Nonlinear extreme ultraviolet spectroscopy at large scale facilities

The development of free-electron lasers has led to enormous progress in the generation of intense laser pulses in the extreme ultraviolet range (from a few eV up to about 300 eV).

In recent years, we have carried out several experiments on the nonlinear interaction of intense femtosecond extreme ultraviolet pulses at the seeded FEL FERMI in Italy (https://www.elettra.eu/lightsources/fermi.html). Exploiting the tunability of the central photon energy and the polarisation control of the radiation, we have reported the first complete experiment, i.e. the full characterisation of the photoionisation process by measuring the amplitude and phases of all partial waves in an ionic system.

In addition, we are actively involved in the development of experimental end stations for the ELI-ALPS facility in Hungary (https://www.eli-alps.hu/) for the implementation of nonlinear spectroscopy using isolated attosecond pulses.