Extinction correction in white X-ray and neutron diffraction

Extinction effects in white-beam X-ray and neutron diffraction are considered following the formulation developed for monochromatic-beam diffraction by Becker & Coppens [Acta Cryst. (1974), A30, 129-147]. In white-beam diffraction, a small deviation of the wavelength from the Bragg condition Δλ is a variable which represents the line profile of the diffraction peaks, so that by using the new parameter Δλ the theory is converted to one in white-beam diffraction. It is shown that for a convex crystal, primary extinction y_p agrees with the results calculated already for monochromatic diffraction. The same relation is shown to hold in secondary extinction y_s. It is concluded that extinction theory derived for monochromatic diffraction is applicable without any modification in white-beam diffraction.