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The dispersive and absorptive components of the index of refraction measure the response of a material to excitation by light and are therefore needed to fully reconcile theoretical models with the results of experiments aimed at understanding and eventually controlling the behavior of magnetic multilayers. Resonant scattering occurs when the wavelength is near an absorption edge, resulting in an enhanced intensity of reflected light and a shift in the position of the Bragg peak relative to that expected from the Bragg equation. Detailed measurements of the intensity of reflected light as a function of the angle and wavelength near the Bragg peak can give a direct measure of the dispersive part of the index of refraction for wavelengths around the absorption edges. Known as anomalous diffraction when applied to crystals, this technique has also been used for multilayers for many years. Absorption measurements not only can directly yield the absorptive component but can also indirectly reveal the dispersive component via a mathematical technique known as the Kramers-Kronig transformation.