of the anisotropic Raman response was observed. This work provides direct evidence of the correlation between anisotropic properties and crystallographic direction and represents a turning point in the discussion of the angular-dependent electronic properties of black phosphorus.
Angular dependence of electron emission induced by grazing-ion surface collisions
Gravielle, M. S.; Miraglia, J. E.; Otero, G. G.; Sánchez, E. A.; Grizzi, O.
2004-04-01
In this work, electron emission spectra produced by impact of fast protons on Al(111) surfaces are theoretically and experimentally studied. Contributions coming from the different electronic sources of the metal—atomic inner shells and valence band—are analyzed as a function of the angle of electron emission. In the forward direction, the inner-shell ionization process is the dominant mechanism. The valence emission, instead, becomes important when the ejection angle is separated from the specular-reflection direction. In both angular regions, theoretical and experimental values are in reasonable agreement. The energy shift and broadening of the convoy electron peak at glancing observation angles are well described by the present model, which takes into account the influence of the induced surface field on the ionized electron.
General expressions of the electron yield in 57Fe integral conversion electron Mössbauer spectroscopy were derived depending on the glancing angle of the γ photons, on the source polarization and on the isotopic abundance of the source and the absorber (blackness effects) using an exponential escape function of the electrons originating from all Mössbauer-resonance-related processes. The present approach provides a firm theoretical basis to determine the alignment and direction of magnetization in the absorber. The intensity formulae were justified by least squares fits of α-57Fe spectral intensities measured in linearly and elliptically polarized source and absorber geometries. The fits reproduce the experimentally set angles with high accuracy. Limits of the current approach and its relation to other, less complete treatments in the literature are discussed
Angular dependence of L X-rays emission for Ag by 10 keV electron-impact
Wang, Xing; Xu, Zhongfeng; Zhang, Ying; Ma, Chao; Zhu, Chengwei
2016-08-01
The characteristic X-ray intensities of Ag-Lα, Lβ1, Lβ2 and Lγ1 are measured in electron-impact ionization at energy of 10 keV. The emission angle in this work ranges from 0° to 20° at interval of 5°. The angular dependence of L X-ray intensity ratios has been investigated for Lα / Lβ1, Lβ2 / Lβ1 and Lγ1 / Lβ1. It is found from the experimental results that the emissions of Lβ1, Lβ2 and Lγ1 X-rays are spatially isotropic, while the Lα X-rays exhibit anisotropic emission. Consequently, the alignment behavior of vacancy states is discussed with thorough analysis of vacancy transfer process.
Angular and temperature dependences of ion-electron emission of highly-oriented pyrolytic graphite
The results of the study of ion-electron emission yield, γ, for highly-oriented pyrolytic graphite under 30 keV N2+ ion bombardment on target irradiation temperature in ion incidence angle range from 0 deg to 80 deg relative normal to (0001) face are presented. The ion fluences were 1018-1019 ion/cm2. Irradiation temperature was varied from room temperature to 400 deg C. At normal ion incidence a step-like increase of electron yield has been found. This effect and the changes of γ(T) with ion incidence angle are discussed in terms of electron path length change and increasing the ion beam transparency of lattice
Dependency injection with AngularJS
Knol, Alex
2013-01-01
This book is a practical, hands-on approach to using dependency injection and implementing test-driven development using AngularJS. Dependency Injection with AngularJS is aimed at developers who are aware of AngularJS but need to get started with using it in real life applications. Also, developers who want to get into test-driven development with AngularJS can use this book as practical guide. Even if you know about dependency injection, it can serve as a good reference on how it is used within AngularJS. Readers are expected to have some experience with JavaScript.
An orbital angular momentum spectrometer for electrons
Harvey, Tyler; Grillo, Vincenzo; McMorran, Benjamin
2016-05-01
With the advent of techniques for preparation of free-electron and neutron orbital angular momentum (OAM) states, a basic follow-up question emerges: how do we measure the orbital angular momentum state distribution in matter waves? Control of both the energy and helicity of light has produced a range of spectroscopic applications, including molecular fingerprinting and magnetization mapping. Realization of an analogous dual energy-OAM spectroscopy with matter waves demands control of both initial and final energy and orbital angular momentum states: unlike for photons, final state post-selection is necessary for particles that cannot be annihilated. We propose a magnetic field-based mechanism for quantum non-demolition measurement of electron OAM. We show that OAM-dependent lensing is produced by an operator of form U =exp iLzρ2/ℏb2 where ρ =√{x2 +y2 } is the radial position operator, Lz is the orbital angular momentum operator along z, and b is the OAM dispersion length. We can physically realize this operator as a term in the time evolution of an electron in magnetic round lens. We discuss prospects and practical challenges for implementation of a lensing orbital angular momentum measurement. This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under the Early Career Research Program Award # DE-SC0010466.
The dynamics of the O(1D) + Xe electronic quenching reaction was investigated in a crossed beam experiment at four collision energies. Marked large-scale oscillations in the differential cross sections were observed for the inelastic scattering products, O(3P) and Xe. The shape and relative phases of the oscillatory structure depend strongly on collision energy. Comparison of the experimental results with time-independent scattering calculations shows qualitatively that this behavior is caused by Stueckelberg interferences, for which the quantum phases of the multiple reaction pathways accessible during electronic quenching constructively and destructively interfere
Angular Momentum Decomposition for an Electron
Burkardt, Matthias; BC, Hikmat
2008-01-01
We calculate the orbital angular momentum of the `quark' in the scalar diquark model as well as that of the electron in QED (to order $\\alpha$). We compare the orbital angular momentum obtained from the Jaffe-Manohar decomposition to that obtained from the Ji relation and estimate the importance of the vector potential in the definition of orbital angular momentum.
Sing, M; Meyer, J; Hoinkis, M; Glawion, S; Blaha, P; Gavrila, G; Jacobsen, Claus Schelde; Claessen, R
2007-01-01
We have performed angle-dependent near-edge x-ray absorption fine structure measurements in the Auger electron yield mode on the correlated quasi-one-dimensional organic conductor tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) in order to determine the orientation of the molecules in the...... the one-dimensional Hubbard model. Thereby, recent theoretical results are corroborated which invoke long-range Coulomb repulsion as alternative explanation to understand the spectral dispersions of TTF-TCNQ quantitatively within an extended Hubbard model....
Bellei, C.; Divol, L.; Kemp, A. J.; Key, M. H.; Larson, D. J.; Strozzi, D. J.; Marinak, M. M.; Tabak, M.; Patel, P. K. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States)
2013-05-15
The energy and angular distributions of the fast electrons predicted by particle-in-cell (PIC) simulations differ from those historically assumed in ignition designs of the fast ignition scheme. Using a particular 3D PIC calculation, we show how the ignition energy varies as a function of source-fuel distance, source size, and density of the pre-compressed fuel. The large divergence of the electron beam implies that the ignition energy scales with density more weakly than the ρ{sup −2} scaling for an idealized beam [S. Atzeni, Phys. Plasmas 6, 3316 (1999)], for any realistic source that is at some distance from the dense deuterium-tritium fuel. Due to the strong dependence of ignition energy with source-fuel distance, the use of magnetic or electric fields seems essential for the purpose of decreasing the ignition energy.
We have performed angle-dependent near-edge x-ray absorption fine structure measurements in the Auger electron yield mode on the correlated quasi-one-dimensional organic conductor tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) in order to determine the orientation of the molecules in the topmost surface layer. We find that the tilt angles of the molecules with respect to the one-dimensional axis are essentially the same as in the bulk. Thus, we can rule out surface relaxation as the origin of the renormalized band widths which were inferred from the analysis of photoemission data within the one-dimensional Hubbard model. Thereby, recent theoretical results are corroborated which invoke long-range Coulomb repulsion as alternative explanation to understand the spectral dispersions of TTF-TCNQ quantitatively within an extended Hubbard model
Probabilistic calculation for angular dependence collision
This collision probabilistic method is broadly used in cylindrical geometry (in one- or two-dimensions). It constitutes a powerful tool for the heterogeneous Response Method where, the coupling current is of the cosine type, that is, without angular dependence at azimuthal angle θ and proportional to μ (cosine of the θ polar angle). (Author)
Time-dependent angularly averaged inverse transport
Bal, Guillaume; Jollivet, Alexandre
2009-01-01
This paper concerns the reconstruction of the absorption and scattering parameters in a time-dependent linear transport equation from knowledge of angularly averaged measurements performed at the boundary of a domain of interest. We show that the absorption coefficient and the spatial component of the scattering coefficient are uniquely determined by such measurements. We obtain stability results on the reconstruction of the absorption and scattering parameters with respect to the measured al...
Time-dependent angularly averaged inverse transport
This paper concerns the reconstruction of the absorption and scattering parameters in a time-dependent linear transport equation from knowledge of angularly averaged measurements performed at the boundary of a domain of interest. Such measurement settings find applications in medical and geophysical imaging. We show that the absorption coefficient and the spatial component of the scattering coefficient are uniquely determined by such measurements. We obtain stability results on the reconstruction of the absorption and scattering parameters with respect to the measured albedo operator. The stability results are obtained by a precise decomposition of the measurements into components with different singular behavior in the time domain
Time-dependent angularly averaged inverse transport
Bal, Guillaume
2009-01-01
This paper concerns the reconstruction of the absorption and scattering parameters in a time-dependent linear transport equation from knowledge of angularly averaged measurements performed at the boundary of a domain of interest. We show that the absorption coefficient and the spatial component of the scattering coefficient are uniquely determined by such measurements. We obtain stability results on the reconstruction of the absorption and scattering parameters with respect to the measured albedo operator. The stability results are obtained by a precise decomposition of the measurements into components with different singular behavior in the time domain.
Orbital angular momentum is dependent on polarization
Li, Chun-Fang
2009-01-01
It is shown that the momentum density of free electromagnetic field splits into two parts. One has no contribution to the net momentum due to the transversality condition. The other yields all the momentum. The angular momentum that originates from the former part is spin, and the angular momentum that originates from the latter part is orbital angular momentum. Expressions for the spin and orbital angular momentum are given in terms of the electric vector in reciprocal space. The spin and or...
Role of electron-molecule angular scattering in shaping the electron-velocity distribution
Kunhardt, E.E.; Tzeng, Y.
1986-09-01
Five models has been studied to elucidate the role of electron-molecule angular scattering in shaping the velocity distribution for electrons in nitrogen at E/N values of 300 and 1500 Td. The angular dependence of the differential scattering cross sections for elastic and inelastic collisions has been observed to have significant effects on the shape of the velocity distribution, the rate coefficients, and the transport parameters. The velocity distribution is most sensitive to the angular dependence of elastic scattering. Moreover, for a given elastic differential scattering cross section, variations in the angular dependence of inelastic scattering cause significant changes in the distribution. The magnitude of these changes depends on the relative action of the inelastic collisions with respect to the elastic collisions for a given energy interval, i.e., whether the scattering by the inelastic collisions is isotropic, forward, or backward in a given energy interval.
Angular dependence of spin-orbit spin-transfer torques
Lee, Ki-Seung
2015-04-06
In ferromagnet/heavy-metal bilayers, an in-plane current gives rise to spin-orbit spin-transfer torque, which is usually decomposed into fieldlike and dampinglike torques. For two-dimensional free-electron and tight-binding models with Rashba spin-orbit coupling, the fieldlike torque acquires nontrivial dependence on the magnetization direction when the Rashba spin-orbit coupling becomes comparable to the exchange interaction. This nontrivial angular dependence of the fieldlike torque is related to the Fermi surface distortion, determined by the ratio of the Rashba spin-orbit coupling to the exchange interaction. On the other hand, the dampinglike torque acquires nontrivial angular dependence when the Rashba spin-orbit coupling is comparable to or stronger than the exchange interaction. It is related to the combined effects of the Fermi surface distortion and the Fermi sea contribution. The angular dependence is consistent with experimental observations and can be important to understand magnetization dynamics induced by spin-orbit spin-transfer torques.
A Stern-Gerlach-like approach to electron orbital angular momentum measurement
Harvey, Tyler R
2016-01-01
Many methods now exist to prepare free electrons into orbital angular momentum states, and the predicted applications of these electron states as probes of materials and scattering processes are numerous. The development of electron orbital angular momentum measurement techniques has lagged behind. We show that coupling between electron orbital angular momentum and a spatially varying magnetic field produces an angular momentum-dependent focusing effect. We propose a design for an orbital angular momentum measurement device built on this principle. As the method of measurement is non-interferometric, the device works equally well for mixed, superposed and pure final orbital angular momentum states. The energy and orbital angular momentum distributions of inelastically scattered electrons may be simultaneously measurable with this technique.
Angular dependent light emission from planar waveguides
We have investigated the angular dependence of amplified spontaneous emission (ASE) and laser emission from an asymmetric and free-standing polymer thin films doped with rhodamine 6G, which is transversely pumped by a pulsed Nd:YAG laser. A semi-leaky waveguide or quasi-waveguide structure has been developed by spin coating technique. In these waveguides, the light was confined by the film/air-film/glass substrate interfaces. At the film/substrate interface, a portion of light will reflect back into the film (guided mode) and the remaining refracted to the substrate resulting in cutoff modes. A blue-shift in ASE has been observed when the pump power was increased from 8 to 20 mW allowing a limited range of tuning of emission wavelength. To study the directionality of the ASE from the waveguide, we have measured the output intensity and FWHM of emission spectra as a function of viewing angle (θ) from the plane parallel to film. From the detailed examination of the output emission spectra, as +θ increases from 0° there has been an initial decrease in output intensity, but at a particular angle ≈10° an increase in output intensity was observed. This additional peak in output intensity as +θ is a clear indication of coexistence of the cutoff mode. We also present a compact solid-state laser based on leaky mode propagation from the dye-doped polymer free-standing film (∼50 μm thickness) waveguide. The partial reflections from the broad lateral surfaces of the free-standing films provided the optical feedback for the laser emission with high directionality. For a pump power of 22 mW, an intense line with FWHM <0.2 nm was observed at 578 nm
Karras, G.; Kosmidis, C.
2010-10-01
The angular distribution of the fragment ions ejected from the interaction of methyl iodide clusters with 20 fs strong laser pulses is studied by means of a mass spectrometer. Three types of angular distributions, one isotropic and two anisotropic, have been observed and their dependence on the laser intensity has been studied. There is strong evidence that the ions exhibiting anisotropic angular distribution with a maximum in the direction parallel to the laser polarization vector are produced via an electron impact ionization process.
Relativistic calculations of angular dependent photoemission time delay
Kheifets, A S; Deshmukh, P C; Dolmatov, V K; Manson, S T
2016-01-01
Angular dependence of photoemission time delay for the valence $np_{3/2}$ and $np_{1/2}$ subshells of Ar, Kr and Xe is studied in the dipole relativistic random phase approximation. Strong angular anisotropy of the time delay is reproduced near respective Cooper minima while the spin-orbit splitting affects the time delay near threshold.
Quantitative measurement of orbital angular momentum in electron microscopy
Clark, L; Guzzinati, G; Verbeeck, J
2014-01-01
Electron vortex beams have been predicted to enable atomic scale magnetic information measurement, via transfer of orbital angular momentum. Research so far has focussed on developing production techniques and applications of these beams. However, methods to measure the outgoing orbital angular momentum distribution are also a crucial requirement towards this goal. Here, we use a method to obtain the orbital angular momentum decomposition of an electron beam, using a multi-pinhole interferometer. We demonstrate both its ability to accurately measure orbital angular momentum distribution, and its experimental limitations when used in a transmission electron microscope.
Quantitative measurement of orbital angular momentum in electron microscopy
Clark, L.; Béché, A.; Guzzinati, G.; Verbeeck, J.
2014-01-01
Abstract: Electron vortex beams have been predicted to enable atomic scale magnetic information measurement, via transfer of orbital angular momentum. Research so far has focused on developing production techniques and applications of these beams. However, methods to measure the outgoing orbital angular momentum distribution are also a crucial requirement towards this goal. Here, we use a method to obtain the orbital angular momentum decomposition of an electron beam, using a multipinhole int...
Angular dependence of the coercivity in arrays of ferromagnetic nanowires
We present a new magnetic model for polycrystalline nanowires arrays in porous anodic aluminum oxide. The principal consideration here is the crystalline structure and the morphology of the wires and them the dipolar interactions between the crystals into the wire. Other aspect here is the direct calculation of the dipolar energy for the interaction of one wire with the others in the array. The free energy density was formulated for polycrystalline nanowires arrays in order to determinate the anisotropy effective field. It was using the microstructure study by scanning and transmission electron microscopy for the estimation of the real structure of the wires. After the structural analysis we used the angular dependences for the coercivity field and for the remnant magnetization to determine the properties of the wires. All analysis were made by the theory treatment proposed by Stoner and Wohlfarth
The nanoplasmonic field enhancement effects in the energetic electron emission from few-nm-sized silver clusters exposed to intense femtosecond dual pulses are investigated by high-resolution double differential electron spectroscopy. For moderate laser intensities of 1014 W cm−2, the delay-dependent and angular-resolved electron spectra show laser-aligned emission of electrons up to keV kinetic energies, exceeding the ponderomotive potential by two orders of magnitude. The importance of the nanoplasmonic field enhancement due to resonant Mie-plasmon excitation observed for optimal pulse delays is investigated by a direct comparison with molecular dynamics results. The excellent agreement of the key signatures in the delay-dependent and angular-resolved spectra with simulation results allows for a quantitative analysis of the laser and plasmonic contributions to the acceleration process. The extracted field enhancement at resonance verifies the dominance of surface-plasmon-assisted re-scattering. (paper)
Angular dependence of anisotropic magnetoresistance in magnetic systems
Zhang, Steven S.-L.; Zhang, Shufeng
2014-05-01
Anisotropic magnetoresistance (AMR), whose physical origin is attributed to the combination of spin dependent scattering and spin orbital coupling (SOC), usually displays simple angular dependence for polycrystalline ferromagnetic metals. By including generic spin dependent scattering and spin Hall (SH) terms in the Ohm's law, we explicitly show that various magneto-transport phenomena such as anomalous Hall (AH), SH, planar Hall (PH) and AMR could be quantitatively related for bulk polycrystalline ferromagnetic metals. We also discuss how AMR angular dependence is affected by the presence of interfacial SOC in magnetic layered structure.
Electronic orbital angular momentum and magnetism of graphene
Luo, Ji, E-mail: ji.luo@upr.edu
2014-10-01
Orbital angular momentum (OAM) of graphene electrons in a perpendicular magnetic field is calculated and corresponding magnetic moment is used to investigate the magnetism of perfect graphene. Variation in magnetization demonstrates its decrease with carrier-doping, plateaus in a large field, and de Haas–van Alphen oscillation. Regulation of graphene's magnetism by a parallel electric field is presented. The OAM originates from atomic-scale electronic motion in graphene lattice, and vector hopping interaction between carbon atomic orbitals is the building element. A comparison between OAM of graphene electrons, OAM of Dirac fermions, and total angular momentum of the latter demonstrates their different roles in graphene's magnetism. Applicability and relation to experiments of the results are discussed. - Highlights: • Orbital angular momentum of graphene electrons is calculated. • Orbital magnetic moment of graphene electrons is obtained. • Variation in magnetization of graphene is calculated. • Roles of different kinds of angular momentum are investigated.
Electronic orbital angular momentum and magnetism of graphene
Orbital angular momentum (OAM) of graphene electrons in a perpendicular magnetic field is calculated and corresponding magnetic moment is used to investigate the magnetism of perfect graphene. Variation in magnetization demonstrates its decrease with carrier-doping, plateaus in a large field, and de Haas–van Alphen oscillation. Regulation of graphene's magnetism by a parallel electric field is presented. The OAM originates from atomic-scale electronic motion in graphene lattice, and vector hopping interaction between carbon atomic orbitals is the building element. A comparison between OAM of graphene electrons, OAM of Dirac fermions, and total angular momentum of the latter demonstrates their different roles in graphene's magnetism. Applicability and relation to experiments of the results are discussed. - Highlights: • Orbital angular momentum of graphene electrons is calculated. • Orbital magnetic moment of graphene electrons is obtained. • Variation in magnetization of graphene is calculated. • Roles of different kinds of angular momentum are investigated
Modeling of the angular dependence of plasma etching
An understanding of the angular dependence of etching yield is essential to investigate the origins of sidewall roughness during plasma etching. In this article the angular dependence of polysilicon etching in Cl2 plasma was modeled as a combination of individual angular-dependent etching yields for ion-initiated processes including physical sputtering, ion-induced etching, vacancy generation, and removal. The modeled etching yield exhibited a maximum at ∼60 degree sign off-normal ion angle at low flux ratio, indicative of physical sputtering. It transformed to the angular dependence of ion-induced etching with the increase in the neutral-to-ion flux ratio. Good agreement between the modeling and the experiments was achieved for various flux ratios and ion energies. The variation of etching yield in response to the ion angle was incorporated in the three-dimensional profile simulation and qualitative agreement was obtained. The surface composition was calculated and compared to x-ray photoelectron spectroscopy (XPS) analysis. The modeling indicated a Cl areal density of 3x1015 atoms/cm2 on the surface that is close to the value determined by the XPS analysis. The response of Cl fraction to ion energy and flux ratio was modeled and correlated with the etching yields. The complete mixing-layer kinetics model with the angular dependence effect will be used for quantitative surface roughening analysis using a profile simulator in future work.
Angular correlation of electrons and positrons in internal pair conversion
The angular distribution of electrons and positrons which are emitted in internal pair conversion (IPC) is calculated. Coulomb-distorted waves are used as electron wave functions. Nuclear transitions of various multipolarities L>0 and of magnetic (ML) and electric (EL) type are considered as well as E0-conversion. Analytical expressions for the angular correlation are derived which are evaluated numerically assuming a finite extension of the nucleus and, for the EL and ML conversion, also in point-nucleus approximation. The calculated angular correlations are compared with results obtained within the Born approximation and, for the E0 case, with experimental data. (orig.)
Angular dependent transport properties of MgB2 films with columnar grains
We studied the angular dependence of the transport properties of MgB2 films with columnar grains grown by hybrid physical chemical vapor deposition method, one sample with unreacted boron in the volume and the other sample with no traceable impurity phase. The angular dependence of resistivity and critical current density in applied magnetic fields for both samples showed a flux pinning effect by the grain boundaries between columnar grains. The temperature dependence of the upper critical fields was analyzed by using the dirty-limit two-gap model. We found that the unreacted boron in the body of the film had negative effect on flux pinning and intraband electron diffusivities
Angular and energetic dependence of photographic dosemeters for beta radiation
Photographic dosemeters (Agfa-Gevaert) used in personal monitoring at IPEN/CNEN-SP (Brazil) are studied. The angular (between O and 1800) and energetic dependence in beta radiation exposures are discussed. The dosemeters are analysed with and without dosemeter - holder and retroscatter material. (M.A.C.)
Kinetic description of electron plasma waves with orbital angular momentum
Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)
2012-11-15
We describe the kinetic theory of electron plasma waves with orbital angular momentum or twisted plasmons. The conditions for a twisted Landau resonance to exist are established, and this concept is introduced for the first time. Expressions for the kinetic dispersion relation and for the electron Landau damping are derived. The particular case of a Maxwellian plasma is examined in detail. The new contributions to wave dispersion and damping due the orbital angular momentum are discussed. It is shown that twisted plasmons can be excited by rotating electron beams.
Kinetic description of electron plasma waves with orbital angular momentum
We describe the kinetic theory of electron plasma waves with orbital angular momentum or twisted plasmons. The conditions for a twisted Landau resonance to exist are established, and this concept is introduced for the first time. Expressions for the kinetic dispersion relation and for the electron Landau damping are derived. The particular case of a Maxwellian plasma is examined in detail. The new contributions to wave dispersion and damping due the orbital angular momentum are discussed. It is shown that twisted plasmons can be excited by rotating electron beams.
Angular distribution of electron temperature and density in a laser-ablation plume
Toftmann, B.; Schou, Jørgen; Hansen, T.N.; Lunney, J.G.
2000-01-01
The angular distribution of electron temperature and density in a laser-ablation plume has been studied for the first time. The electron temperature ranges from 0.1 to 0.5 eV and is only weakly dependent on the angle in the low-intensity range studied here. In contrast, the typical ion energy is...
Measuring the orbital angular momentum of electron beams
Giulio Guzzinati; Laura Clark; Armand B\\xe9ch\\xe9; Jo Verbeeck
2014-01-01
Abstract: The recent demonstration of electron vortex beams has opened up the new possibility of studying orbital angular momentum (OAM) in the interaction between electron beams and matter. To this aim, methods to analyze the OAM of an electron beam are fundamentally important and a necessary next step. We demonstrate the measurement of electron beam OAM through a variety of techniques. The use of forked holographic masks, diffraction from geometric apertures, and diffraction from a knife ed...
Transition radiation from electrons with orbital angular momentum
Konkov, Anatoly S.; Potylitsyn, Alexander P.; Polonskaya, Marina S.
2013-01-01
Several experimental groups have recently obtained the so called vortex electrons (electrons with orbital angular momentum (OAM) of l = 100h) with energies of 300 keV. The gyromagnetic ratio of such electrons becomes proportional to the OAM value, which leads to the corresponding increase of the electron magnetic moment. In this paper we investigate the transition radiation from the "charge + magnetic moment" system using the theory of classical electrodynamics. The circular polarization of o...
Obtaining the Electron Angular Momentum Coupling Spectroscopic Terms, jj
Orofino, Hugo; Faria, Roberto B.
2010-01-01
A systematic procedure is developed to obtain the electron angular momentum coupling (jj) spectroscopic terms, which is based on building microstates in which each individual electron is placed in a different m[subscript j] "orbital". This approach is similar to that used to obtain the spectroscopic terms under the Russell-Saunders (LS) coupling…
Recent developments in electron photon angular correlations
The application of the electron photon coincidence technique to evaluate the role of spin-orbit interactions in electron impact excitation of heavy atoms is reviewed. Excitation of the 63P1 level of Hg is described in detail. The use of polarized electrons in this excitation governed by the selection rule ΔMsub(L)=0 is discussed. Experiments in which the time evolution of excited states can be observed are described. A recent theoretical development is reviewed, in which experimental observables are linked to specific dynamical effects during the excitation. (Auth.)
Angular dependence of Wigner time delay: Relativistic Effects
Mandal, A.; Deshmukh, P. C.; Manson, S. T.; Kkeifets, A. S.
2016-05-01
Laser assisted photoionization time delay mainly consists of two parts: Wigner time delay, and time delay in continuum-continuum transition. Wigner time delay results from the energy derivative of the phase of the photoionization amplitude (matrix element). In general, the photoionization time delay is not the same in all directions relative to the incident photon polarization, although when a single transition dominates the amplitude, the resultant time delay is essentially isotropic. The relativistic-random-phase approximation is employed to determine the Wigner time delay in photoionization from the outer np subshells of the noble gas atoms, Ne through Xe. The time delay is found to significantly depend on angle, as well as energy. The angular dependence of the time delay is found to be quite sensitive to atomic dynamics and relativistic effects, and exhibit strong energy and angular variation in the neighborhood of Cooper minima. Work supported by DOE, Office of Chemical Sciences and DST (India).
