Theory for multi-wavelength anomalous diffraction with X-ray free electron laser

Multi-wavelength anomalous diffraction (MAD) has been widely employed to determine phase information in X-ray crystallography. The method uses the contrast of the scattering power of heavy atoms at the absorption edges. However, when the X-ray source becomes extremely brilliant, the sample encounters severe electronic radiation damage, especially to heavy atoms, which makes the interpretation of MAD rather difficult. Recently, a theoretical paper discussing this problem has been published. The theory uses a Karle-Hendrickson-type equation in the high-intensity regime, and demonstrates the calculation of relevant coefficients with detailed electronic damage dynamics of heavy atoms. For more information, see the paper, "Multiwavelength Anomalous Diffraction at High X-Ray Intensity", S-K.Son et al., Phys. Rev. Lett. 107, 218102 (2011).