The X-ray free electron lasers (XFELs) [1] are nowadays used to study the structure and dynamics in matter with unprecedented temporal and spatial resolutions. However, some fundamental electron processes in the matter are too fast to be followed, even with the shortest available XFEL pulses. In this work we report on a new experimental approach to study sub-femtosecond processes in matter....
In recent years generation and control, both in amplitude and in phase, of multiple harmonics at the seeded Free Electron Lasers (FELs) FERMI have opened the way to a new class of experiments based on the wave mixing paradigm. For these experiments, the simultaneous acquisition of the whole spectrum of harmonics is required to monitor the stability of the emission, the relative intensity ratio...
