Showing papers on "Synchrotron radiation published in 1978"
TL;DR: The linear X-ray polarization of the Crab Nebula has been precisely measured at 2.6 keV and 5.2 keV with the OSO 8 graphite crystal polarimeters as discussed by the authors.
Abstract: The linear X-ray polarization of the Crab Nebula has been precisely measured at 2.6 keV and 5.2 keV with the OSO 8 graphite crystal polarimeters. The 1.4 ms time resolution of these instruments permitted the removal of any contribution to the polarization from the pulsar. The nebular polarization is 19.2% plus or minus 1.0% at a position angle of 156.4 plus or minus 1.4 deg at 2.6 keV. At 5.2 keV the corresponding results are 19.5% plus or minus 2.8% at 152.6 plus or minus 4.0 deg.
323 citations
IBM1
TL;DR: Using angle-resolved photoemission and synchrotron radiation, the authors determined the energy-versus-momentum valence-band dispersion relations for a Ni(111) crystal.
Abstract: Using angle-resolved photoemission and synchrotron radiation, we have determined the energy-versus-momentum valence-band dispersion relations for a Ni(111) crystal. The temperature-dependent ferromagnetic exchange splitting has been directly observed. Both the $d$-band width (\ensuremath{\sim}3.4 eV at $L$) and exchange splitting (0.31 eV) are much smaller than theoretical estimates (\ensuremath{\sim}4.5 eV wide at $L$ with \ensuremath{\sim}0.7-eV splitting, respectively, at 293 K).
200 citations
180 citations
TL;DR: In this article, a two parallel crystal monochromator was used in the soft X-ray range with the synchrotron radiation emitted by the A.C.O. storage ring.
151 citations
TL;DR: In this paper, non-Rydberg effects in the photoabsorption spectra of atoms are described, which correspond to the creation of a vacancy within the subvalence shells of the atom or to the simultaneous excitation of two electrons.
Abstract: Non-Rydberg effects in the photoabsorption spectra of atoms are described. They are observed at photon energies which correspond to the creation of a vacancy within the subvalence shells of the atom or to the simultaneous excitation of two electrons. The importance of synchrotron radiation as an experimental tool for the investigation of non-Rydberg effects is stressed, and many examples are given. Many of the non-Rydberg properties can be understood by analogy with elementary one dimensional potential well theory.
125 citations
TL;DR: In this paper, a Ge crystal is shaped to an elongated triangle and mounted as a cantilever so that a cylindrical curvature is obtained with a single micrometer screw; thus, the focus distance can be purposely adjusted.
116 citations
TL;DR: In this paper, the 14-keV level of the Fe/sup 57/ nucleus was excited using synchroton radiation, and the conversion electrons emitted in the decay of that state were observed.
Abstract: We have excited the 14-keV level of the Fe/sup 57/ nucleus using synchroton radiation, and observed the conversion electrons emitted in the decay of that state. We believe this to be the first observation of nuclear excitation via synchrotron-produced x rays.
85 citations
CERN1
TL;DR: In this paper, the spectrum of a weak undulator field is calculated by going into a moving frame and the spectrum consists of one line with its width depending on the solid angle of the accepted radiation.
76 citations
TL;DR: Using monochromatised synchrotron radiation as an excitation source, threshold photoelectron-photoion coincidence experiments have been performed on energy-selected states of O2+.
Abstract: Using monochromatised synchrotron radiation as an excitation source, threshold photoelectron-photoion coincidence experiments have been performed on energy-selected states of O2+. Predissociation is observed for the b4 Sigma g- and c4 Sigma u- states. Two dissociation continua are observed between 23 and 24.5 eV.
65 citations
64 citations
TL;DR: In this paper, the authors used the polarized character of the radiation at the Wisconsin Synchrotron Radiation Center to determine the symmetry of the states in the mirror plane of GaAs.
Abstract: New occupied surface states are observed on the (110) cleavage face of GaAs. Using the polarized character of the radiation at the Wisconsin Synchrotron Radiation Center the symmetry of the states in the mirror plane are determined. Among current calculations of the electronic structure, only that which includes bond length relaxation yields results that are consistent with the observations.
TL;DR: In this paper, the design and performance of a focusing monochromator system for collecting and focusing the highly directional, broad band synchrotron radiation has been described and evaluated.
TL;DR: The sources, properties and uses of synchrotron radiation are discussed in detail in this article, where applications considered include X-ray microscopy, absorption spectroscopy, and diffraction analysis.
