Showing papers on "Synchrotron radiation published in 1985"
TL;DR: In this paper, the magnetic scattering of x rays is discussed in a way which allows consideration of the effects of electron binding, and the cross section is reduced by (ℏω/mc2)2 (about 5×10−4).
Abstract: The scattering of x rays is used to determine the electric charge distribution in matter. Since x rays are electromagnetic radiation, we should expect that they will be sensitive not only to the charge distribution, but also to the magnetization density. That this is indeed the case has been pointed out and studied experimentally. In this paper the magnetic scattering is discussed in a way which allows consideration of the effects of electron binding. The cross section, compared with that for neutron scattering from magnetically ordered materials, is reduced by (ℏω/mc2)2 (about 5×10−4). With a synchrotron radiation source, however, this factor can be made up, and magnetic x‐ray Bragg peaks can be collected in the same time as neutron peaks. Special effects of interest include high momentum resolution, polarization phenomena which separate spin and orbital densities, and resonance effects which give a large enhancement of the x‐ray cross section and which may make the study of surface magnetism possible.
339 citations
TL;DR: Polarized synchrotron radiation can be used to determine accurately the magnitude, the orientation, and the temperature and magnetic field dependence of the local rare-earth magnetic moment in a large variety of magnetically ordered materials and thin films.
Abstract: A theory is presented which predicts an anomalously large magnetic dichroism in the ${M}_{4,5}$ x-ray absorption-edge structure of rare earths in magnetically ordered materials. Polarized synchrotron radiation can therefore be used to determine accurately the magnitude, the orientation, and the temperature and magnetic field dependence of the local rare-earth magnetic moment in a large variety of magnetically ordered materials and thin films.
309 citations
TL;DR: Direct high-resolution measurements of the nominally incommensurate magnetic satellite reflections reveal new lock-in behavior which is explained within a simple spin-discommensuration model and demonstrates additional advantages of synchrotron radiation for magnetic-structure studies.
Abstract: We present the results of magnetic x-ray scattering experiments on the rare-earth metal holmium using synchrotron radiation. Direct high-resolution measurements of the nominally incommensurate magnetic satellite reflections reveal new lock-in behavior which we explain within a simple spin-discommensuration model. As a result of magnetoelastic coupling, the spin-discommensuration array produces additional x-ray diffraction satellites. Their observation further substantiates the model and demonstrates additional advantages of synchrotron radiation for magnetic-structure studies.
214 citations
TL;DR: In this article, the electrons sont acceleres a des energies relativistes par des chocs dans le vent pres de l'etoile, and emettent un rayonnement radio a travers le mecanisme synchrotron.
Abstract: Nouveau modele de l'emission radio d'etoiles chaudes. Les electrons sont acceleres a des energies relativistes par des chocs dans le vent pres de l'etoile, et emettent un rayonnement radio a travers le mecanisme synchrotron. On derive le spectre d'energie et le spectre radio des particules
129 citations
TL;DR: In this article, the absolute energy of X-rays from a synchrotron source were used to determine the zinc metal K absorption edge and to measure systematic errors in the angular settings of a typical rotation table used for X-ray spectroscopy.
Abstract: A new apparatus and technique to determine the absolute energy of X-rays from a synchrotron source were used to establish the absolute energy of the zinc metal K absorption edge [9661.1(2) eV] and to measure systematic errors in the angular settings of a typical rotation table used for X-ray spectroscopy. These errors have a period of 1° associated with the worm gear of the rotation table and should provide a warning to other synchrotron radiation spectroscopists that systematic errors exist in experimental data. The technique relies on determining the orientation of a static silicon crystal with respect to the incoming beam by establishing degenerate reflections with differing Miller indices. Absolute energies can be determined for X-rays with energies greater than 6 keV. An analysis of the system shows that the technique is also useful for the accurate characterization of the monochromator resolution.
123 citations
TL;DR: In this paper, the gradient de l'indice spectral 1,4-5,0 GHz was observed in 5 radiogalaxies 3C lumineuses, where the radiation was due to an ensemble isotrope d'electrons subissant des pertes par rayonnement synchrotron.