Angular dependence of dosimetric films for gamma radiation
In most situations, radiations workers are subjected to radiation exposures at randon angles of incidence. Consequentetly, the personnel dose estimates would be lower since calibration is usually accomplished with stationary films positioned perpendicular to beam on radiation, i.e., at normal incidence. In oder to obtain an error estimate due to angular dependence the radiation incidence angle related to badges having Agfa Gevaert Struturix D2 and D10 (commonly used in individual dosimeter) was variated between 0 and 900. (author)
Angular distribution of electron temperature and density in a laser-ablation plume
Toftmann, B.; Schou, Jørgen; Hansen, T.N.; Lunney, J.G.
2000-01-01
The angular distribution of electron temperature and density in a laser-ablation plume has been studied for the first time. The electron temperature ranges from 0.1 to 0.5 eV and is only weakly dependent on the angle in the low-intensity range studied here. In contrast, the typical ion energy is ...... about 2 orders of magnitude larger, and its angular distribution is mon peaked about the target normal. The derived Values of the electron density are in agreement with the measured values of ion density....
Angular Dependence of 3 Omega 0/2 Spectra from Laser-produced Plasmas
Scattered light at three-halves of the incident laser frequency from solid targets is observed at five different angles. When the incident laser intensity is low enough, rescattering of two plasmon decay (TPD) instability electron plasma waves by ion acoustic waves is not significant. In this regime, Thomson scattering measurements of the electron temperature and the plasma flow velocity allow quantitative comparison of the angular dependence of the spectrum to theory
Polarization radiation of vortex electrons with large orbital angular momentum
Ivanov, Igor P
2013-01-01
Vortex electrons, i.e. freely propagating electrons whose wavefunction has helical wavefronts, could emerge as a novel tool for the physics of electromagnetic (EM) radiation. They carry non-zero intrinsic orbital angular momentum (OAM) $\\ell$ and, for $\\ell \\gg 1$, a large OAM-induced magnetic moment, $\\mu \\approx \\ell \\mu_B$ ($\\mu_B$ is the Bohr magneton), which affects the radiation of EM waves. Here, we consider in detail its influence on two forms of polarization radiation, namely on Cherenkov and transition radiation. Due to large $\\ell$, we can neglect quantum or spin-induced effects, which are of order $\\hbar \\omega/E_e \\ll 1$, but retain the magnetic moment contribution $\\ell \\hbar \\omega/E_e \\lesssim 1$, which makes the quasiclassical approach to polarization radiation applicable. We discuss magnetic moment contribution to polarization radiation, which has never been experimentally observed, and study how its visibility depends on kinematical parameters and permittivity of the medium. In particular, ...
Transition radiation from electrons with orbital angular momentum
Konkov, Anatoly S; Polonskaya, Marina S
2013-01-01
Several experimental groups have recently obtained the so called vortex electrons (electrons with orbital angular momentum (OAM) of l = 100h) with energies of 300 keV. The gyromagnetic ratio of such electrons becomes proportional to the OAM value, which leads to the corresponding increase of the electron magnetic moment. In this paper we investigate the transition radiation from the "charge + magnetic moment" system using the theory of classical electrodynamics. The circular polarization of optical transition radiation amounts up to 70%, which allows to use this effect for the independent measurement of the electron orbital momentum value.
The velocity and angular momentum of a free Dirac electron
Lin, Lu
1998-01-01
It is shown that, in Dirac theory, there is a spatial velocity of a free electron which commutes with the Hamiltonian, so it is a conserved quantity of the motion. Furthermore, there is a spatial orbital angular momentum which also commutes with the Hamiltonian and is a constant of the motion.
Measuring the Orbital Angular Momentum of Electron Beams
Guzzinati, Giulio; Béché, Armand; Verbeeck, Jo
2014-01-01
The recent demonstration of electron vortex beams has opened up the new possibility of studying orbital angular momentum (OAM) in the interaction between electron beams and matter. To this aim, methods to analyze the OAM of an electron beam are fundamentally important and a necessary next step. We demonstrate the measurement of electron beam OAM through a variety of techniques. The use of forked holographic masks, diffraction from geometric apertures, diffraction from a knife-edge and the application of an astigmatic lens are all experimentally demonstrated. The viability and limitations of each are discussed with supporting numerical simulations.
Angular dependence of silicon oxide etching yield in fluorocarbon chemistries
High density fluorocarbon plasma for silicon oxide etching has various ion and neutral species. Profile evolution modeling can provide understanding of many difficulties caused by the complexity of the plasma in etching. In this research we have measured etching and deposition rates as functions of ion impinging angle, sample temperature, which are necessary for profile evolution modeling of silicon oxide etching in inductively coupled plasma. Angular dependence of etching yield of oxide in fluorocarbon plasma shows very unique behavior unlike typical ion-induced chemical etching or physical sputtering. Ion-induced deposition model is suggested and tested
Angular momentum of non-paraxial light beam: Dependence of orbital angular momentum on polarization
Li, Chun-Fang
2009-01-01
It is shown that the momentum density of free electromagnetic field splits into two parts. One has no contribution to the net momentum due to the transversality condition. The other yields all the momentum. The angular momentum that is associated with the former part is spin, and the angular momentum that is associated with the latter part is orbital angular momentum. Expressions for the spin and orbital angular momentum are given in terms of the electric vector in reciprocal space. The spin ...
Waro Nakanishi; Satoko Hayashi; Akito Tanioku
2009-01-01
Nuclear couplings for the Se-Se bonds, 1 J(Se, Se), are analyzed on the basis of the molecular orbital (MO) theory. The values are calculated by employing the triple ζ basis sets of the Slater type at the DFT level. 1 J(Se, Se) are calculated modeled by MeSeSeMe (1a), which shows the typical torsional angular dependence on ϕ(CMeSeSeCMe). The dependence explains well the observed 1 J obsd (Se, Se) of small values (≤ 64 Hz) for RSeSeR′ (1) (simple derivatives of 1a) and large values (330–380 Hz...
Angular dependence of primordial trispectra and CMB spectral distortions
Shiraishi, Maresuke; Liguori, Michele
2016-01-01
Under the presence of anisotropic sources in the inflationary era, the trispectrum of the primordial curvature perturbation is sensitive to the angles between each wave vector. We examine the imprints left by curvature trispectra, in which the angular dependence is described by Legendre polynomials, on the $TT\\mu$ bispectrum, generated by the correlation between temperature anisotropies (T) and chemical potential spectral distortions ($\\mu$) of the Cosmic Microwave Background (CMB). Due to the angular dependence of the primordial signal, the corresponding $TT\\mu$ bispectrum strongly differs in shape from $TT\\mu$ sourced by the usual $g_{\\rm NL}$ or $\\tau_{\\rm NL}$ local trispectra, enabling us to obtain an unbiased estimation. From a Fisher matrix analysis, we find that, in a cosmic-variance-limited (CVL) survey of $TT\\mu$, a minimum detectable value of the quadrupolar Legendre coefficient is $d_2 \\sim 0.01$, which is 4 orders of magnitude better than the best value attainable from the $TTTT$ CMB trispectrum....
Angular dose dependency of MatriXX and its calibration
Objective: To characterize angular dependency of MatriXX and develop a method for its calibration in order to verify treatment plan with original gantry angles. Methods: Absolute dose calibration was carried with thimble ionization chamber on the linear accelerator, so as to make sure 1 MU=1 cGy at the depth of maximum dose (dmax). A MatriXX was put into a Mutlicube phantom, and the ionization chamber matrix was calibrated with absolute dose. In order to determine a correction factor CF as a function of gantry angle θ, open beam fields of 10 cm×10 cm size were irradiated for gantry angles θ=0°-180° (every 5°) and every 1°for lateral angles θ in the range of 85°-95°. CF was defined as the ratio of the dose measured with ionization chamber and the dose from MatriXX. Results: Relatively large discrepancies in response to posterior VS, anterior fields for MatriXX detectors (up to 10%) were found during the experiment and relatively large variability of response as a function of gantry angle. The pass rate of treatment plan in lateral beams was lower than that of other beams. The isodose distribution of corrected MatriXX matched well with the outcome from the treatment planning system. Conclusions: The angular dose dependency of MatriXX must be considered when it is used to verify the treatment plan with original gantry angles. (authors)
Unveiling the orbital angular momentum and acceleration of electron beams.
Shiloh, Roy; Tsur, Yuval; Remez, Roei; Lereah, Yossi; Malomed, Boris A; Shvedov, Vladlen; Hnatovsky, Cyril; Krolikowski, Wieslaw; Arie, Ady
2015-03-01
New forms of electron beams have been intensively investigated recently, including vortex beams carrying orbital angular momentum, as well as Airy beams propagating along a parabolic trajectory. Their traits may be harnessed for applications in materials science, electron microscopy, and interferometry, and so it is important to measure their properties with ease. Here, we show how one may immediately quantify these beams' parameters without need for additional fabrication or nonstandard microscopic tools. Our experimental results are backed by numerical simulations and analytic derivation. PMID:25793830
Unveiling the orbital angular momentum and acceleration of electron beams
Shiloh, Roy; Lereah, Yossi; Malomed, Boris A; Shvedov, Vladlen; Hnatovsky, Cyril; Krolikowski, Wieslaw; Arie, Ady
2014-01-01
New forms of electron beams have been intensively investigated recently, including vortex beams carrying orbital angular momentum, as well as Airy beams propagating along a parabolic trajectory. Their traits may be harnessed for applications in materials science, electron microscopy and interferometry, and so it is important to measure their properties with ease. Here we show how one may immediately quantify these beams' parameters without need for additional fabrication or non-standard microscopic tools. Our experimental results are backed by numerical simulations and analytic derivation.
Palov, A. P.; Mankelevich, Yu A.; Rakhimova, T. V.; Baklanov, M. R.
2016-03-01
Ion-stimulated etching of dielectrics in radio frequency plasma results in positive charging of a trench bottom because of the significant difference in the angular distribution functions of ions and electrons. They are anisotropic for ions and quasi-isotropic for electrons. The charging leads to a decrease in the energy of the ions bombarding the trench bottom and to undesirable sputtering of the walls near the trench bottom because of the curving of the ion trajectories. This process is normally investigated by Monte Carlo methods in the absence of experimental data. In this paper the analytical dependence of the ion flux bombarding the trench bottom on a trench aspect ratio and ion angular distribution function is obtained. Numerical calculations of the electric potential on the trench bottom for a set of trench aspect ratios and angles of the ion angular distribution function were performed based on a Monte Carlo method to demonstrate the ion flux and electric potential correlated well with each other. The proposed formula for an ion flux is suggested to be helpful for analyzing charging the trenches with different aspect ratios in plasma with an arbitrary angular ion distribution function.
Angular dependence of interactions in polycrystalline Co nanowire arrays
Ordered Co nanowire arrays with a constant geometry (∼40 nm diameter, ∼10 μm length and ∼100 nm interwire distance) were ac pulse electrodeposited into anodic aluminum oxide template under different deposition current densities (5.31, 7.08 and 8.85 mA/cm2). Microstructure and magnetic properties of the samples were studied using X-ray diffraction (XRD) pattern, selected area diffraction (SAED) pattern and first-order reversal curve (FORC) diagrams. SAED patterns showed inhomogeneous polycrystalline structure along the length of a nanowire. FORC diagrams revealed two-phase magnetic behavior in which soft and hard magnetic phases related to triplet cobalt crystalline directions. Despite the fact that angular dependence of hysteresis loops provides information about magnetization reversal, angular FORC offers additional information on the magnetostatic and interphase interactions depending on angle between the field and nanowires axis (α). Different magnetic behaviors were seen by change in α; interacting two-phase behavior in α = 0° which reduced to a non-interacting behavior for α > 60° may be attributed to reduce delay in magnetization reversal of two phases. Increasing the reversible portion of the major hysteresis loop in α = 90° is a possible source of difference between the hard to soft ratio obtained from FORC diagrams and XRD patterns. - Highlights: • Increasing α cause to reduce demagnetizing interaction and remove additional feature in 90°. • Magnetic behavior of Co-hcp(002) change from hard to soft phase as α increased from 0 to 90°. • Increasing reversible portion in 90° is source of different hard-soft ratio obtained from FORC and XRD
Angular-dependent Raman study of a- and s-plane InN
Angular-dependent polarized Raman spectroscopy was utilized to study nonpolar a-plane (11¯20) and semipolar s-plane (101¯1) InN epilayers. The intensity dependence of the Raman peaks assigned to the vibrational modes A1(TO), E1(TO), and E2h on the angle ψ that corresponds to rotation around the growth axis, is very well reproduced by using expressions taking into account the corresponding Raman tensors and the experimental geometry, providing thus a reliable technique towards assessing the sample quality. The s- and a-plane InN epilayers grown on nitridated r-plane sapphire (Al2O3) exhibit good crystalline quality as deduced from the excellent fitting of the experimental angle-dependent peak intensities to the theoretical expressions as well as from the small width of the Raman peaks. On the contrary, in the case of the s-plane epilayer grown on non-nitridated r-plane sapphire, fitting of the angular dependence is much worse and can be modeled only by considering the presence of two structural modifications, rotated so as their c-axes are almost perpendicular to each other. Although the presence of the second variant is verified by transmission electron and atomic force microscopies, angular dependent Raman spectroscopy offers a non-destructive and quick way for its quantification. Rapid thermal annealing of this sample did not affect the angular dependence of the peak intensities. The shift of the E1(TO) and E2h Raman peaks was used for the estimation of the strain state of the samples
Angular dependent rebalance method for solving the neutron transport equation
objective of this thesis is to develop an acceleration technique that has good stability and rapid convergence for general discrete ordinates transport methods. For this purpose, the author develops a new general nonlinear iteration method based on angular dependent rebalance factor concept called the Angular Dependent Rebalance (ADR) Method. The acceleration method uses a lower-order equation at each iteration to improve the result of the higher-order equation. In deriving the lower-order equation, the rebalance factor is used similarly as in the conventional fine-mesh rebalance (FMR) method. However, in the ADR method, the rebalance factor is angular space. In fact, the angular dependency of the rebalance factor is approximated by the DPN expansion method and the low order SN expansion method for the case of one-dimensional geometry and by the S2 method for the case of two-dimensional geometry. As a result, the lower-order equation of the ADR method resembles the transport equation. Therefore, the lower equation is very easily derived and simple to implement for various kinds of the numerical transport methods in general geometries. Also, the ADR method avoids the 'consistent differencing' issues in DSA because the lower-order equation is derived exactly from the transport equation except for the approximation in angular dependency of the rebalance factor. Unlike previous methods, the ADR method allows the inconsistent combination of lower-order equation and higher-order equation and these inconsistent combinations do not generate numerical instabilities. The similarity of the lower-order equation to the transport equation requires an effective iterative method for solving the lower-order equation. The speedup of ADR with respect to SI is highly dependent on how efficiently the lower-order equation is solved. In this thesis, three methods are considered as an effective solver to solve the lower-order equation of ADR. First is the two cyclic iterative method (or
Measurements of electron density profiles using an angular filter refractometer
Haberberger, D., E-mail: dhab@lle.rochester.edu; Ivancic, S.; Hu, S. X.; Boni, R.; Barczys, M.; Craxton, R. S.; Froula, D. H. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14636 (United States)
2014-05-15
A novel diagnostic technique, angular filter refractometry (AFR), has been developed to characterize high-density, long-scale-length plasmas relevant to high-energy-density physics experiments. AFR measures plasma densities up to 10{sup 21} cm{sup −3} with a 263-nm probe laser and is used to study the plasma expansion from CH foil and spherical targets that are irradiated with ∼9 kJ of ultraviolet (351-nm) laser energy in a 2-ns pulse. The data elucidate the temporal evolution of the plasma profile for the CH planar targets and the dependence of the plasma profile on target radius for CH spheres.
Measuring the angular dependence of betatron x-ray spectra in a laser-wakefield accelerator
Albert, F. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Pollock, B. B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Shaw, J. L. [Univ. of California, Los Angeles, CA (United States); Marsh, K. A. [Univ. of California, Los Angeles, CA (United States); Ralph, J. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Chen, Y. -H. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Alessi, D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Pak, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Clayton, C. E. [Univ. of California, Los Angeles, CA (United States); Glenzer, S. H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Joshi, C. [Univ. of California, Los Angeles, CA (United States)
2014-07-22
This paper presents a new technique to measure the angular dependence of betatron x-ray spectra in a laser-wakefield accelerator. Measurements are performed with a stacked image plates spectrometer, capable of detecting broadband x-ray radiation up to 1 MeV. It can provide measurements of the betatron x-ray spectrum at any angle of observation (within a 40 mrad cone) and of the beam profile. A detailed description of our data analysis is given, along with comparison for several shots. As a result, these measurements provide useful information on the dynamics of the electrons are they are accelerated and wiggled by the wakefield.
ELECTRON ANGULAR DISTRIBUTIONS IN DISSOCIATIVE PHOTOIONIZATION OF THE HYDROGEN MOLECULE.
Jhon F. Pérez-Torres
2009-06-01
Full Text Available Se propone un método para calcular distribuciones angulares de electrones ionizados en la molécula de hidrógeno fija en el espacio sometida a pulsos láser intensos y ultracortos, basado en la solución desde primeros principios de la ecuación de Schrödinger dependiente del tiempo. Esta solución nos permite tener una visión temporal de la interferencias generadas en el canal de ionización disociativa (en el espectro de energía cinética de los protones debido a la presencia de la autoionización de estados doblemente excitados de la molécula de hidrógeno. Se muestra específicamente cómo la autoionización durante el proceso de fotoionización disociativa también puede inducir una asimetría en la distribución angular del electrón ionizado con respecto a la inversión nuclear, un efecto no intuitivo a pesar de estar tratando con un sistema homonuclear.
Angular distributions of electrons emitted from free and deposited Na{sub 8} clusters
Baer, Matthias [Institut fuer Theoretische Physik, Universitaet Erlangen (Germany); Dinh, Phuong Mai; Suraud, Eric [Laboratoire de Physique Theorique, IRSAMC, UPS and CNRS, Universite de Toulouse (France); Moskaleva, Lyudmila V.; Roesch, Notker [Department Chemie and Catalysis Research Center, Theoretische Chemie, Technische Universitaet Muenchen, Garching (Germany); Reinhard, Paul-Gerhard [Institut fuer Theoretische Physik, Universitaet Erlangen (Germany); Laboratoire de Physique Theorique, IRSAMC, UPS and CNRS, Universite de Toulouse (France)
2010-05-15
We explore from a theoretical perspective angular distributions of electrons emitted from a Na{sub 8} cluster after excitation by a short laser pulse. The tool of the study is time-dependent density-functional theory (TDDFT) at the level of the local-density approximation (LDA) augmented by a self-interaction correction (SIC) to put emission properties in order. We consider free Na{sub 8} and Na{sub 8} deposited on the surfaces MgO(001) or Ar(001). For the case of free Na{sub 8}, we distinguish between a hypothetical situation of known cluster orientation and a more realistic ensemble of orientations. We also consider the angular distributions for emission from separate single-electron levels. (Abstract Copyright [2010], Wiley Periodicals, Inc.)
Angular dependence to the threshold intensity of scattered radiation for passing ionic-sound waves
Present article is devoted to angular dependence to the threshold intensity of scattered radiation for passing ionic-sound waves. The angular dependence of intensity of scattered radiation in two-dimensional field of localization of a wave of a rating of passing ionic-sound waves at any scattering angles was considered. (author)
Spin-to-orbital angular momentum conversion and spin-polarization filtering in electron beams
Karimi E.; Marrucci L.; Grillo V.; Santamato E.
2012-01-01
We propose the design of a space-variant Wien filter for electron beams that induces a spin half-turn and converts the corresponding spin angular momentum variation into orbital angular momentum of the beam itself by exploiting a geometrical phase arising in the spin manipulation. When applied to a spatially coherent input spin-polarized electron beam, such a device can generate an electron vortex beam, carrying orbital angular momentum. When applied to an unpolarized input beam, the proposed...
The Geometric phase and fractional orbital angular momentum states in electron vortex beams
Bandyopadhyay, Pratul; Chowdhury, Debashree
2016-01-01
We study here fractional orbital angular momentum (OAM) states in electron vortex beams (EVB) from the perspective of geometric phase. We have considered the skyrmionic model of an electron, where it is depicted as a scalar electron orbiting around the vortex line, which gives rise to the spin degrees of freedom. The geometric phase acquired by the scalar electron orbiting around the vortex line induces the spin-orbit interaction, which leads to the fractional OAM states with non-quantized monopole charge associated with the corresponding geometric phase. This involves tilted vortex in EVBs. The monopole charge undergoes the renormalization group (RG) flow, which incorporates a length scale dependence making the fractional OAM states unstable upon propagation. It is pointed out that when EVBs move in an external magnetic field, the Gouy phase associated with the Laguerre-Gaussian modes modifies the geometric phase factor and a proper choice of the radial index helps to have a stable fractional OAM state.
Depth and latitude dependence of the solar internal angular velocity
Rhodes, E.J. Jr.; Cacciani, A.; Korzennik, S.; Tomczyk, S.; Ulrich, R.K.; Woodard, M.F. (Southern California Univ., Los Angeles, CA (USA) JPL, Pasadena, CA (USA) Roma I Universita (Italy) California Univ., Los Angeles (USA))
1990-03-01
One of the design goals for the dedicated helioseismology observing state located at Mount Wilson Observatory was the measurement of the internal solar rotation using solar p-mode oscillations. In this paper, the first p-mode splittings obtained from Mount Wilson are reported and compared with those from several previously published studies. It is demonstrated that the present splittings agree quite well with composite frequency splittings obtained from the comparisons. The splittings suggest that the angular velocity in the solar equatorial plane is a function of depth below the photosphere. The latitudinal differential rotation pattern visible at the surface appears to persist at least throughout the solar convection zone. 43 refs.
Depth and latitude dependence of the solar internal angular velocity
Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik, Sylvain; Tomczyk, Steven; Ulrich, Roger K.; Woodard, Martin F.
1990-01-01
One of the design goals for the dedicated helioseismology observing state located at Mount Wilson Observatory was the measurement of the internal solar rotation using solar p-mode oscillations. In this paper, the first p-mode splittings obtained from Mount Wilson are reported and compared with those from several previously published studies. It is demonstrated that the present splittings agree quite well with composite frequency splittings obtained from the comparisons. The splittings suggest that the angular velocity in the solar equatorial plane is a function of depth below the photosphere. The latitudinal differential rotation pattern visible at the surface appears to persist at least throughout the solar convection zone.
Spectral dependence of angular distribution halfwidths of Vavilov-Cherenkov radiation
Angular distributions of Vavilov-Cherenkov radiation have been measured. This radiaiton is excited during 210 keV electron propagation in a mica 2.5 mm thick target in a spectral range from 2500 up to 5000 A. A formula for diffraction halfwidth of angular distribution has been derived, its applicability limits are pointed out. Experimental halfwidth agrees with the calculated ones. The deviation of angular distribution maximum from Vavilov-Cherenkov radiation angle is analyzed. This deviation is due to radiator boundaries and multiple scattering of electrons
A new coarse-mesh rebalance method is developed and tested to accelerate one-dimensional discrete ordinates neutron transport equation. The method is based on the use of angular dependent rebalance factors. Unlike the original Coarse-Mesh Rebalance method, Fourier analysis and numerical results show that this Angular Dependent Coarse-Mesh Rebalance(ADCMR) method is unconditionally stable for any optical thickness and that the acceleration effect is significant
Sensitivity in frequency dependent angular rotation of optical vortices.
Rumala, Yisa S
2016-03-10
This paper presents robust strategies to enhance the rotation sensitivity (and resolution) of a coherent superposition of optical vortices emerging from a single spiral phase plate (SPP) device when light's optical frequency (or wavelength) going into the SPP device is varied. The paper discusses the generation and measurement of ultrasmall rotation. Factors that affect the ability to perform precision rotation measurements include the linewidth and stability of the input light source, the number of photon counts making position rotation measurements on the CCD detector, SPP reflectivity, the length of SPP device, and the angular modulation frequency of the intensity pattern due to a coherent superposition of optical vortices in a single SPP device. This paper also discusses parameters to obtain a high-sensitivity single shot measurement and multiple measurements. Furthermore, it presents what I believe is a new scaling showing the enhancement in sensitivity (and resolution) in the standard quantum limit and Heisenberg limit. With experimentally realizable parameters, there is an enhancement of rotation sensitivity by at least one order of magnitude compared to previous rotation measurements with optical vortices. Understanding robust strategies to enhance the rotation sensitivity in an SPP device is important to metrology in general and for building compact SPP sensors such as gyroscopes, molecular sensors, and thermal sensors. PMID:26974798
Electron-photon angular correlations in electron-helium collisions for 31P excitations
Electron-photon angular correlations have been measured by detecting, in delayed coincidence, electrons inelastically scattered from helium and photons emitted in decays from the 31P level. The measurements have been carried out using both the 31P-11S (53.7nm) line and the 31P-21S (501.6nm) line. Analysis of the data yields the ratio of differential cross sections for exciting 31P magnetic sublevels and the absolute value of the relative phase between the corresponding excitation amplitudes for electron scattering angles between 100 and 300 at incident electron energies in the range 50 eV to 150 eV. Data of the atomic orientation is also presented. The results are compared with the predictions of the first Born approximation and a recent multichannel eikonal calculation. (author)
Electronic interaction anisotropy between atoms in arbitrary angular momentum states
Krems, R.V.; Groenenboom, G.C.; Dalgarno, A.
2004-01-01
A general tensorial expansion for the interaction potential between two atoms in arbitrary angular momentum states is derived and the relations between the expansion coefficients and the Born-Oppenheimer potentials of the diatomic molecule are obtained. It is demonstrated that a complete expansion o
Angular dependence of surfactant-mediated forces between carbon nanotubes.
Müter, Dirk; Angelikopoulos, Panagiotis; Bock, Henry
2012-12-27
We employ dissipative particle dynamics to examine surfactant-mediated forces between two carbon nanotubes. Calculations are performed varying both the distance and the angle between the nanotubes. For small distances, a repulsive region is observed, followed by an overall attractive interval with strong oscillations in the force. Decreasing the angle between the tubes leads to a steady increase in the force, but the relative dependence on the separation distance is preserved. We find that the force scales linearly with the size of the overlap area between the tubes. This allows us to express the angle dependence by a simple equation, whereas the distance dependence is represented by a master curve. For the parallel case, the behavior is significantly different. PMID:23116052
ANGULAR VELOCITY AND CORIOLIS EFFECT IN TIME-DEPENDENT QUANTUM MECHANICAL SU2 ROTATION
FAN HONG-YI; SUN MING-ZHAI
2001-01-01
Starting from a time-dependent rotation U (t) in SU2 group element space, we derive its corresponding quantum mechanical dynamic Coriolis term and the relationship between U (t) and rotational angular velocity. Throughout our discussion, the technique of integration within an ordered product of operators is fully used, which has the advantage that the correspondence between the classical rotation and the quantum rotation is in a transparent fashion. A new angular-velocity formula is also derived.
