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XUV four-wave mixing at FERMI.

Bencivenga F., Calvi A., Capotondi F., Cucini R., Foglia L., Kiskinova M., Manfredda M., Masciovecchio C., Mincigrucci R., Pedersoli E., Principi E., Simoncig A.
  Lunedì 11/09   14:30 - 18:30   Aula A224   II - Fisica della materia
Free electron laser (FEL) sources have permitted to develop ultrafast table-top methods into the extreme ultraviolet (XUV) and x-ray domain. In this context we exploited the fully coherent XUV pulses delivered by the FERMI FEL facility to demonstrate advanced experimental methods, such as those based on non-linear optics, into the XUV regime. We hereby report on the results of four-wave-mixing (FWM) experiments based on XUV transient grating (X-TG) and coherent Raman scattering (X-CRS). Both approaches represent relevant steps towards the development of x-ray FWM methods, which, to date, have been discussed only on theoretical grounds. Such methods could be used, $e.g.$, to probe collective atomic dynamics in the "mesoscopic" ($0.1-1 nm^{-1}$) wavevector range, which is not accessible by other means and is relevant for the understanding of thermal and mechanical properties in disordered systems and nanostructures. These applications are being developed at FERMI in user-dedicated infrastructures, which are presented as well in the present contribution.