Abstract: On a etudie le gradient de l'indice spectral 1,4-5,0 GHz observe dans 5 radiogalaxies 3C lumineuses. Les observations ont ete comparees a un modele dans lequel la radiation est due a un ensemble isotrope d'electrons subissant des pertes par rayonnement synchrotron. On en deduit l'âge des electrons en divers points des lobes et par suite les vitesses de separation des points chauds et du materiau des lobes
123 citations
TL;DR: In this paper, the garnet-perovskite phase transformation in CaGeO3 was investigated in the pressure-temperature region to 6.5 GPa and 1200°C using a cubic anvil type of high-pressure apparatus combined with synchrotron radiation.
Abstract: The garnet-perovskite phase transformation in CaGeO3 was investigated in the pressure-temperature region to 6.5 GPa and 1200°C using a cubic anvil type of high-pressure apparatus combined with synchrotron radiation. In-situ measurements with an energy dispersive x-ray diffraction system enable us to carry out dynamical observation of the transformation. The equilibrium phase boundary between the garnet and perovskite phases was determined as P(GPa)= 6.9 - 0.0008T(°C). The negative P-T slope definitely established in the present study is in reasonable agreement with the value, −0.0023(8) GPa/°C, that was calculated from the thermochemical data on the enthalpy of transition. The molar volume change accompanied with this transformation was estimated to be about 13% at about 6 GPa and 1000°C.
121 citations
TL;DR: In this paper, the effects of random field errors on the performance of practical undulators are explored. But the results of these effects are limited by limiting conditions on its validity, and they are based on two universal functions, which are simple combinations of the basic undulator parameters, and are compared with the predictions of the universal functions.
Abstract: Undulators and wigglers are central components of free-electron lasers and proposed new high-brightness synchrotron radiation light sources. This paper explores the effects of random field errors on the performance of practical undulators. An approximate theory of these effects is derived, along with limiting conditions on its validity. The result of this work is a description of the loss of radiated intensity by two universal functions. The functions’ arguments are simple combinations of the basic undulator parameters. Simple numerical simulation methods are presented, and numerical results are compared with the predictions of the universal functions. Finally, possible solutions to the problem of random errors in undulators are discussed.
102 citations
TL;DR: In this article, a method for the calculation of the synchrotron-self-Compton model in spherical geometries, especially in the partially-observable regime, was presented, where an approximation to the Klein-Nishina cross section was used to model the effects of variable electron and incident photon cutoffs.
Abstract: Both spatial and spectral accuracies are stressed in the present method for the calculation of the synchrotron-self-Compton model in spherical geometries, especially in the partially opaque regime of the synchrotron spectrum of inhomogeneous sources that can span a few frequency decades and contribute a significant portion of the scattered flux. A formalism is developed that permits accurate calculation of incident photon density throughout an optically thin sphere. An approximation to the Klein-Nishina cross section is used to model the effects of variable electron and incident photon cutoffs, as well as the decrease in the cross section at high energies. General results are derived for the case of inhomogeneous sources with power law profiles in both electron density and magnetic field.
95 citations
TL;DR: A modern 1- to 2-billion-electron-volt synchrotron radiation facility (based on high-brightness electron beams and magnetic undulators) would generate coherent (laser-like) soft x-rays of wavelengths as short as 10 angstroms, which could be used for phase- and element-sensitive microprobing of biological assemblies and material interfaces as well as reserch on the production of electronic microstructures with features smaller than 1000Angstroms.
Abstract: A modern 1- to 2-billion-electron-volt synchrotron radiation facility (based on high-brightness electron beams and magnetic undulators) would generate coherent (laser-like) soft x-rays of wavelengths as short as 10 angstroms. The radiation would also be broadly tunable and subject to full polarization control. Radiation with these properties could be used for phase- and element-sensitive microprobing of biological assemblies and material interfaces as well as reserch on the production of electronic microstructures with features smaller than 1000 angstroms. These short wavelength capabilities, which extend to the K-absorption edges of carbon, nitrogen, and oxygen, are neither available nor projected for laboratory XUV lasers. Higher energy storage rings (5 to 6 billion electron volts) would generate significantly less coherent radiation and would be further compromised by additional x-ray thermal loading of optical components.
95 citations
01 Jan 1985
TL;DR: In this article, the analysis of the basic scattering functions in terms of a multipole expansion provides a promising strategy, once the possibilities of synchrotron radiation are fully exploited so as to allow for the required high precision of the scattering measurements.