Calculating the angular standard deviation of electron beams using Fermi-Eyges theory
Knowledge of the angular distribution of an electron beam at the applicator face is a necessary parameter in defining a beam when the Hogstrom pencil beam method of dose calculation is used. The angular spread can be found experimentally using penumbra widths measured at various distances from the applicator face. Using knowledge of the geometry and composition of the scattering foils of the linear accelerator, the angular standard deviation was calculated theoretically using Fermi-Eyges theory. The obtained angular spread values agree with experimentally derived values to within experimental error for electron energies from 6 to 21 MeV. The Fermi-Eyges calculation is fast, and can be used as a quick check to validate experimental angular spread values. (author)
Influence of the angular scattering of electrons on the runaway threshold in air
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.
A study of angular dependence in the ablation rate of polymers by nanosecond pulses
Pedder, James E. A.; Holmes, Andrew S.
2006-02-01
Measurements of ablation rate have traditionally been carried out only at normal incidence. However, in real-world applications ablation is often carried out at oblique angles, and it is useful to have prior knowledge of the ablation rate in this case. Detailed information about the angular dependence is also important for the development of ablation simulation tools, and can provide additional insight into the ablation mechanism. Previously we have reported on the angular dependence of direct-write ablation at 266 nm wavelength in solgel and polymer materials. In this paper we present a systematic study of angular dependence for excimer laser ablation of two polymer materials of interest for microfabrication: polycarbonate and SU8 photoresist. The results are used to improve simulation models to aid in mask design.
Angular dependence of magnetoresistance in silicon with nanoclusters of manganese atoms
In silicon samples doped by manganese a significant angular dependence of magnetoresistance has been experimentally observed. In samples in which the greater part of atoms is located in clusters, the negative magnetoresistance has maximal value at φ=90 deg and 270 deg and minimal one at φ=0 deg, 180 deg and 360 deg. In overcompensated samples, where nanoclusters did not reveal, on the contrary, the magnetoresistance has maximal value at φ=0 deg, 180 deg and 360 deg and minimal value at φ=90 deg and 270 deg. A character of angular dependence of magnetoresistance does not affected by temperature and level of lighting of samples. (authors)
Measured multipole moments of continuum electron transfer angular distributions
The velocity space distribution of electrons emitted near the forward direction from collisions involving fast, highly stripped oxygen ions with gaseous and solid targets is presented and described in terms of multipole moments of the ejected charge distribution, which permits direct comparison with recent theory. The measurements are produced by employing position-sensitive electron detection to combine emission angle definition with conventional electrostatic spectrometry. Agreement obtained between theory and distributions observed for binary continuum electron loss processes coupled with a similar multipole content observed with solid targets suggests a model of convoy electron production dominated by electron loss from the projectile within the bulk of the target. Further, the connection between multipoles of the projectile electron emission distribution in single collisions and the state of excitation of that projectile excited states may provide the basis for a probe of the state of ions traversing bulk solid matter. 14 refs., 3 figs., 1 tab
Angular Momentum-Phase Coherent State for an Electron in Uniform Magnetic Field
FAN Hong-Yi; FAN Yue
2001-01-01
Based on the newly constructed state ｜l, r》 [Fan et al., Chin. Phys. Lett. 16(1999)706], where l is the angular momentum quantum number and r denotes the electron's orbit radius in a uniform magnetic field, we propose a new angular momentum-phase coherent state by introducing a new operator A. A and A+ are annihilation and creation operators in the ｜l, r》 space, respectively. The coherent state is A's eigenket and possesses non-orthonormal and overcomplete properties. It is constructed on the certain superposition of zero-angular momentum states along the radius direction.
Determination of the angular dependence of the detector matrix Matrix X-evolution of IBA
The objective of this work consists in determining the correction for the angular dependence of the detector-Evolution Matrix x matrix (IBA, Germany), when used in the multi cube dummy (IBA, Germany), verification of treatment VMAT IMRT, using the software OP'IMRT (IBA, Germany).
Spin dependent electron response functions
Full text: In two-dimensional (2d) electronic systems (realized, e.g., in semiconductor quantum wells), correlation effects are more pronounced than in the bulk. This manifests itself in a lower value of the density parameter rs, where the system freezes into a crystal. A precursor of this transition is a minimum in the plasmon dispersion, which even may re-appear below the particle-hole continuum at high frequencies. Based on the dynamic many body theory of E. Krotscheck's group we study the excitations of 2d partially spin-polarized electron liquids at various rs and wave vectors. QMC data from the literature are used as an input for computing the spin dependent response functions. (author)
An angular-selective electron source for the KATRIN experiment
The KATRIN experiment is going to search for the average mass of the electron antineutrino with a sensitivity of 0.2 eV/c2. It uses a retardation spectrometer of MAC-E filter type to accurately measure the shape of the electron spectrum at the endpoint of tritium beta decay. In order to achieve the planned sensitivity the transmission properties of the spectrometer have to be understood with high precision for all initial conditions. For this purpose an electron source has been developed that emits single electrons at adjustable total energy and adjustable emission angle. The emission is pointlike and can be moved across the full flux tube that is imaged onto the detector. Here, we demonstrate that this novel type of electron source can be used to investigate the transmission properties of a MAC-E filter in detail
An angular-selective electron source for the KATRIN experiment
Beck, M; Hein, H; Bauer, S; Baumeister, H; Bonn, J; Ortjohann, H -W; Ostrick, B; Rosendahl, S; Streubel, S; Valerius, K; Zboril, M; Weinheimer, C
2014-01-01
The KATRIN experiment is going to search for the average mass of the electron antineutrino with a sensitivity of 0.2 eV/c2. It uses a retardation spectrometer of MAC-E filter type to accurately measure the shape of the electron spectrum at the endpoint of tritium beta decay. In order to achieve the planned sensitivity the transmission properties of the spectrometer have to be understood with high precision for all initial conditions. For this purpose an electron source has been developed that emits single electrons at adjustable total energy and adjustable emission angle. The emission is pointlike and can be moved across the full flux tube that is imaged onto the detector. Here, we demonstrate that this novel type of electron source can be used to investigate the transmission properties of a MAC-E filter in detail.
Temperature and angular momentum dependence of the quadrupole deformation in sd-shell
P A Ganai; J A Sheikh; I Maqbool; R P Singh
2009-11-01
Temperature and angular momentum dependence of the quadrupole deformation is studied in the middle of the sd-shell for 28Si and 27Si isotopes using the spherical shell model approach. The shell model calculations have been performed using the standard universal sd-shell (USD) interaction and the canonical partition function constructed from the calculated eigensolutions. It is shown that the extracted average quadrupole moments show a transitional behaviour as a function of temperature and the infered transitional temperature is shown to vary with angular momentum. The quadrupole deformation of the individual eigenstate is also analysed.
Temperature and angular momentum dependence of the quadrupole deformation in sd-shell
Ganai, P A; Maqbool, I; Singh, R P
2009-01-01
Temperature and angular momentum dependence of the quadrupole deformation is studied in the middle of the sd-shell for 28Si and 27Si isotopes using the spherical shell model approach. The shell model calculations have been performed using the standard USD interaction and the canonical partition function constructed from the calculated eigen-solutions. It is shown that the extracted average quadrupole moments show a transitional behavior as a function of temperature and the inferred transitional temperature is shown to vary with angular-momentum. The quadrupole deformation of the individual eigen-states is also analyzed.
Unveiling orbital angular momentum and acceleration of light beams and electron beams
Arie, Ady
Special beams, such as the vortex beams that carry orbital angular momentum (OAM) and the Airy beam that preserves its shape while propagating along parabolic trajectory, have drawn significant attention recently both in light optics and in electron optics experiments. In order to utilize these beams, simple methods are needed that enable to easily quantify their defining properties, namely the OAM for the vortex beams and the nodal trajectory acceleration coefficient for the Airy beam. Here we demonstrate a straightforward method to determine these quantities by astigmatic Fourier transform of the beam. For electron beams in a transmission electron microscope, this transformation is easily realized using the condenser and objective stigmators, whereas for light beam this can be achieved using a cylindrical lens. In the case of Laguerre-Gauss vortex beams, it is already well known that applying the astigmatic Fourier transformation converts them to Hermite-Gauss beams. The topological charge (and hence the OAM) can be determined by simply counting the number of dark stripes of the Hermite-Gauss beam. We generated a series of electron vortex beams and managed to determine the topological charge up to a value of 10. The same concept of astigmatic transformation was then used to unveil the acceleration of an electron Airy beam. The shape of astigmatic-transformed depends only on the astigmatic measure and on the acceleration coefficient. This method was experimentally verified by generating electron Airy beams with different known acceleration parameters, enabling direct comparison to the deduced values from the astigmatic transformation measurements. The method can be extended to other types of waves. Specifically, we have recently used it to determine the acceleration of an optical Airy beams and the topological charge of so-called Airy-vortex light beam, i.e. an Airy light beam with an embedded vortex. This work was supported by DIP and the Israel Science
Previous studies have shown that glass displays extracted from mobile phones are suitable as emergency dosimeters in case of an accidental radiation overexposure using the thermoluminescence (TL) method. So far these studies have focused only on recovering the absorbed dose to the material. However, dose in air or dose to the victim carrying the device might be significantly different. Therefore the aim of this work was to investigate photon energy dependence and angular response of glass display used in modern mobile phones. An over-response of about a factor of five is observed for low photon energies compared to the response to Cs-137 (662 keV) which is in reasonable agreement with calculated values mass energy-absorption coefficients of glass and air. Little variation in the energy dependence can be seen for glass displays coming from three different mobile phone models. The angular response for display glass is flat with regard to air kerma within the incident angle of ±60°, independent of the irradiation setup used (with a water phantom or with air kerma reference conditions). For incident angles of 90° the shielding effect of the mobile phones becomes important. With the dosimetric characterization of the photon energy and angular dependencies the absorbed dose in a glass display can be transferred to a reference air kerma dose and provides a useful option for retrospective accident dosimetry. - Highlights: • Determination of the photon energy dependence and angular response for display glass used as an accident dosimeter. • Over-response of about a factor of five for low photon energies. • Flat angular response within incident angles between ±60°
Neutrinoless double beta decay. Electron angular correlation as a probe of new physics
The angular distribution of the final electrons in the so-called long range mechanism of the neutrinoless double beta decay (0ν2β) is derived for the general Lorentz invariant effective Lagrangian. Possible theories beyond the SM are classified from their effects on the angular distribution, which could be used to discriminate among various particle physics models inducing 0ν2β decays. However, additional input on the effective couplings will be required to single out the light Majorana-neutrino mechanism. Alternatively, measurements of the effective neutrino mass and angular distribution in 0ν2β decays can be used to put independent bounds on the parameters of the underlying physics models. This is illustrated for the mass of the right-handed WR boson of the left-right symmetric model for assumed values of the angular correlation coefficient and either the effective Majorana neutrino mass or the half-life of the decay. (Orig.)
Angular dependence of coercivity with temperature in Co-based nanowires
Bran, C., E-mail: cristina.bran@icmm.csic.es [Institute of Materials Science of Madrid, CSIC, 28049 Madrid (Spain); Espejo, A.P. [Departamento de Física, Universidad de Santiago de Chile (USACH) and Center for the Development of Nanoscience and Nanotechnology (CEDENNA), Avenida Ecuador 3493, 9170124 Santiago (Chile); Palmero, E.M. [Institute of Materials Science of Madrid, CSIC, 28049 Madrid (Spain); Escrig, J. [Departamento de Física, Universidad de Santiago de Chile (USACH) and Center for the Development of Nanoscience and Nanotechnology (CEDENNA), Avenida Ecuador 3493, 9170124 Santiago (Chile); Vázquez, M. [Institute of Materials Science of Madrid, CSIC, 28049 Madrid (Spain)
2015-12-15
The magnetic behavior of arrays of Co and CoFe nanowire arrays has been measured in the temperature range between 100 and 300 K. We have paid particular attention to the angular dependence of magnetic properties on the applied magnetic field orientation. The experimental angular dependence of coercivity has been modeled according to micromagnetic analytical calculations, and we found that the propagation of a transversal domain wall mode gives the best fitting with experimental observations. That reversal mode holds in the whole measuring temperature range, for nanowires with different diameters and crystalline structure. Moreover, the quantitative strength of the magnetocrystalline anisotropy and its magnetization easy axis are determined to depend on the crystalline structure and nanowires diameter. The evolution of the magnetocrystalline anisotropy with temperature for nanowires with different composition gives rise to an opposite evolution of coercivity with increasing temperature: it decreases for CoFe while it increases for Co nanowire arrays.
Angular dependence of coercivity with temperature in Co-based nanowires
The magnetic behavior of arrays of Co and CoFe nanowire arrays has been measured in the temperature range between 100 and 300 K. We have paid particular attention to the angular dependence of magnetic properties on the applied magnetic field orientation. The experimental angular dependence of coercivity has been modeled according to micromagnetic analytical calculations, and we found that the propagation of a transversal domain wall mode gives the best fitting with experimental observations. That reversal mode holds in the whole measuring temperature range, for nanowires with different diameters and crystalline structure. Moreover, the quantitative strength of the magnetocrystalline anisotropy and its magnetization easy axis are determined to depend on the crystalline structure and nanowires diameter. The evolution of the magnetocrystalline anisotropy with temperature for nanowires with different composition gives rise to an opposite evolution of coercivity with increasing temperature: it decreases for CoFe while it increases for Co nanowire arrays
Energy and angular dependence of the personal dosemeter in use at ITN-DPRSN
In this paper the characterization of the dosimetry system and of the personal dosemeter in terms of the stability of the reader calibration factors and of the linearity of the response for the 137Cs reference radiation is presented. The energy and angular dependence of the whole body dosemeter are also shown. The energy dependence was determined performing irradiations with the X-ray narrow series beams N30, N40, N60, N80, N100, N120 and with the gamma reference radiations of 137Cs and 60Co [ISO 4037-1, 1996. X and Gamma Reference Radiation for Calibrating Dosemeters and Doserate Meters and for Determining Their Response as a Function of Photon Energy-Part 1: Radiation Characteristics and Production Methods. International Organization for Standardization, Geneva] in terms of Hp(10) incident on the ISO water slab phantom. The angular dependence of the dosemeter was determined for the angles 0 deg., ±20 deg., ±40 deg. and ±60 deg. with normal using the above mentioned radiation fields. All irradiations were performed at the Laboratorio de Metrologia das Radiacoes lonizantes of ITN-DPRSN. The experiments presented in this paper show the thermoluminescence dosimetry (TLD) system is stable and presents a linear behaviour over and extended dose range. The measurements allowed the determination of the energy dependence at normal incidence and of the angular dependence of the dosemeter currently in use. Further studies are being carried out in order to implement correction factors for supralinearity and low energy measurements
Q- and Z-dependence of angular momentum transfer in deeply inelastic collisions of 86Kr with 209Bi
The dependence of the in-plane and out-of-plane angular correlations of fragments from fissioning heavy products on the kinetic energy and Z of the light reaction partner have been measured. From the dependence of the angular correlations on Q-value and hence energy loss, together with existing data from which the total angular-integrated cross section as a function of energy loss can be extracted, the dependence of the angular momentum transferred to the heavy product on the initial orbital angular momentum or impact parameter has been determined. The resulting dependence is qualitatively consistent with the sticking limit for a reaction intermediate of touching deformed fragments. More specific nuclear models generally underestimate the angular momentum transfer, although the one-body proximity-friction model accounts for the major fraction of the angular momentum transfer. A recent model incorporating both one-body proximity friction and collective excitations accounts quite well for the observed angular momentum transfer. The Z-dependence of the anisotropy shows the importance of angular momentum fractionation for the less probable events, where the Z of the fissioning system is appreciably less than that of the target. The transferred angular momentum is shown to be fairly strongly aligned along the perpendicular to the reaction plane, with alignment values of 0.6 to 0.8. The component of angular momentum not along the perpendicular to the reaction plane is found to be primarily oriented perpendicular rather than parallel to the recoil directions. The absolute fission probabilities are found to be qualitatively consistent with J-dependent calculations using the J-values deduced from the angular correlations. (Auth.)
Angular dependence of thermoluminescent dosemeters for gamma and beta radiation in nuclear medicine
The gamma and beta radiation sources are widely used in Nuclear Medicine for diagnostic and therapeutic purposes. Workers of these services receive dose of whole body and end due to the activities of the therapeutic dose preparation and testing, administration radiopharmaceuticals and obtention of image. Hands receive higher doses than other parts of the body. Currently the individual monitoring for the gamma radiation is already well established; However, the determination of the dose due to beta radiation still faces some difficulties. In this work it was studied the angular dependence of thermoluminescent dosemeters detectors in beams of gamma and beta radiation. Detectors of CaSO4:Dy + Teflon produced at IPEN - the Brazilian Institute for Nuclear and Energy Researches - were used. The angular dependence was studied varying the angle between 0 and 180 deg. The results obtained proved to be suitable for use in individual monitoring of workers exposed to beta and gamma radiation
Oliveira, A. B.; Rodriguez-Suarez, R. L.; Michea, S.; Vega, H.; Azevedo, A.; Rezende, S. M.; Aliaga, C.; Denardin, J.
2014-07-01
The angular dependence of the hysteresis shift has been investigated in ferromagnetic/antiferromagnetic (NiFe/IrMn) bilayers grown by oblique deposition under the influence of a static magnetic field applied perpendicular to the uniaxial anisotropy direction induced during the growth process. It was found that at low oblique deposition angles, the unidirectional anisotropy field is much greater than the uniaxial anisotropy field and the corresponding anisotropies directions are noncollinear. In these conditions, the angular dependence of the hysteresis loop shift exhibits the well know cosine like shape but demanding a phase shift. Contrary to this, at high oblique deposition angle (70°), the uniaxial anisotropy plays the fundamental role and the anisotropies directions are collinear. In this case, the exchange bias displays a jump phenomenon. The numerical calculations are consistent with the experimental data obtained from magneto-optical Kerr effect and ferromagnetic resonance.
Angular dependence of recoil proton polarization in high-energy gamma d to p n
We measured the angular dependence of the three recoil proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily.. Transverse polarizations are not well described, but suggest isovector dominance
WIND TURBINE SIMULATION FOR TIME-DEPENDENT ANGULAR VELOCITY, TORQUE, AND POWER
YONGHO LEE
2013-01-01
Albeit the prediction of time-dependent properties of wind turbines is not required for common applications, such time-varying properties may play an important role during transient operations occurring due to various reasons. Unlike the conventional numerical simulations of wind turbine rotations that fix the angular velocity to an assumed value, the present work numerically simulates the time-varying turbine rotation in both unsteady and quasi-steady operation regimes, without specifying th...
An Extended Greuling-Goertzel Approximation with a Pn-Approximation in the Angular Dependence
The slowing-down spectrum has been calculated for different media. It is given in slab geometry as a function of space at the beginning of the epithermal region (10 eV). The angular dependence is also shown. The basic method is that given by E. Greuling, F. Clark and G. Goertzel in a NDA report, but in this report it is permissible to include more terms in the legendre expansion
The first-order neutron transport equation is solved by the least-squares finite element method based on the discrete ordinates discretization. The angular dependent rebalance (ADR) acceleration arithmetic and its extrapolate method are given. The numerical results of some benchmark problems demonstrate that the arithmetic can shorten the CPU time to 34% ∼ 50% and it is effective even for the strong scattering problem. (authors)
Angular dependence of recoil proton polarization in high-energy \\gamma d \\to p n
X. Jiang; J. Arrington; F. Benmokhtar; A. Camsonne; J.P. Chen; S. Choi; E. Chudakov; F. Cusanno; A. Deur; D. Dutta; F. Garibaldi; D. Gaskell; O. Gayou; R. Gilman; C. Glashauser; D. Hamilton; O. Hansen; D.W. Higinbotham; R.J. Holt; C.W. de Jager; M.K. Jones; L.J. Kaufman; E.R. Kinney; K. Kramer; L. Lagamba; R. de Leo; J. Lerose; D. Lhuillier; R. Lindgren; N. Liyanage; K. McCormick; Z.-E. Meziani; R. Michaels; B. Moffit; P. Monaghan; S. Nanda; K.D. Paschke; C.F. Perdrisat; V. Punjabi; I.A. Qattan; R.D. Ransome; P.E. Reimer; B. Reitz; A. Saha; E.C. Schulte; R. Sheyor; K. Slifer; P. Solvignon; V. Sulkosky; G.M. Urciuoli; E. Voutier; K. Wang; K. Wijesooriya; B. Wojtsekhowski; L. Zhu
2007-02-26
We measured the angular dependence of the three recoil proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily.. Transverse polarizations are not well described, but suggest isovector dominance.
Angular dependence of recoil proton polarization in high-energy \\gamma d \\to p n
Jiang, X; Benmokhtar, F; Camsonne, A; Chen, J P; Choi, S; Chudakov, E; Cusanno, F; De Jager, C W; De Leo, R; Deur, A; Dutta, D; Garibaldi, F; Gaskell, D; Gayou, O; Gilman, R; Glashauser, C; Hamilton, D; Hansen, O; Higinbotham, D W; Holt, R J; Jones, M K; Kaufman, L J; Kinney, E R; Krämer, K; Lagamba, L; Lerose, J; Lhuillier, D; Lindgren, R; Liyanage, N; McCormick, K; Meziani, Z E; Michaels, R; Moffit, B; Monaghan, P; Nanda, S; Paschke, K D; Perdrisat, C F; Punjabi, V; Qattan, I A; Ransome, R D; Reimer, P E; Reitz, B; Saha, A; Schulte, E C; Sheyor, R; Slifer, K J; Solvignon, P; Sulkosky, V; Urciuoli, G M; Voutier, E; Wang, K; Wijesooriya, K; Wojtsekhowski, B; Zhu, L
2007-01-01
We measured the angular dependence of the three recoil proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily.. Transverse polarizations are not well described, but suggest isovector dominance.
Liu, Hongxue; Lu, Jiwei; Wolf, Stuart; Hodgson, Jim; Rutgers, Maarten
2013-01-01
We demonstrate a versatile variable field module (VFM) with capability of both field and angular dependent measurements up to 1800 Oe for scanning probe system. The magnetic field strength is changed by adjusting the distance between a rare earth magnet and the probe tip and is monitored in-situ by a built-in Hall sensor. Rotating the magnet allows the field vector to change from the horizontal to vertical direction and makes it possible to do angular dependent measurements. The capability of the VFM system is demonstrated by degaussing a floppy disk media with increasing magnetic field. Angular dependent measurements clearly show the evolution of magnetic domain structures, with a completely reversible magnetic force microscopy phase contrast observed when the magnetic field is rotated by 180{\\deg}. A further demonstration of out-of-plane and in-plane magnetic switching of CoFe2O4 pillars in CoFe2O4-BiFeO3 nanocomposites was presented and discussed.
Angular distribution of neutral hydrogen following collisional electron detachment from H-
The angular distribution of neutral hydrogen following electron detachment from H- has been measured for H- on nitrogen and hydrogen gas, both for neutral atoms left in the 2S state, and for all neutrals independent of the state of excitation. The results are essentially in agreement with calculations based on the Born approximation, although there is some disagreement in detail
Electron-photon angular correlation measurements for the 2 1P state of helium
Electron-photon angular correlations have been measured by detecting in delayed coincidence, electrons inelastically scattered from helium and photons emitted in decays from the 21P state at incident electron energies of 60 and 80 eV. Analysis of the data yields values for the ratio lambda of the differential cross sections for magnetic sublevel excitations and the phase difference X between the corresponding probability amplitudes. The measurements extend over the angular range 10-1200 of electron scattering angles. The present data are in good agreement with the experimental results of Hollywood et al, (J. Phys. B.; 12: 819 (1979)), and show a marked discrepancy at large scattering angles with the recent data of Steph and Golde. (Phys. Rev.; A in press (1980)). The experimental results are compared with some recent theories. (author)
Angular dependent torque measurements on CaFe0.88Co0.12AsF
Xiao, H.; Gao, B.; Ma, Y. H.; Li, X. J.; Mu, G.; Hu, T.
2016-08-01
Out-of-plane angular dependent torque measurements were performed on CaFe0.88Co0.12AsF (Ca1 1 1 1) single crystals. In the normal state, the torque data shows \\sin 2θ angular dependence and H 2 magnetic field dependence, as a result of paramagnetism. In the mixed state, the torque signal is a combination of the vortex torque and paramagnetic torque, and the former allows the determination of the anisotropy parameter γ. At T = 11.5 K, γ (11.5 K ≃ 0.5 T c) = 19.1, which is similar to the result of SmFeAsO0.8F0.2, γ ≃ 23 at T≃ 0.4{{T}\\text{c}} . So the 11 1 1 is more anisotropic compared to 11 and 122 families of iron-based superconductors. This may suggest that the electronic coupling between layers in 1 1 1 1 is less effective than in 11 and 122 families.
Resonant structure of the 3d electron's angular distribution in a free Mn+Ion
The 3d-electron angular anisotropy parameter of the free Mn+ ion is calculated using the open-quotes spin-polarizedclose quotes random-phase approximation with exchange. Strong resonance structure is discovered, which is due to interference with the powerful 3p → 3d discrete excitation. The effect of the 3p → 4s transition is also noticeable. The ordering of these respective resonances with phonon energy increase proved to be opposite in angular anisotropy parameter to that in 3d-photoionization cross section. A paper describing these results was published
WIND TURBINE SIMULATION FOR TIME-DEPENDENT ANGULAR VELOCITY, TORQUE, AND POWER
YONGHO LEE
2013-02-01
Full Text Available Albeit the prediction of time-dependent properties of wind turbines is not required for common applications, such time-varying properties may play an important role during transient operations occurring due to various reasons. Unlike the conventional numerical simulations of wind turbine rotations that fix the angular velocity to an assumed value, the present work numerically simulates the time-varying turbine rotation in both unsteady and quasi-steady operation regimes, without specifying the angular velocity of the turbine a priori, but by calculating the actual time-dependent angular velocity and aerodynamic torque along with other properties in the course of simulation. In the present work, successful results obtained by an efficient computational fluid dynamics technique are shown, as a demonstration, for a vertical-axis wind turbine with a two-dimensionalSavonius rotor, and the cycle-averaged output powers are compared with experimental power curves and a theory developed on the basis of experimental observations.
Angular correlations in multi-jet final states from k perpendicularto -dependent parton showers
Angular correlations in final states with multiple hadronic jets have recently been measured in DIS production at HERA. Next-to-leading-order QCD results for these observables turn out to be affected by sizeable theoretical uncertainties in the kinematic region of the data. We investigate the effects of multiple QCD radiation at higher order using parton-shower methods based on transverse-momentum dependent parton distributions and matrix elements. We observe that significant contributions to the angular correlations measured in three-jet production arise from regions in which transverse momenta in the initial-state shower are not ordered. We present Monte Carlo results for azimuthal two-jet and three-jet distributions, for jet multiplicities and for correlations in the transverse-momentum imbalance between the leading jets. We discuss the comparison with experimental data. (orig.)
