Pietro Carrara is currently working at SPRINT Laboratory high harmonic generation beamline. His activity is mostly devoted to the implementation and optimization of the XUV source from High Harmonics Generation in gas phase, starting from a mode-locked pulsed IR laser, used for time-resolved photoemission experiments. He is also developing a new set-up for Transient Grating experiments, also with in-vacuum sample environment, exploiting the SPRINT laser sources.
The femtosecond evolution of the electronic temperature of laser-excited gold nanoparticles is measured, by means of ultrafast time-resolved photoemission spectroscopy induced by extreme-ultraviolet radiation pulses. The temperature of the electron gas is deduced by recording and fitting high-resolution photo emission spectra around the Fermi edge of gold nanoparticles providing a direct, unambiguous picture of the ultrafast electron-gas dynamics. These results will be instrumental to the refinement of existing models of femtosecond processes in laterally-confined and bulk condensed-matter systems, and for understanding more deeply the role of hot electrons in technological applications.
Struct. Dyn., 7, 014303, (2020)
Coherent narrowband light source for ultrafast photoelectron spectroscopy in the 17–31 eV photon energy range
R. Cucini, T. Pincelli, G. Panaccione, D. Kopic, F. Frassetto, P. Miotti, G.M. Pierantozzi, S. Peli, A. Fondacaro, A. De Luisa, A. De Vita, P. Carrara, D. Krizmancic, D.T. Payne, F. Salvador, A. Sterzi, L. Poletto, F. Parmigiani, G. Rossi, and F. Cilento
Here, we report on a novel narrowband High Harmonic Generation (HHG) light source designed for ultrafast photoelectron spectroscopy (PES) on solids. Notably, at 16.9 eV photon energy, the harmonics bandwidth equals 19 meV. This result has been obtained by seeding the HHG process with 230 fs pulses at 515 nm. The ultimate energy resolution achieved on a polycrystalline Au sample at 40 K is ∼22 meV at 16.9 eV. These parameters set a new benchmark for narrowband HHG sources and have been obtained by varying the repetition rate up to 200 kHz and, consequently, mitigating the space charge, operating with ≈3×107 electrons/s and ≈5×108 photons/s. By comparing the harmonics bandwidth and the ultimate energy resolution with a pulse duration of ∼105 fs (as retrieved from time-resolved experiments on bismuth selenide), we demonstrate a new route for ultrafast space-charge-free PES experiments on solids close to transform-limit conditions.
University of Milan Master's Degree Thesis, (2020)
Characterization of a High Harmonics Generation source for spectroscopic pump-probe experiments and first results on Fe(100)/MgO surface
P. Carrara (Supervisors: G. Rossi, G. Panaccione, R. Cucini)
The present thesis work has been performed within a new-born laboratory called Spin Polar-ization Research Instrument in the Nanoscale and Time domain (SPRINT laboratory), as apart of the research infrastructures circuit NFFA-Trieste (Nano Foundries and Fine Analysis -belonging to the wider NFFA-Europe circuit) and hosted in the experimental hall of the freeelectron laser FERMI@Elettra.The SPRINT laboratory rises as an answer to the urgent request of the scientific communityof extension of photoemission spectroscopies (PES), not only energy-, but possibly also angle-and spin-resolved, to the time domain in the sub-picosecond regime. The integration of a PESapparatus within a setup for stroboscopic measurements (that is in a pump-probe scheme) pavesthe way to time resolved study of the relaxation of optically populated electronic states, thusenabling the study the ultrafast dynamics of the excitations inside the materials, with greatbenefit from both the fundamental and the technological point of view.
Strada Statale 14 - km 163,5 - 34149 Trieste, ITALY
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NFFA is a Progetto Internazionale financed by MIUR through CNR
(Istituto Officina dei Materiali, Trieste) and Elettra-Sincrotrone Trieste
and managed by the Commissione NFFA chaired by Giorgio Rossi
(Università di Milano and IOM-CNR).