Abstract: Resonance (or anomalous) X-ray scattering of partially ordered macromolecular structures, amorphous materials and solutions is encountered in the near edge region of X-ray absorption edges where the resonant real part f' of atomic form factors shows the strongest dispersion. The requirements of spectral brilliance in the near absorption edges can only be met by synchrotron radiation emitted from high energy electron (positron) storage rings. Resonance scattering yields three basic scattering functions. This compares to contrast variation in neutron scattering. The relations to isomorphous replacement methods of crystallography are discussed. The analysis of the basic scattering functions in terms of a multipole expansion provides a promising strategy, once the possibilities of synchrotron radiation are fully exploited so as to allow for the required high precision of the scattering measurements.
01 Jan 1985
TL;DR: In this paper, a short introductory chapter on the generation and properties of synchrotron radiation is presented, followed by instrumentation available for research on polymers are discussed and finally the results obtained up to now in polymer science.
Abstract: This article starts with a short introductory chapter on the generation and properties of synchrotron radiation. Afterwards instrumentation available for research on polymers are discussed and finally the results obtained up to now in polymer science.
TL;DR: Using the dynamical theory of Bragg diffraction, it is shown that there is a direct relationship between the phase of the x-ray standing-wave field and the phase-factor phases, which are determined from the phases of the modulations in these secondary yields.
Abstract: Using the dynamical theory of Bragg diffraction, we show that there is a direct relationship between the phase of the x-ray standing-wave field and the phase of the structure factor. For an experimental demonstration, we monitor the Ga and As K fluorescence and resonant Raman scattering yields, while scanning through the (111) and (200) Bragg diffraction rocking curves of GaAs perfect single crystals. The phases of the (111) and (200) GaAs structure factors are determined from the phases of the modulations in these secondary yields. With the use of monochromatized synchrotron radiation, with a variable photon energy between 10 and 15 keV, the effect of anomalous dispersion on the structure-factor phases is clearly seen in the vicinity of the Ga and As K absorption edges. We use this feature, in conjunction with the measured absorption spectrum, for directly determining the dispersion parameters f' and f'' for atoms which appear in single-crystal structures.
TL;DR: In this article, a method for simultaneous measurements of small-angle x-ray scattering and differential scanning calorimetry is described, which is made possible through a combination of the high flux afforded by the storage ring at the Stanford Synchrotron Radiation Laboratory, a linear position-sensitive detector with rapid response time, and a differential scan calorimeter developed for optical microscopy.
Abstract: A method is described for performing simultaneous measurements of small-angle x-ray scattering and differential scanning calorimetry. The experiment is made possible through a combination of the high flux afforded by the storage ring at the Stanford Synchrotron Radiation Laboratory, a linear position-sensitive detector with rapid response time, and a differential scanning calorimeter developed for optical microscopy. The feasibility of the technique is illustrated by examining the melting and crystallization of a polyethylene specimen. This example demonstrates the power of the technique and the accuracy and reliability of the scattering and thermal data.
01 Jan 1985
TL;DR: Inverse square law for a uniformly bright sphere as discussed by the authors is used to define specific intensity and its moments, which is defined as the specific intensity or brightness of a sphere in terms of specific intensity.