Study of angular dependences of ion component parameters in CO2-laser-produced plasma
CO2-laser-produced plasma ion component parameters were studied for aluminium and lead targets at laser intensity of P = 4x1013 W cm-2 and pulse duration of τ = 15 ns experimentally and numerically. Angular dependences of ion number density for different charge states, average velocity and its spread were measured by time-of-flight method. Ion charge state distribution shows high-charge and low-charge state groups at normal expansion direction. Ions in these groups have different average expansion velocity and longitudinal velocity spread. Angular distribution of high-charge states is narrower than that of the low-charge state ion group, maximum yield of low-charge states occur at some angle from normal. For Al target results show similar trends as for Pb target, but simulations have indicated that the effect of laser ponderomotive force is more pronounced in this case
Angular dependence of OSL commercial detectors in standard beta radiation beams
Full text: Optical stimulated luminescence (OSL) is a very successful dosimetry technique, in particular using the Al2O3:C crystals as dosimeter. This detector has become the main OSL material as a personal dosimeter. Commercial dosimeters of Al2O3:C have been developed and tested; however, most of the tests have been performed with gamma beams. Beta radiation dosimetry might be performed with Al2O3:C detectors, if the crystals are sufficient thin to avoid the radiation attenuation. The dosimeter thickness is also important to allow a satisfactory accuracy of the measured dose, despite the incidence radiation angle or the beta energy. Previous studies show that the Al2O3:C dosimeters present a very high energy dependence that can be minimized by using filters. This work aims to compare the angular dependence of commercial Al2O3:C dosimeters with and without the filters used to minimize the beta energy dependence of Al2O3:C, when the detectors were exposed to standard beta beams. The beta irradiations of the OSL detectors were performed using the beta secondary standard system of the Calibration Laboratory at IPEN, with 90Sr + 90Y, 85Kr and 147Pm sources, manufactured by Buchler GmbH and Co, Germany, calibrated by the primary standard laboratory Physikalisch-Technische Bundesanstalt (PTB), Germany. The OSL measurements were evaluated using a microStar reader and software of Landauer. The angular dependence was determined by using a goniometer. The incident radiation angle was varied from 0 deg to 180 deg. The results show that that the angular dependence curves present similar behavior, despite the use of filters
L-subshell resolved photon angular distribution of radiative electron capture into He-like uranium
The photon angular distributions for radiative electron capture (REC) into the j=1/2 and j=3/2 L-subshell levels were measured and calculated for U90+→C collisions at 89 MeV/u. The experiment provides the first study of the photon angular distribution of REC into a projectile p-state (j=3/2) which was found to exhibit a slight backward peaking in the laboratory frame. For radiative capture to the j=1/2 states the measured angular distribution deviates considerably from symmetry around 90 . The results demonstrate that the usual sin2θlab distribution is not valid in the high-Z regime. (orig.)
Electronic Properties of Tin and Bismuth from Angular Correlation of Annihilation Photons
Mogensen, O.E.; Trumpy, Georg
1969-01-01
liquid-metal curves are smaller and of another form than the tails of polycrystalline curves; no Gaussian with only one adjustable constant factor can give a fit to both tails. No useful method for interpreting liquid-metal angular-correlation curves seems to exist. Two deformed bismuth samples gave......A linear slit setup has been used to obtain results of angular-correlation measurements in (a) tin single crystals in three orientations: [001], [100], and [110], (b) bismuth single crystals in four orientations: [111], [100], [1¯10], and [2¯1¯1], (c) solid and liquid tin and bismuth, and (d......) deformed bismuth. For both metals, the single-crystal angular-correlation curves lie near to the free-electron parabola. The tin curves show more anisotropy than the bismuth curves. An important result is the clear anisotropy found in the high-momentum part of the curves—the tails—for both metals. Little...
Depth dose and angular dose distribution experiments with high energy electron-photon radiation
India's first synchrotron radiation source, Indus-1, is commissioned at the Centre for Advanced Technology (CAT), Indore. Radiation environment of this facility is quite different in comparison to that of nuclear or irradiator facilities and proton or heavy ion accelerator facilities. The primary particle accelerated being the electron, the radiation environment mainly comprises of Bremsstrahlung photons followed by photo-neutrons, whereas electron contamination too exists within the containment area. Due to the complex nature of the radiation viz. high energy, broad energy spectrum, pulsed, mixed field, sharp angular distribution etc. quantification of radiation dose becomes a difficult task. In this paper, experiments on depth dose and angular dose distribution done with 450 MeV electron-photon radiation are described
On the angular dependence of the photoemission time delay in helium
Ivanov, I A; Lindroth, E; Kheifets, A S
2016-01-01
We investigate an angular dependence of the photoemission time delay in helium as measured by the RABBITT (Reconstruction of Attosecond Beating By Interference of Two-photon Transitions) technique. The measured time delay $ \\tau_a=\\tau_W+\\tau_{cc} $ contains two distinct components: the Wigner time delay $\\tau_W$ and the continuum-continuum CC) correction $\\tau_{cc}$. In the case of helium with only one $1s\\to Ep$ photoemission channel, the Wigner time delay $\\tau_W$ does not depend on the photoelectron detection angle relative to the polarization vector. However, the CC correction $\\tau_{cc}$ shows a noticeable angular dependence. We illustrate these findings by performing two sets of calculations. In the first set, we solve the time-dependent Schr\\"odinger equation for the helium atom ionized by an attosecond pulse train and probed by an IR pulse. In the second approach, we employ the lowest order perturbation theory which describes absorption of the XUV and IR photons. Both calculations produce close resul...
Angular-momentum-dominated electron beams and flat-beam generation
Sun, Yin-e
2005-06-01
In the absence of external forces, if the dynamics within an electron beam is dominated by its angular momentum rather than other effects such as random thermal motion or self Coulomb-repulsive force (i.e., space-charge force), the beam is said to be angular-momentum-dominated. Such a beam can be directly applied to the field of electron-cooling of heavy ions; or it can be manipulated into an electron beam with large transverse emittance ratio, i.e., a flat beam. A flat beam is of interest for high-energy electron-positron colliders or accelerator-based light sources. An angular-momentum-dominated beam is generated at the Fermilab/NICADD photoinjector Laboratory (FNPL) and is accelerated to an energy of 16 MeV. The properties of such a beam is investigated systematically in experiment. The experimental results are in very good agreement with analytical expectations and simulation results. This lays a good foundation for the transformation of an angular-momentum-dominated beam into a flat beam. The round-to-flat beam transformer is composed of three skew quadrupoles. Based on a good knowledge of the angular-momentum-dominated beam, the quadrupoles are set to the proper strengths in order to apply a total torque which removes the angular momentum, resulting in a flat beam. For bunch charge around 0.5 nC, an emittance ratio of 100 {+-} 5 was measured, with the smaller normalized root-mean-square emittance around 0.4 mm-mrad. Effects limiting the flat-beam emittance ratio are investigated, such as the chromatic effects in the round-to-flat beam transformer, asymmetry in the initial angular-momentum-dominated beam, and space-charge effects. The most important limiting factor turns out to be the uncorrelated emittance growth caused by space charge when the beam energy is low, for example, in the rf gun area. As a result of such emittance growth prior to the round-to-flat beam transformer, the emittance ratio achievable in simulation decreases from orders of thousands to
Complete and incomplete jump phenomenon in the angular dependence of the noncollinear exchange bias
The angular dependence of the exchange bias (ADEB) has been investigated in detail for ferromagnetic/antiferromagnetic bilayers with noncollinear uniaxial and unidirectional anisotropies. Two different types of the jump phenomenon, complete and incomplete jump phenomena, have been proved to occur at the orientations of the intrinsic easy and hard axes. A special position for the intrinsic easy and hard axes, which makes an angular deviation of 58.2826° from the uniaixal anisotropy axis, has been deduced by analyzing the magnetization reversal processes based on the principle of minimal energy. When the angular deviation of the intrinsic easy or hard axis from the uniaxial anisotropy axis is above the critical value of 58.2826°, the complete jump phenomenon will be shown in the ADEB. On the contrary, once this angular deviation is not more than 58.2826°, the incomplete jump phenomenon occurs, and the critical angle will be observed in the ADEB. The determined formula of the critical angle is also obtained by analyzing the magnetization reversal processes. Additionally, the extreme value problem of the exchange bias is studied in this paper. The coercivity always reaches its maximum value when the external field points along the intrinsic easy axis. The minimal coercivity occurs at the orientation of the critical angle. However, there are two orientations of the applied field to gain the maximal exchange bias field. One is the direction of the intrinsic hard axis when the complete jump phenomenon occurs at this orientation. The other one is the orientation of the critical angle under the condition that the incomplete jump phenomenon takes place at the intrinsic hard axis. The numerical calculations are consistent with the involved experimental observations, indicating that our method is valid to study the ADEB and it is an effective method to achieve the maximal exchange bias field as well as the maximal or minimal coercivity by adjusting the orientation of the
Equivalence between deep energy-dependent and shallow angular momentum dependent potentials
Recently Baye showed that supersymmetry can be applied to determine a shallow l-dependent potential phase equivalent to a deep potential, assumed to be energy-independent and have Panli forbidden states (PFS), for α-α scattering. The PFS are eliminated by this procedure. Such deep potentials are generated as equivalent local potentials (ELP) to the Resonating Group Model (RGM) and are generally energy-dependent. To eliminate this E-dependence as required for the application of Baye's method, l-dependent, but E-independent, deep local potentials were generated by the exact inversion method of Marchenko. Subsequently, the supersymmetric method was used to eliminate the PFS, ensuring that the generalized Levinson theorem is satisfied. As an example, the method was applied to the simple model of two dineutrons scattering in the RGM, where the deep ELP of Horiuchi has a substantial energy-dependence and one PFS only for l=O. 16 refs., 5 figs
Angular dependence of the spin textures in two-dimensional chiral magnets
Tang, Dan [Institute of Materials Physics and Chemistry, Northeastern University, Shenyang 110004 (China); Institute of Applied Physics and Technology, Liaoning Technical University, Huludao 125105 (China); Qi, Yang, E-mail: qiyang@imp.neu.edu.cn [Institute of Materials Physics and Chemistry, Northeastern University, Shenyang 110004 (China)
2015-05-28
The angular dependence of spin textures in thin helimagnetic films is investigated by a Monte Carlo simulation. When an external field is applied at an angle relative to the film normal, we find that the skyrmion states with broken axis-symmetric structure are able to persist over a wide range of angles by changing the spin orientation. In addition, the uniaxial anisotropy is able to stabilize the distorted skyrmions. This behavior reflects the robust topological stability of skyrmion states in helimagnets and favors their application in spintronic devices.
Effect of Angular Velocity on Sensors Based on Morphology Dependent Resonances
Amir R. Ali
2014-04-01
Full Text Available We carried out an analysis to investigate the morphology dependent optical resonances shift (MDR of a rotating spherical resonator. The spinning resonator experiences an elastic deformation due to the centrifugal force acting on it, leading to a shift in its MDR. Experiments are also carried out to demonstrate the MDR shifts of a spinning polydimethylsiloxane (PDMS microsphere. The experimental results agree well with the analytical prediction. These studies demonstrated that spinning sensor based on MDR may experience sufficient shift in the optical resonances, therefore interfering with its desirable operational sensor design. Also the results show that angular velocity sensors could be designed using this principle.
Effect of angular velocity on sensors based on morphology dependent resonances.
Ali, Amir R; Ioppolo, Tindaro
2014-01-01
We carried out an analysis to investigate the morphology dependent optical resonances shift (MDR) of a rotating spherical resonator. The spinning resonator experiences an elastic deformation due to the centrifugal force acting on it, leading to a shift in its MDR. Experiments are also carried out to demonstrate the MDR shifts of a spinning polydimethylsiloxane (PDMS) microsphere. The experimental results agree well with the analytical prediction. These studies demonstrated that spinning sensor based on MDR may experience sufficient shift in the optical resonances, therefore interfering with its desirable operational sensor design. Also the results show that angular velocity sensors could be designed using this principle. PMID:24759108
Russo, Juan M.; Castillo, Jose E.; Aspnes, Eric D.; Kostuk, Raymond K.; Rosenberg, Glenn
2010-08-01
Dual aperture holographic planar concentrator (DA-HPC) technology consists of bifacial cells separated by strips of holographic film that diffract the light from the spacing into the cells for direct incident, diffuse, roof-reflected and albedo irradiance. The holographic film is angularly dependent of the seasonal sun angle. DA-HPC modules are compared to single aperture conventional modules for clear and cloudy days as well as for a seasonal period of eight months. Direct-current IV and alternating-current power curves are used to compare modules with comparable silicon active area and cell efficiency.
Angular-dependent interatomic potential for the aluminum-hydrogen system
Apostol, F.; Mishin, Y.
2010-10-01
We report on the development of an angular-dependent interatomic potential for hydrogen and the aluminum-hydrogen system. The potential reproduces properties of diatomic hydrogen gas, accurate solution energies of hydrogen atoms in crystalline Al, the energetic preference of the tetrahedral interstitial site occupation over octahedral, the hydrogen diffusion barrier in Al, and a number of other properties. Some of the results predicted by the potential have been tested by molecular dynamics simulations. It is suggested that the new potential can be used in atomistic simulations of the effect of dissolved hydrogen on deformation and fracture of Al, a problem which is relevant to hydrogen-induced degradation of Al alloys.
Angular dependence of the coercivity and remanence of ordered arrays of Co nanowires
The angular dependence of the coercivity and remanence of ordered hexagonal arrays of Co nanowires prepared using anodic aluminum oxide templates was investigated. The experimental evolution of coercivity as a function of the angle, in which the external field is applied, is interpreted considering micromagnetic simulations. Depending on the angle between the axis of the wire and the applied magnetic field direction our results show that the magnetization reversal mode changes from vortex to a transverse domain wall. Besides, we observed that the dipolar interactions cause a reduction in coercive fields, mainly in the direction of easy magnetization of the nanowires. Good agreement between numerical and experimental data is obtained. - Highlights: ► Angular dependence of the coercivity and remanence of Co nanowire arrays. ► Results show that the magnetization reversal mode changes from vortex to a transverse domain wall. ► Dipolar interactions cause a reduction in coercive fields, which is the strongest in the direction of easy magnetization of the nanowire.
Angular dependence of the FMR linewidth and the anisotropy of the relaxation time in iron garnets
Kobelev, A. V.; Shvachko, Yu. N.; Ustinov, V. V.
2016-01-01
This work is devoted to the problem of extracting the contribution of the anisotropy of relaxation to the angular dependence of the FMR linewidth and to the opportunity of determining the values of the parameters of relaxation. The results of the FMR study of films based on the yttrium iron garnet prepared by the method of liquid-phase epitaxy are given. The orientational dependence of the linewidth has been calculated using the traditional method of measuring an FMR spectrum and a method based on scanning at an angle to the resonance field for obtaining the minimum linewidth. A model for calculating the linewidth has been proposed that takes into account the anisotropy of the relaxation term in the equation of motion of the magnetic moment. The model leads to a dependence that agrees well with the experimental data, which makes it possible to state that the anisotropy of relaxation most likely takes place in the samples under consideration at the temperatures employed.
Smeenk, C.T.L.; Arissian, L; Sokolov, A. V.; Spanner, M.; Lee, K F; Staudte, A.; Villeneuve, D. M.; Corkum, P B
2013-01-01
The multiphoton ionization rate of molecules depends on the alignment of the molecular axis with respect to the ionizing laser polarization. By studying molecular frame photo-electron angular distributions from N$_2$, O$_2$ and benzene, we illustrate how the angle-dependent ionization rate affects the photo-electron cutoff energy. We find alignment can enhance the high energy cutoff of the photo-electron spectrum when probing along a nodal plane or when ionization is otherwise suppressed. Thi...
The magnetic field generated by an electron bound in angular-momentum eigenstates
The magnetic field generated by an electron bound in a spherically symmetric potential is calculated for eigenstates of the orbital and total angular momentum. General expressions are presented for the current density in such states and the magnetic field is calculated through the vector potential, which is obtained from the current density by direct integration. The method is applied to the hydrogen atom, for which we reproduce and extend known results. (author)
Research on the the device of non-angular vibration for opto-electronic platform
An, Yuan; Song, Chun-peng; Kuang, Rong-jun; Jin, Guang
2010-10-01
The opto-electronic platform is the main equipment for aviation reconnaissance. It is a surveillance system with the function of search, recognition orientation and tracking by opto- electronic instruments. It is made up of opto- electronic instruments which are used to get high quality image , and stabilization tracking system to control stabilization and gesture of platform for exact tracking. The opto-electronic platform purpose is to achieve high quality image. Besides the impact of optic system, the image quality of the system is influenced greatly in the vibration environment .The research worked by Zhao peng which demonstrated the affection caused by angular vibration was worse than which caused by line vibration, and what was multiplied direct ratio with plane altitude. So it is necessary to design a new device which could be used widely and has good angular vibration isolation effect. According to the theory of parallelogram, the non-angular vibration device had been designed with spatial links, and the theory of non-angular vibration was analyzed. The three-dimensional model was set with UG, the analysis was done by ADAMS/vibration software. The acceleration and displacement response of the device in each direction was calculated by inspiriting it with sine wave of the acceleration in three directions, and the stiffness and damp were studied. All the work prove the design principle of the device is reasonable, and the device is adopted to keep the platform motion moving horizontally, at the meantime the device is good at isolating vibration in all directions.
Energy-dependent photoelectron angular distributions from two-color two-photon above threshold ionizations are investigated to determine the partial-wave characteristics of free-free electronic transitions in helium. Sideband photoelectron energies ranging from 0.18 to 13.0 eV are measured with different wavelengths of the perturbative infrared dressing field as well as different individually selected high-order harmonics. Using the experimentally measured cross-section ratios and anisotropy parameters together with analytical expressions derived from second-order perturbation theory, the partial-wave branching fractions going to the S and D waves in the positive and negative sidebands are determined as a function of photoelectron kinetic energy. The results provide a sensitive test for theoretical models of two-color two-photon above threshold ionization in atoms and molecules.
Matsuura, Yutaka; Kitai, Nobuyuki; Hosokawa, Seiichi; Hoshijima, Jun
2016-08-01
The relation of the coercive force decrease ratio (CFDR) and the angular dependence of the coercive force (ADCF) of ferrite magnets and their temperature properties were investigated. When we compared that against the angle of the magnetization reverse area obtained from these calculation results, which was obtained from the Gaussian distribution of the grain alignment and the postulation that every grain follows the Kondorskii law or the 1/cos θ law, and against the angle of the reverse magnetization area calculated from the experiment CFDR data of these magnets, it was found that this latter expanded at room temperature, to 36° from the calculated angle, for magnet with α=0.96. It was also found that, as temperature increased from room temperature to 413 K, the angle of the reverse magnetization area of ferrite magnets obtained from the experiment data expanded from 36° to 41°. When we apply these results to the temperature properties of ADCF, it seems that the calculated ADCF could qualitatively and reasonably explain these temperature properties, even though the difference between the calculated angular dependence and the experimental data still exists in the high angle range. These results strongly suggest that the coercive force of these magnets is determined by the magnetic domain wall motion. The magnetic domain walls are strongly pinned at tilted grains, and when the domain walls are de-pinned from their pinning sites, the coercive force is determined.
Radiation management departments place more emphasis on the accuracy of measurements than on the increase in the average dose and personal exposure dose from the use of radiation equipment and radioactive isotopes. Although current measurements are taken using devices, such as film badge dosimeters, pocket dosimeters and thermoluminescent dosimeters (TLDs), this study compared the angular dependence between the widely used TLDs and photoluminescent dosimeter (PLDs) in order to present primary data and evaluate the utility of PLD as a new dosimeter device. For X-ray fluoroscopy, a whole body phantom was placed on a table with a setting for the G-I technical factors fixed at a range of approximately 40 cm with a range of ±90o at an interval scale of 15o from the center location of an average radiological worker for PLDs (GD-450) and TLDs (Carot). This process was repeated 10 times, and at each time, the cumulative dosage was interpreted from 130 dosimeters using TLDs (UD-710R, Panasonic) and PLDs (FGD-650). The TLD and PLD showed a 52% and 23% decrease in the depth dosage from 0o to -90o, respectively. Therefore, PLDs have a lower angular dependence than TLDs.
Dong, Kyung-Rae [Department of Radiological Technology, Gwangju Health College University (Korea, Republic of); Department of Nuclear Engineering, Chosun University (Korea, Republic of); Kweon, Dae Cheol [Department of Radiologic Science, Shin Heung College University (Korea, Republic of); Chung, Woon-Kwan, E-mail: wkchung@chosun.ac.kr [Department of Nuclear Engineering, Chosun University (Korea, Republic of); Goo, Eun-Hoe [Department of Diagnostic Radiology, Seoul National University Hospital (Korea, Republic of); Department of Physics, Soonchunhyang University (Korea, Republic of); Dieter, Kevin [Department of Physical Therapy, Gwangju Health College University (Korea, Republic of); Choe, Chong-Hwan [Department of White Memorial Medical Center (United States)
2011-02-15
Radiation management departments place more emphasis on the accuracy of measurements than on the increase in the average dose and personal exposure dose from the use of radiation equipment and radioactive isotopes. Although current measurements are taken using devices, such as film badge dosimeters, pocket dosimeters and thermoluminescent dosimeters (TLDs), this study compared the angular dependence between the widely used TLDs and photoluminescent dosimeter (PLDs) in order to present primary data and evaluate the utility of PLD as a new dosimeter device. For X-ray fluoroscopy, a whole body phantom was placed on a table with a setting for the G-I technical factors fixed at a range of approximately 40 cm with a range of {+-}90{sup o} at an interval scale of 15{sup o} from the center location of an average radiological worker for PLDs (GD-450) and TLDs (Carot). This process was repeated 10 times, and at each time, the cumulative dosage was interpreted from 130 dosimeters using TLDs (UD-710R, Panasonic) and PLDs (FGD-650). The TLD and PLD showed a 52% and 23% decrease in the depth dosage from 0{sup o} to -90{sup o}, respectively. Therefore, PLDs have a lower angular dependence than TLDs.
We present quantifiable images of the angular distributions (AD's) of parametric x radiation (PXR), and vacuum-ultraviolet transition radiation (vuv TR) from 230 MeV electrons interacting with a silicon crystal. Both AD's are highly polarized. The vuv TR and optical TR data provide measurements of the beam energy and effective divergence angle. Using these quantities and separately known values of the electronic susceptibility |χ0|, we show that the measured PXR AD is in good agreement with the predictions of single crystal theory. Our analysis suggests a method to measure |χ0| using PXR AD's
Angular dependence of depth doses in a tissue slab irradiated with monoenergetic photons
This report presents dose equivalents from external photon irradiation, normalised to air kerma free in air, on the central axis of a cuboid slab of ICRU tissue for various depths, photon energies and angles of beam incidence. The data were calculated by a Monte Carlo method using an idealised planar parallel source of monoenergetic photons. The data presented here aim at facilitating the calibration of individual dosimeters; they provide also an estimate of the quantity 'personal dose equivalent' defined by the ICRU. A detailed evaluation of the dependence of the calculated conversion coefficients on depth in the slab, photon energy and angle of incidence is given. A comparison with published measured an calculated values of angular dependence factors is made. (orig.)
Using the computer experiment methods directional effects of relativistic electrons' coherent reflection from crystal surface at glancing incidence were studied in conditions when it is due to multiple transversal scattering of particles by atomic chains (axial surface channeling). Directional dependencies of backscattering coefficients, ranges and depths of reflected electrons' penetration in crystal and their angular distributions have been calculated. It has allowed to elicit the directional effects of strings that lead to reflection at grazing angles close to the beam incident angle with respect to atomic chain as well as kinetic effects of surface plane that result in specular reflection and dominate at large beam misalignments with respect to low-index crystallographic directions
Gibson, S T; Cavanagh, S J; Lewis, B R [Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia); Gascooke, J R [School of Chemistry, Physics and Earth Sciences, Flinders University, SA 5001 (Australia); Mabbs, R [Department of Chemistry, Washington University, St Louis MO 63930-4899 (United States); Sanov, A, E-mail: Stephen.Gibson@anu.edu.a, E-mail: Steven.Cavanagh@anu.edu.a [Department of Chemistry, University of Arizona, Tucson AZ 85721-0041 (United States)
2009-11-01
The photodetachment spectrum of O{sub 2}{sup -} has been measured at a number of wavelengths using velocity-map imaging. The electron kinetic-energy resolution (< 5 meV) is sufficient to resolve the anion fine-structure splitting, vibrational and electronic structure. The electron angular distribution varies with the electron kinetic-energy, with a different behaviour for each vibronic band.
Measurement of the Angular Distribution of Electrons from $W\\to e\
Abbott, B
2001-01-01
We present a preliminary measurement of the electron angular distribution parameter alpha2 in W to e nu events using data collected by the D0 detector during the 1994--1995 Tevatron run. We compare our results with next-to-leading order perturbative QCD, which predicts an angular distribution of 1 +/- alpha1 cos theta* +alpha_2 cos^2 theta*, where theta* is the angle between the charged lepton and the antiproton in the Collins-Soper frame. In the presence of QCD corrections, the parameters alpha1 and alpha2 become functions of pT(W), the W boson transverse momentum. We present the first measurement of alpha_2 as a function of pT(W). This measurement is of importance, because it provides a test of next-to-leading order QCD corrections which are a non-negligible contribution to the W mass measurement.
Influence of the angular scattering of electrons on the runaway threshold in air
Chanrion, O.; Bonaventura, Z.; Bourdon, A.;
2016-01-01
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...... 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....... 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...
Paris-Mandoki, Asaf; Gorniaczyk, Hannes; Tresp, Christoph; Mirgorodskiy, Ivan; Hofferberth, Sebastian
2016-08-01
Förster resonances provide a highly flexible tool to tune both the strength and the angular shape of interactions between two Rydberg atoms. We give a detailed explanation about how Förster resonances can be found by searching through a large range of possible quantum number combinations. We apply our search method to SS, SD and DD pair states of 87Rb with principal quantum numbers from 30 to 100, taking into account the fine structure splitting of the Rydberg states. We find various strong resonances between atoms with a large difference in principal quantum numbers. We quantify the strength of these resonances by introducing a figure of merit {\\tilde{C}}3 which is independent of the magnetic quantum numbers and geometry to classify the resonances by interaction strength. We further predict to what extent excitation exchange is possible on different resonances and point out limitations of the coherent hopping process. Finally, we discuss the angular dependence of the dipole–dipole interaction and its tunability near resonances.
Paris-Mandoki, Asaf; Tresp, Christoph; Mirgorodskiy, Ivan; Hofferberth, Sebastian
2016-01-01
F\\"orster resonances provide a highly flexible tool to tune both the strength and the angular shape of interactions between two Rydberg atoms. We give a detailed explanation about how F\\"orster resonances can be found by searching through a large range of possible quantum number combinations. We apply our search method to $SS$, $SD$ and $DD$ pair states of $^{87}$Rb with principal quantum numbers from 30 to 100, taking into account the fine structure splitting of the Rydberg states. We find various strong resonances between atoms with a large difference in principal quantum numbers. We quantify the strength of these resonances by introducing a figure of merit $\\tilde C_3$ which is independent of the magnetic quantum number and geometry to classify the resonances by interaction strength. We further predict to what extent interaction exchange is possible on different resonances and point out limitations of the coherent hopping process. Finally, we discuss the angular dependence of the dipole-dipole interaction ...
