Phase Determination by the Wavelength-Modulated Diffraction Method

Abstract

A new diffraction method for the determination of the phase of Bragg reflections is described. Diffracted intensity is recorded while changing continually the wavelength of radiation over a range in the vicinity of the absorption edge of an atom contained in a crystal. The intensity gradient with respect to the wavelength of the hkl reflection is shown to be in a simple relation to the real and imaginary parts of F (hkl) . The phase can be determined by solving two simultaneous linear equations with the intensity gradients measured at two wavelengths as input parameters. The situation is particularly simple when the crystal is centrosymmetric. The method presented here is free from the problem of intensity scaling encountered in other methods of phase determination.