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Article Dans Une Revue Journal of Physics: Condensed Matter Année : 2014

Effects of dispersion and absorption in resonant Bragg diffraction of x-rays

Résumé

Resonant diffraction of xraysby crystals with anisotropic optical properties is investigated theoretically, to assess how the intensity of a Bragg spot is influenced by effects related to dispersion (birefringence) and absorption (dichroism). Starting from an exact but opaque expression, simple analytic results are found to expose how intensity depends on dispersion and absorption in the primary and secondary beams and, also, the azimuthal angle (rotation of the crystal about the Bragg wavevector). If not the full story for a given application, our results are more than adequate to explore consequences of dispersion and absorption in the intensity of a Bragg spot. Results are evaluated for antiferromagnetic copper oxide, and low quartz. For CuO, one of our results reproduces all salient features of a previously published simulation of the azimuthal angle dependence of a magnetic Bragg peak. It is transparent in our analytic result that dispersion and absorption effects alone cannot reproduce published experimental data. Available data for the azimuthal angle dependence of spacegroup forbidden reflections (0, 0, l), with l /= 3n, of low quartz depart from symmetry imposed by the triad axis of rotation symmetry. The observed asymmetry can be induced by dispersion and absorption even though absorption coefficients are constant, independent of the azimuthal angle, in this class of reflections.
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Dates et versions

hal-00956668 , version 1 (07-03-2014)

Identifiants

Citer

S. Lovesey, V. Scagnoli, A. N. Dobrynin, Yves Joly, S. P. Collins. Effects of dispersion and absorption in resonant Bragg diffraction of x-rays. Journal of Physics: Condensed Matter, 2014, 26 (26), pp.125504. ⟨10.1088/0953-8984/26/12/125504⟩. ⟨hal-00956668⟩

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