Plimley, Brian; Coffer, Amy; Zhang, Yigong; Vetter, Kai
2016-08-01
Previously, scientific silicon charge-coupled devices (CCDs) with 10.5-μm pixel pitch and a thick (650 μm), fully depleted bulk have been used to measure gamma-ray-induced fast electrons and demonstrate electron track Compton imaging. A model of the response of this CCD was also developed and benchmarked to experiment using Monte Carlo electron tracks. We now examine the trade-off in pixel pitch and electronic noise. We extend our CCD response model to different pixel pitch and readout noise per pixel, including pixel pitch of 2.5 μm, 5 μm, 10.5 μm, 20 μm, and 40 μm, and readout noise from 0 eV/pixel to 2 keV/pixel for 10.5 μm pixel pitch. The CCD images generated by this model using simulated electron tracks are processed by our trajectory reconstruction algorithm. The performance of the reconstruction algorithm defines the expected angular sensitivity as a function of electron energy, CCD pixel pitch, and readout noise per pixel. Results show that our existing pixel pitch of 10.5 μm is near optimal for our approach, because smaller pixels add little new information but are subject to greater statistical noise. In addition, we measured the readout noise per pixel for two different device temperatures in order to estimate the effect of temperature on the reconstruction algorithm performance, although the readout is not optimized for higher temperatures. The noise in our device at 240 K increases the FWHM of angular measurement error by no more than a factor of 2, from 26° to 49° FWHM for electrons between 425 keV and 480 keV. Therefore, a CCD could be used for electron-track-based imaging in a Peltier-cooled device.
Angular dependence study on dose distribution of MatriXX 2-D chamber array
With the gantry angles of 0 degree 80 degree and 280 degree 360 degree (0 degree), the off axis distance (OAR) profiles curves of 6 MV X-ray were obtained by Monte Carlo simulation, 3-D water phantom measurement and MatriXX measurement. Comparing the three types of curves, we analyzed the angular dependence of MatriXX 2-D chamber array. The results revealed that the three types of curves agreed well with the gantry angles of 0 degree 60 degree and 300 degree 360 degree(0 degree). Curves and centre point dose on plane from Monte Carlo simulation differed obviously from those of MatriXX measurement in gantry angles of 70 degree 90 degree and 270 degree 290 degree. It is possible to verify the dose distribution of intensity modulated radiation therapy (IMRT) plan using the Multi-Gantry-Angle Composite (MGAC). (authors)
The first-order neutron transport equation was solved by the least-squares finite element method based on the discrete ordinates discretization. For the traditional source iteration method is very slowly for the optically thick diffusive medium, sometime even divergent especially for the scattering ratio is close to unity, so the acceleration method should be proposed. There is only diffusive synthetical acceleration (DSA) for the discontinuous finite element method (DFEM) and almost no one for the least- squares finite element method. The additive angular dependent rebalance (AADR) acceleration arithmetic and its extrapolate method were given, in which the additive modification was used. It was applied to solve the transport equation with fixed source, fission source, in optically thick diffusive regions and with unstructured-mesh. The numerical results of benchmark problems demonstrate that the arithmetic can shorten the CPU time about 1.5-2 times and give high precise. (authors)
We have investigated the angular dependence of the magnetic properties of cylindrical nanostructures comprised of a pair of nanotube and nanowire segments. We compared the magnetic behavior of these structures with the properties observed in an isolated nanowire and nanotube. Thus, we observed that the hysteresis curves of the cylindrical nanostructure with wire–tube morphology exhibits a step or plateau corresponding to a partial pinning of the domain wall at the interface between wire and tube sections. However, this step gradually disappears as we change the angle at which the external magnetic field is applied, thus enabling control of nucleation and release of a domain wall. Moreover, for small angles the nucleation and propagation of domain walls is observed, while for large angles is observed a quasi-coherent rotation. Finally, the possibility to alter the magnetization reversal mode in such nanostructures provides an attractive way to control the motion of magnetic domain walls. (papers)
Light scattering by fractal dust aggregates: I. Angular dependence of scattering
Tazaki, Ryo; Okuzumi, Satoshi; Kataoka, Akimasa; Nomura, Hideko
2016-01-01
In protoplanetary disks, micron-sized dust grains coagulate to form highly porous dust aggregates. Because the optical properties of these aggregates are not completely understood, it is important to investigate how porous dust aggregates scatter light. In this study, the light scattering properties of porous dust aggregates were calculated using a rigorous method, the T-matrix method, and the results were then compared with those obtained using the Rayleigh-Gans-Debye (RGD) theory and Mie theory with the effective medium approximation (EMT). The RGD theory is applicable to moderately large aggregates made of nearly transparent monomers. This study considered two types of porous dust aggregates, ballistic cluster-cluster agglomerates (BCCAs) and ballistic particle-cluster agglomerates (BPCAs). First, the angular dependence of the scattered intensity was shown to reflect the hierarchical structure of dust aggregates; the large-scale structure of the aggregates is responsible for the intensity at small scatteri...
On the angular dependence and scattering model of polar mesospheric summer echoes at VHF
Sommer, Svenja; Stober, Gunter; Chau, Jorge L.
2016-01-01
We present measurements of the angular dependence of polar mesospheric summer echoes (PMSE) with the Middle Atmosphere Alomar Radar System in Northern Norway (69.30° N, 16.04° E). Our results are based on multireceiver and multibeam observations using beam pointing directions with off-zenith angles up to 25° as well as on spatial correlation analysis (SCA) from vertical beam observations. We consider a beam filling effect at the upper and lower boundaries of PMSE in tilted beams, which determines the effective mean angle of arrival. Comparing the average power of the vertical beam to the oblique beams suggests that PMSE are mainly not as aspect sensitive as in contrast to previous studies. However, from SCA, times of enhanced correlation are found, indicating aspect sensitivity or a localized scattering mechanism. Our results suggest that PMSE consist of nonhomogeneous isotropic scattering and previously reported aspect sensitivity values might have been influenced by the inhomogeneous nature of PMSE.
Angular and dose dependence of CR-39 neutron response for shape-selected tracks
Tam, N C; Lakosi, L
1999-01-01
A shape selection method corresponding to an energy discrimination was used to eliminate unwanted events disturbing evaluation of CR-39 detectors in detecting tracks induced by particles both of perpendicular and oblique incidence. The angular dependence of the response was examined, detecting fast neutrons from sup 2 sup 5 sup 2 Cf with shape selection technique at various angles and distances. Also, the CR-39 track detectors with the sup 2 sup 5 sup 2 Cf source were exposed to high gamma-intensity of a sup 6 sup 0 Co irradiation facility in the range 0.1 to 4.5 kGy, similar to the exposures inside spent fuel assemblies. Using the two functions the lower limit of burnup could be determined by the method.
Mineo, H.; Lin, S. H.; Fujimura, Y.
2013-02-01
The results of a theoretical investigation of coherent π-electron dynamics for nonplanar (P)-2,2'-biphenol induced by ultrashort linearly polarized UV pulses are presented. Expressions for the time-dependent coherent angular momentum and ring current are derived by using the density matrix method. The time dependence of these coherences is determined by the off-diagonal density matrix element, which can be obtained by solving the coupled equations of motion of the electronic-state density matrix. Dephasing effects on coherent angular momentum and ring current are taken into account within the Markov approximation. The magnitudes of the electronic angular momentum and current are expressed as the sum of expectation values of the corresponding operators in the two phenol rings (L and R rings). Here, L (R) denotes the phenol ring in the left (right)-hand side of (P)-2,2'-biphenol. We define the bond current between the nearest neighbor carbon atoms Ci and Cj as an electric current through a half plane perpendicular to the Ci-Cj bond. The bond current can be expressed in terms of the inter-atomic bond current. The inter-atomic bond current (bond current) depends on the position of the half plane on the bond and has the maximum value at the center. The coherent ring current in each ring is defined by averaging over the bond currents. Since (P)-2,2'-biphenol is nonplanar, the resultant angular momentum is not one-dimensional. Simulations of the time-dependent coherent angular momentum and ring current of (P)-2,2'-biphenol excited by ultrashort linearly polarized UV pulses are carried out using the molecular parameters obtained by the time-dependent density functional theory (TD-DFT) method. Oscillatory behaviors in the time-dependent angular momentum (ring current), which can be called angular momentum (ring current) quantum beats, are classified by the symmetry of the coherent state, symmetric or antisymmetric. The bond current of the bridge bond linking the L and R
Probing new physics in the neutrinoless double beta decay using electron angular correlation
The angular correlation of the electrons emitted in the neutrinoless double beta decay (0ν2β) is presented using a general Lorentz invariant effective Lagrangian for the leptonic and hadronic charged weak currents. We show that the coefficient K in the angular correlation dΓ/dcosθ∝(1-Kcosθ) is essentially independent of the nuclear matrix element models and present its numerical values for the five nuclei of interest (76Ge, 82Se, 100Mo, 130Te, and 136Xe), assuming that the 0ν2β decays in these nuclei are induced solely by a light Majorana neutrino, νM. This coefficient varies between K=0.81 (for the 76Ge nucleus) and K=0.88 (for the 82Se and 100Mo nuclei), calculated taking into account the effects from the nucleon recoil, the S and P waves for the outgoing electrons and the electron mass. Deviation of K from its values derived here would indicate the presence of new physics (NP) in addition to a light Majorana neutrino, and we work out the angular coefficients in several νM+NP scenarios for the 76Ge nucleus. As an illustration of the correlations among the 0ν2β observables (half-life T1/2, the coefficient K, and the effective Majorana neutrino mass ||) and the parameters of the underlying NP model, we analyze the left-right symmetric models, taking into account current phenomenological bounds on the right-handed WR-boson mass and the left-right mixing parameter ζ
Probing new physics in the neutrinoless double beta decay using electron angular correlation
The angular correlation of the electrons emitted in the neutrinoless double beta decay (0ν2β) is presented using a general Lorentz invariant effective Lagrangian for the leptonic and hadronic charged weak currents. We show that the coefficient K in the angular correlation dΓ/dcos θ ∝(1-K cos θ) is essentially independent of the nuclear matrix element models and present its numerical values for the five nuclei of interest (76Ge, 82Se, 100Mo, 130Te, and 136Xe), assuming that the 0ν2β-decays in these nuclei are induced solely by a light Majorana neutrino, νM. This coefficient varies between K=0.82 (for the 76Ge nucleus) and K=0.88 (for the 82Se and 100Mo nuclei), calculated taking into account the effects from the nucleon recoil, the S and P-waves for the outgoing electrons and the electron mass. Deviation of K from its values derived here would indicate the presence of New Physics (NP) in addition to a light Majorana neutrino, and we work out the angular coefficients in several νM+NP scenarios for the 76Ge nucleus. As an illustration of the correlations among the 0ν2β observables (half-life T1/2, the coefficient K, and the effective Majorana neutrino mass vertical stroke left angle m right angle vertical stroke) and the parameters of the underlying NP model, we analyze the left-right symmetric models, taking into account current phenomenological bounds on the right-handed WR-boson mass and the left-right mixing parameter ζ. (orig.)
The x-ray drive on a capsule in an inertial confinement fusion setup is crucial for ignition. Unfortunately, a direct measurement has not been possible so far. We propose an angular radiation temperature simulation to predict the time-dependent drive on the capsule. A simple model, based on the view-factor method for the simulation of the radiation temperature, is presented and compared with the experimental data obtained using the OMEGA laser facility and the simulation results acquired with VISRAD code. We found a good agreement between the time-dependent measurements and the simulation results obtained using this model. The validated model was then used to analyze the experimental results from the Shenguang-III prototype laser facility. More specifically, the variations of the peak radiation temperatures at different view angles with the albedo of the hohlraum, the motion of the laser spots, the closure of the laser entrance holes, and the deviation of the laser power were investigated. Furthermore, the time-dependent radiation temperature at different orientations and the drive history on the capsule were calculated. The results indicate that the radiation temperature from “U20W112” (named according to the diagnostic hole ID on the target chamber) can be used to approximately predict the drive temperature on the capsule. In addition, the influence of the capsule on the peak radiation temperature is also presented
Jing, Longfei; Yang, Dong; Li, Hang; Zhang, Lu; Lin, Zhiwei; Li, Liling; Kuang, Longyu [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Jiang, Shaoen, E-mail: jiangshn@vip.sina.com; Ding, Yongkun [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900 (China); Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); Huang, Yunbao, E-mail: huangyblhy@gmail.com [Mechatronics School of Guangdong University of Technology, Guangzhou 510080 (China)
2015-02-15
The x-ray drive on a capsule in an inertial confinement fusion setup is crucial for ignition. Unfortunately, a direct measurement has not been possible so far. We propose an angular radiation temperature simulation to predict the time-dependent drive on the capsule. A simple model, based on the view-factor method for the simulation of the radiation temperature, is presented and compared with the experimental data obtained using the OMEGA laser facility and the simulation results acquired with VISRAD code. We found a good agreement between the time-dependent measurements and the simulation results obtained using this model. The validated model was then used to analyze the experimental results from the Shenguang-III prototype laser facility. More specifically, the variations of the peak radiation temperatures at different view angles with the albedo of the hohlraum, the motion of the laser spots, the closure of the laser entrance holes, and the deviation of the laser power were investigated. Furthermore, the time-dependent radiation temperature at different orientations and the drive history on the capsule were calculated. The results indicate that the radiation temperature from “U20W112” (named according to the diagnostic hole ID on the target chamber) can be used to approximately predict the drive temperature on the capsule. In addition, the influence of the capsule on the peak radiation temperature is also presented.
Orbital angular momentum transfer in the excitation of the 2/sup 1/P state of helium by electrons
Beijers, J.P.M.; Eck, J. van; Heideman, H.G.M.
1984-04-28
The orbital angular momentum transfer in the excitation of the 2/sup 1/P state of helium by electrons at incident electron energies of 50, 60 and 80 eV has been studied. This was done in an electron-photon coincidence experiment. At 80 eV the orbital angular momentum transferred by the electron to the atom appears to change sign at a certain scattering angle. At lower energies of 50 and 60 eV no sign reversal is observed.
The results of the experiment on measuring the energy dependence of fission fragment angular anisotropy in resonance neutron induced fission of 235U aligned target in energy region up to 42 eV are presented. The agreement with the data of Pattenden and Postma in resonances is good enough, while the theoretical curve, calculated using the R-matrix multilevel two fission channel approach, does not seem to describe the energy dependence of fission fragment angular anisotropy property. The necessity of taking into account the interference between levels with different spins is discussed. 11 refs., 2 figs
Hori, Masahiro; Aoki, Teruo; Tanikawa, Tomonori; Hachikubo, Akihiro; Sugiura, Konosuke; Kuchiki, Katsuyuki; Niwano, Masashi
2013-10-20
A model of angular-dependent emissivity spectra of snow and ice in the 8-14 μm atmospheric window is constructed. Past field research revealed that snow emissivity varies depending on snow grain size and the exitance angle. Thermography images acquired in this study further revealed that not only welded snow particles such as sun crust, but also disaggregated particles such as granular snow and dendrite crystals exhibit high reflectivity on their crystal facets, even when the bulk snow surface exhibits blackbody-like behavior as a whole. The observed thermal emissive behaviors of snow particles suggest that emissivity of the bulk snow surface can be expressed by a weighted sum of two emissivity components: those of the specular and blackbody surfaces. Based on this assumption, a semi-empirical emissivity model was constructed; it is expressed by a linear combination of specular and blackbody surfaces' emissivities with a weighting parameter characterizing the specularity of the bulk surface. Emissivity spectra calculated using the model succeeded in reproducing the past in situ measured directional spectra of various snow types by employing a specific weighting parameter for each snow type. PMID:24216578
Based on simple random sampling (SRS), we propose a Monte Carlo method for the faster computation of the smoothed part of the density of nuclear states. To test the applicability of the SRS approach we study in this framework the excitation energy (E), angular momentum (J) and parity dependence of nuclear level densities for an independent particle system. As an illustrative example, we consider a pf-shell nucleus, 48Cr. It is found that the values of a few lower order moments for the state density I(E) calculated using SRS and combinatorial (or direct counting) methods are almost the same and a locally smoothed part of the state density can be constructed using these moments in a univariate Edgeworth expansion. We calculate the energy dependent spin-cutoff factor and parity asymmetry and find that for both cases the SRS approach works quite well. We use the SRS moments to construct different forms of the bivariate distribution for I(E,M) (M is the z-component of J) namely (a) a bivariate Edgeworth expansion, (b) a product of the univariate Edgeworth expansion (I(E)) and a Gaussian form for conditional M distribution I(M vertical stroke E) and (c) a product of the univariate Edgeworth expansions for both I(E) and I(M vertical stroke E) and compare the resulting fixed-J level density Il(E,J) with the corresponding combinatorial results. (orig.)
Effect of the third π ∗ resonance on the angular distributions for electron-pyrimidine scattering
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.
We present measurements of electron-impact excitation cross sections into levels of the 4p55p configuration from the J=0 and J=2 metastable levels of krypton. Metastable-atom targets were generated using two different sources, a hollow-cathode discharge and via charge-exchange collisions between a fast Kr+ beam and Cs atoms. The metastable atoms are excited to 4p55p levels by a monoenergetic electron beam and the fluorescence from the levels are used to determine the excitation cross sections. Laser quenching of the hollow-cathode target is used to separate the signal contributions from excitation of the two metastable levels. Like excitation from the metastable levels of Ar, cross sections for dipole-allowed excitations are generally larger than ones for dipole-forbidden excitations. Krypton differs from Ar and Ne, however, in having a larger spin-orbit coupling for the 4p5 core so that the energy levels of each excited configuration segregate into two tiers based on the value of the core angular momentum. Cross sections for dipole-allowed excitation with a change in the core angular momentum are not only much smaller than their core-preserving counterparts, but also have different energy dependence. The measured cross sections are compared with recent theoretical calculations and with previous experimental work
On solving the orientation gradient dependency of high angular resolution EBSD
Maurice, Claire, E-mail: maurice@emse.fr [Ecole des Mines de Saint-Etienne, UMR CNRS 5146 LCG, 158 cours Fauriel, F-42023 Saint-Etienne (France); Driver, Julian H. [Ecole des Mines de Saint-Etienne, UMR CNRS 5146 LCG, 158 cours Fauriel, F-42023 Saint-Etienne (France); Fortunier, Roland [Universite de Lyon, ENISE, UMR CNRS 5513 LTDS, 58 rue Jean Parot, F-42100 Saint-Etienne (France)
2012-02-15
Current high angular resolution electron backscatter diffraction (HR-EBSD) methods are successful at measuring pure elastic strains but have difficulties with plastically deformed metals containing orientation gradients. The strong influences of these rotations have been systematically studied using simulated patterns based on the many-beam dynamic theory of EBSP formation; a rotation of only 1 Degree-Sign can lead to apparent elastic strains of several hundred microstrains. A new method is proposed to correct for orientation gradient effects using a two-step procedure integrating finite strain theory: (i) reference pattern rotation and (ii) cross-correlation; it reduces the strain errors on the simulated patterns to tens of microstrains. An application to plastically deformed ferritic steel to generates elastic strain maps with significantly reduced values of both strains and residual errors in regions of rotations exceeding 1 Degree-Sign . -- Highlights: Black-Right-Pointing-Pointer Many-beam theory simulations show that HR-EBSD is sensitive to orientation gradients. Black-Right-Pointing-Pointer Finite strain theory and rotation processing the reference EBSP solves the problem. Black-Right-Pointing-Pointer New method succesfully applied to plastically strained IF steel.
Masir, M. Ramezani; Vasilopoulos, P.; Matulis, A.; Peeters, F. M.
2010-01-01
We evaluate the transmission through magnetic barriers in graphene-based nanostructures. Several particular cases are considered: a magnetic step, single and double barriers, δ -function barriers as well as barrier structures with inhomogeneous magnetic field profiles but with average magnetic field equal to zero. The transmission exhibits a strong dependence on the direction of the incident wave vector. In general the resonant structure of the transmission is significantly more pronounced for (Dirac) electrons with linear spectrum compared to that for electrons with a parabolic one.
Jursinic, Paul A., E-mail: pjursinic@wmcc.org [West Michigan Cancer Center, 200 North Park Street, Kalamazoo, Michigan 49007 (United States)
2015-10-15
Purpose: A type of in vivo dosimeter, an optically stimulated luminescent dosimeter, OSLD, may have dose sensitivity that depends on the angle of incidence of radiation. This work measures how angular dependence of a nanoDot changes with the geometry of the phantom in which irradiation occurs and with the intrinsic structure of the nanoDot. Methods: The OSLDs used in this work were nanoDot dosimeters (Landauer, Inc., Glenwood, IL), which were read with a MicroStar reader (Landauer, Inc., Glenwood, IL). Dose to the OSLDs was delivered by 6 MV x-rays. NanoDots with various intrinsic sensitivities were irradiated in numerous phantoms that had geometric shapes of cylinders, rectangles, and a cube. Results: No angular dependence was seen in cylindrical phantoms, cubic phantoms, or rectangular phantoms with a thickness to width ratio of 0.3 or 1.5. An angular dependence of 1% was observed in rectangular phantoms with a thickness to width of 0.433–0.633. A group of nanoDots had sensitive layers with mass density of 2.42–2.58 g/cm{sup 3} and relative sensitivity of 0.92–1.09 and no difference in their angular dependence. Within experimental uncertainty, nanoDot measurements agree with a parallel-plate ion chamber at a depth of maximum dose. Conclusions: When irradiated in cylindrical, rectangular, and cubic phantoms, nanoDots show a maximum angular dependence of 1% or less at an incidence angle of 90°. For a sample of 78 new nanoDots, the range of their relative intrinsic sensitivity is 0.92–1.09. For a sample of ten nanoDots, on average, the mass in the sensitive layer is 73.1% Al{sub 2}O{sub 3}:C and 26.9% polyester. The mass density of the sensitive layer of a nanoDot disc is between 2.42 and 2.58 g/cm{sup 3}. The angular dependence is not related to Al{sub 2}O{sub 3}:C loading of the nanoDot disc. The nanoDot at the depth of maximum dose has no more angular dependence than a parallel-plate ion chamber.
Purpose: A type of in vivo dosimeter, an optically stimulated luminescent dosimeter, OSLD, may have dose sensitivity that depends on the angle of incidence of radiation. This work measures how angular dependence of a nanoDot changes with the geometry of the phantom in which irradiation occurs and with the intrinsic structure of the nanoDot. Methods: The OSLDs used in this work were nanoDot dosimeters (Landauer, Inc., Glenwood, IL), which were read with a MicroStar reader (Landauer, Inc., Glenwood, IL). Dose to the OSLDs was delivered by 6 MV x-rays. NanoDots with various intrinsic sensitivities were irradiated in numerous phantoms that had geometric shapes of cylinders, rectangles, and a cube. Results: No angular dependence was seen in cylindrical phantoms, cubic phantoms, or rectangular phantoms with a thickness to width ratio of 0.3 or 1.5. An angular dependence of 1% was observed in rectangular phantoms with a thickness to width of 0.433–0.633. A group of nanoDots had sensitive layers with mass density of 2.42–2.58 g/cm3 and relative sensitivity of 0.92–1.09 and no difference in their angular dependence. Within experimental uncertainty, nanoDot measurements agree with a parallel-plate ion chamber at a depth of maximum dose. Conclusions: When irradiated in cylindrical, rectangular, and cubic phantoms, nanoDots show a maximum angular dependence of 1% or less at an incidence angle of 90°. For a sample of 78 new nanoDots, the range of their relative intrinsic sensitivity is 0.92–1.09. For a sample of ten nanoDots, on average, the mass in the sensitive layer is 73.1% Al2O3:C and 26.9% polyester. The mass density of the sensitive layer of a nanoDot disc is between 2.42 and 2.58 g/cm3. The angular dependence is not related to Al2O3:C loading of the nanoDot disc. The nanoDot at the depth of maximum dose has no more angular dependence than a parallel-plate ion chamber
Impact of surface-polish on the angular and wavelength dependence of fiber focal ratio degradation
Eigenbrot, Arthur D; Wood, Corey M
2012-01-01
We present measurements of how multimode fiber focal-ratio degradation (FRD) and throughput vary with levels of fiber surface polish from 60 to 0.5 micron grit. Measurements used full-beam and laser injection methods at wavelengths between 0.4 and 0.8 microns on 17 meter lengths of Polymicro FBP 300 and 400 micron core fiber. Full-beam injection probed input focal-ratios between f/3 and f/13.5, while laser injection allowed us to isolate FRD at discrete injection angles up to 17 degrees (f/1.6 marginal ray). We find (1) FRD effects decrease as grit size decreases, with the largest gains in beam quality occurring at grit sizes above 5 microns; (2) total throughput increases as grit size decreases, reaching 90% at 790 nm with the finest polishing levels; (3) total throughput is higher at redder wavelengths for coarser polishing grit, indicating surface-scattering as the primary source of loss. We also quantify the angular dependence of FRD as a function of polishing level. Our results indicate that a commonly a...
Angular Dependence of the Facular-Sunspot Coverage Relation as Derived by MDI Magnetograms
Criscuoli, S.
2016-07-01
Previous studies have shown that the variation over the solar magnetic activity cycle of the area of facular/network features identified from broad-band and narrow-band imagery is positively correlated with the sunspot area and number, the relation being described as either linear or quadratic. On the other hand, the temporal variation of the spatial distributions of faculae, network and sunspots follows patterns that are less obviously correlated, so that we expect the relation that describes variation of the area coverage of different types of magnetic features to vary with the position over the disk. In this work we employ Michelson Doppler Interferometer (MDI) full-disk magnetograms acquired during solar cycle 23 and at the beginning of cycle 24 to investigate the relation between the coverage of magnetic elements characterized by different amounts of magnetic flux and located at different angular distances from disk center with the sunspot number. In agreement with some previous studies we find that daily data are best described by a quadratic function while data averaged over six months are best described by a linear function. In both cases the coefficients of the fits show large dependence on the position over the disk and the magnetic flux. We also find that toward disk center six-month averaged data show asymmetries between the ascending and the descending phases. The implications for solar irradiance modeling are discussed.
Improved angular momentum evolution model for solar-like stars II. Exploring the mass dependence
Gallet, Florian
2015-01-01
We developed angular momentum evolution models for 0.5 and 0.8 $M_{\\odot}$ stars. The parametric models include a new wind braking law based on recent numerical simulations of magnetised stellar winds, specific dynamo and mass-loss rate prescriptions, as well as core/envelope decoupling. We compare model predictions to the distributions of rotational periods measured for low mass stars belonging to star forming regions and young open clusters. Furthermore, we explore the mass dependence of model parameters by comparing these new models to the solar-mass models we developed earlier. Rotational evolution models are computed for slow, median, and fast rotators at each stellar mass. The models reproduce reasonably well the rotational behaviour of low-mass stars between 1~Myr and 8-10~Gyr, including pre-main sequence to zero-age main sequence spin up, prompt zero-age main sequence spin down, and early-main sequence convergence of the surface rotation rates. Fast rotators are found to have systematically shorter di...
