Abstract
Imaging of atomic structure with X-rays is an essential diagnostics tool for modern natural sciences. The best spatial resolution in coherent X-ray imaging of non-periodic nanostructures is limited by overall low cross sections for elastic X-ray scattering. One possible pathway to overcome the present limitations is to extract structural information from inelastic scattering processes which have higher cross sections with X-rays and reach into higher scattering angles. One such process is metal K-shell fluorescence, which can exhibit two-photon interference effects and thus, carries structural maps of the fluorescencing sample[1]. This approach has two significant strengths. First, it relies on X-ray fluorescence which is emitted uniformly into all directions. Second, the structural information is extracted from an element-specific X-ray fluorescence line, which combines high spatial resolution with spectroscopic sensitivity. In theory, incoherent fluorescence imaging can be applied to crystalline and non-crystalline samples and deliver 3D maps of the nanoscale. We confirmed the presence of such speckles and measured a projection of the FEL nano-focus spot on a metal foil.
