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1.
We have calculated thef-sum rule for magnetic neutron scattering off electrons. Correlations alter the cross-section significantly at intermediate scattering vectors. Field induced effects are most significant at small scattering vectors, and the sum rule diverges in the limit of zero scattering vector. This feature is attributed to the field induced coupling of neutrons to the lowest energy Landau level and the collective density oscillation (hybrid mode). Our interpretation is based on an RPA calculation of the response function for neutron scattering from a magnetized plasma. The contribution to the cross-section from the electron-phonon interaction is also assessed, and it is found to increase with decreasing scattering vector. 相似文献
2.
ZHU Jiaqing 《Chinese Journal of Lasers》1995,4(1):25-29
TheResearchofScatteringCross-SectionandEnergy-ExtractioninFELTheResearchofScatteringCross-SectionandEnergy-ExtractioninFEL¥ZH... 相似文献
3.
A. Vančura 《Czechoslovak Journal of Physics》1964,14(11):810-816
A multi-channel model of weak scattering is developed, based on the four-fermion theory of weak interactions using the Bethe-Salpeter equation. It leads to several relations among the crosssections of different weak scattering processes. In the low energy limit the cross-section of all included reactions are expressed with the help of a single constant. 相似文献
4.
A. Michels J. Weissmüller 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):57-65
This paper presents a calculation of the magnetic small-angle neutron scattering cross-section resulting from a dilute ensemble
of superparamagnetic particles exhibiting uniaxial magnetic anisotropy. We focus on the two experimentally relevant scattering
geometries in which the incident neutron beam is perpendicular or parallel to an applied magnetic field, and we discuss several
orientations of the anisotropy axes with respect to the field. Magnetic anisotropy has no influence on the magnetic small-angle
neutron scattering when the particles are mobile, as is the case e.g. in ferrofluids, but, when the particles are embedded
in a rigid non-magnetic matrix and the orientations of the anisotropy axes are fixed, significant deviations compared to the
case of negligible anisotropy are expected. For the particluar situation in which the anisotropy axes are parallel to the
applied field, closed-form expressions suggest that an effective anisotropy energy or anisotropy-energy distribution can be
determined from experimental scattering data.
Received 8 November 2001 相似文献
5.
P. A. Alekseev J. -M. Mignot E. V. Nefedova K. S. Nemkovskii V. N. Lazukov I. P. Sadikov A. Ochiai 《JETP Letters》2004,79(2):81-84
The dynamic magnetic susceptibility spectrum in a single-crystal sample of the intermediate-valence compound Sm0.67Y0.33S is studied by inelastic neutron scattering with neutron momentum transfer and sample temperatures varying over wide ranges. Two coupled collective modes have been found in the spectrum. Unlike the higher energy mode, whose intensity approximately follows the form factor of Sm2+, the lower energy mode exhibits a stronger angular dependence than could be expected from the form factor for the localized f electrons. The total intensity of the inelastic component of the magnetic response decreases with increasing temperature; this is accompanied by the appearance of a broad quasi-elastic signal of a magnetic nature at significantly lower temperatures than follows from the calculated intensities of the transitions within the excited multiplet of the Sm2+ ion. An analysis of the observed features allows the suggestion to be made that the fine structure of the magnetic excitation spectrum in (Sm,Y)S is associated with the formation of an exciton-like intermediate-valence state on Sm ions rather than with the crystal-electric-field effects. 相似文献
6.
7.
G. Feldman M. Andersson J. R. M. Annand R. Codling K. Fissum K. Hansen S. Henshaw L. Isaksson M. A. Kovash M. Lundin D. E. Mittelberger L. Myers A. M. Nathan B. Schröder S. Stave H. R. Weller 《Few-Body Systems》2008,44(1-4):325-328
A new program of Compton scattering on deuterium is under way at the tagged-photon facility at MAX-Lab in Lund, Sweden. We will measure differential cross sections between 60° and 150° over the photon energy range 60–115?MeV in 5?MeV steps, with the ultimate goal of obtaining new precision information on the electric and magnetic polarizabilities of the neutron. 相似文献
8.
9.
A SEMI-CLASSICAL ANALYSIS ON THE REACTION 12C+209Bi AT BOMBARDING ENERGIES SLIGHTLY ABOVE THE COULOMB BARRIER
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For reactions induced by light heavy ion such as 12C, at bombarding energy slightly above the coulomb barrier, using semi-classical theory, neglecting macroscopic frictional force, the reaction mechnisms are sorted by the orbital angular momentum of the entrance channel from the classical deflection functions fitting elastic scattering. Moreover, inserting a transfer probability factor representing the Q-Window effect into the semi-classical angular distribution formula of Kalinkin and Grabowski, we obtain a formula for the differential cross-section per unit energy interval. The calculated results, including the elastic scattering angular distributions, energy spectrum and angular distributions of emitted α-particles in quasi-elastic process, complete fusion cross-section, fusion-fission cross-sections and the exitation functions of evaporated neutron, agree with the experimental data on the reaction 12C+209Bi reported by our Institute. 相似文献
10.