Light Scattering by Fractal Dust Aggregates. I. Angular Dependence of Scattering
Tazaki, Ryo; Tanaka, Hidekazu; Okuzumi, Satoshi; Kataoka, Akimasa; Nomura, Hideko
2016-06-01
In protoplanetary disks, micron-sized dust grains coagulate to form highly porous dust aggregates. Because the optical properties of these aggregates are not completely understood, it is important to investigate how porous dust aggregates scatter light. In this study, the light scattering properties of porous dust aggregates were calculated using a rigorous method, the T-matrix method, and the results were then compared with those obtained using the Rayleigh–Gans–Debye (RGD) theory and Mie theory with the effective medium approximation (EMT). The RGD theory is applicable to moderately large aggregates made of nearly transparent monomers. This study considered two types of porous dust aggregates—ballistic cluster–cluster agglomerates (BCCAs) and ballistic particle–cluster agglomerates. First, the angular dependence of the scattered intensity was shown to reflect the hierarchical structure of dust aggregates; the large-scale structure of the aggregates is responsible for the intensity at small scattering angles, and their small-scale structure determines the intensity at large scattering angles. Second, it was determined that the EMT underestimates the backward scattering intensity by multiple orders of magnitude, especially in BCCAs, because the EMT averages the structure within the size of the aggregates. It was concluded that the RGD theory is a very useful method for calculating the optical properties of BCCAs.
Angular Momentum Dependent Quark Potential of QCD Traits and Dynamical O(4) Symmetry
Compean, C B
2006-01-01
A common quark potential that captures the essential traits of the QCD quark-gluon dynamics is expected to (i) interpolate between a Coulomb-like potential (associated with one-gluon exchange) and the infinite wall potential (associated with trapped but asymptotically free quarks), (ii) reproduce in the intermediary region the linear confinement potential (associated with multi-gluon self-interactions) as established by lattice QCD calculations of hadron properties. We first show that the exactly soluble trigonometric Rosen-Morse potential possesses all these properties. Next we observe that this potential, once interpreted as angular momentum dependent, acquires a dynamical O(4) symmetry and reproduces exactly quantum numbers and level splittings of the non-strange baryon spectra in the SU(2)_I* O(4) classification scheme according to which baryons cling on to multi-spin parity clusters of the type (K/2,K/2)*[(1/2,0) + (0, 1/2)], whose relativistic image is \\psi_{\\mu_{1}...\\mu_{K}}. Finally, we bring exact e...
Juang, Fuh-Shyang; Laih, Li-Hong; Lin, Chia-Ju; Hsu, Yu-Jen
2002-04-01
An optical microcavity structure was used in organic light emitting diodes. We succeeded in fabricating a device with sharply directed emission vertical to an emission surface. The device shows green emission (bright green) at normal position which turns red (bright red) at the 30° position. The angular dependences of the electroluminescence and the emission patterns versus viewing angle in the microcavity OLED were studied. The resonance wavelength λ decreases with viewing angle. The emission peak at 490 nm is directed vertically to the device surface more sharply than that at 632 nm. The microcavity structure shows non-Lambertian emission. The spectra appear more blue off-axis and the intensity of the green-like emission decreases rapidly with increasing viewing angle. A significantly narrow linewidth of 7.4 nm in the 0° direction for the 490 nm peak was observed. The full-widths at half maximum (FWHM) of the green-like spectra are much smaller than those of the red-like ones, indicating better cavity quality.
Tomographic imaging of the angular-dependent coherent-scatter cross section.
Westmore, M S; Fenster, A; Cunningham, I A
1997-01-01
A new special-purpose computed tomographic (CT) imaging system is described which produces images based on measurements of the low-angle (0-10 degrees) x-ray diffraction properties of an object. Low-angle scatter in the diagnostic x-ray energy range is dominated by coherent scatter, and the system uses first-generation CT geometry to acquire a diffraction pattern for each pencil beam. The patterns are used to reconstruct a series of images which represent the coherent-scatter intensity at a series of scatter angles. To demonstrate the potential of coherent-scatter CT (CSCT), the scanner has been built and used to image a phantom consisting of a water-filled Lucite cylinder containing rods of polyethylene, Lucite, polycarbonate, and nylon. In this paper, the system is described and a sequence of CSCT images of this phantom is shown. Coherent-scatter cross sections of these materials are generated for each pixel from this sequence of images and compared with cross sections measured separately. The resulting excellent agreement shows that the angular-dependent coherent-scatter cross section can be accurately imaged in a tomographic slice through an object. These cross sections give material-specific information about the object. The long-term goal of this research is to make measurements of bone-mineral content for every pixel in a tomographic slice. PMID:9029536
H. M. Al-Khateeb; M. K. Alqadi; F. Y. Alzoubi; N. Y. Ayoub
2007-01-01
The dipole-dipole interaction model is used to calculate the angular dependence of lateral and levitation forces on a small permanent magnet and a cylindrical superconductor in the Meissner state lying laterally offthe symmetric axis of the cylinder. Under the assumption that the lateral displacement of the magnet is small compared with the physical dimensions of the system, we obtain analytical expressions for the lateral and levitation forces as functions of geometrical parameters of the superconductor as well as the height, the lateral displacement and the orientation of magnetic moment of the magnet. The effect of thickness and radius of the superconductor on the levitation force is similar to that for a symmetric magnet/superconducting cylinder system, but within the range of lateral displacement. The splitting in the levitation force increases with the increasing angle of orientation of the magnetic moment of the magnet. For a given lateral displacement of the magnet, the lateral force vanishes when the magnetic moment is perpendicular to the surface of the superconductor and has a maximum value when the moment is parallel to the surface. For a given orientation of the magnetic moment, the lateral force has a linear relationship with the lateral displacement. The stability of the magnet above the superconducting cylinder is discussed in detail.
Angular Distribution of Electrons in Photoionization of Atoms Adsorbed on a Graphene Sheet
Baltenkov, A S
2013-01-01
Within the framework of a model representing the potential of a graphene sheet U(z) as an electro-neutral layer formed by smeared carbon atoms, the effect of this potential on spectral characteristics of atoms adsorbed on a graphene sheet has been studied. Since the distance between the adsorbed atom nucleus and sheet surface significantly exceeds the radii of inner atomic shells the potential U(z) makes influence on the continuum wave functions only. Their behavior in the upper semi-space (z>0) and in the lower one (z<0) where the adsorbed atom is located is defined by a jump of the logarithmic derivative of the wave function for z=0. The photoelectron angular distributions have been calculated for different mutual positions of the polarization vector e and the axis Z normal to the sheet surface. It has been shown that the existence of the electron waves reflected from the potential U(z) leads to evident asymmetry of the angular distribution relative to the plane z=0. The experimental observation of this ...
Wallis, David; Hansen, Lars N; Ben Britton, T; Wilkinson, Angus J
2016-09-01
Dislocations in geological minerals are fundamental to the creep processes that control large-scale geodynamic phenomena. However, techniques to quantify their densities, distributions, and types over critical subgrain to polycrystal length scales are limited. The recent advent of high-angular resolution electron backscatter diffraction (HR-EBSD), based on diffraction pattern cross-correlation, offers a powerful new approach that has been utilised to analyse dislocation densities in the materials sciences. In particular, HR-EBSD yields significantly better angular resolution (densities to be analysed. We develop the application of HR-EBSD to olivine, the dominant mineral in Earth's upper mantle by testing (1) different inversion methods for estimating geometrically necessary dislocation (GND) densities, (2) the sensitivity of the method under a range of data acquisition settings, and (3) the ability of the technique to resolve a variety of olivine dislocation structures. The relatively low crystal symmetry (orthorhombic) and few slip systems in olivine result in well constrained GND density estimates. The GND density noise floor is inversely proportional to map step size, such that datasets can be optimised for analysing either short wavelength, high density structures (e.g. subgrain boundaries) or long wavelength, low amplitude orientation gradients. Comparison to conventional images of decorated dislocations demonstrates that HR-EBSD can characterise the dislocation distribution and reveal additional structure not captured by the decoration technique. HR-EBSD therefore provides a highly effective method for analysing dislocations in olivine and determining their role in accommodating macroscopic deformation. PMID:27337604
Yasuzuka, Syuma; Uji, Shinya; Konoike, Takako; Terashima, Taichi; Graf, David; Choi, Eun Sang; Brooks, James S.; Yamamoto, Hiroshi M.; Kato, Reizo
2016-08-01
This paper reports the experimental results of the Shubnikov-de Haas (SdH) effect and angular-dependent magnetoresistance oscillation (AMRO) for the organic conductor β''-(ET)(TCNQ). We observed several two dimensional (2D) SdH frequencies, whose cross-sectional areas of the Fermi surfaces (FSs) correspond to only a few percent of the first Brillouin zone. Such small 2D FSs are not predicted by band-structure calculations, suggesting that these FS pockets are created by an imperfect nesting of FSs at low temperatures. It is found that the AMRO consists of a long-period oscillation and a short-period one. The long-period oscillation is associated with the Yamaji oscillation corresponding to the α orbit, whose shape and area are consistent with previous magneto-optical measurement. The short-period oscillation is not caused by peaks instead but dips. The dip structure is discussed in terms of the AMRO of a quasi-2D electron system with a periodic potential caused by the possible density-wave related to the ET layers or the 4kF charge-density-wave associated with the TCNQ layers.
McTaggart, R J
1998-01-01
The angular distributions of the charmonium resonances J/ Y (3097) and Y (3686) in their exclusive decay to an electron-positron pair are studied. Experiment 835 at the Fermi National Accelerator Laboratory produced charmonium resonances by annihilating protons with antiprotons in the Fixed Target Mode of the Antiproton Accumulator: A stochastically cooled antiproton beam collides with a hydrogen gas jet, which forms clusters under the right pressure and low temperature. The charmonium decay products are detected out of a large hadronic background with the help of a segmented lead glass sampling calorimeter, which is sensitive to the high mass electron-positron charmonium decay, and a set of Cerenkov threshold detectors that provide good electron/pion separation. Several factors influence the angular distribution parameter l taken from the angular distribution, including the energy scale of the resonance, the coupling strength of the charmonium atom, and how quarks and gluons interact in the dissolution...
Mirzanian, S. M.; Shokri, A. A.; Mikaili Agah, K.; Elahi, S. M.
2015-09-01
We investigate theoretically the effects of Dresselhaus spin-orbit coupling (DSOC) on the spin-dependent current and shot noise through II-VI diluted magnetic semiconductor/nonmagnetic semiconductor (DMS/NMS) barrier structures. The calculation of transmission probability is based on an effective mass quantum-mechanical approach in the presence of an external magnetic field applied along the growth direction of the junction and also applied voltage. We also study the dependence of spin-dependent properties on external magnetic field and relative angle between the magnetizations of two DMS layers in CdTe/CdMnTe heterostructures by including the DSOC effect. The results show that the DSOC has great different influence on transport properties of electrons with spin up and spin down in the considered system and this aspect may be utilized in designing new spintronics devices.
Brady, J.W. Jr.; Doll, J.D.; Thompson, D.L.
1978-10-15
The angular and velocity distributions for gas/solid-surface collisions are examined. It is shown that the envelope of the scattered phase-space distribution is quite sensitive to the gas/surface interaction potential.
Qin, S; Chen, T; Wang, L; Tu, Y; Yue, N; Zhou, J
2014-08-01
The focus of this study is the angular dependence of two types of Metal Oxide Semiconductor Field Effect Transistor (MOSFET) dosimeters (MOSFET20 and OneDose/OneDosePlus) when used for surface dose measurements. External beam radiationat different gantry angles were delivered to a cubic solid water phantom with a MOSFET placed on the top surface at CAX. The long axis of the MOSFET was oriented along the gantry axis of rotation, with the dosimeter (bubble side) facing the radiation source. MOSFET-measured surface doses were compared against calibrated radiochromic film readings. It was found that both types of MOSFET dosimeters exhibited larger than previously reported angular dependence when measuring surface dose in beams at large oblique angles. For the MOSFET20 dosimeter the measured surface dose deviation against film readings was as high as 17% when the incident angle was 72 degrees to the norm of the phantom surface. It is concluded that some MOSFET dosimeters may have a strong angular dependence when placed on the surface of water-equivalent material, even though they may have an isotropic angular response when surrounded by uniform medium. Extra on-surface calibration maybe necessary before using MOSFET dosimeters for skin dose measurement in tangential fields. PMID:24206205
Sonia Garcia Pereira Cecatti
2006-12-01
Full Text Available As dependências energética e angular de diferentes materiais termoluminescentes foram estudadas com o objetivo de verificar que tipo de detector seria o mais adequado para a monitoração de trabalhadores envolvidos com a radiação beta. Três tipos de pastilhas de CaSO4:Dy + teflon foram estudados. A dependência energética foi verificada usando-se fontes padrões de radiação beta (147Pm, 204Tl e 90Sr+90Y. A dependência angular foi verificada irradiando-se as amostras com feixes de radiação beta, variando-se o ângulo de incidência entre 0° e 90°. Os dosímetros de CaSO4:Dy + teflon + 10% C mostram-se os mais adequados para uso na monitoração de trabalhadores expostos à radiação beta, em relação às características estudadas.Energy and angular dependences of different thermoluminescent materials were studied with the objective to verify which type of detector would be the most appropriate for beta monitoring of workers. Three types of CaSO4:Dy + teflon pellets were studied. The energy dependence was evaluated using standard beta radiation sources (147Pm, 204Tl and 90Sr+90Y. For the angular dependence study, the pellets were exposed to beta radiation of the 90Sr+90Y source, varying the incidence angle between 0° and 90°. In relation to the studied characteristics, the CaSO4:Dy + 10% C dosimeters were the most adequate for use in beta monitoring of workers.
The development of analytical techniques based on measurements of electron elastic-backscattering probabilities stimulated an interest in the theoretical description of such phenomena. The most accurate and reliable theoretical models involve Monte Carlo (MC) simulations of electron trajectories in solids; however, this approach generally requires considerable computer effort. It has been shown that the performance of a modified analytical theory originally proposed by Oswald et al (1993 J. Electron Spectrosc. Relat. Phenom. 61 251), designated with the acronym OKGM, compares reasonably well with MC calculations. The MC data are usually underestimated by the OKGM model, and the mean percentage deviation, averaged over nine elements and five energies up to 5 keV, is equal to 8.8% for typical experimental configurations. However, the agreement between ratios of backscattering probabilities from MC simulations and the OKGM model agree much better due to the fact that underestimation of backscattering probability by the OMGM theory is partially cancelled. The percentage deviation between ratios from these theoretical models decreases to 3.14%. The OKGM model should then be useful for determining inelastic mean free paths (IMFPs) from measured elastic-peak intensities. The accuracy of the obtained IMFPs is comparable with IMFPs from MC simulations. (paper)
Orbital angular momentum in electron diffraction and its use to determine chiral crystal symmetries
Juchtmans, Roeland; Verbeeck, Jo
2015-10-01
In this work we present an alternative way to look at electron diffraction in a transmission electron microscope. Instead of writing the scattering amplitude in Fourier space as a set of plane waves, we use the cylindrical Fourier transform to describe the scattering amplitude in a basis of orbital angular momentum (OAM) eigenstates. We show how working in this framework can be very convenient when investigating, e.g., rotation and screw-axis symmetries. For the latter we find selection rules on the OAM coefficients that unambiguously reveal the handedness of the screw axis. Detecting the OAM coefficients of the scattering amplitude thus offers the possibility to detect the handedness of crystals without the need for dynamical simulations, the thickness of the sample, nor the exact crystal structure. We propose an experimental setup to measure the OAM components where an image of the crystal is taken after inserting a spiral phase plate in the diffraction plane and perform multislice simulations on α quartz to demonstrate how the method indeed reveals the chirality. The experimental feasibility of the technique is discussed together with its main advantages with respect to chirality determination of screw axes. The method shows how the use of a spiral phase plate can be extended from a simple phase imaging technique to a tool to measure the local OAM decomposition of an electron wave, widening the field of interest well beyond chiral space group determination.
The present thesis describes the measurement of α and proton anisotropies in the Darmstadt-Heidelberg crystal ball relative to the spin direction and in dependence on the prompt detector multiplicity for 155,159,161Ho compound nuclei from the fusion reactions 37Cl+124Sn at 200 and 251 MeV incident energy, 37Cl+118Sn at 251 MeV, as well as 173 MeV 18O+141Pr. A novel and reliable procedure for the determination of the anisotropy is given which regards the broadening of the spin distribution by measurement of the E2-inertia ellipsoid at limited photon number as well as the statistical particle cascade on a purely experimental base. Only for the correction for ''defects'' of the crystal ball simulation calculations are necessary. The main results are: (1) Detection of a superdeformation (vertical strokeδvertical stroke≥0.6) of α emitting nuclei in the range of the neutron number 85≤N≤89. vertical strokeδvertical stroke grows with increasing angular momentum of the emitting nuclei and reaches the value vertical strokeδvertical stroke≅0.6 in the 251 MeV 37Cl+124Sn→161Ho reaction at I≅80ℎ, in the 37Cl+118Sn→155Ho reaction at I≅55ℎ. (2) The α emitting residual nuclei formed in the 251 MeV 37Cl+118Sn reaction (anti N 85) show significantly larger deformations than those formed in 251 MeV 37Cl+124Sn (anti N 88). The extremely large deformation of the formed nuclei seems to confirm the shape isomerism of 156Er (N=88) predicted by Aberg and the superdeformation at 152Dy reported by Nyako et al. as nuclear property of the transition region. (orig.)
Zou, L. K.; Zhang, Y.; Gu, L.; Cai, J. W.; Sun, L.
2016-02-01
Angular-dependent magnetoresistance (MR) is considered to be intrinsic to spintronic materials, represented by the classical anisotropic MR (AMR) phenomenon and the recently emerged spin Hall MR (SMR). So far, isotropic AMR, AMR with geometric size effect and interfacial effect, and SMR have been treated separately to explain distinct MR correlations observed in various systems. Current study shows all four types of MR correlations can be reproduced in Fe thin films depending on the film thickness, texture, interface, and morphology. Results suggest previous explanations of the thin-film MR correlations are incomplete and it is inappropriate to use a specific MR angular-dependent correlation as the sole criterion in determining the origin of AMR or ascertaining the exclusive existence of SMR.
Blazhevich, S. V.; Koskova, T. V.; Ligidov, A. Z.; Noskov, A. V.
2016-07-01
Diffracted transition radiation (DTR) generated by a divergent beam of relativistic electrons crossing a single-crystal plate in different (Laue, Bragg) scattering geometry has been considered for the general case of asymmetric reflection of the electron coulomb field relative to the entrance target surface. The expressions for spectral-angular density of DTR and parametric X-ray Radiation (PXR) has been derived. Then DTR and PXR has been considered in case of a thin target, when multiple scattering of electron is negligibly small, which is important for divergence measurement in real time regime. Numerical calculation of spectral-angular density of DTR by a beam of relativistic electrons has been made using averaging over the bivariate Gauss distribution as angular distribution of relativistic electrons in the beam. It has been shown that in Bragg scattering geometry the angular density of DTR is bigger, than in Laue geometry, which can be explained by the existence of the frequency range, in which the incident wave propagation vector takes complex value even under absence of absorption. In this range, all of photons are reflected in Bragg direction. It means that the range of total reflection defines the width of DTR spectrum.
Andreas Burkart
2015-01-01
Full Text Available In this study we present a hyperspectral flying goniometer system, based on a rotary-wing unmanned aerial vehicle (UAV equipped with a spectrometer mounted on an active gimbal. We show that this approach may be used to collect multiangular hyperspectral data over vegetated environments. The pointing and positioning accuracy are assessed using structure from motion and vary from σ = 1° to 8° in pointing and σ = 0.7 to 0.8 m in positioning. We use a wheat dataset to investigate the influence of angular effects on the NDVI, TCARI and REIP vegetation indices. Angular effects caused significant variations on the indices: NDVI = 0.83–0.95; TCARI = 0.04–0.116; REIP = 729–735 nm. Our analysis highlights the necessity to consider angular effects in optical sensors when observing vegetation. We compare the measurements of the UAV goniometer to the angular modules of the SCOPE radiative transfer model. Model and measurements are in high accordance (r2 = 0.88 in the infrared region at angles close to nadir; in contrast the comparison show discrepancies at low tilt angles (r2 = 0.25. This study demonstrates that the UAV goniometer is a promising approach for the fast and flexible assessment of angular effects.
Surrogate Reaction Measurement of Angular Dependent 239Pu (n , f) Probabilities
Koglin, Johnathon; Burke, Jason; Casperson, Robert; Jovanovic, Igor
2015-10-01
The surrogate method has previously been used to measure (n , f) cross sections of difficult to produce actinide isotopes. These measurements have inaccuracies at excitation energies below 1.5 MeV where the distribution of angular momentum states populated in the compound nucleus created by neutron absorption significantly differs from that arising from direct reactions. A method to measure the fission probability of individual angular momentum states arising from 239Pu (d , pf) and 239Pu (α ,α' f) reactions has been developed. This experimental apparatus consists of charged particle detectors with 40 keV FWHM resolution at 13 angles up and downstream of the particle beam. A segmented array of photovoltaic (solar) cells is used to measure the angular distribution of fission fragments. This distribution uniquely identifies the populated angular momentum states. These are fit to expected distributions to determine the contribution of each state. The charged particle and fission rates matrix obtained from this analysis determines fission probabilities of specific angular momentum states in the transition nucleus. Development of this scheme and first results will be discussed.
The influence of single crystal input surface orientation on the diffracted transition radiation (DTR) under fixed orientation of atomic planes relative to relativistic electron beam is investigated. The analytical expressions of relativistic electrons DTR and parametric X-radiation spectral-angular density are deduced. Calculations f DTR silicon and germanium crystals reveal the significant dependence of DTR parameters on input surface orientation
The VMI study on angular distribution of ejected electrons from Eu 4f76p1/26d autoionizing states
张开; 沈礼; 董程; 戴长建
2015-01-01
The combination of a velocity mapping imaging technique and mathematical transformation is adopted to study the angular distribution of electrons ejected from the Eu 4f76p1/26d autoionizing states, which are excited with a three-step excitation scheme via different Eu 4f76s6d 8DJ (J=5/2, 7/2, and 9/2) intermediate states. In order to determine the energy dependence of angular distribution of the ejected electrons, the anisotropic parameters are measured in the spectral profile of the 6p1/26d autoionizing states by tuning the wavelength of the third-step laser across the ionic resonance lines of the Eu 6s+→ 6p+. The configuration interaction is discussed by comparing the angular distributions of ejected electrons from the different states. The present study reveals the profound variations of anisotropic parameters in the entire region of autoionization resonance, highlighting the complicated nature of the autoionization process for the lowest member of 6p1/26d autoionization series.
Orbital angular momentum in electron diffraction and its use to determine chiral crystal symmetries
Juchtmans, Roeland
2015-01-01
In this work we present an alternative way to look at electron diffraction in a transmission electron microscope. In stead of writing the scattering amplitude in Fourier space as a set of plane waves, we use the cylindrical Fourier transform to describe the scattering amplitude in a basis of orbital angular momentum (OAM) eigenstates. We show how working in this framework can be very convenient when investigating e.g. rotation and screw axis symmetries. For the latter we find selection rules on the OAM-coefficients that unambiguously reveal the handedness of the screw axis. Detecting the OAM-coefficients of the scattering amplitude thus offers the possibility to detect the handedness of crystals without the need for dynamical simulations, the thickness of the sample nor the exact crystal structure. We propose an experimental setup to measure the OAM-components where an image of the crystal is taken after inserting a spiral phase plate in the diffraction plane and perform mulsti-slice simulations on $\\alpha$-q...
Leonov, A A; Bonvicini, V; Topchiev, N P; Adriani, O; Aptekar, R L; Arkhangelskaja, I V; Arkhangelskiy, A I; Bergstrom, L; Berti, E; Bigongiari, G; Bobkov, S G; Boezio, M; Bogomolov, E A; Bonechi, S; Bongi, M; Bottai, S; Boyarchuk, K A; Castellini, G; Cattaneo, P W; Cumani, P; Dedenko, G L; De Donato, C; Dogiel, V A; Gorbunov, M S; Gusakov, Yu V; Hnatyk, B I; Kadilin, V V; Kaplin, V A; Kaplun, A A; Kheymits, M D; Korepanov, V E; Larsson, J; Loginov, V A; Longo, F; Maestro, P; Marrocchesi, P S; Mikhailov, V V; Mocchiutti, E; Moiseev, A A; Mori, N; Moskalenko, I V; Naumov, P Yu; Papini, P; Pearce, M; Picozza, P; Popov, A V; Rappoldi, A; Ricciarini, S; Runtso, M F; Ryde, F; Serdin, O V; Sparvoli, R; Spillantini, P; Suchkov, S I; Tavani, M; Taraskin, A A; Tiberio, A; Tyurin, E M; Ulanov, M V; Vacchi, A; Vannuccini, E; Vasilyev, G I; Yurkin, Yu T; Zampa, N; Zirakashvili, V N; Zverev, V G
2014-01-01
The measurements of gamma-ray fluxes and cosmic-ray electrons and positrons in the energy range from 100 MeV to several TeV, which will be implemented by the specially designed GAMMA-400 gamma-ray telescope, concern with the following broad range of science topics. Searching for signatures of dark matter, surveying the celestial sphere in order to study gamma-ray point and extended sources, measuring the energy spectra of Galactic and extragalactic diffuse gamma-ray emission, studying gamma-ray bursts and gamma-ray emission from the Sun, as well as high precision measuring spectra of high-energy electrons and positrons, protons and nuclei up to the knee. To clarify these scientific problems with the new experimental data the GAMMA-400 gamma-ray telescope possesses unique physical characteristics comparing with previous and present experiments. For gamma-ray energies more than 100 GeV GAMMA-400 provides the energy resolution of ~1% and angular resolution better than 0.02 deg. The methods developed to reconstru...
Hu, T.; Xiao, H; Sayles, T. A.; M.B. Maple; Maki, Kazumi; Dora, B.; Almasan, C. C.
2006-01-01
In-plane angular dependent resistivity ADR was measured in the non-Fermi liquid regime of CeCoIn$_5$ single crystals at temperatures $T \\le 20$ K and in magnetic fields $H$ up to 14 T. Two scaling behaviors were identified in low field region where resistivity shows T-linear dependence, separated by a critical angle $\\theta_{c}$ which is determined by the anisotropy of CeCoIn$_5$; i.e., ADR depends only on the perpendicular (parallel) field component below (above) $\\theta_c$. These scaling be...
