Dynamical diffraction of x-rays under conditions of a rapidly changing structure factor: theory and possible applications for femtosecond x-rays

摘要

The diffraction of x-rays in crystalline materials is governed by the amplitudes of the Fourier transform of the electron density, commonly called the structure factors. A change in these amplitudes can be induced by a high-power laser and can lead to a number of interesting effects, like a sweep of the beam propagation direction that could be used in a device for time-resolved x-ray detection that bears some similarity to a streak camera and can potentially reach few-femtosecond resolution. Another effect that becomes relevant on subpicosecond timescales is the generation of frequency-shifted x-rays, which could be used in Mossbauer spectroscopy, or for the concentration of x-ray photons into a narrow energy band. Even small changes in the structure factors can produce a large effect through coherent interaction with the x-rays in a large crystalline volume. A theoretical treatment, based on the Takagi-Taupin theory of dynamical diffraction, is presented.