Carlo Callegari
A5085728559- Quantum, superfluid, helium dynamics
- Advanced Chemical Physics Studies
- Laser-Matter Interactions and Applications
- Cold Atom Physics and Bose-Einstein Condensates
- Atomic and Subatomic Physics Research
- Advanced X-ray Imaging Techniques
- Atomic and Molecular Physics
- Particle Accelerators and Free-Electron Lasers
- Spectroscopy and Quantum Chemical Studies
- Advanced Electron Microscopy Techniques and Applications
- Mass Spectrometry Techniques and Applications
- Laser-Plasma Interactions and Diagnostics
- Inorganic Fluorides and Related Compounds
- Physics of Superconductivity and Magnetism
- Particle accelerators and beam dynamics
- Spectroscopy and Laser Applications
- Molecular Junctions and Nanostructures
- Advanced Fiber Laser Technologies
- X-ray Spectroscopy and Fluorescence Analysis
- Inorganic Chemistry and Materials
- Laser Design and Applications
- Diamond and Carbon-based Materials Research
- Mechanical and Optical Resonators
- Quantum optics and atomic interactions
- Molecular Spectroscopy and Structure
Elettra-Sincrotrone Trieste S.C.p.A.
2016-2025
Institute of Structure of Matter
2018-2022
Institut de Nanociència i Nanotecnologia de la Universitat de Barcelona
2021
Universitat de Barcelona
2021
AREA Science Park
2012-2017
Center for Biomolecular Nanotechnologies
2014
Sapienza University of Rome
2014
University of Nova Gorica
2014
Institute of Inorganic Methodologies and Plasmas
2014
University of Ljubljana
2014
Very high frequency (VHF) nanoelectromechanical systems (NEMS) provide unprecedented sensitivity for inertial mass sensing. We demonstrate in situ measurements real time with noise floor approximately 20 zg. Our best resolution corresponds to 7 zg, equivalent 30 xenon atoms or the of an individual 4 kDa molecule. Detailed analysis ultimate such devices based on these experimental results indicates that NEMS can ultimately sensing intact, electrically neutral macromolecules single-Dalton (1...
Abstract Rabi oscillations are periodic modulations of populations in two-level systems interacting with a time-varying field 1 . They ubiquitous physics applications different areas such as photonics 2 , nano-electronics 3 electron microscopy 4 and quantum information 5 While the theory developed by was intended for fermions gyrating magnetic fields, Autler Townes realized that it could also be used to describe coherent light–matter interactions within rotating-wave approximation 6 Although...
In this article, recent developments in helium nanodroplet isolation (HENDI) spectroscopy are reviewed, with an emphasis on the infrared region of spectrum. We discuss how molecular beam and matrix can be usefully combined into a method that provides unique tool to tackle physical chemical problems which had been outside our experimental possibilities. Next, reviewing methodology, we present design criteria for droplet formation its seeding chromophore(s) interest, followed by discussion...
FERMI@Elettra comprises two free electron lasers (FELs) that will generate short pulses (τ∼25–200 fs) of highly coherent radiation in the XUV and soft x-ray region. The use external laser seeding together with a harmonic upshift scheme to obtain wavelengths give capability producing high-quality, longitudinally photon pulses. This capability, possibilities temporal synchronization control output polarization, open up new experimental opportunities are not possible currently available FELs....
The FERMI facility in Trieste, Italy, is ideal for generating and measuring light characterized by tunable polarization states the vacuum ultraviolet spectral range. New results reveal a high degree of (>0.9) over 26--55 nanometers.
Abstract The recent development of ultrafast extreme ultraviolet (XUV) coherent light sources bears great potential for a better understanding the structure and dynamics matter. Promising routes are advanced control nonlinear spectroscopy schemes in XUV energy range, yielding unprecedented spatial temporal resolution. However, their implementation has been hampered by experimental challenge generating pulse sequences with precisely controlled timing phase properties. In particular, direct...
Abstract The light-induced ultrafast switching between molecular isomers norbornadiene and quadricyclane can reversibly store release a substantial amount of chemical energy. Prior work observed signatures dynamics in both upon ultraviolet excitation but could not follow the electronic relaxation all way back to ground state experimentally. Here we study after exciting (201 nanometres) using time-resolved gas-phase extreme photoelectron spectroscopy combined with non-adiabatic simulations....