Abstract: The sources, properties and uses of synchrotron radiation are discussed in detail The production of synchrotron radiation from storage rings and synchrotrons is reviewed Applications considered include X-ray microscopy, absorption spectroscopy, and diffraction analysis
TL;DR: In this article, a typical example of low misfit quaternary heterojunction Ga 0.7 Al 0.3 As 1- y P y /GaAs has been characterized by several X-ray techniques.
TL;DR: In this article, the authors developed a system for the storage ring DORIS with the following properties: 1) monochromatic excitation in a photon energy range of 5 eV up to 50 eV (E ΔE ≈ 500) ; 2) energy resolution of luminescence in an energy range between 2 eV and 20 eV.
TL;DR: In this paper, the origin of the restoring force is discussed, and the model of Neel (1954) incorporating a restoring force proportional to wall displacement is discussed in the cubic antiferromagnets KNiF3 and KCoF3.
Abstract: Domain wall movement has been studied directly in the cubic antiferromagnets KNiF3 and KCoF3. Using synchrotron radiation from the 5 GeV electron synchrotron NINA, X-ray topographs were recorded in fields up to 1–5 T and at temperatures down to 4–2 K. Walls move so as to align spins perpendicular to the applied field and wall motion is reversible over a considerable distance. Quantitative agreement has been found with theoretical predictions using the model of Neel (1954) incorporating a restoring force proportional to wall displacement. The origin of this restoring force is discussed.
TL;DR: A system capable of measuring the energy of charged particles emitted from a sample at any angle relative to the sample or the incident beam of exciting particles, operated at constant pass energy with a series of electrostatic lenses is constructed and tested.
Abstract: We have constructed and tested a system capable of measuring the energy of charged particles emitted from a sample at any angle relative to the sample or the incident beam of exciting particles. The energy analysis is accomplished by a 180° spherical deflecting‐type analyzer, operated at constant pass energy with a series of electrostatic lenses. The analyzer system is properly apertured to accept incoming particles from a spot of 1.5 mm diameter at the sample and within a cone of 2.5° half‐angle. The lens system used has constant transmission independent of the incident energy. The energy analyzer is independently rotatable about two orthogonal axes, giving it complete freedom of access to any angle of collection relative to the sample orientation. The sample can rotate about two orthogonal axes so that any angle of incidence can be used. Specific examples are given of the performance of the system when used for the measurement of the angular distribution of photoelectrons excited by synchrotron radiation.
TL;DR: In this article, a superconducting wiggler magnet was installed on the storage ring VEPP-3 in order to shift the spectrum of the synchrotron radiation generated to a shortr wavelength range and to enhance the SR intensity.
TL;DR: In this paper, a theoretical study of diffraction properties of curved monochromators for X-ray synchrotron radiation was performed by extending a simple model recently developed and fruitfully employed to describe the neutrasonic properties of curvature radii.
Abstract: A theoretical study is presented concerning the diffraction characteristics of curved monochromators for X-ray synchrotron radiation used at the laboratories of Hamburg, Orsay and Stanford. The investigation was performed by extending to the X-ray case a simple model recently developed and fruitfully employed to describe the neutron diffraction properties of curved monochromators. Several diffraction patterns were obtained corresponding to different monochromator materials (Ge, Si) used by the different laboratories, for different reflecting planes (111), (220). asymmetry angles, X-ray wavelengths (Mo Kα, Cu Kα, Cr Kα) and curvature radii. The results are discussed in physical terms and their implications on the design of curved monochromators for synchrotron radiation are presented. In particular, the study shows that all the monochromators used in the different laboratories should behave practically as perfect crystals and therefore should have a very low integrated reflectivity corresponding to an optimized wavelength passband Δλ/λ ≃10−4. The gain that can be obtained by increasing the curvature, by introducing a gradient in the lattice spacing or by any other kind of imperfection is quite limited and much lower than the desirable value. The adopted model can help in obtaining a possible moderate gain in intensity by also taking into consideration other parameters, such as crystal material, reflecting plane, asymmetry of the reflection and X-ray wavelength.
TL;DR: For a long time only an unwanted but inevitable by-product of ring accelerators in elementary particle research, synchrotron radiation is now becoming a most widely used tool in atomic, molecular and solid-state spectroscopy, surface physics, structural research on solids, soft X-ray microscopy, lithography.
Abstract: Synchrotron radiation is intense electromagnetic radiation with a continuous spectral distribution emitted by high-energy electron (or positron) synchrotrons or storage rings in the visible, vacuum ultraviolet and X-ray regions. For a long time only an unwanted but inevitable by-product of ring accelerators in elementary particle research, synchrotron radiation is now becoming a most widely used tool in atomic, molecular and solid-state spectroscopy, surface physics, structural research on solids, soft X-ray microscopy, lithography. It is not yet clear how large the field of applications really is nor which line of research will prove to be the most fruitful one in the long run.
