Kinematical limit in the theory of X-ray magnetic reflectivity

A general formalism, based on the Takagi–Taupin equations, for calculating rocking curves in perfect t\times l crystals is presented. It includes nonsymmetrical scattering, refraction, and ordinary and anomalous absorption. t and l may be varied independently. In the limit of a semi-infinite crystal, the standard results from the fundamental theory are retrieved. For crystal dimensions less than the extinction length, the theory converges to the kinematical limit. Simulations for germanium and silicon show significant influence of crystal finiteness. When dynamical effects are prominent, the curves exhibit various degrees of asymmetry and the full width at half-maximum is generally larger than the corresponding Darwin width. This is attributed to combined Laue and Bragg contributions which are shifted with respect to each other owing to refraction.

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Determination of crystal imperfection by X-ray diffraction in a strong acoustic field

Journal of Applied Crystallography ◽

10.1107/s0021889891010531 ◽

1992 ◽

Vol 25 (2) ◽

pp. 88-91 ◽

Cited By ~ 7

Author(s):

E. Zolotoyabko ◽

I. Polikarpov ◽

V. Panov ◽

D. Schvarkov

Keyword(s):

Lattice Distortion ◽

Ultrasonic Field ◽

X Ray Diffraction ◽

Diffraction Intensity ◽

Quartz Crystals ◽

Model Calculations ◽

X Ray ◽

Crystal Imperfection ◽

Kinematical Limit

A study of X-ray diffraction in single silicon and quartz crystals in a strong ultrasonic field has been carried out. The dependence of diffraction intensity I(w) on sound amplitude w has been obtained right up to the kinematical limit Ik = I(∞). It is shown that the ratio η = I(∞)/I(0) depends on the crystal quality. Experimental data for different reflections, sound frequencies and X-ray wavelengths are compared with the model calculations for several lattice-distortion mechanisms.

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Space and Time Distribution of Hard X-Ray Emission in a Loop at the Beginning of a Flare

International Astronomical Union Colloquium ◽

10.1017/s0252921100025446 ◽

1994 ◽

Vol 144 ◽

pp. 275-277

Author(s):

M. Karlický ◽

J. C. Hénoux

Keyword(s):

Time Distribution ◽

Electron Bombardment ◽

Spatial Evolution ◽

Superthermal Electrons ◽

Flare Loop ◽

X Ray ◽

Superthermal Electron ◽

Flare Loops ◽

Chromospheric Evaporation ◽

Temporal And Spatial

AbstractUsing a new ID hybrid model of the electron bombardment in flare loops, we study not only the evolution of densities, plasma velocities and temperatures in the loop, but also the temporal and spatial evolution of hard X-ray emission. In the present paper a continuous bombardment by electrons isotropically accelerated at the top of flare loop with a power-law injection distribution function is considered. The computations include the effects of the return-current that reduces significantly the depth of the chromospheric layer which is evaporated. The present modelling is made with superthermal electron parameters corresponding to the classical resistivity regime for an input energy flux of superthermal electrons of 109erg cm−2s−1. It was found that due to the electron bombardment the two chromospheric evaporation waves are generated at both feet of the loop and they propagate up to the top, where they collide and cause temporary density and hard X-ray enhancements.

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Some Problems in Understanding the Solar Corona

International Astronomical Union Colloquium ◽

10.1017/s025292110002491x ◽

1994 ◽

Vol 144 ◽

pp. 1-9

Author(s):

A. H. Gabriel

Keyword(s):

Solar Corona ◽

Solar Atmosphere ◽

Theoretical Modelling ◽

Total System ◽

Major Advance ◽

X Ray ◽

Proper Perspective ◽

Space Observations

The development of the physics of the solar atmosphere during the last 50 years has been greatly influenced by the increasing capability of observations made from space. Access to images and spectra of the hotter plasma in the UV, XUV and X-ray regions provided a major advance over the few coronal forbidden lines seen in the visible and enabled the cooler chromospheric and photospheric plasma to be seen in its proper perspective, as part of a total system. In this way space observations have stimulated new and important advances, not only in space but also in ground-based observations and theoretical modelling, so that today we find a well-balanced harmony between the three techniques.

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White-Light Coronal Structures: Streamers and CMEs

International Astronomical Union Colloquium ◽

10.1017/s0252921100025045 ◽

1994 ◽

Vol 144 ◽

pp. 82

Author(s):

E. Hildner

Keyword(s):

Emission Line ◽

Electron Density ◽

White Light ◽

Coronal Mass Ejections ◽

X Rays ◽

Solar Cycles ◽

Temperature Function ◽

X Ray ◽

Eclipse Observations ◽

Coronal Structures

AbstractOver the last twenty years, orbiting coronagraphs have vastly increased the amount of observational material for the whitelight corona. Spanning almost two solar cycles, and augmented by ground-based K-coronameter, emission-line, and eclipse observations, these data allow us to assess,inter alia: the typical and atypical behavior of the corona; how the corona evolves on time scales from minutes to a decade; and (in some respects) the relation between photospheric, coronal, and interplanetary features. This talk will review recent results on these three topics. A remark or two will attempt to relate the whitelight corona between 1.5 and 6 R⊙to the corona seen at lower altitudes in soft X-rays (e.g., with Yohkoh). The whitelight emission depends only on integrated electron density independent of temperature, whereas the soft X-ray emission depends upon the integral of electron density squared times a temperature function. The properties of coronal mass ejections (CMEs) will be reviewed briefly and their relationships to other solar and interplanetary phenomena will be noted.