Chen SH Mallamace F Faraone A Gambadauro P Lombardo D Chen WR 《The European physical journal. E, Soft matter》2002,9(3):283-286
We detect in a tri-block co-polymer micellar system an ergodic-to-nonergodic-to-ergodic transition, as a function of temperature,
in a range of concentrations, by photon correlation measurements. The shear viscosity is also shown to jump two order of magnitude
at these transition temperatures. Surprisingly, the structure factor as measured by small angle neutron scattering shows a
marked narrowing at the structural arrest state. Rationalization of these results with the existence of an attractive branch
in the phase diagram of an attractive colloid system predicted by mode coupling theory is made.
Received 9 Aprile 2002 相似文献
11.
T.J. Hicks 《物理学进展》2013,62(4):243-298
Neutron polarization analysis experiments of the past 25 years are reviewed. In that time the technique has progressed from a curiosity to being a useful tool to be used when needed. In early experiments, the polarization of the scattered beam was analysed in the same direction as the polarization of the incident beam but, in some later experiments, full three-dimensional polarization analysis has been employed. This article starts by writing down the interactions which the neutron has with condensed matter and deriving the cross-sections for scattering and final polarizations of the scattered beam. This is done displaying the spin state functions of the neutron explicitly. A variety of experiments is then reviewed, commencing with the elastic and inelastic scattering experiments performed by Moon, Riste and Koehler in the late 1960s. Elastic scattering experiments where it is important to separate nuclear and magnetic cross-sections such as antiferromagnetic defect scattering are reviewed together with separation out of the nuclear spin scattering for various purposes. Of particular interest are the fully three-dimensional analysis experiments which reveal more about the structure and domain populations of certain antiferromagnets. Inelastic experiments for which polarization analysis is vital are those on paramagnets at high temperatures where it is necessary to discriminate against phonon scattering. Spin glasses are treated as frozen paramagnets. Polarization analysis also has another role to play in the separation of magnetic modes in both paramagnets and ordered magnets, and several of these experiments are reviewed. Finally it is possible to tag the polarization of a neutron beam in time and space and to measure the result at another time and place and this through various techniques yields information about the change in neutron energy on scattering. The techniques of pseudo-random flipping time of flight, neutron spectral modulation and neutron spin-echo spectroscopy are briefly reviewed but the techniques of polarized-neutron-beam management are left to another review. 相似文献
12.
The coherent (Rayleigh) to incoherent (Compton) scattering cross-section ratio of elements, in the range 6 ≤ Z ≤ 82, are determined experimentally for 145 keV incident gamma photons. An HPGe (High purity germanium) semiconductor detector is employed, at scattering angle of 50°, 70° and 90°, to record the spectra originating from interactions of incident gamma photons with the target under investigation. The intensity ratio of Rayleigh to Compton scattered peaks observed in the recorded spectra, and corrected for photo-peak efficiency of gamma detector and absorption of photons in the target and air, along with the other required parameters provides the differential cross-section ratio. The measured values of cross-section ratio are found to agree with theoretical predictions (corresponding to 4.939, 6.704 and 8.264 Å−1 photon momentum transfer) based upon non-relativistic form factor, relativistic form factor, modified form factor and S-matrix theory. 相似文献
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14.
Motivated by the discovery of a new family of 122 iron-based superconductors, we present the theoretical results on the ground state phase diagram, spin wave, and dynamic structure factor obtained from the extended J1-J2 Heisenberg model. In the reasonable physical parameter region of K2Fe4Se5, we find that the block checkerboard antiferromagnetic order phase is stable. There are two acoustic spin wave branches and six optical spin wave branches in the block checkerboard antiferromagnetic phase, which have analytic expressions at the high-symmetry points. To further compare the experimental data on neutron scattering, we investigate the saddlepoint structure of the magnetic excitation spectrum and the inelastic neutron scattering pattern based on linear spin wave theory. 相似文献
15.
Vitaly N. Nedoreshta Sergei P. Roshchupkin Alexey I. Voroshilo 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2013,67(3):1-11
The theory of nonresonant scattering of a photon by an electron in the field of an intense pulsed light wave is developed. The approximation when a pulse width is considerably greater than the characteristic time of wave oscillation is considered. The nonresonant kinematic region is determined. The general relativistic expression for the nonresonant cross-section is derived for the range of the external field intensities if η 0 ? 1, η0 2 ? 1 (see Eq. (12)) is valid. The obtained differential cross-section of the process has form of a sum over partial differential cross-sections. Each of them corresponds to the process with emission (absorption) of a certain number of wave photons. It is shown, that for nonrelativistic energy the cross-section summed over all possible partial processes differs considerably from the cross-section of Compton scattering if the external field is absent and may exceed the latter over than 200%. 相似文献
16.