TL;DR: In this article, design considerations on crystal monochromators using single or multiple dynamical diffractions for synchrotron X-radiation (SXR) are described.
TL;DR: In this paper, the results of powder-profile refinement using a solid-state detector with synchrotron radiation are presented, where the data are collected very rapidly and the usual structural parameters are refined together with line-shape, zero error and instrument function.
Abstract: Results of powder-profile refinement using a solid-state detector with synchrotron radiation are presented. The data are collected very rapidly and the usual structural parameters are refined together with line-shape, zero error and instrument function. The results are in excellent agreement with previously published parameters. The rapidity and precision of the method means that it will be possible in the near future to find structural parameters of a powdered material in a few s or min and thus allow simultaneous structure refinement with changing sample environment.
TL;DR: In this paper, the authors present theoretical calculations involving one particular process, namely virtual Coster-Kronig process, which gives good agreement with experimental 5s binding energy and gives the correct order of magnitude for the relative intensities of the satellites corresponding to the 5s2 Sp4 5d 2S and 5s 2 5p4 6d2S final states.
Abstract: ACO synchrotron radiation has been used to obtain photoelectron spectra of the outer shell of xenon in the 75-100 electron volts energy range. Satellite peaks corresponding to the formation of excited ionic states have been observed, in addition to the main peaks corresponding to the production of the 5s 2 5p5 2P and 5s 5p6 2S states of Xe+. A comparison is presented of the intensities of the satellites relative to the main lines for different energies of the incident radiation. There are several ways to excite satellite lines, via core rearrangement, virtual super Coster-Kronig processes, ground state correlation and final state cattering processes involving the primary photoelectron. In this paper we present theoretical calculations involving one particular process, namely virtual Coster-Kronig process, which gives good agreement with experimental 5s binding energy and gives the correct order of magnitude for the relative intensities of the satellites corresponding to the 5s2 Sp4 5d 2S and 5s2 5p4 6d 2S final states.
TL;DR: This experiment demonstrates that accurate diffractometer measurements are possible with synchrotron radiation produced by an electron storage ring, and affects the diffraction intensities in a manner similar to isomorphous substitution.
Abstract: Diffraction of monochromatized synchrotron radiation by crystals of cesium hydrogen tartrate has been used to measure the magnitude and phase of x-ray scattering for cesium near the L III absorption edge. In this wavelength region the scattering amplitude of cesium is reduced by as much as 25 electrons per atom, compared to scattering of copper Kα x-rays. This change, which varies as a function of wavelength, affects the diffraction intensities in a manner similar to isomorphous substitution, and it is large enough to have promise for phase determination in the study of macromolecular structures. This experiment also demonstrates that accurate diffractometer measurements are possible with synchrotron radiation produced by an electron storage ring.
TL;DR: In this article, the characteristics of an ultrarelativistic charged particle in a general, large-scale, electromagnetic field, taking into consideration the effects of strong radiative damping, were studied.
Abstract: This paper studies the characteristics of an ultrarelativistic charged particle in a general, large-scale, electromagnetic field, taking into consideration the effects of strong radiative damping. Formal solutions of the Lorentz-Dirac equation in an arbitrary external field are given. They are applied to cases of astrophysical interest. The final energy of the particle and the rate and characteristic frequency of the radiation are derived.
TL;DR: In this article, the relativistic gyroresonance with the runaway electrons is found to result in a level of spontaneous emission which, for frequencies in the neighborhood of the electron plasma frequency, is significantly enhanced over the thermal radiation.
Abstract: The emissivity of spontaneous synchrotron radiation is computed for a plasma consisting of a background thermal plasma in addition to an energetic runaway electron component. The analysis is performed for both the ordinary and extraordinary modes, for frequencies in the vicinity of the electron plasma frequency and the higher harmonics of the electron gyrofrequency, and for the case when the electron plasma frequency is approximately the same as or smaller than the cyclotron frequency. The relativistic gyroresonance with the runaway electrons is found to result in a level of spontaneous emission which, for frequencies in the neighborhood of the electron plasma frequency, is significantly enhanced over the thermal radiation.
TL;DR: In this paper, the source characteristics of synchrotron radiation have been discussed and how they affect the maximum attainable resolution of the monochromator with respect to the relativistic electron bunch.
TL;DR: The time dependence of delayed radiation has been found when the pulse of synchrotron radiation undergoes the resonance Bragg scattering by nuclei in a crystal that have an isomeric Mossbauer level.