Abstract: Chapter 1 Fundamentals of Radiative Transfer 1.1 The Electromagnetic Spectrum Elementary Properties of Radiation 1.2 Radiative Flux Macroscopic Description of the Propagation of Radiation Flux from an Isotropic Source-The Inverse Square Law 1.3 The Specific Intensity and Its Moments Definition of Specific Intensity or Brightness Net Flux and Momentum Flux Radiative Energy Density Radiation Pressure in an Enclosure Containing an Isotropic Radiation Field Constancy of Specific Intensity Along Rays in Free Space Proof of the Inverse Square Law for a Uniformly Bright Sphere 1.4 Radiative Transfer Emission Absorption The Radiative Transfer Equation Optical Depth and Source Function Mean Free Path Radiation Force 1.5 Thermal Radiation Blackbody Radiation Kirchhoff's Law for Thermal Emission Thermodynamics of Blackbody Radiation The Planck Spectrum Properties of the Planck Law Characteristic Temperatures Related to Planck Spectrum 1.6 The Einstein Coefficients Definition of Coefficients Relations between Einstein Coefficients Absorption and Emission Coefficients in Terms of Einstein Coefficients 1.7 Scattering Effects Random Walks Pure Scattering Combined Scattering and Absorption 1.8 Radiative Diffusion The Rosseland Approximation The Eddington Approximation Two-Stream Approximation Problems References Chapter 2 Basic Theory of Radiation Fields 2.1 Review of Maxwell's Equations 2.2 Plane Electromagnetic Waves 2.3 The Radiation Spectrum 2.4 Polarization and Stokes Parameters 62 Monochromatic Waves Quasi-monochromatic Waves 2.5 Electromagnetic Potentials 2.6 Applicability of Transfer Theory and the Geometrical Optics Limit Problems References Chapter 3 Radiation from Moving Charges 3.1 Retarded Potentials of Single Moving Charges: The Lienard-Wiechart Potentials 3.2 The Velocity and Radiation Fields 3.3 Radiation from Nonrelativistic Systems of Particles Larmor's Formula The Dipole Approximation The General Multipole Expansion 3.4 Thomson Scattering (Electron Scattering) 3.5 Radiation Reaction 3.6 Radiation from Harmonically Bound Particles Undriven Harmonically Bound Particles Driven Harmonically Bound Particles Problems Reference Chapter 4 Relativistic Covariance and Kinematics 4.1 Review of Lorentz Transformations 4.2 Four-Vectors 4.3 Tensor Analysis 4.4 Covariance of Electromagnetic Phenomena 4.5 A Physical Understanding of Field Transformations 129 4.6 Fields of a Uniformly Moving Charge 4.7 Relativistic Mechanics and the Lorentz Four-Force 4.8 Emission from Relativistic Particles Total Emission Angular Distribution of Emitted and Received Power 4.9 Invariant Phase Volumes and Specific Intensity Problems References Chapter 5 Bremsstrahlung 5.1 Emission from Single-Speed Electrons 5.2 Thermal Bremsstrahlung Emission 5.3 Thermal Bremsstrahlung (Free-Free) Absorption 5.4 Relativistic Bremsstrahlung Problems References Chapter 6 Synchrotron Radiation 6.1 Total Emitted Power 6.2 Spectrum of Synchrotron Radiation: A Qualitative Discussion 6.3 Spectral Index for Power-Law Electron Distribution 6.4 Spectrum and Polarization of Synchrotron Radiation: A Detailed Discussion 6.5 Polarization of Synchrotron Radiation 6.6 Transition from Cyclotron to Synchrotron Emission 6.7 Distinction between Received and Emitted Power 6.8 Synchrotron Self-Absorption 6.9 The Impossibility of a Synchrotron Maser in Vacuum Problems References Chapter 7 Compton Scattering 7.1 Cross Section and Energy Transfer for the Fundamental Process Scattering from Electrons at Rest Scattering from Electrons in Motion: Energy Transfer 7.2 Inverse Compton Power for Single Scattering 7.3 Inverse Compton Spectra for Single Scattering 7.4 Energy Transfer for Repeated Scatterings in a Finite, Thermal Medium: The Compton Y Parameter 7.5 Inverse Compton Spectra and Power for Repeated Scatterings by Relativistic Electrons of Small Optical Depth 7.6 Repeated Scatterings by Nonrelativistic Electrons: The Kompaneets Equation 7.7 Spectral Regimes for Repeated Scattering by Nonrelativistic Electrons Modified Blackbody Spectra y"1 Wien Spectra y"1 Unsaturated Comptonization with Soft Photon Input Problems References Chapter 8 Plasma Effects 8.1 Dispersion in Cold, Isotropic Plasma The Plasma Frequency Group and Phase Velocity and the Index of Refraction 8.2 Propagation Along a Magnetic Field Faraday Rotation 8.3 Plasma Effects in High-Energy Emission Processes Cherenkov Radiation Razin Effect Problems References Chapter 9 Atomic Structure 9.1 A Review of the Schrodinger Equation 9.2 One Electron in a Central Field Wave Functions Spin 9.3 Many-Electron Systems Statistics: The Pauli Principle Hartree-Fock Approximation: Configurations The Electrostatic Interaction LS Coupling and Terms 9.4 Perturbations, Level Splittings, and Term Diagrams Equivalent and Nonequivalent Electrons and Their Spectroscopic Terms Parity Spin-Orbit Coupling Zeeman Effect Role of the Nucleus Hyperfine Structure 9.5 Thermal Distribution of Energy