A5080420296- Particle Accelerators and Free-Electron Lasers
- Particle accelerators and beam dynamics
- Gyrotron and Vacuum Electronics Research
- Advanced X-ray Imaging Techniques
- Electron and X-Ray Spectroscopy Techniques
- Advanced Electron Microscopy Techniques and Applications
- Advanced Chemical Physics Studies
- Laser-Plasma Interactions and Diagnostics
- Spectroscopy and Quantum Chemical Studies
- Laser-Matter Interactions and Applications
- Terahertz technology and applications
- 2D Materials and Applications
- Laser Design and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Photochemistry and Electron Transfer Studies
- Magnetic properties of thin films
- Perovskite Materials and Applications
- Metallurgical Processes and Thermodynamics
- Photonic and Optical Devices
- Electronic and Structural Properties of Oxides
- Photocathodes and Microchannel Plates
- Topological Materials and Phenomena
- X-ray Diffraction in Crystallography
- Molecular Junctions and Nanostructures
- Mass Spectrometry Techniques and Applications
Zhejiang University
2024-2025
SLAC National Accelerator Laboratory
2015-2024
Wuhan Institute of Technology
2023-2024
University of Duisburg-Essen
2016-2024
Chinese Institute for Brain Research
2024
Beijing Tian Tan Hospital
2024
Capital Medical University
2024
Yangzhou University
2024
TU Dortmund University
2024
Stanford University
2017-2024
A high-gain harmonic-generation free-electron laser is demonstrated. Our approach uses a laser-seeded to produce amplified, longitudinally coherent, Fourier transform-limited output at harmonic of the seed laser. carbon dioxide wavelength 10.6 micrometers produced saturated, amplified second-harmonic wavelength, 5.3 micrometers. The experiment verifies theoretical foundation for technique and prepares way application this in vacuum ultraviolet region spectrum, with ultimate goal extending...
Ultrafast electron probes are powerful tools, complementary to x-ray free-electron lasers, used study structural dynamics in material, chemical, and biological sciences. High brightness, relativistic beams with femtosecond pulse duration can resolve details of the dynamic processes on atomic time length scales. SLAC National Accelerator Laboratory recently launched Electron Diffraction (UED) microscopy Initiative aiming at developing next generation ultrafast scattering instruments. As first...
Conical intersections play a critical role in excited-state dynamics of polyatomic molecules because they govern the reaction pathways many nonadiabatic processes. However, ultrafast probes have lacked sufficient spatial resolution to image wave-packet trajectories through these directly. Here, we present simultaneous experimental characterization one-photon and two-photon excitation channels isolated CF3I using gas-phase electron diffraction. In channel, mapped out real-space coherent...
The ultrafast laser excitation of matters leads to nonequilibrium states with complex solid-liquid phase-transition dynamics. We used electron diffraction at mega-electron volt energies visualize the melting gold on atomic scale length. For energy densities approaching irreversible regime, we first observed heterogeneous time scales 100 1000 picoseconds, transitioning homogeneous that occurs catastrophically within 10 20 picoseconds higher densities. showed evidence for coexistence solid and...
Absorption of light in hybrid perovskite solar cells leads to ultrafast large-amplitude deformations the inorganic sublattice.
Self-amplified spontaneous emission in a free-electron laser has been proposed for the generation of very high brightness coherent x-rays. This process involves passing high-energy, high-charge, short-pulse, low-energy-spread, and low-emittance electron beam through periodic magnetic field long series high-quality undulator magnets. The radiation produced grows exponentially intensity until it reaches saturation point. We report on demonstration self-amplified gain, exponential growth, at...
We report the first experimental results on a high-gain harmonic-generation (HGHG) free-electron laser (FEL) operating in ultraviolet. An 800 nm seed from Ti:sapphire has been used to produce saturated amplified radiation at 266 third harmonic. The confirm predictions for HGHG FEL operation: stable central wavelength, narrow bandwidth, and small pulse-energy fluctuation.
A 580-MW peak power, radially polarized C${\mathrm{O}}_{2}$ laser beam ($\ensuremath{\lambda}=10.6$ \ensuremath{\mu}m) focused by an axicon accelerated 40-MeV electrons \ensuremath{\le}3.7 MeV over a 12-cm interaction length (31 MeV/m), using the inverse Cherenkov effect in which gas is used to slow light wave. This represents first direct observation of acceleration this and demonstrates effectiveness radially-polarized-axicon-focused geometry. The observed energy gain agrees with model predictions.
