Mission statement

EIS-TIMEX is aimed at exploiting the unique characteristics of the FERMI seeded free electron laser for investigating the sub-picosecond response of matter to ultrashort laser/FEL pulses exposure. The beamline mainly uses photon-in photon-out techniques combining the FEL beam with an additional synchronized ultrashort pulse (pump-probe approach) with a remarkable temporal jitter of less than 10 fs. Notably, EIS-TIMEX has developed experimental schemes to use the 3rd harmonic emission of FERMI thus extending the spectral range of the experiments from the extreme ultraviolet (EUV, 20-300 eV) to the soft x-ray (300-900 eV).

 

 

Main scientific cases of interest for EIS-TIMEX:

 

    1. Matter at extreme conditions (MEC). Study of the ultrafast rearrangement of the electronic (and atomic) structure in condensed matter driven by the absorption of a single intense laser pulse. Isochorically heated matter (typically self-standing foils) can transiently reach conditions of temperature and pressure not accessible through conventional techniques. Importantly, the method limits undesired chemical contamination of the excited sample. Main experimental technique: time resolved XAS. 

    2. Ultrafast carrier dynamics in photocatalysts. Study of light driven charge transfer in functional materials exposed to ultrashort laser pulses. The absorption coefficient of materials changes in the sub-picosecond time scale upon light driven charge transfer. Main experimental technique: time resolved XAS, whose chemical sensitivity can be effectively used to identify the atomic species involved in the charge transfer. 

    3. Real time molecular motion. Study in the time domain of low frequency vibrational modes (about 1 THz) in complex molecules coherently activated by ultrashort laser pulses. Main experimental technique: time resolved XAS combined with Impulsive Stimulated Raman Scattering (ISRS). The approach exhibits both atomic and enantiomeric selectivity.

    4. Nonlinear optics in the EUV. Study of structural properties of buried interfaces between opaque materials through second harmonic generation in the EUV range. Study of spectral effects on matter exposed to EUV ultrashort pulses with particular attention to epsilon-near-zero (ENZ) materials. This research takes advantage of the WEST EUV single shot spectrometer operated in transmission geometry downstream of the experimental chamber of EIS-TIMEX.

 

 

Future upgrades at EIS-TIMEX:

 

    1. Ultrafast electron diffraction probe combined with an EUV FEL pump. An electron gun (100 keV) triggered by the SLU laser of FERMI is synchronized with the FERMI FEL pulse with a jitter smaller than 10 fs. The electron bunch (10 fC) is compressed to 100 fs through an RF compression cavity. The scheme has been already successfully tested at EIS-TIMEX, however it is not available as the electron gun is not currently at disposal of the FERMI staff. The plan is to get funding from European projects for purchasing the gun. This upgrade might serve the scientific case n. 1. 

    2. FEL-pump/FEL-probe setup for XAS in the soft x-ray range on isochorically heated metals. This setup exploits the 1st stage emission of FEL-2 as the pump and the third harmonic of the 2nd stage emission as the probe. The method has been already tested, however it is currently not available for external users as it requires some upgrades of the FERMI delay-line. This upgrade serves the scientific case n. 1. 

    3. Liquid-jet setup for the study of water and molecules diluted in liquid solvents. This setup is currently under design and preparation and will be employed for the scientific cases 2 and 3. Pilot experiments are planned in 2024.

    4. High pressure gas capillary setup. This setup is currently under design and preparation and will be employed on studies of stimulated emission from gases and nonlinear effects in low density matter, therefore mainly for the scientific case n. 4. The first experiment is scheduled for October 2023.