Nonlinear Attosecond Metrology and Coherent Control at Seeded Free-Electron Lasers.

• Applicant: Professor Dr. Giuseppe Sansone
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 547508320

The research project titled "Nonlinear Attosecond Metrology and Coherent Control at Seeded Free-Electron Lasers" is centered around two experimental beamtimes awarded to Prof. Dr. Sansone's research group at the seeded free-electron laser FERMI in Trieste, Italy. The primary objectives of the project are twofold, drawing from the extensive expertise in attosecond metrology and spectroscopy acquired by the Sansone group through the use of tabletop sources based on high-order harmonic generation, as well as the expertise in generation and characterization developed during previous beamtimes at FERMI. The first primary aim of this proposal is to showcase an innovative approach in attosecond metrology, which relies on the nonlinear interaction between two replicas of an attosecond pulse train with an infrared laser pulse. This approach capitalizes on the experience gained at FERMI in four-wave mixing experiments. Specifically, the objective is to demonstrate a new method for determining the group-delay dispersion of three consecutive harmonics based on the measurement of visible/ultraviolet pulses, where spectral detection is less challenging than in the extreme ultraviolet (XUV) region. This approach aligns with recent experimental results obtained with the mini-TIMER instrument at FERMI for the temporal characterization of XUV pulses using an XFROG approach, as well as with the latest investigation involving XUV transient gratings generated by pulses with different central energies. The second primary goal of this proposal is to exhibit the coherent control of photoelectron emission in a molecule (nitrogen) using the combination of three coherent harmonics of the seeded FEL FERMI. Specifically, by exploiting the control of the relative phase between the harmonics, the aim is to investigate the effect of an intermediate autoionizing resonance on the photoionization process and on the subsequent nuclear dynamics induced in the molecular ion. Using an atomic reference, the intention is to characterize the additional phase contribution of the resonance on the photoionization process.

• DFG Programme: Research Grants
• International Connection: Spain, Sweden, USA
• Cooperation Partners: Professor Dr. Fernando Martín; Professor Dr. Johan Mauritsson; Dr. Jeremy Rouxel; Professor Dr. Uwe Thumm