Transverse x-ray coherence in nuclear scattering of synchrotron radiation

The time response of nuclei excited by pulsed synchrotron radiation is affected by correlations in the nuclear response transverse to the beam direction. The coherent addition of the radiation scattered by nuclei having a distribution of Doppler shifts accelerates the decay in the forward scattering from a rotating foil of Fe-57 stainless steel. A model based on Huygens's construction shows good agreement with the data, allowing estimation of the source size or transverse coherence length. Implications for spectroscopic experiments using nuclear forward scattering are discussed.