D. Bernard F. Moulin F. Amiranoff A. Braun J.P. Chambaret G. Darpentigny G. Grillon S. Ranc F. Perrone 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(1):141-145
We have searched for stimulated photon scattering in vacuum at a center of mass photon energy of 0.8 eV. The QED contribution
to this process is equivalent to four wave mixing in vacuum. No evidence for scattering was observed. The corresponding upper limit of the cross-section is .
Received 29 September 1999 相似文献
17.
Electric and Magnetic form factors of neutron are calculated via electron-deuteron scattering at 1.511 ~5.507 GeV energy using SLAC group data. Our results show that the neutron electric form factor is not equal to zero;rather it has a small value, indicating that in spite of the fact that total charge is almost neutral, there is a nonuniformcharge distribution within the neutron, and that magnetic form factor follows the dipole fit. 相似文献
18.
A. B. Arbuzov V. V. Bytev E. A. Kuraev E. Tomasi-Gustafsson Yu. M. Bystritskiy 《Physics of Particles and Nuclei》2011,42(1):1-54
We consider several applications of the simplest nonlinear QED phenomena described by the light-by-light (LBL) scattering
tensor. Among the relevant processes we present the splitting of high energy photon in a Coulomb field, calculate the asymptotics
of differential photon photon elastic scattering. We show that LBL mechanism of the four photon mode of neutral pion decay
have a dominant role compared, for instance, with the quark loop Feynman amplitude contribution. The mechanisms of creation
of two and three gluon jets at colliding electro-positron beams is analyzed. We calculate also the contribution of LBL mechanism
to the ortho-positronium decay width. One Of the important application is the analytic calculation of the QED contribution
to the anomalous magnetic moment of the muon arising from LBL mechanism realized through electron positron loops, which is
enhanced by the logarithm of the ratio of muon to electron masses. The modification of the QED kernel, which takes into account
the QED polarization operator is used to extract the pure strong interaction contribution. We consider as well the problem
of the Coulomb law modification. At second part of review we consider Moeller scattering process and RC to it. We show that
RC are in agreement with renormalization group approach and could be taken into account in form of Drell-Yan process cross-section. 相似文献
19.
Jiang-Ping HuShou-Cheng Zhang 《Journal of Physics and Chemistry of Solids》2002,63(12):2277-2282
A key prediction of the SO(5) theory is the antiferromagnetic vortex state. Recent neutron scattering experiment on LSCO superconductors revealed enhanced antiferromagnetic order in the vortex state. Here we review theoretical progress since the original proposal and present a theory of static and dynamic antiferromanetic vortices in LSCO superconductors. It is shown that the antiferromagnetic region induced by the vortices can be greater than the coherence length, due to the light effective mass of the dynamic antiferromagnetic fluctuations at optimal doping, and close proximity to the antiferromagentic state in the underdoped regime. Systematic experiments are proposed to unambiguously determine that the field induced magnetic scattering originates from the vortices and not from the bulk. 相似文献
20.
A.K. Soper 《Molecular physics》2013,111(16):1667-1684
Time-of-flight neutron diffraction methods are widely used to study the structure of liquids and glasses. The scattering nuclei in these experiments suffer nuclear recoil in the course of the neutron scattering process, which gives rise to distortions to both the self and distinct structure factors extracted from the data. These distortions are in general difficult to evaluate quantitatively, especially when the mass of the nucleus is similar to that of the neutron, such as when hydrogen is present in the material being studied. Traditional treatments of this effect generally assume the neutron energy is lower than the excitation energy of an atom, but for time-of-flight diffraction this is never the case, and the experiments typically sample a wide range of energy transfers from sub-meV to tens of eV. In addition, by attempting to produce an analytical correction, such methods invariably make a long list of approximations which can be difficult to justify in particular cases. Here, a model for the scattering kernal is developed based on the well known harmonic oscillator model [A.C. Zemach and R.J. Glauber, Phys. Rev. 101, 118 (1956)]. This is shown to have the correct first and second moments of the scattering kernal for both the self and distinct scattering, and is used to estimate the self and distinct scattering from a diatomic ‘dumbell’ molecule. The model gives a realistic account of the single atom scattering from light and heavy water over a wide range of incident neutron energies, but is not yet accurate enough to perform quantitative corrections. In lieu of a quantitative approach, a ‘top hat’ convolution method is developed to perform the subtraction of self scattering from real data, and to allow data from multiple detector banks to be merged into a single structure factor. The harmonic oscillator model is also used to address the question of inelasticity effects on the interference scattering. For the intramolecular correlations at least at low scattering angles up to ~40° it is found that the effect of inelasticity is rather small – around 0.6% on the estimated OH bond length for H2O. Although the emphasis here is on time-of-flight diffraction, the model is quite general and can just as easily be applied to the case of fixed wavelength neutron diffraction where it also gives accurate results. 相似文献