Gaus, Michael; Jin, Haiyun; Demapan, Darren; Christensen, Anders S; Goyal, Puja; Elstner, Marcus; Cui, Qiang
2015-09-01
We report the parametrization of a density functional tight binding method (DFTB3) for copper in a spin-polarized formulation. The parametrization is consistent with the framework of 3OB for main group elements (ONCHPS) and can be readily used for biological applications that involve copper proteins/peptides. The key to our parametrization is to introduce orbital angular momentum dependence of the Hubbard parameter and its charge derivative, thus allowing the 3d and 4s orbitals to adopt different sizes and responses to the change of charge state. The parametrization has been tested by applying to a fairly broad set of molecules of biological relevance, and the properties of interest include optimized geometries, ligand binding energies, and ligand proton affinities. Compared to the reference QM level (B3LYP/aug-cc-pVTZ, which is shown here to be similar to the B97-1 and CCSD(T) results, in terms of many properties of interest for a set of small copper containing molecules), our parametrization generally gives reliable structural properties for both Cu(I) and Cu(II) compounds, although several exceptions are also noted. For energetics, the results are more accurate for neutral ligands than for charged ligands, likely reflecting the minimal basis limitation of DFTB3; the results generally outperform NDDO based methods such as PM6 and even PBE with the 6-31+G(d,p) basis. For all ligand types, single-point B3LYP calculations at DFTB3 geometries give results very close (∼1-2 kcal/mol) to the reference B3LYP values, highlighting the consistency between DFTB3 and B3LYP structures. Possible further developments of the DFTB3 model for a better treatment of transition-metal ions are also discussed. In the current form, our first generation of DFTB3 copper model is expected to be particularly valuable as a method that drives sampling in systems that feature a dynamical copper binding site. PMID:26575916
Perini, Ana P.; Neves, Lucio P.; Xavier, Marcos; Caldas, Linda V.E., E-mail: mxavier@ipen.b, E-mail: lcaldas@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Khoury, Helen J., E-mail: khoury@ufpe.b [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear
2011-07-01
In this paper a pencil-type ionization chamber designed and manufactured at Instituto de Pesquisas Energeticas e Nucleares was evaluated for dosimetric applications in computed tomography beams. To evaluate the performance of this chamber two tests were undertaken: linearity of response and angular dependence. The results obtained in these tests showed good results, within the international recommendations. Moreover, this homemade ionization chamber is easy to manufacture, of low cost and efficient. (author)
Juchtmans, Roeland; Verbeeck, Jo
2016-02-01
The orbital angular momentum (OAM) of light and matter waves is a parameter that has been getting increasingly more attention over the past couple of years. Beams with a well-defined OAM, the so-called vortex beams, are applied already in, e.g., telecommunication, astrophysics, nanomanipulation, and chiral measurements in optics and electron microscopy. Also, the OAM of a wave induced by the interaction with a sample has attracted a lot of interest. In all these experiments it is crucial to measure the exact (local) OAM content of the wave, whether it is an incoming vortex beam or an exit wave after interacting with a sample. In this work we investigate the use of spiral phase plates (SPPs) as an alternative to the programmable phase plates used in optics to measure OAM. We derive analytically how these can be used to study the local OAM components of any wave function. By means of numerical simulations we illustrate how the OAM of a pure vortex beam can be measured. We also look at a sum of misaligned vortex beams and show how, by using SPPs, the position and the OAM of each individual beam can be detected. Finally, we look at the OAM induced by a magnetic dipole on a free-electron wave and show how the SPP can be used to localize the magnetic poles and measure their "magnetic charge." Although our findings can be applied to study the OAM of any wave function, our findings are of particular interest for electron microscopy where versatile programmable phase plates do not yet exist.
We investigate the design for a scattering with angular limitation in projection electron-beam lithography (SCALPEL) based electron projection system with a demagnification of -4. By a ''field-flip'' process we can construct a doublet in which the magnetic field has a flat feature in most of the optic column but opposite sign at two sides connected by a sharp transition region. Such a theoretical model can give a near zero chromatic aberration of rotation and much smaller field curvature and astigmatism. Compared with the conventional doublet, the total image blur caused by aberrations at 1/√(2) mm off-axis distance and 1.5 mrad semiangle aperture at the mask side is about only 24 nm for a column length of 400 mm. A shorter column, less than the current 400 mm, is also favored for further reducing the total aberration. These guarantee that we can choose a much larger aperture angle (compared with present 0.5 mrad) and beam current density in such a SCALPEL projection system to achieve higher throughput while still maintaining current resolution. A practical issue for possible magnetic lens design is also discussed. (c) 2000 American Vacuum Society
Electron-photon angular-correlation measurements for the 2P state of hydrogen at 35 eV
Electron-photon angular correlations have been measured for excitation of the 2P states of hydrogen at an incident energy of 35 eV. The data presented relate to electron-scattering angles from theta/sub e/ = 80 to theta/sub e/ = 1200 and yield values for the parameters lambdaand R. The experimental results are compared with several theories. In general, none of the theories is found to be adequate at this energy
Angular correlation measurements have been made of the Lsub(β) fluorescence arising from the excitation of the 32Psub(j) states of atomic hydrogen detected in coincidence with electrons scattered with n = 3 energy loss. Data are presented for incident energies of 54.4 and 100 eV and electron scattering angles 20 and 25 deg, and compared with the predictions of the first Born approximation. (author)
Chwirot, S.; Slevin, J.
1987-11-28
Angular correlation measurements have been made of the L/sub ..beta../ fluorescence arising from the excitation of the 3/sup 2/P/sub j/ states of atomic hydrogen detected in coincidence with electrons scattered with n = 3 energy loss. Data are presented for incident energies of 54.4 and 100 eV and electron scattering angles 20 and 25 deg, and compared with the predictions of the first Born approximation.
Unusual distance dependences of electron transfer rates.
Kuss-Petermann, Martin; Wenger, Oliver S
2016-07-28
Usually the rates for electron transfer (kET) decrease with increasing donor-acceptor distance, but Marcus theory predicts a regime in which kET is expected to increase when the transfer distance gets longer. Until recently, experimental evidence for such counter-intuitive behavior had been very limited, and consequently this effect is much less well-known than the Gaussian free energy dependence of electron transfer rates leading to the so-called inverted driving-force effect. This article presents the theoretical concepts that lead to the prediction of electron transfer rate maxima at large donor-acceptor distances, and it discusses conditions that are expected to favor experimental observations of such behavior. It continues with a consideration of specific recent examples in which electron transfer rates were observed to increase with increasing donor-acceptor distance, and it closes with a discussion of the importance of this effect in the context of light-to-chemical energy conversion. PMID:27353891
Juchtmans, Roeland
2015-01-01
The orbital angular momentum (OAM) of light and matter waves is a parameter that is getting increasingly more attention over the past couple of years. Beams with a well defined OAM, the so-called vortex beams, are applied already in e.g. telecommunication, astrophysics, nanomanipulation and chiral measurements in optics and electron microscopy. Also the OAM of a wave induced by the interaction with a sample, shows great potential of interest. In all these experiments it is crucial to measure the exact (local) OAM content of the wave, whether it is an incoming vortex beam or an exit wave after interacting with a sample. In this work we investigate the use of spiral phase plates as an alternative to the programmable phase plates used in optics to measure OAM. We derive analytically how these can be used to study the local OAM components of any wave function. By means of numerical simulations we illustrate how the OAM of a pure vortex beam can be measured. We also look at a sum of misaligned vortex beams and sho...
Felfli, Z
2015-01-01
Core-polarization interactions are investigated in low-energy electron elastic scattering from the atoms In,Sn,Eu,Au and At through the calculation of their electron affinities. The complex angular momentum method wherein is embedded the vital electron-electron correlations is used. The core-polarization effects are studied through the well investigated rational function approximation of the Thomas-Fermi potential,which can be analytically continued into the complex plane. The EAs are extracted from the large resonance peaks in the calculated low-energy electron atom scattering total cross sections and compared with those from measurements and sophisticated theoretical methods. It is concluded that when the electron-electron correlation effects and core polarization interactions are accounted for adequately the importance of relativity on the calculation of the electron affinities of atoms can be assessed. For At, relativistic effects are estimated to contribute a maximum of about 3.6 percent to its (non-rela...
Dasgupta, Basudeb; Sen, Manibrata
2016-01-01
It has been recently pointed out that neutrino fluxes from a supernova can show substantial flavor conversions almost immediately above the core. Using linear stability analyses and numerical solutions of the fully nonlinear equations of motion, we perform a detailed study of these fast conversions, focussing on the region just above the supernova core. We carefully specify the instabilities for evolution in space or time, and find that neutrinos travelling towards the core make fast conversions more generic, i.e., possible for a wider range of flux ratios and angular asymmetries. Using fluxes and angular distributions predicted by supernova simulations, we find that fast conversions can occur within tens of nanoseconds, only a few meters away from the putative neutrinospheres. If these fast flavor conversions indeed take place, they would have important implications for the supernova explosion mechanism and nucleosynthesis.
Seregin, A.A.
1976-03-01
In framework of a phenomenological collective nuclear theory the dependence of the moment of inertia on the angular velocity squared is studied. It is shown that this theory may explain the S shape of dependence of J on ..omega../sup 2/ if the collective motion potential V(..beta..) has two points of inflection. Anomalies in the low-lying part of the energy spectrum of the nuclei /sup 184/Hg and /sup 186/Hg are related to inflection points of the potential.
Vasques, Richard
2013-01-01
This paper extends a recently introduced theory describing particle transport for random statistically homogeneous systems in which the distribution function p(s) for chord lengths between scattering centers is non-exponential. Here, we relax the previous assumption that p(s) does not depend on the direction of flight \\Omega; this leads to an extended generalized linear Boltzmann equation that includes angular-dependent cross sections, and to an extended generalized diffusion equation that accounts for anisotropic behavior resulting from the statistics of the system.
Geerkens, A.; Frenck, H.J.; Ewert, S. [Technical Univ. of Cottbus (Germany)] [and others
1994-12-31
The angular dependence of the critical current density and the magnetoresistance of high-T{sub c}-films in high and low magnetic fields and for different temperatures were measured to investigate the flux pinning and the superconducting properties. A comparison of the results for the different superconductors shows their increasing dependence on the angle {Theta} between the magnetic field and the c-axis of the film due to the anisotropy of the chosen superconductor. Furthermore the influence of the current direction to the {Theta}-rotation plane is discussed.
An additive angular-dependent re-balance (AADR) factor acceleration method is described to accelerate the source iteration of discrete ordinates transport calculation. The formulation of the AADR method follows that of the angular-dependent re-balance (ADR) method in that the re-balance factor is defined only on the cell interface and in that the low-order equation is derived by integrating the transport equation (high-order equation) over angular subspaces. But, the re-balance factor is applied additively. While the AADR method is similar to the boundary projection acceleration and the alpha-weighted linear acceleration, it is more general and does have distinct features. The method is easily extendible to DPN and low-order SN re-balancing, and it does not require consistent discretizations between the high- and low-order equations as in diffusion synthetic acceleration. We find by Fourier analysis and numerical results that the AADR method with a chosen form of weighting functions is unconditionally stable and very effective. There also exists an optimal weighting parameter that leads to the smallest spectral radius. The AADR acceleration method described in this paper is simple to implement, unconditionally stable, and very effective. It uses a physically based weighting function with an optimal parameter, leading to the best spectral radius of ρ<0.1865, compared to ρ<0.2247 of DSA. The application of the AADR acceleration method with the LMB scheme on a test problem shows encouraging results
Reactor analysis methods. 6. Angular Dependence of the Fast Flux in Reactor Lattices
We study the high-energy ('fast') angular flux in an infinite lattice of fuel and moderator, finding that the flux is a bumpy, irregular function of azimuthal direction. We approximate the problem as an infinite lattice of identical pins (with cladding and gap homogenized into the fuel) in a sea of moderator. A unit cell in this lattice has a quarter-circle fuel pin inside a square of moderator, with the center of the circle at one corner of the square. To facilitate easy calculation with different transport codes, we have approximated this geometry by using square fuel pins, as shown in Fig. 1. In our idealized two-dimensional (2-D) problem, the pins and moderator are infinite in the axial direction. The materials have the following properties: 1. The fast-neutron source is in the fuel only. 2. There is within-group scattering in the fuel but almost none in the moderator. (Most scatters in the moderator will remove the neutron from the fast group.) 3. The fuel pin is n) to represent accurately, and difficult for Monte Carlo methods to sample adequately. We remark that the variation in the polar variable μ is relatively smooth (as is true in most 2-D problems). We further remark that homogenized pin cells do not produce complicated angular variations -this is a challenge encountered when we attack the transport problem with heterogeneous pin cells. (When Smith began using a long characteristic code to solve heterogeneous instead of homogenized pin cells he initially obtained large errors; subsequent discussion led us to perform the study reported here). Finally, we remark that the square fuel pins do not cause the complex behavior; preliminary investigations (and geometrical reasoning) indicate that round pins generate similar complexities. Within the discrete ordinates framework, this problem calls for a 'product' quadrature (which uses separate quadratures for the γ and μ integrals) because there is far more complexity in γ than in m. We have experimented
Calibrations of instrument efficiency of surface contamination meters are usually made with extended reference sources which are standardized in terms of 2π surface β-particle emission rates from the source surface including backscattered particles. Extended sources supplied from various metrology institutes or calibration laboratories, but the source-types such as structure, preparation method, backing and covering materials vary between manufacturers. In this work first we show how the calibration results are dependent on the source type. Second, in order to clarify the possible reason of such discrepancy, we examined the isotropy of β-particle fluences by the use of a proportional counter and also observed the angular dependence of β-particle spectra by the use of small plastic scintillation spectrometer, where the source mount can rotate relative to the detector window at various obliquities. The discrepancy in the instrument-calibration of surface contamination meters, which are mainly used under the conditions of large source-to-detector geometry, can be explained. - Highlights: ► We show how the calibration results are dependent on the source type. ► We examined the isotropy of β-particle fluences and observed the angular dependence. ► Discrepancy of instrument efficiencies using different type of sources is explained.
Epitaxial thin films of HoNi2B2C and related superconducting rare earth borocarbide compounds act as a suitable basis for numerous investigations on structural and superconductive properties such as Tc, Hc2 and Jc. A new batch of HoNi2B2C thin films was grown on ceramic single crystal magnesium oxide substrates under ultra-high vacuum conditions using pulsed laser deposition. A detailed view on the deposition parameters and the physical film properties is presented and angular Hc2- and Jc-measurements are shown. (orig.)
Spin and temperature dependence of nuclear deformation using alpha-gamma angular correlations
Alpha-particle angular distributions with respect to the spin direction of residual nuclei have been measured in heavy-ion fusion reactions. The spin direction was determined by measuring the γ-ray angular distributions, for each event, using the spin spectrometer. α-particle anisotropies have been extracted for the compound nuclear systems: 110Sn*(94 MeV), 114Sn*(80 MeV), 138Nd*(82 MeV), 164Yb*(67 MeV) and 170Yb*(135 MeV) as a function of the α-particle energy and γ-ray multiplicity. The results are compared with statistical model calculations using transmission coefficients from a spherically symmetric optical model potential. The trend of the anisotropy coefficients below the evaporation Coulomb barrier is consistent with spherical emitting shapes in the case of the Sn* isotopes. Small deformation effects are suggested by the 138Nd* and 164Yb* data. The 170Yb* data indicate a large deformation which increases considerably with increasing spin. These results are in agreement with findings for similar systems in which the decay of the giant resonances built on excited states have been studied. 16 refs., 5 figs
Braeuning, H. [Kansas State Univ., Physics Dept., Manhattan, KS (United States)]|[Lawrence Berkeley National Lab., Berkeley, CA (United States); Doerner, R.; Braeuning-Demian, A. [Universitaet Frankfurt, Inst. fuer Kernphysik, Frankfurt (Germany)] [and others
1997-10-14
Recoil ion momentum spectroscopy has been used to map the entire five-dimensional momentum space of the photo double ionization of helium at 20 eV above threshold. Angular asymmetry parameters for the relative motion of the electrons and the recoil ion have been determined and are found to be close to similar data at 1 eV above threshold. In addition the asymmetry parameter of one photoelectron is found to be in good agreement with recent theory. (author).
Misewich, J.; Zacharias, H.; Loy, M.M.T.
1985-09-01
Infrared laser excitation has been utilized to excite part of a molecular beam of NO to a single well-defined quantum state, NO(v = 1, J = 3/2, ..cap omega.. = 1/2), which is scattered from a cleaved LiF(100) surface. Laser spectroscopic detection techniques then allow the determination of rotational and electronic distributions as well as state-specific angular and velocity distributions for scattering from a single initial vibrational-rotational state.
To investigate the influence of expansion of double kinks on flux pinning properties in films with high density of columnar defects (CDs), heavy ions were irradiated onto YBCO thin films along the c-axis. The n-value exhibited a peak around B ‖ c-axis in angular dependences as well as Jc for films even with Bϕ = 12 T, while the inverse correlation between Jc and n-value was observed around B ‖ ab. The introduction of a large amount of CDs into YBCO thin films also led to much larger dynamic critical exponent z. (author)
Adams, J; Ahammed, Z; Amonett, J; Anderson, B D; Anderson, M; Arkhipkin, D; Averichev, G S; Bai, Y; Balewski, J; Barannikova, O; Barnby, L S; Baudot, J; Bekele, S; Belaga, V V; Bellingeri-Laurikainen, A; Bellwied, R; Bezverkhny, B I; Bhardwaj, S; Bhasin, A; Bhati, A K; Bichsel, H; Bielcik, J; Bielcikova, J; Bland, L C; Blyth, C O; Blyth, S L; Bonner, B E; Botje, M; Bouchet, J; Brandin, A V; Bravar, A; Bystersky, M; Cadman, R V; Cai, X Z; Caines, H; Calderón de la Barca-Sanchez, M; Castillo, J; Catu, O; Cebra, D; Chajecki, Z; Chaloupka, P; Chattopadhyay, S; Chen, H F; Chen, J H; Chen, Y; Cheng, J; Cherney, M; Chikanian, A; Choi, H A; Christie, W; Coffin, J P; Cormier, T M; Cosentino, M R; Cramer, J G; Crawford, H J; Das, D; Das, S; Daugherity, M; De Moura, M M; Dedovich, T G; De Phillips, M; Derevshchikov, A A; Didenko, L; Dietel, T; Djawotho, P; Dogra, S M; Dong, W J; Dong, X; Draper, J E; Du, F; Dunin, V B; Dunlop, J C; Dutta-Majumdar, M R; Eckardt, V; Edwards, W R; Efimov, L G; Emelianov, V; Engelage, J; Eppley, G; Erazmus, B; Estienne, M; Fachini, P; Fatemi, R; Fedorisin, J; Filimonov, K; Filip, P; Finch, E; Fine, V; Fisyak, Yu; Fu, J; Gagliardi, C A; Gaillard, L; Gans, J; Ganti, M S; Ghazikhanian, V; Ghosh, P; González, J E; Gorbunov, Y G; Gos, H; Grebenyuk, O; Grosnick, D P; Guertin, S M; Guimaraes, K S F F; Guo, Y; Gupta, N; Gutíerrez, T D; Haag, B; Hallman, T J; Hamed, A; Harris, J W; He, W; Heinz, M; Henry, T W; Hepplemann, S; Hippolyte, B; Hirsch, A; Hjort, E; Hoffmann, G W; Horner, M J; Huang, H Z; Huang, S L; Hughes, E W; Humanic, T J; Igo, G; Jacobs, P; Jacobs, W W; Jakl, P; Jia, F; Jiang, H; Jones, P G; Judd, E G; Kabana, S; Kang, K; Kapitan, J; Kaplan, M; Keane, D; Kechechyan, A; Khodyrev, V Yu; Kim, B C; Kiryluk, J; Kisiel, A; Kislov, E M; Koetke, D D; Kollegger, T; Kopytine, M; Kotchenda, L; Kouchpil, V; Kowalik, K L; Krämer, M; Kravtsov, P; Kravtsov, V I; Krüger, K; Kuhn, C; Kulikov, A I; Kumar, A; Kuznetsov, A A; Lamont, M A C; Landgraf, J M; Lange, S; La Pointe, S; Laue, F; Lauret, J; Lebedev, A; Lednicky, R; Lee, C H; Lehocka, S; Le Vine, M J; Li, C; Li, Q; Li, Y; Lin, G; Lindenbaum, S J; Lisa, M A; Liu, F; Liu, H; Liu, J; Liu, L; Liu, Z; Ljubicic, T; Llope, W J; Long, H; Longacre, R S; López-Noriega, M; Love, W A; Lu, Y; Ludlam, T; Lynn, D; Ma, G L; Ma, J G; Ma, Y G; Magestro, D; Mahapatra, D P; Majka, R; Mangotra, L K; Manweiler, R; Margetis, S; Markert, C; Martin, L; Matis, H S; Matulenko, Yu A; McClain, C J; McShane, T S; Melnik, Yu M; Meschanin, A; Miller, M L; Minaev, N G; Mioduszewski, S; Mironov, C; Mischke, A; Mishra, D K; Mitchell, J; Mohanty, B; Molnár, L; Moore, C F; Morozov, D A; Munhoz, M G; Nandi, B K; Nattrass, C; Nayak, T K; Nelson, J M; Netrakanti, P K; Nikitin, V A; Nogach, L V; Nurushev, S B; Odyniec, Grazyna Janina; Ogawa, A; Okorokov, V; Oldenburg, M; Olson, D; Pachr, M; Pal, S K; Panebratsev, Yu A; Panitkin, S Y; Pavlinov, A I; Pawlak, T; Peitzmann, T; Perevozchikov, V; Perkins, C; Peryt, W; Petrov, V A; Phatak, S C; Picha, R; Planinic, M; Pluta, J; Poljak, N; Porile, N; Porter, J; Poskanzer, A M; Potekhin, M V; Potrebenikova, E V; Potukuchi, B V K S; Prindle, D; Pruneau, C; Putschke, J; Rakness, G; Raniwala, R; Raniwala, S; Ray, R L; Razin, S V; Reinnarth, J; Relyea, D; Retière, F; Ridiger, A; Ritter, H G; Roberts, J B; Rogachevski, O V; Romero, J L; Rose, A; Roy, C; Ruan, L; Russcher, M J; Sahoo, R; Sakrejda, I; Salur, S; Sandweiss, J; Sarsour, M; Sazhin, P S; Schambach, J; Scharenberg, R P; Schmitz, N; Schweda, K; Seger, J; Selyuzhenkov, I; Seyboth, P; Shabetai, A; Shahaliev, E; Shao, M; Sharma, M; Shen, W Q; Shimansky, S S; ESichtermann; Simon, F; Singaraju, R N; Smirnov, N; Snellings, R; Sood, G; Sørensen, P; Sowinski, J; Speltz, J; Spinka, H M; Srivastava, B; Stadnik, A; Stanislaus, T D S; Stock, R; Stolpovsky, A; Strikhanov, M N; Stringfellow, B C; Suaide, A A P; Sugarbaker, E R; Sumbera, M; Sun, Z; Surrow, B; Swanger, M; Symons, T J M; Szanto, A; de Toledo; Tai, A; Takahashi, J; Tang, A H; Tarnowsky, T J; Thein, D; Thomas, J H; Timmins, A R; Timoshenko, S; Tokarev, M; Trainor, T A; Trentalange, S; Tribble, R E; Tsai, O D; Ulery, J; Ullrich, T; Underwood, D G; Van Buren, G; Van der Kolk, N; Van Leeuwen, M; Van der Molen, A M; Varma, R; Vasilevski, I M; Vasilev, A N; Vernet, R; Vigdor, S E; Viyogi, Y P; Vokal, S; Waggoner, W T; Wang, F; Wang, G; Wang, J S; Wang, X L; Wang, Y; Watson, J W; Webb, J C; Westfall, G D; Wetzler, A; Whitten, C; Wieman, H; Wissink, S W; Witt, R; Wood, J; Wu, J; Xu, N; Xu, Q H; Xu, Z; Yepes, P; Yoo, I K; Yurevich, V I; Zhan, W; Zhang, H; Zhang, W M; Zhang, Y; Zhang, Z P; Zhao, Y; Zhong, C; Zoulkarneev, R; Zoulkarneeva, Y; Zubarev, A N; Zuo, J X
2006-01-01
We present the first study of the energy dependence of $p_t$ angular correlations inferred from event-wise mean transverse momentum $$ fluctuations in heavy ion collisions. We compare our large-acceptance measurements at CM energies $\\sqrt{s_{NN}} =$ 19.6, 62.4, 130 and 200 GeV to SPS measurements at 12.3 and 17.3 GeV. $p_t$ angular correlation structure suggests that the principal source of $p_t$ correlations and fluctuations is minijets (minimum-bias parton fragments). We observe a dramatic increase in correlations and fluctuations from SPS to RHIC energies, increasing linearly with $\\ln \\sqrt{s_{NN}}$ from the onset of observable jet-related $$ fluctuations near 10 GeV.
Study on Angular Dependence in Micro-cavity OLED%微腔OLED的视角特性研究
袁桃利; 张方辉; 牟强; 马颖; 张思璐
2012-01-01
The angular dependence of QLED is studied and it showed that the brightness and current efficiency gradually decreased with increased view angle, the intensity and current efficiency at 50 degrees dropped to 1/3 and 40% respectively with respect to the normal direction. And Color coordinates produce drift at a certain extent with increased view angle, but spectral peak and FWHM didn＇t change depend on the angle. Reasons for the occurrence of angular dependence were discussed.%文章研究了微腔OLED的视角特性,结果表明,亮度和发光效率随着视角的增加逐渐减小,当视角增加到50°时,其亮度降为正面输出的1/3;发光效率下降了约40%左右;色坐标随着视角的增加产生漂移,而光谱峰值和半高宽基本不随视角的变化而变化。同时分析并讨论了视角特性产生的原因。
Local electron tomography using angular variations of surface tangents: Stomo version 2
Petersen, T. C.; Ringer, S. P.
2012-03-01
In a recent publication, we investigated the prospect of measuring the outer three-dimensional (3D) shapes of nano-scale atom probe specimens from tilt-series of images collected in the transmission electron microscope. For this purpose alone, an algorithm and simplified reconstruction theory were developed to circumvent issues that arise in commercial "back-projection" computations in this context. In our approach, we give up the difficult task of computing the complete 3D continuum structure and instead seek only the 3D morphology of internal and external scattering interfaces. These interfaces can be described as embedded 2D surfaces projected onto each image in a tilt series. Curves and other features in the images are interpreted as inscribed sets of tangent lines, which intersect the scattering interfaces at unknown locations along the direction of the incident electron beam. Smooth angular variations of the tangent line abscissa are used to compute the surface tangent intersections and hence the 3D morphology as a "point cloud". We have published the explicit details of our alternative algorithm along with the source code entitled "stomo_version_1". For this work, we have further modified the code to efficiently handle rectangular image sets, perform much faster tangent-line "edge detection" and smoother tilt-axis image alignment using simple bi-linear interpolation. We have also adapted the algorithm to detect tangent lines as "ridges", based upon 2nd order partial derivatives of the image intensity; the magnitude and orientation of which is described by a Hessian matrix. Ridges are more appropriate descriptors for tangent-line curves in phase contrast images outlined by Fresnel fringes or absorption contrast data from fine-scale objects. Improved accuracy, efficiency and speed for "stomo_version_2" is demonstrated in this paper using both high resolution electron tomography data of a nano-sized atom probe tip and simulated absorption-contrast images
Artru, Xavier
2014-01-01
The tunneling ionization of a hydrogen atom excited in the presence of a static electric field is investigated for the case where, before being extracted, the electron has an orbital angular momentum L perpendicular to the field E. The escaping electron has a nonzero mean transverse velocity in the direction of E cross . This asymmetry is similar to the Collins effect in the fragmentation into hadrons of a transversely polarized quark. In addition, the linear Stark effect make and oscillate in time. The degree of asymmetry is calculated at leading order in E for an initial state of maximum transverse . The conditions for the observation of this asymmetry are discussed.
