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In x-ray spectroscopy Bragg reflection off of a crystal is used for spectral analysis. In x-ray diffraction the same principle is used for monochromatizing the x-ray beam from an x-ray tube. For visible light, however, an optical prism is used to decompose the spectrum. I understand that Bragg scattering would not be feasible for visible light as the wavelength range of visible light (390-700nm vs. 0.01-10nm for x-ray) is much larger than atomic spacing in most crystals (a few angstroms), and the Bragg angle has to be very shallow(?).

Is it feasible to use a prism instead of Bragg reflection in x-ray spectral analysis (i.e., is there a material with low x-ray attenuation and suitable refraction index)? Is there any table of refraction indices for different materials at various wavelengths (alternatively, a table of relative permittivity and relative permeability)?

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There is http://henke.lbl.gov/optical_constants/

But no, prisms are not suitable for x-rays: dispersion is small, there will always be absorption. And there are anomalous effects near absorption edges.

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  • $\begingroup$ As a numerical example, aluminum has an index of refraction of 1.000008 for x-rays with a wavelength $1.6\times 10^{-10}$ m. $\endgroup$ – Ben Crowell Nov 26 '17 at 23:16
  • $\begingroup$ @BenCrowell Generally in the x-ray region, $n$ is slightly less than unity. (Except near absorption edges.) For example, holes in aluminum can be used as positive lenses spie.org/newsroom/… $\endgroup$ – Pieter Nov 26 '17 at 23:29

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