Controllo coerente ultraveloce e imaging mediante diffrazione coerente utilizzando impulsi nella regione spettrale dell'estremo ultravioletto e dei raggi X.

Responsabili di progetto

Giuseppe Sansone, Kiyoshi Ueda

Accordo

GIAPPONE - JSPS - Japan Society for the Promotion of Science

Bando

CNR-JSPS 2016-2017

Dipartimento

Scienze fisiche e tecnologie della materia

Area tematica

Scienze fisiche e tecnologie della materia

Stato del progetto

Nuovo

Proposta di ricerca

Free electron lasers operating in the extreme ultraviolet [1-2] and hard X-ray regimes [3-4] offer new opportunities for the investigation of the dynamics of atoms and molecules under unprecedented conditions. FERMI@Elettra [2] and SACLA@RIKEN [4] present complementary characteristics in terms of photon energies: while FERMI provides users with radiation in the vacuum ultraviolet and soft X-ray range (12-300 eV), SACLA offers photon energy tunable from 4 up to 20 keV.
The main goal of this research project is to exploit the complementary pulses offered by the two FEL facilities operating in Italy and Japan to investigate two complementary and novel research directions:
a) Attosecond coherent control in the vacuum ultraviolet (VUV) and soft X-ray spectral range and
b) Coherent diffractive imaging.
The Italian and Japanese teams have already a strong ongoing collaboration that has resulted in the participation to six beam times at FERMI during the last years (December 2012-April 2015) and two publications [5,6]. In particular in December 2015, participants to the Italian and Japanese teams have demonstrated, for the first time ever, coherent control in the VUV spectral region by coherently combining two color fields and by adjusting with a few attoseconds (1 as=10-18 s) time resolution their relative phase [7]. This experiment opens new perspectives for the application of coherent control schemes (such as two or multiple pathways interference) and experimental techniques (such as pulse shaping) in an unprecedented spectral range. Moreover the possibility to change with a resolution of only few attoseconds the relative timing between multi-color fields will give access to a new class of experiments such as multiphoton ionization of atoms and molecules in VUV pulses shaped on the attosecond timescale. In this context we plan to extend to VUV pulses generated by FELs some of the techniques (such as sidebands oscillations [8] and measurement of photoemission delays [9]) which have been already implemented by the attosecond community, with the strong advantages of a much finer phase control and definitely larger energies per pulse offered by FERMI. For the accomplishment of this goal we plan to submit applications for beam times at FERMI; however in the first phase of the project we will take advantage of two beam times that have already been awarded to the Italian and Japanese teams during the Winter 2015 at FERMI. These opportunities will definitely reduce the risk connected to the award of beam time. On the other hand due to our excellent track- record (7 beam times, two by Sansone, two by Prince, one by Piseri, and two by Japanese colleagues) awarded at FERMI during the last three years), we are confident to receive additional beam times at FERMI during this period. As risk strategy it is worth to mention that, in the framework of the LDM collaboration, the group headed by Carlo Callegari and Kevin Prince can often benefit from several days of beam times per year that could be used for feasibility study of the proposed coherent control experiment.
In the first year we plan to run an innovative experiment for the measurement of the time delay between the two-photon vs single-photon ionization using phase-controlled two-color pulses.
In the second year we plan to run the experiment for creation the attosecond pulse train and its characterization.

The photo-induced reaction dynamics of relatively large nanoparticles (>100 nm) can be very effectively studied in pump-probe experiments using FERMI and SACLA. FERMI provides us with Fourier-transform-limited pulse with much narrower photon band width than any other SASE FEL facilities and thus best suited for photoelectron spectroscopy. At the same time, its intrinsic synchronization and pulse-shape stability provides us high temporal resolution. On the other hand, SACLA provides us with extremely short (< 10 fs) x-ray pulses and best suited for time-resolved structure study. Coherent Diffraction Imaging employed in the present study is a unique tool for structural investigation of nano-objects that cannot be crystallized due to their specific physical-chemical properties or to the restrictions imposed by preparation conditions. SACLA has proven to be able to provide high resolution (better than 7 nm) for real space 3D reconstruction of inorganic nanocrystal images. Japanese colleagues succeeded also coherent x-ray scattering imaging on rare-gas nanoclusters. Also for these experiments
In the first year, at FERMI, we will run the UV-pump VUV probe photoelectron spectroscopy on metal clusters, focusing on plasmon resonance excitation by the UV radiation. At SACLA, we will study reaction dynamics of rare gas nanoclusters induced by intense IR laser and intense X-ray pulse. The latter can be performed using unique two-color time-delayed X-ray pulses of SALCA.
In the second year, at SACLA, we will perform coherent x-ray scattering experiment for the metal nanoclusters, and then pump-probe experiment employing the pump-probe x-ray scattering technique established via the rare-gas nanocluster pump-probe experiment. Our Japanese colleagues have excellent track- record (8 beam times) awarded at SACLA during the last four years besides many proposals accepted by their foreign colleagues and thus we are confident to receive beam times at SACLA during this period.

[1] W. Ackermann et al. Nat Photonics 1, 336-342 (2007).
[2] E. Allaria et al. Nat Photonics 6, 699-704 (2012).
[3] P. Emma et al. Nat Photonics 4, 641-647 (2010).
[4] T. Ishikawa et al. Nat Photonics 6, 540-544 (2012)
[5] T. Mazza et al., accepted for publication in .J Phys. B: At. Mol. Phys.
[6] A. Dubrouil et al. accepted for publication in .J Phys. B: At. Mol. Phys.
[7] K. Prince et al. submitted
[8] P.M. Paul et al. Science 292, 1689-1692 (2001).
[9] M. Schultze et al. Science 328, 1658-1662, (2010).

Obiettivi della ricerca

a) Attosecond coherent control in the vacuum ultraviolet (VUV) and soft X-ray spectral range
The first main objective of the project is to implement for the first time coherent control schemes (based on the combination and phase shaping of multi-color fields) in the extreme ultraviolet range. This goal represents a milestone in the extension to this spectral range of other techniques well known and widely applied in other domains (for example 2D near infrared spectroscopy). In particular the collaboration plan to exploit the unique characteristics of FERMI ensured by the seeding process.
2) Coherent diffractive imaging
The second objective of the project is the time-resolved investigation of reaction dynamics occurring in large clusters by monitoring the coherent diffraction pattern generated by intense X-ray pulses. The application of intense X-ray pulses from FEL sources has enormous potential for the purpose of developing such technique, which was confirmed in numerous experiments on sub-micrometric objects of different nature (faceted nanoparticles, protein nano-crystals, viruses). Collaboration for the application of FEL to the characterization of free clusters was established between groups participating to this proposal (Milano University UNIMI and Tohoku University, also with the participation of Kyoto University and RIKEN) and led to a first joint proposal to use the SCSS FEL facility for morphological investigation of free metal nanoparticles via photoionization.

Ultimo aggiornamento: 30/04/2024