Okabayashi, Jun; Sukegawa, Hiroaki; Wen, Zhenchao; Inomata, Koichiro; Mitani, Seiji
2013-09-01
Perpendicular magnetic anisotropy (PMA) in Heusler alloy Co2FeAl thin films sharing an interface with a MgO layer is investigated by angular-dependent x-ray magnetic circular dichroism. Orbital and spin magnetic moments are deduced separately for Fe and Co 3d electrons. In addition, the PMA energies are estimated using the orbital magnetic moments parallel and perpendicular to the film surfaces. We found that PMA in Co2FeAl is determined mainly by the contribution of Fe atoms with large orbital magnetic moments, which are enhanced at the interface between Co2FeAl and MgO. Furthermore, element specific magnetization curves of Fe and Co are found to be similar, suggesting the existence of ferromagnetic coupling between Fe and Co PMA directions.
Angular dependence of the facular-sunspot coverage relation as derived by MDI magnetograms
Criscuoli, Serena
2016-01-01
Previous studies have shown that the variation over the solar magnetic activity cycle of the area of facular/network features identified on broad band and narrow band imagery is positively correlated with the sunspot area and number, the relation between the area coverages being described as either linear or quadratic. On the other hand, the temporal variation of the spatial distributions of faculae, network and sunspots follows patterns that are less obviously correlated, so that we expect the relation that describes variation of the area coverage of different types of magnetic features to vary with the position over the disk. In this work we employ MDI full-disk magnetograms acquired during Cycle 23 and at the beginning of Cycle 24 to investigate the relation between the coverage of magnetic elements characterized by different amounts of magnetic flux and located at different angular distances from disk center with the sunspot number. In agreement with some previous studies we find that daily data are best ...
The radiative electron capture into medium- and high-Z, lithium-like ions is studied in the framework of the density matrix theory. For these few-electron ions, detailed computations have been carried out for the angular distribution of the emitted X-rays following the capture into the low-lying 1s22s2ljLJ1,3 beryllium-like levels, including the 1s22s2S01 ground state. In these computations, emphasis is placed on the many-electron effects which arise especially at low collision energies. For slow projectiles of a few MeV/u, the interelectronic effects may reduce the angle-differential cross-sections by about 5% when compared with effective one-electron calculations
S Mondal; R K Singh; R Shanker
2003-06-01
Relative cross sections, differential in energy and angle, for electrons ejected from CH4 and C3H8 molecules under 16.0 keV electron impact have been measured. Electrons were analyzed by a 45° parallel plate electrostatic analyzer at emission angles varying from 60° to 135° with energies from 50 eV to 1000 eV. The angular distributions of electrons exhibit structures which are found to arise from Coulomb and non-Coulomb interactions. Furthermore, the double differential cross sections of electrons ejected from C3H8 molecule are found to be higher in magnitude than those from CH4. This result supports the fact that the number of ejected electrons participating in collisions with C3H8 molecules is more than that in CH4. Also, the angular distributions of C–K-shell Auger electrons emitted from the target molecules have been studied and shown to be isotropic within the experimental uncertainty.
Angular dependence of the redeposition rates during SiO2 etching in a CF4 plasma
The angular dependence of the redeposition rates during SiO2 etching in a CF4 plasma was studied using three types of Faraday cages located in a transformer coupled plasma etcher. The SiO2 substrates were fixed on sample holder slopes that have different angles to the cathode. The substrate was subjected to one of three processes depending on the design of the Faraday cage, i.e., redeposition of sputtered particles from the SiO2 bottom surface (case I), substrate etching by incident ions (case II), or simultaneous etching and redeposition (case III). Both the redeposition and the etch rates were measured by changing the substrate-surface angle and the self-bias voltage in the range of -100 to -800 V. The redeposition-only rates (case I) at -450 and -800 V closely followed the quadratic curve of the angle whereas the rates at -100 V followed the cubic curve, indicating different mechanisms of the bottom SiO2 etching depending on the energy regimes. The steep increase of the redeposition rate with the angle was attributed to three factors: the substrate-bottom distance, the angular distribution of emitted particles from the bottom surface, and the particle incident angle on the substrate surface. The etch-only rate curves (case II) closely followed the cosine of the surface angle. The etch-rate curve changed into a reverse-S shape when the substrate was subjected to simultaneous etching and redeposition (case III). The net etch rate for case III decreased drastically above 60 deg. , showing a negative value, i.e., a net redeposition, beyond 75 deg. . The drastic decrease in the net etch rate coincided with the steep increase in the redeposition rate, implying the significant effect of redeposition
Chen, Yunzhong; Sun, J.R.; Zhao, T.Y.;
2009-01-01
directions was observed with the appearance of magnetic-field-induced metal-insulator transition, which further led to a sign crossover in the AMR effect. The AMR crossover may give a direct evidence of the drastic modification of electronic structure or possible orbital reconstruction with the magnetic...
Rozhkova, E. I.; Pivovarov, Yu. L.
2016-07-01
The Cherenkov radiation (ChR) angular distribution is usually described by the Tamm-Frank (TF) theory, which assumes that relativistic charged particle moves uniformly and rectilinearly in the optically transparent radiator. According to the TF theory, the full width at half maximum (FWHM) of the ChR angular distribution inversely depends on the radiator thickness. In the case of relativistic heavy ions (RHI) a slowing-down in the radiator may sufficiently change the angular distribution of optical radiation in vicinity of the Cherenkov cone, since there appears a mixed ChR-Bremsstrahlung radiation. As a result, there occurs a drastic transformation of the FWHM of optical radiation angular distribution in dependence on the radiator thickness: from inversely proportional (TF theory) to the linearly proportional one. In our paper we present the first analysis of this transformation taking account of the gradual velocity decrease of RHI penetrating through a radiator.
Electron-gamma perturbed angular correlation studies on high-TC superconductors
Recent results on the study of high-TC superconductors using the e--γperturbed angular correlation technique are presented. The basic features of the experimental equipment and its installation at the ISOLDE facility are briefly described. Results obtained from 197mHg implanted into high quality Y1Ba2Cu3O6+δ epitaxy thin films are presented and discussed
Erpenbeck, A.; Härtle, R.; Bockstedte, M.; Thoss, M.
2016-03-01
We investigate the role of electronic-vibrational coupling in resonant electron transport through single-molecule junctions, taking into account that the corresponding coupling strengths may depend on the charge and excitation state of the molecular bridge. Within an effective-model Hamiltonian approach for a molecule with multiple electronic states, this requires to extend the commonly used model and include vibrationally dependent electron-electron interaction. We use Born-Markov master equation methods and consider selected models to exemplify the effect of the additional interaction on the transport characteristics of a single-molecule junction. In particular, we show that it has a significant influence on local cooling and heating mechanisms, it may result in negative differential resistance, and it may cause pronounced asymmetries in the conductance map of a single-molecule junction.
Angular dependence of the luminance and contrast in medical monochrome liquid crystal displays
Active-matrix liquid crystal displays (AMLCDs) are light-modulating devices that generate images by differentially transmitting a nearly uniform luminous field provided by a backlight. While emissive displays exhibit a quasi-Lambertian emission with almost constant contrast at off-normal viewing, the anisotropy of the electro-optic effect that controls light transmission in AMLCDs causes a pixel luminance that varies, sometimes strongly, with viewing angle. These variations are not identical for all gray levels and can eventually cause grayscale inversions. In this paper, we measured the luminance emission of a monochrome medical AMLCD, a medical cathode-ray tube monitor, and a color desktop AMLCD, using a collimated photopic probe positioned on a manual rotation arm, and a research radiometer with automatic readout. The probe measures luminance with a small acceptance angle and provides optical shielding from emissions at other viewing directions that contaminate the readings. We obtained luminance response curves versus angle in the vertical, horizontal and at 45 deg. diagonal directions. The display systems were calibrated to reflect the DICOM Part 3.14 standard grayscale display function (GDF) when measured using the manufacturer's probe and software tools. We analyzed the measurements at different viewing directions with respect to their departure from the GDF by computing the normalized contrast (ΔL/L) as a function of the DICOM just-noticeable difference index. Although cathode-ray tubes are known to be quasi-Lambertian emitters, the luminance at normal viewing is higher than the luminance observed at large angles. This decrease in luminance is however proportionally similar for all gray levels, resulting in a relatively flat contrast response for all angles. In addition to being more pronounced, the angular variation in AMLCDs does not follow the same profile at different intensities with the subsequent variation in the achieved display contrast. The
Kurian, P.; Verzegnassi, C.
2016-01-01
We consider in a quantum field theory framework the effects of a classical magnetic field on the spin and orbital angular momentum (OAM) of a free electron. We derive formulae for the changes in the spin and OAM due to the introduction of a general classical background field. We consider then a constant magnetic field, in which case the relevant expressions of the effects become much simpler and conversions between spin and OAM become readily apparent. An estimate of the expectation values for a realistic electron state is also given. Our findings may be of interest to researchers in spintronics and the field of quantum biology, where electron spin has been implicated on macroscopic time and energy scales.
R K Yadav; R Shanker
2007-03-01
The energy and angular distributions of backscattered electrons produced under the impact of 5 keV electrons with thick Al, Ti, Ag, W and Pt targets are measured. The energy range of backscattered electrons is considered between B = 50 eV and 5000 eV. The angle of incidence α and take-off angle are chosen to have values = 0° and 10° and = 100°, 110° and 120° respectively. The measured energy spectra are compared with the available theoretical models for = 0° and 10°. The elastic peak intensity of backscattered electrons is found to be a function of angle of incidence, take-off angle and atomic number of the target material. The considered theories are reasonably in good agreement with experiment for the energy spectra of the backscattered electrons having their reduced energies (= B/0) in the range of 0.20 to 1.00.
We report on the results of measurements of the angular dependence of magnetization of high-Tc superconducting YBa2Cu3O7-δ and La1.85Sr0.15CuO4 thin films and superconducting/ferromagnetic YBa2Cu3O7-δ/Nd0.76Sr0.33MnO3 superlattices. We compare our present results to our results, previously obtained for YBa2Cu3O7-δ and Bi2Sr2CaCu2O8 single crystals. We discuss the influence of the presence of Nd0.67Sr0.33MnO3 sublayers in YBa2Cu3O7-δ/Nd0.67Sr0.33MnO3 superlattices on the critical temperature, flux pinning, and the critical field for the first vortex penetration. (orig.)
Angular dependence of transport current near critical at fields to 4 T in metalorganic thin films
Values of the transport current have been obtained as a function of angle of the magnetic field to the plane of the thin film YBa2Cu3O7-d (YBCO) prepared by metalorganic deposition. Current flowed in the a.b planes at various angles to the applied magnetic fields to 4.2 T. Films with thicknesses near 350 nm were studied. For these thin films and H|c a secondary maximum is observed when Jc > 1 MA/cm2. Near H|a, b a large increase in Ic is observed, and the sharpness, field dependence, and field directional dependence is discussed. The response to currents above Ic is determined and the fit to a power law V approximately In shows a strong correlation between Ic and n. 14 refs., 11 figs., 1 tab
Effect of Angular Velocity on Sensors Based on Morphology Dependent Resonances
Ali, Amir R.; Tindaro Ioppolo
2014-01-01
We carried out an analysis to investigate the morphology dependent optical resonances shift (MDR) of a rotating spherical resonator. The spinning resonator experiences an elastic deformation due to the centrifugal force acting on it, leading to a shift in its MDR. Experiments are also carried out to demonstrate the MDR shifts of a spinning polydimethylsiloxane (PDMS) microsphere. The experimental results agree well with the analytical prediction. These studies demonstrated that spinning senso...
Angular Dependence of ϕ Meson Production for Different Photon Beam Energies
The dependence of ϕ-meson photoproduction on the polar angle is investigated in the framework of a multisource thermal model. We present a detailed comparison between our results and experimental data of the neutral decay mode in the reaction γp→pϕ(KSKL). The results are in good agreement with the experimental data. It is found that the movement factor bz increases linearly with the photon beam energies
Parametric dependencies of JET electron temperature profiles
Schunke, B. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Imre, K.; Riedel, K. [New York Univ., NY (United States)
1994-07-01
The JET Ohmic, L-Mode and H-Mode electron temperature profiles obtained from the LIDAR Thomson Scattering Diagnostic are parameterized in terms of the normalized flux parameter and a set of the engineering parameters like plasma current, toroidal field, line averages electron density... It is shown that the electron temperature profiles fit a log-additive model well. It is intended to use the same model to predict the profile shape for D-T discharges in JET and in ITER. 2 refs., 5 figs.
YouLiang Jing; ZhiFeng Li; Qian Li; PingPing Chen; XiaoHao Zhou; Han Wang; Ning Li; Wei Lu
2016-01-01
We report the dependence of the near-field optical modes in metal-insulator-metal quantum well infrared photodetector (MIM-QWIP) on the incident angles. Three optical modes are observed and attributed to the 2nd- and the 3rd-order surface plasmon polariton (SPP) modes and the localized surface polariton (LSP) mode. In addition to the observation of a responsivity enhancement of 14 times by the LSP mode, the varying pattern of the three modes against the incident angle are revealed, in which t...
THE MASS-DEPENDENCE OF ANGULAR MOMENTUM EVOLUTION IN SUN-LIKE STARS
Matt, Sean P.; Baraffe, Isabelle; Chabrier, Gilles [Department of Physics and Astronomy, University of Exeter, Physics Building, Stocker Road, Exeter, EX4 4QL (United Kingdom); Brun, A. Sacha [Laboratoire AIM Paris-Saclay, CEA/Irfu Université Paris-Diderot CNRS/INSU, F-91191 Gif-sur-Yvette (France); Bouvier, Jérôme, E-mail: s.matt@exeter.ac.uk [Université de Grenoble Alpes, IPAG, F-38000 Grenoble (France)
2015-02-01
To better understand the observed distributions of the rotation rate and magnetic activity of Sun-like and low-mass stars, we derive a physically motivated scaling for the dependence of the stellar wind torque on the Rossby number. The torque also contains an empirically derived scaling with stellar mass (and radius), which provides new insight into the mass-dependence of stellar magnetic and wind properties. We demonstrate that this new formulation explains why the lowest mass stars are observed to maintain rapid rotation for much longer than solar-mass stars, and simultaneously why older populations exhibit a sequence of slowly rotating stars, in which the low-mass stars rotate more slowly than solar-mass stars. The model also reproduces some previously unexplained features in the period-mass diagram for the Kepler field, notably: the particular shape of the ''upper envelope'' of the distribution, suggesting that ∼95% of Kepler field stars with measured rotation periods are younger than ∼4 Gyr; and the shape of the ''lower envelope'', corresponding to the location where stars transition between magnetically saturated and unsaturated regimes.
Angular dependence and symmetry of Rashba spin torque in ferromagnetic heterostructures
Ortiz Pauyac, Christian
2013-06-26
In a ferromagnetic heterostructure, the interplay between Rashba spin-orbit coupling and exchange splitting gives rise to a current-driven spin torque. In a realistic device setup, we investigate the Rashba spin torque in the diffusive regime and report two major findings: (i) a nonvanishing torque exists at the edges of the device even when the magnetization and effective Rashba field are aligned; (ii) anisotropic spin relaxation rates driven by the Rashba spin-orbit coupling assign the spin torque a general expression T = T y (θ) m × (y × m) + T y (θ) y × m + T z (θ) m × (z × m) + T z (θ) z × m, where the coefficients T, y, z depend on the magnetization direction. Our results agree with recent experiments. © 2013 AIP Publishing LLC.
Simulations of the angular dependence of the dipole–dipole interaction among Rydberg atoms
Bigelow, Jacob L.; Paul, Jacob T.; Peleg, Matan; Sanford, Veronica L.; Carroll, Thomas J.; Noel, Michael W.
2016-08-01
The dipole–dipole interaction between two Rydberg atoms depends on the relative orientation of the atoms and on the change in the magnetic quantum number. We simulate the effect of this anisotropy on the energy transport in an amorphous many atom system subject to a homogeneous applied electric field. We consider two experimentally feasible geometries and find that the effects should be measurable in current generation imaging experiments. In both geometries atoms of p character are localized to a small region of space which is immersed in a larger region that is filled with atoms of s character. Energy transfer due to the dipole–dipole interaction can lead to a spread of p character into the region initially occupied by s atoms. Over long timescales the energy transport is confined to the volume near the border of the p region which suggests Anderson localization. We calculate a correlation length of 6.3 μm for one particular geometry.
Angular and Frequency-Dependent Wave Velocity and Attenuation in Fractured Porous Media
Carcione, José M.; Gurevich, Boris; Santos, Juan E.; Picotti, Stefano
2013-11-01
Wave-induced fluid flow generates a dominant attenuation mechanism in porous media. It consists of energy loss due to P-wave conversion to Biot (diffusive) modes at mesoscopic-scale inhomogeneities. Fractured poroelastic media show significant attenuation and velocity dispersion due to this mechanism. The theory has first been developed for the symmetry axis of the equivalent transversely isotropic (TI) medium corresponding to a poroelastic medium containing planar fractures. In this work, we consider the theory for all propagation angles by obtaining the five complex and frequency-dependent stiffnesses of the equivalent TI medium as a function of frequency. We assume that the flow direction is perpendicular to the layering plane and is independent of the loading direction. As a consequence, the behaviour of the medium can be described by a single relaxation function. We first consider the limiting case of an open (highly permeable) fracture of negligible thickness. We then compute the associated wave velocities and quality factors as a function of the propagation direction (phase and ray angles) and frequency. The location of the relaxation peak depends on the distance between fractures (the mesoscopic distance), viscosity, permeability and fractures compliances. The flow induced by wave propagation affects the quasi-shear (qS) wave with levels of attenuation similar to those of the quasi-compressional (qP) wave. On the other hand, a general fracture can be modeled as a sequence of poroelastic layers, where one of the layers is very thin. Modeling fractures of different thickness filled with CO2 embedded in a background medium saturated with a stiffer fluid also shows considerable attenuation and velocity dispersion. If the fracture and background frames are the same, the equivalent medium is isotropic, but strong wave anisotropy occurs in the case of a frameless and highly permeable fracture material, for instance a suspension of solid particles in the fluid.
Artru, X.; Redouane-Salah, E.
2016-02-01
The tunneling ionization of an excited hydrogen atom by a static electric field E is investigated for the case where the initial electron has an orbital angular momentum L nonparallel to E . The outgoing electron has a nonzero mean transverse velocity in the direction of E × . During this process the linear Stark effect makes and oscillate or rotate about E . Measures of the asymmetry are calculated at leading order in E for an initial state 2 P state. The generalization to coherent elliptic Rydberg states is outlined. A subset of these states whose classical Kepler ellipses rotate rigidly about E is particularly interesting for the observation of the asymmetry. The preparation of states with L nonparallel to E and the conditions to get a sizable vT asymmetry are discussed.
Evans, M. W.
1992-07-01
Optical NMR and ESR is a recently introduced technique in which a circularly polarized laser (a "light magnet") is used in an NMR or ESR spectrometer to induce magnetization. The spectral consequencies are developed with a quantum theory similar to the rigorous theory of Zeeman splitting of Russell-Saunders states, a theory which is suitable for atoms and molecules with net electronic angular momentum, and in which the antisymmetric electronic polarizability is finite. The optical NMR and ESR Hamiltonians are developed with the Wigner-Eckhart Theorem. The circularly polarized laser shifts the original NMR or ESR resonance lines, and splits the shifted lines into analytically useful patterns. The theory gives Landé factors which are in agreement with an earlier, simple, semiclassical theory ( J. Phys. Chem.95, 2256-2260 (1991)).
Angular Dependence of Jet Quenching Indicates Its Strong Enhancement Near the QCD Phase Transition
Liao, Jinfeng; Shuryak, Edward
2008-10-22
We study dependence of jet quenching on matter density, using 'tomography' of the fireball provided by RHIC data on azimuthal anisotropy v{sub 2} of high p{sub t} hadron yield at different centralities. Slicing the fireball into shells with constant (entropy) density, we derive a 'layer-wise geometrical limit' v{sub 2}{sup max} which is indeed above the data v{sub 2} < v{sub x}{sup max}. Interestingly, the limit is reached only if quenching is dominated by shells with the entropy density exactly in the near-T{sub c} region. We show two models that simultaneously describe the high p{sub t} v{sub 2} and R{sub AA} data and conclude that such a description can be achieved only if the jet quenching is few times stronger in the near-T{sub c} region relative to QGP at T > T{sub c}. One possible reason for that may be recent indications that the near-T{sub c} region is a magnetic plasma of relatively light color-magnetic monopoles.
YouLiang Jing
2016-04-01
Full Text Available We report the dependence of the near-field optical modes in metal-insulator-metal quantum well infrared photodetector (MIM-QWIP on the incident angles. Three optical modes are observed and attributed to the 2nd- and the 3rd-order surface plasmon polariton (SPP modes and the localized surface polariton (LSP mode. In addition to the observation of a responsivity enhancement of 14 times by the LSP mode, the varying pattern of the three modes against the incident angle are revealed, in which the LSP mode is fixed while the 2nd SPP mode splits into two branches and the 3rd SPP mode red-shifts. The detailed mechanisms are analyzed and numerically simulated. The results fit the experiments very well, demonstrating the wavevector coupling effect between the incident light and the metal gratings on the SPP modes. Our work will pave the way to fully understanding the influence of incident angles on a detector’s response for applying the MIM-QWIP to focal plane arrays.
Jing, YouLiang; Li, ZhiFeng; Li, Qian; Chen, PingPing; Zhou, XiaoHao; Wang, Han; Li, Ning; Lu, Wei
2016-04-01
We report the dependence of the near-field optical modes in metal-insulator-metal quantum well infrared photodetector (MIM-QWIP) on the incident angles. Three optical modes are observed and attributed to the 2nd- and the 3rd-order surface plasmon polariton (SPP) modes and the localized surface polariton (LSP) mode. In addition to the observation of a responsivity enhancement of 14 times by the LSP mode, the varying pattern of the three modes against the incident angle are revealed, in which the LSP mode is fixed while the 2nd SPP mode splits into two branches and the 3rd SPP mode red-shifts. The detailed mechanisms are analyzed and numerically simulated. The results fit the experiments very well, demonstrating the wavevector coupling effect between the incident light and the metal gratings on the SPP modes. Our work will pave the way to fully understanding the influence of incident angles on a detector's response for applying the MIM-QWIP to focal plane arrays.
On the exchange of orbital angular momentum between twisted photons and atomic electrons
We obtain an expression for the matrix element for scattering of a twisted (Laguerre–Gaussian profile) photon from a hydrogen atom. We consider photons incoming with an orbital angular momentum (OAM) of ℓħ, carried by a factor of eiℓϕ not present in a plane-wave or pure Gaussian profile beam. The nature of the transfer of +2ℓ units of OAM from the photon to the azimuthal atomic quantum number of the atom is investigated. We obtain simple formulas for these OAM flip transitions for elastic forward scattering of twisted photons when the photon wavelength λ is large compared with the atomic target size a, and small compared with the Rayleigh range zR, which characterizes the collimation length of the twisted photon beam. (paper)
Yamada, Takahiro; Kawada, Yasushi; Ishizu, Hidetake; Yamamoto, Shinich; Yunoki, Akira; Sato, Yasushi; Unno, Yasuhiro; Hino, Yoshio
2012-09-01
Calibrations of instrument efficiency of surface contamination meters are usually made with extended reference sources which are standardized in terms of 2π surface β-particle emission rates from the source surface including backscattered particles. Extended sources supplied from various metrology institutes or calibration laboratories, but the source-types such as structure, preparation method, backing and covering materials vary between manufacturers. In this work first we show how the calibration results are dependent on the source type. Second, in order to clarify the possible reason of such discrepancy, we examined the isotropy of β-particle fluences by the use of a proportional counter and also observed the angular dependence of β-particle spectra by the use of small plastic scintillation spectrometer, where the source mount can rotate relative to the detector window at various obliquities. The discrepancy in the instrument-calibration of surface contamination meters, which are mainly used under the conditions of large source-to-detector geometry, can be explained. PMID:22424745
Takahashi, Kayori; Kato, Haruhisa; Kinugasa, Shinichi
2011-01-01
A standard method for nanoparticle sizing based on the angular dependence of dynamic light scattering was developed. The dependences of the diffusion coefficients for aqueous suspensions of polystyrene latex on the concentration and scattering angle were accurately measured by using a high-resolution dynamic light-scattering instrument. Precise measurements of the short-time correlation function at seven scattering angles and five concentrations were made for suspensions of polystyrene latex particles with diameters from 30 to 100 nm. The apparent diffusion coefficients obtained at various angles and concentrations showed properties characteristic of polystyrene latex particles with electrostatic interactions. A simulation was used to calculate a dynamic structure factor representing the long-range interactions between particles. Extrapolations to infinite dilution and to low angles gave accurate particle sizes by eliminating the effects of long-range interactions. The resulting particle sizes were consistent with those measured by using a differential mobility analyzer and those obtained by pulsed-field gradient nuclear magnetic resonance measurements. PMID:21747185
Perveaux, A; Lasorne, B; Gatti, F; Robb, M A; Halász, G J; Vibók, Á
2014-01-01
A nonadiabatic scheme for the description of the coupled electron and nuclear motions in the ozone molecule was proposed recently. An initial coherent nonstationary state was prepared as a superposition of the ground state and the excited Hartley band. In this situation neither the electrons nor the nuclei are in a stationary state. The multiconfiguration time dependent Hartree method was used to solve the coupled nuclear quantum dynamics in the framework of the adiabatic separation of the time-dependent Schr\\"odinger equation. The resulting wave packet shows an oscillation of the electron density between the two chemical bonds. As a first step for probing the electronic motion we computed the time-dependent molecular dipole and the Dyson orbitals. The latter play an important role in the explanation of the photoelectron angular distribution. Calculations of the Dyson orbitals are presented both for the time-independent as well as the time-dependent situations. We limited our description of the electronic mot...
Effect of Electronic Monitoring on Social Welfare Dependence
Andersen, Lars Højsgaard; Andersen, Signe Hald
2014-01-01
Research Summary We studied the effect on unemployment social welfare dependence of serving a sentence under elec-tronic monitoring rather than in prison, using Danish registry data and two policy shifts that extended the use of electronic monitoring in Denmark. We found electronic monitoring is ...