Levels and Ionization Thermal Equilibrium: Boltzmann Population of Levels The Saha Equation Problems References Chapter 10 Radiative Transitions 10.1 Semi-Classical Theory of Radiative Transitions The Electromagnetic Hamiltonian The Transition Probability 10.2 The Dipole Approximation 10.3 Einstein Coefficients and Oscillator Strengths 10.4 Selection Rules 10.5 Transition Rates Bound-Bound Transitions for Hydrogen Bound-Free Transitions (Continuous Absorption) for Hydrogen Radiative Recombination - Milne Relations The Role of Coupling Schemes in the Determination of f Values 10.6 Line Broadening Mechanisms Doppler Broadening Natural Broadening Collisional Broadening Combined Doppler and Lorentz Profiles Problems References Chapter 11 Molecular Structure 11.1 The Born-Oppenheimer Approximation: An Order of Magnitude Estimate of Energy Levels 11.2 Electronic Binding of Nuclei The H2+ Ion The H2 Molecule 11.3 Pure Rotation Spectra Energy Levels Selection Rules and Emission Frequencies 11.4 Rotation-Vibration Spectra Energy Levels and the Morse Potential Selection Rules and Emission Frequencies 11.5 Electronic-Rotational-Vibrational Spectra Energy Levels Selection Rules and Emission Frequencies Problems References Solutions Index
Book•
01 Jan 1985TL;DR: In this paper, the basic formulas for the theory of synchrotron radiation were derived and some important practical applications of the theory were discussed, as well as the prospects for the further development of these investigations.
Abstract: In this paper, the basic formulas are derived for the theory of synchrotron radiation and some important practical applications of synchrotron radiation are discussed, as well as the prospects for the further development of these investigations.
TL;DR: In this paper, the anomalous scattering tensor for Pt in K2PtCl4 was measured in experiments with linearly polarized synchrotron radiation and the polarization anisotropy, which is as much as 10 electrons atom-1 for f for f, was reported.
Abstract: X-ray dichroism is observed at the L absorption edges of Pt in K2PtCl4, and the anomalous scattering tensor for Pt in this square-planar complex is measured in experiments with linearly polarized synchrotron radiation. For special azimuthal settings the diffraction intensities of some reflections depend on only one or the other of the principal values of the tensor. The polarization anisotropy, which is as much as 10 electrons atom-1 for f”, is the largest yet reported for anomalous scattering. These phenomena offer a new way to determine diffraction phases, but add complications for previous methods using multiple wavelengths.
TL;DR: The angular distribution of the transition radiation from the beryllium-foil stack was measured for the three electron-beam energies and found to agree well with theoretical predictions, and the use of transition radiation as a source of x rays for lithographic purposes may be practical.
Abstract: The absolute differential production efficiencies (photons/eV sr electron) for x rays emitted from each of three transition radiators were measured for incident electron-beam energies of 17.2, 25, and 54 MeV. The radiators were made of stacks of 1.0-..mu..m-thick foils: 18 foils of beryllium, 18 foils of carbon, and 30 foils of aluminum. The radiation spectra were most intense between 0.5 and 2.5 keV, peaking at 0.8, 1.3, and 1.3 keV, respectively. The angular distribution of the transition radiation from the beryllium-foil stack was measured for the three electron-beam energies and found to agree well with theoretical predictions. Owing to K-shell absorption, the photon-energy spectra from the carbon and aluminum stacks are narrowed. Theoretical calculations, which include both the two-surface interference and photon attenuation in the foil material, agree well with these data. A method of enhancing output using a split-foil stack is considered; cursory experiments with a split stack of Mylar foils showed enhanced emission. The use of transition radiation as a source of x rays for lithographic purposes may be practical.
TL;DR: In this article, high-pressure X-ray diffraction studies have been performed on UN powder for pressures up to 34 GPa using synchrotron radiation and a diamond anvil cell.
Abstract: High-pressure X-ray diffraction studies have been performed on UN powder for pressures up to 34 GPa using synchrotron radiation and a diamond anvil cell. For the cubic low-pressure phase the bulk modulus B0 equals 203(6) GPa and its pressure derivative B′0 equals 6.3(6) in good agreement with other data from the literature. The UN material has been found to transform to a new phase, UN III, at 29 GPa. The transformation is first order with a 3.2% decrease in volume. The UN III phase has been indexed according to a face-centred rhombohedral cell with a = 4.657(5) A and α = 85.8(2)° at 34 GPa. The influence of the 5f electrons in the transformation is discussed.
