B. Diviacco

TL;DR: In this paper, the FERMI free-electron laser operating in the high-gain harmonic generation regime was demonstrated, allowing high stability, transverse and longitudinal coherence and polarization control.

TL;DR: The hitherto unexplored two-photon doubly excited states were experimentally identified using the seeded, fully coherent, intense extreme ultraviolet free-electron laser FERMI and the resulting yield of Ne_{2}^{+} ions was recorded as a function of delay between the extreme ultraviolet pump and UV probe laser pulses.

TL;DR: Ne clusters were resonantly excited by intense free electron laser (FEL) radiation at FERMI and it was found that the relaxation of cluster surface atoms proceeds via a sequence of interatomic or intermolecular Coulombic decay (ICD) processes while ICD of bulk atoms is additionally affected by the surrounding excited medium via inelastic electron scattering.

TL;DR: An experimental characterization of the process of coherent harmonic generation in single-pass free electron lasers provides an experimental confirmation of recent theoretical studies that predict no coherent on-axis signal.

TL;DR: It is demonstrated that a storage-ring free-electron laser can also achieve harmonic generation (down to 36.5 nm), presenting both experimental and theoretical results, and offering a reliable interpretation of the peculiar underlying physical processes involved.