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Iron K-Line Emission from X-Ray Binaries

International Astronomical Union Colloquium ◽

10.1017/s0252921100107389 ◽

1988 ◽

Vol 102 ◽

pp. 47-50

Author(s):

K. Masai ◽

S. Hayakawa ◽

F. Nagase

Keyword(s):

Accretion Disk ◽

Radiative Recombination ◽

Characteristic Temperature ◽

Line Emission ◽

Ionization Front ◽

Continuum Radiation ◽

X Ray ◽

Low Mass ◽

X Ray Binaries

AbstractEmission mechanisms of the iron Kα-lines in X-ray binaries are discussed in relation with the characteristic temperature Txof continuum radiation thereof. The 6.7 keV line is ascribed to radiative recombination followed by cascades in a corona of ∼ 100 eV formed above the accretion disk. This mechanism is attained for Tx≲ 10 keV as observed for low mass X-ray binaries. The 6.4 keV line observed for binary X-ray pulsars with Tx> 10 keV is likely due to fluorescence outside the He II ionization front.

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Diagnostics of Gold Laser Plasmas

International Astronomical Union Colloquium ◽

10.1017/s0252921100108085 ◽

1988 ◽

Vol 102 ◽

pp. 357-360

Author(s):

J.C. Gauthier ◽

J.P. Geindre ◽

P. Monier ◽

C. Chenais-Popovics ◽

N. Tragin ◽

...

Keyword(s):

Experimental Results ◽

Pure Gold ◽

Electronic Temperature ◽

X Ray ◽

Laser Plasmas ◽

Collisional Radiative Model ◽

Radiative Model

AbstractIn order to achieve a nickel-like X ray laser scheme we need a tool to determine the parameters which characterise the high-Z plasma. The aim of this work is to study gold laser plasmas and to compare experimental results to a collisional-radiative model which describes nickel-like ions. The electronic temperature and density are measured by the emission of an aluminium tracer. They are compared to the predictions of the nickel-like model for pure gold. The results show that the density and temperature can be estimated in a pure gold plasma.

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Axial Observation of X-Ray Spectra from a Beam-Foil Source

International Astronomical Union Colloquium ◽

10.1017/s0252921100108048 ◽

1988 ◽

Vol 102 ◽

pp. 339-342

Author(s):

J.M. Laming ◽

J.D. Silver ◽

R. Barnsley ◽

J. Dunn ◽

K.D. Evans ◽

...

Keyword(s):

Spectral Resolution ◽

Heavy Ion ◽

Ion Beams ◽

Beam Axis ◽

Doppler Broadening ◽

X Ray ◽

Beam Foil

AbstractNew observations of x-ray spectra from foil-excited heavy ion beams are reported. By observing the target in a direction along the beam axis, an improvement in spectral resolution, δλ/λ, by about a factor of two is achieved, due to the reduced Doppler broadening in this geometry.

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Observed and Theoretical Spectra in the 10–100Å Interval

International Astronomical Union Colloquium ◽

10.1017/s0252921100107869 ◽

1988 ◽

Vol 102 ◽

pp. 259-261

Author(s):

W.A. Brown ◽

M.E. Bruner ◽

L.W. Acton

Keyword(s):

Sounding Rocket ◽

Full Spectrum ◽

X Ray

AbstractThe soft x-ray spectra recorded in two sounding rocket flights in 1982 and 1985 are compared with with predicted spectra. The poster presents the processed densitometer trace of the full spectrum together with the new spectrum from the 1985 experiment. This note compares the intensities of the lines with predictions.

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Quaternary structure of Limulus polyphemus hemocyanin

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100081747 ◽

1978 ◽

Vol 36 (2) ◽

pp. 176-177

Author(s):

T. Wichertjes ◽

E.J. Kwak ◽

E.F.J. Van Bruggen

Keyword(s):

Electron Microscopy ◽

Functional Properties ◽

Horseshoe Crab ◽

Temperature Jump ◽

Quaternary Structure ◽

Crystallographic Analysis ◽

Limulus Polyphemus ◽

Oxygen Binding ◽

X Ray ◽

Intact Molecule

Hemocyanin of the horseshoe crab (Limulus polyphemus) has been studied in nany ways. Recently the structure, dissociation and reassembly was studied using electron microscopy of negatively stained specimens as the method of investigation. Crystallization of the protein proved to be possible and X-ray crystallographic analysis was started. Also fluorescence properties of the hemocyanin after dialysis against Tris-glycine buffer + 0.01 M EDTA pH 8.9 (so called “stripped” hemocyanin) and its fractions II and V were studied, as well as functional properties of the fractions by NMR. Finally the temperature-jump method was used for assaying the oxygen binding of the dissociating molecule and of preparations of isolated subunits. Nevertheless very little is known about the structure of the intact molecule. Schutter et al. suggested that the molecule possibly consists of two halves, combined in a staggered way, the halves themselves consisting of four subunits arranged in a square.

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