TL;DR: Following state-selective pulsed synchrotron radiation excitation of Xe2, Kr2, and Ar2, oscillatory bound-free structures of the first continua were observed in time-resolved fluorescence spectra.
01 Jan 1985-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, the effect of monochromatic excitation for the selective excitation of a particular element is demonstrated. But the experimental geometry optimal for a high signal to background ratio is investigated experimentally.
Abstract: Energy dispersive X-ray fluorescence measurements were made for trace elements using synchrotron radiation from a dedicated electron storage ring at the Photon Factory in Japan. Monochromatization of the excitation beam by a crystal monochromator is effective in improving the signal to background ratio, while the synchrotron continuum excitation attains an absolute detectability of better than pg. Trace elements in a thin sample down to 60 ppb are detected by monochromatic excitation when there is no line interference. The experimental geometry optimal for a high signal to background ratio is investigated experimentally. The practical advantages of monochromatic excitation for the selective excitation of a particular element are demonstrated; these include enhanced sensitivity, suppression of the effects of the matrix element, and removal of overlapping peaks. The effects of higher order reflections and the residual tail part of the diffraction curve are also discussed in connection with quantitative analysis.
TL;DR: In this article, simultaneous VLA observations of microwave bursts at 6 and 2 cm in a solar active region were presented and discussed using the full-day synthesis, I and V maps of the active region are produced.
Abstract: Simultaneous VLA observations of microwave bursts at 6 and 2 cm in a solar active region are presented and discussed. Using the full-day synthesis, I and V maps of the active region are produced. The radiation mechanisms at these wavelengths are discussed and the upper and lower bounds on the magnetic field of the active region are derived. The magnetic fields in the microwave burst source are estimated from the brightness temperature and the degree of circular polarization. It is concluded that the 6 cm radiation originates from the bulk heated plasma, whereas the 2 cm radiation is due to the nonthermal particles generated in the energy-release process. The delay between the peaks of emission at the two wavelengths is interpreted using a dc electric field model of flares. Depending on the strength of the electric field and the density in the flaring region, delays in either sense can be observed.
Journal Article•
TL;DR: In this article, a formalisme for le calcul du spectre synchrotron auto-compton d'une large classe de sources heterogenes allongees (jets) is presented.
Abstract: On presente un formalisme pour le calcul du spectre synchrotron auto-Compton d'une large classe de sources heterogenes allongees (jets). La densite des electrons relativistes, l'energie maximum des electrons et le champ magnetique sont supposes etre des lois de puissance d'une coordonnee radiale. Application a PKS 2155-304 et PKS 0537-441. Les resultats sont compares a ceux d'un modele homogene
TL;DR: By using ultra-high-flux synchrotron x-radiation from a wiggler source, good Laue diffraction data have been obtained from protein microcrystals of size 30 X 35 X 10 microns3, mounted wet in glass capillaries.
Abstract: By using ultra-high-flux synchrotron x-radiation from a wiggler source, good Laue diffraction data have been obtained from protein microcrystals of size 30 X 35 X 10 microns3, mounted wet in glass capillaries. At the flux level of 10(13)-10(14) photons per sec/mm2, the radiation damage is still low enough to allow a large survey of reciprocal space for a microcrystal and a complete survey for a normal-sized protein crystal. The development of sources for ultra-high-intensity synchrotron radiation is thus an important improvement in the technique for determination of structure through protein crystallography as well as in other cases where crystal size is often a limiting factor.
15 Sep 1985-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The characteristics of synchrotron radiation in the infrared region have been investigated at the Berlin electron storage ring BESSY using Fourier spectroscopy as discussed by the authors, and it was found that BESSy at 100 mA beam current delivers higher fluxes than a conventional source only in the spectral region below 30 cm−1, provided the interferometer is the throughput-limiting element.
Abstract: The characteristics of synchrotron radiation in the infrared region have been investigated at the Berlin electron storage ring BESSY using Fourier spectroscopy. In accordance with calculation, it was found that BESSY at 100 mA beam current delivers higher fluxes than a conventional source only in the spectral region below 30 cm−1, provided the interferometer is the throughput-limiting element. If, however, the throughput is limited by small sample size or, if the experiment requires a large f-number, the high brightness of synchrotron radiation could already yield flux advantages at several hundred wavenumbers. The possible application in one particular experiment - infrared reflection-absorption spectroscopy of adsorbed molecules on metal single crystal surfaces - is discussed. In the course of the investigations described here, it was also established that the short light pulses of the synchrotron radiation (∼ 100 ps) do not adversely affect the resolution in Fourier transform spectroscopy.