We have demonstrated nonlinear cross-phase modulation in electro-optic crystals using intense, single-cycle terahertz (THz) radiation. Individual THz pulses, generated by coherent transition radiation emitted subpicosecond electron bunches, peak energies of up to 100 microJ per pulse. The time-dependent electric field the intense pulses induces through Pockels effect, leading spectral shifting, broadening, and copropagating laser pulses. observed THz-induced agrees well with a phase-shift model.
Observing the motion of nuclear wavepackets during a molecular reaction, in both space and time, is crucial for understanding controlling outcome photoinduced chemical reactions. We have imaged vibrational wavepacket isolated iodine molecules using ultrafast electron diffraction with relativistic electrons. The time-varying interatomic distance was measured precision 0.07 {\AA} temporal resolution 230 fs full-width at half-maximum (FWHM). method not only sensitive to position but also shape...
Electronic and nuclear dynamics in one Because of the complex, ultrafast interplay between electronic degrees freedom, probing both excited states within a single time-resolved experiment is great challenge. Yang et al. used electron diffraction combination with ab initio nonadiabatic molecular simulations to study relaxation isolated pyridine molecules after photoexcitation S 1 state (see Perspective by Domcke Sobolewski). They showed that evolution structural changes can be recorded...
We report the experimental demonstration of femtosecond electron diffraction using high-brightness MeV beams. High-quality, single-shot patterns for both polycrystalline aluminum and single-crystal 1T-TaS2 are obtained utilizing a 5 fC (∼3 × 104 electrons) pulse electrons at 2.8 MeV. The high quality confirms that beam has normalized emittance ∼50 nm rad. transverse longitudinal coherence length is ∼11 ∼2.5 nm, respectively. timing jitter between pump laser probe was found to be ∼100 fs...
Abstract Imaging changes in molecular geometries on their natural femtosecond timescale with sub-Angström spatial precision is one of the critical challenges chemical sciences, as nuclear geometry determine reactivity. For photoexcited molecules, dynamics photoenergy conversion path and efficiency. Here we report a gas-phase electron diffraction experiment using megaelectronvolt (MeV) electrons, where captured rotational wavepacket nonadiabatically laser-aligned nitrogen molecules. We...
Topological defects, potential information carriers, were written into and erased from a solid with femtosecond light pulses.
Two-dimensional materials are subject to intrinsic and dynamic rippling that modulates their optoelectronic electromechanical properties. Here, we directly visualize the dynamics of these processes within monolayer transition metal dichalcogenide MoS2 using femtosecond electron scattering techniques as a real-time probe with atomic-scale resolution. We show optical excitation induces large-amplitude in-plane displacements ultrafast wrinkling on nanometer length-scales, developing picosecond...
A transient metal Vanadium dioxide is known to have a coupled structural and electronic transition that can be accessed through light, thermal, or electrical excitation. Ultrafast optical studies of this insulator-to-metal indicate it mediated by the formation metallic phase retains structure original insulating phase. Sood et al. show similar sequence occurs when material electrically excited with series voltage pulses. Using ultrafast electron diffraction, researchers monitored vanadium...
We present the first demonstration of THz-driven bunch compression and timing stabilization a few-fC relativistic electron beam with kinetic energy 2.5 MeV using quasi-single-cycle strong field THz radiation in shorted parallel-plate structure. Compression by nearly factor 3 produced 39 fs rms length reduction jitter more than 2, to 31 rms, offering significant improvement performance for applications like ultrafast diffraction. This technique provides critical step towards unprecedented...
We demonstrate single-shot temporal characterization of relativistic electron bunches using single-cycle terahertz (THz) field streaking. A transverse deflecting structure consisting a metal slit enables efficient coupling the THz and bunch. The intrinsically stable carrier envelope phase strong gradient pulses allow simultaneous, self-calibrated determination time-of-arrival with subfemtosecond precision bunch duration single-femtosecond precision, respectively, opening up new opportunities...
Complex systems, which consist of a large number interacting constituents, often exhibit universal behavior near phase transition. A slowdown certain dynamical observables is one such recurring feature found in vast array contexts. This phenomenon, known as critical slowing-down, well studied mostly thermodynamic transitions. However, it less understood highly nonequilibrium settings, where the time takes to traverse boundary becomes comparable timescale fluctuations. Using transient optical...