Final Report Summary - TIMER (TIME-Resolved Spectroscopy of Nanoscale Dynamics in Condensed Matter Physics)
The scientific interest in pushing the knowledge of dynamics towards shorter and shorter times and length-scales in chemistry, physics and biology draws back more than a century. Femtochemistry is a neologism currently used to describe a vast array of theoretical and experimental activities aiming at investigating how the material properties evolve in the femtosecond (fs) time domain.
However, the experimental control and theoretical understanding of physical, chemical and biochemical processes in complex systems on such an ultrafast scale and at the nanometer (nm) length scale is not yet fully possible, due to the inadequacy of existing experimental facilities.
Pulsed table-top lasers have allowed the development of non-linear methods. Non-linear methods have provided important information on different dynamical processes in a large variety of systems and timescales ranging, e.g. from sub-picosecond reconstruction of wavefunctions in reacting molecules to microsecond dynamics in complex bio-systems However, the relatively long photon wavelength and pulse duration of table-top lasers impose constraints for accessing the required nanometer/fs spatial/temporal resolution and/or selectively probing specific atomic species. TIMER is the first experimental facility that allows pushing the optical non-linear method towards the soft x-ray regime. TIMER uses the emission of intense photon pulses produced by the FERMI Free Electron Laser (FEL) accelerator based in Trieste (Italy). Differently from the other existing FEL's, based on the Self Amplification of Spontaneous Emission (SASE) scheme, the working principle of FERMI is based on an amplification mechanism obtained by seeding the emitting electron bunch with an external laser pulse, controlled in all relevant photon parameters. While SASE operation results in photon pulses with a time/energy structure that is the envelope of a series of sub-pulses with random intensity, time duration, bandwidth and phase, in the “seeded” scheme the radiation properties are entangled with those of the seed laser. A remarkable advantage is the preservation of the time-coherence of the seed in the emitted FEL radiation. This latter feature is undoubtedly an added-value for several “conventional” FEL-based applications, while it is mandatory for non-linear wave-mixing experiments. TIMER team had to face several technological challenges to demonstrate that FEL source may be used as a conventional laser and, therefore, can allow bringing advanced table-top techniques (such non-linear spectroscopies) into the realm of soft x-ray. In particular we constructed two experimental stations: one of them (already available to international users) uses the high photon flux delivered by the source to create extreme thermodynamic states of matter, whose dynamics can be then characterized with fs time-resolution by a vast array of experimental methods; the second one will exploit the unique characteristics of FERMI pulses to carry out experiments based on non-linear XUV/x-ray optics.
The techniques developed within TIMER will represent a permanent experimental infrastructure for multidisciplinary applications, available for international users. Therefore the benefits in terms of scientific outcome and know-how sharing will extend for many years beyond the end of the project.
However, the experimental control and theoretical understanding of physical, chemical and biochemical processes in complex systems on such an ultrafast scale and at the nanometer (nm) length scale is not yet fully possible, due to the inadequacy of existing experimental facilities.
Pulsed table-top lasers have allowed the development of non-linear methods. Non-linear methods have provided important information on different dynamical processes in a large variety of systems and timescales ranging, e.g. from sub-picosecond reconstruction of wavefunctions in reacting molecules to microsecond dynamics in complex bio-systems However, the relatively long photon wavelength and pulse duration of table-top lasers impose constraints for accessing the required nanometer/fs spatial/temporal resolution and/or selectively probing specific atomic species. TIMER is the first experimental facility that allows pushing the optical non-linear method towards the soft x-ray regime. TIMER uses the emission of intense photon pulses produced by the FERMI Free Electron Laser (FEL) accelerator based in Trieste (Italy). Differently from the other existing FEL's, based on the Self Amplification of Spontaneous Emission (SASE) scheme, the working principle of FERMI is based on an amplification mechanism obtained by seeding the emitting electron bunch with an external laser pulse, controlled in all relevant photon parameters. While SASE operation results in photon pulses with a time/energy structure that is the envelope of a series of sub-pulses with random intensity, time duration, bandwidth and phase, in the “seeded” scheme the radiation properties are entangled with those of the seed laser. A remarkable advantage is the preservation of the time-coherence of the seed in the emitted FEL radiation. This latter feature is undoubtedly an added-value for several “conventional” FEL-based applications, while it is mandatory for non-linear wave-mixing experiments. TIMER team had to face several technological challenges to demonstrate that FEL source may be used as a conventional laser and, therefore, can allow bringing advanced table-top techniques (such non-linear spectroscopies) into the realm of soft x-ray. In particular we constructed two experimental stations: one of them (already available to international users) uses the high photon flux delivered by the source to create extreme thermodynamic states of matter, whose dynamics can be then characterized with fs time-resolution by a vast array of experimental methods; the second one will exploit the unique characteristics of FERMI pulses to carry out experiments based on non-linear XUV/x-ray optics.
The techniques developed within TIMER will represent a permanent experimental infrastructure for multidisciplinary applications, available for international users. Therefore the benefits in terms of scientific outcome and know-how sharing will extend for many years beyond the end of the project.