TL;DR: The sum of the oscillator strengths for all the observed transitions between the 2p3p initial-state and the 2 p3 s 3p finalstate configurations was found to be equal to 0.22(4).
Abstract: We have obtained oscillator strengths for transitions between a laser-excited initial state and autoionizing final states. In the case of sodium, a laser was used to populate the 3p initial state, and synchrotron radiation was used to excite the autoionizing resonances. These transitions are of the type 2p3p P-+ 2p(P)3s3p(>P)>S,>*P,>*D\\ they decay to 2pS + e. The sum of the oscillator strengths for all the observed transitions between the 2p3p initial-state and the 2p3 s 3p finalstate configurations was found to be equal to 0.22(4).
TL;DR: From diagnostics three distinct processes of UV-induced degradation of TiO2/SiO2 dielectric mirrors were identified, one of which was a surface absorption of the upper SiO2-air interface; it was not affected by annealing.
Abstract: Due to its low gain, the Orsay storage ring free-electron laser necessitates the use of high reflectivity mirrors. Three techniques for measuring the mirror losses are presented, based on cavity decay time measurements using either an external laser, the synchrotron radiation stored in the cavity, or the free-electron laser itself. The high signal-to-noise ratio allowed the detection of loss variations as low as 10−7/sec1/2. From these diagnostics three distinct processes of UV-induced degradation of TiO2/SiO2 dielectric mirrors were identified. One was a surface absorption of the upper SiO2–air interface; it was not affected by annealing. The other two corresponded to a volume absorption of the layers which completely recovered after annealing.
01 Jan 1985
TL;DR: By using ultra-high-flux synchrotron x-radiation from a wiggler source, good Laue diffraction data have been obtained from protein microcrystals of size 30 X 35 X 10 microns, mounted wet in glass capillaries.
Abstract: Byusing ultra-high-flux synchrotron x-radi- ation fromawiggler source, goodLauediffraction data have beenobtained fromprotein microcrystals ofsize 30x35X 10 Am3, mounted wetinglass capillaries. Attheflux level of 1013-1014 photons persec/mm2, theradiation damage isstill lowenough toallow alarge survey ofreciprocal space fora microcrystal andacomplete survey foranormal-sized protein crystal. Thedevelopment ofsources forultra-high-inten sity synchrotron radiation isthus animportant improvement inthe technique fordetermination ofstructure through protein crystallography aswell asinother cases wherecrystal size is often alimiting factor. Theavailability ofsynchrotron radiation fromelectron stor- agerings during thepast decade hasopened newpossibilities forthecollection ofx-ray diffraction datafrombiological macromolecules (1-4). A newgeneration ofultra-high-flux sources ofsynchrotron x-radiation isnowbecoming avail- able. Thesearebased ontheinsertion instorage rings of periodic, magnetic field devices called wigglers orundula- tors, whichenhance thealready intense emission ofx- radiation from"conventional" bending magnets. Theutili- zation ofintense tunable synchrotron x-radiation such asthat produced bythewigglers attheStanford Synchrotron Radi- ation Laboratory inStanford, California (SSRL), andthe Synchrotron Radiation Source inDaresbury, United King- dom(SRS), hasgreatly extended andaccelerated thescien- tific development inmanyfields ofmaterials research. This progress hasserved asthescientific caseforthese new sources. Indeed, anewgeneration ofdedicated storage rings isnowbeing proposed inEurope andintheU.S.A.' to combine theultra-high flux ofperiodic magnets with atiny source size anddivergence toyield extremely high x-ray brilliance. To assess thefeasibility ofusing suchultra-high-flux sources forprotein crystallography, wehavecarried outa series ofexperiments using thewhitebeamfromthe Daresbury SRSwiggler. Understandard SRSandwiggler operating conditions, theintensity ofthefocused monochro- matic beamispresently -1011_1012 photons persec/mm2: 8X/A=0.1%. Thewhite beam, though unfocused, yields a polychromatic (0.2 A'Xc4A)photon intensity level atthe