Noun
absorption edge (plural absorption edges)
(physics) The boundary of a dark band in an x-ray spectrum.
By recording full sets of reflections at three different wavelengths (far below, far above and in the middle of the absorption edge) one can solve for the substructure of the anomalously diffracting atoms and hence the structure of the whole molecule. Source: Internet
To obtain the phases, full sets of reflections are collected with known alterations to the scattering, either by modulating the wavelength past a certain absorption edge or by adding strongly scattering (i. Source: Internet