Quantum entanglement between the degrees of freedom encountered in classical world is challenging to observe due surrounding environment. To elucidate this issue, we investigate generated over ultrafast timescales a bipartite quantum system comprising two massive particles: free-moving photoelectron, which expands mesoscopic length scale, and light-dressed atomic ion, represents hybrid state light matter. Although photoelectron spectra are measured classically, allows us reveal information...
Nanometer-sized helium droplets, each containing about 10(4) atoms, were used as an inert substrate on which to form previously unobserved, spin-3/2 (quartet state) alkali trimers. Dispersed fluorescence measurements reveal that, upon electronic excitation, the quartet trimers undergo intersystem crossing doublet manifold, followed by dissociation of trimer into atom and a covalently bound singlet dimer. As shown this work, aggregates spin-polarized metals represent ideal species for optical...
Helium cluster isolation spectroscopy is a recently developed spectroscopic method that involves the formation of beam large helium clusters (104 atoms per cluster), capture by or molecules interest in low-pressure pick-up cell, and study isolated species. Here we exploit unique feature this allowing selective preparation high-spin molecular species (e.g., triplet dimers) over their low-spin (singlet) counterparts to measure spectra several alkali dimers manifold. By probing via...
Physisorption on solid surfaces is important in both fundamental studies and technology. Adsorbates can also be critical for the performance of miniature electromechanical resonators sensors. Advances resonant nanoelectromechanical systems (NEMS), particularly mass sensitivity attaining single-molecule level, make it possible to probe surface physics a new regime, where small number adatoms cause detectable frequency shift high quality factor (Q) NEMS resonator, adsorbate fluctuations result...
FERMI@Elettra is a free electron-laser (FEL)-based user facility that, after two years of commissioning, started preliminary users' dedicated runs in 2011. At variance with other FEL facilities, has been designed to deliver improved spectral stability and longitudinal coherence. The adopted scheme, which uses an external laser initiate the process, demonstrated be capable generating pulses close Fourier transform limit. We report on first instance wavelength tuning, both narrow large range...
The low density matter end-station at the new seeded free electron laser FERMI@Elettra is a versatile instrument for study of atoms, molecules and clusters by means ion spectroscopies. Beams helium droplets as well metals can be produced three different pulsed valves. atomic molecular beams may seeded, pure, or doped with other atoms molecules. electrons ions ionization fragmentation samples intense light FERMI analysed available spectrometers, to give mass spectra energy angular...
Abstract The first steps in photochemical processes, such as photosynthesis or animal vision, involve changes electronic and geometric structure on extremely short time scales. Time-resolved photoelectron spectroscopy is a natural way to measure changes, but has been hindered hitherto by limitations of available pulsed light sources the vacuum-ultraviolet soft X-ray spectral region, which have insufficient resolution energy simultaneously. unique combination intensity, resolution,...
FERMI is a novel class of free-electron laser that capable producing femtosecond pulses ultraviolet and x-ray light, essential to studying ultrafast processes in matter. A new investigation characterizes FERMI's pulse shape confirms it routinely generates Gaussian lasting few tens femtoseconds.
The ionization dynamics of He nanodroplets irradiated with intense femtosecond extreme ultraviolet pulses up to 1013 W/cm2 power density have been investigated by photoelectron spectroscopy. Helium droplets were resonantly excited atomiclike 2p states a photon energy 21.4 eV, below the potential (Ip), and directly into continuum 42.8 eV photons. While electron emission following direct above Ip is well explained within model based on sequence events, resonant excitation provides evidence...
Intense, circularly polarized extreme-ultraviolet and near-infrared (NIR) laser pulses are combined to double ionize atomic helium via the oriented intermediate He^{+}(3p) resonance state. Applying angle-resolved electron spectroscopy, we find a large photon helicity dependence of spectrum angular distribution electrons ejected from by NIR multiphoton absorption. The measured circular dichroism is unexpectedly found vary strongly as function intensity. experimental data well described...
We present a superfluid hydrodynamic model for the increase in moment of inertia, $\ensuremath{\Delta}I$, molecules rotating liquid ${}^{4}\mathrm{He}$. The static inhomogeneous He density around each molecule (calculated using Orsay-Paris ${}^{4}\mathrm{He}$ functional) is assumed to adiabatically follow rotation molecule. find that $\ensuremath{\Delta}I$ values created by viscousless and irrotational flow are good agreement with observed increases several [OCS, $(\mathrm{HCN}{)}_{2}$,...