2
$\begingroup$

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)?

$\endgroup$
2
$\begingroup$

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.

$\endgroup$
  • $\begingroup$ 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

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.