A5040559676- Advanced Chemical Physics Studies
- Laser-Matter Interactions and Applications
- Mass Spectrometry Techniques and Applications
- Spectroscopy and Quantum Chemical Studies
- Photochemistry and Electron Transfer Studies
- X-ray Spectroscopy and Fluorescence Analysis
- Spectroscopy and Laser Applications
- Advanced Fiber Laser Technologies
- Electron and X-Ray Spectroscopy Techniques
- Advanced X-ray Imaging Techniques
- Ion-surface interactions and analysis
- Atomic and Molecular Physics
- Laser-Plasma Interactions and Diagnostics
- Advanced Electron Microscopy Techniques and Applications
- Nuclear Physics and Applications
- Photonic Crystal and Fiber Optics
- Quantum optics and atomic interactions
- Analytical Chemistry and Chromatography
- Radical Photochemical Reactions
- Atomic and Subatomic Physics Research
- Radioactive element chemistry and processing
- Particle physics theoretical and experimental studies
- Particle Detector Development and Performance
- Molecular spectroscopy and chirality
- Cold Atom Physics and Bose-Einstein Condensates
Linac Coherent Light Source
2021-2025
SLAC National Accelerator Laboratory
2020-2025
University of California, Davis
2025
University of Ottawa
2017-2023
Menlo School
2020-2023
National Research Council Canada
2017-2022
Stanford University
2019-2022
University College London
2016-2021
Heriot-Watt University
2019
Hungarian Academy of Sciences
2019
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....
Identifying multiple rival reaction products and transient species formed during ultrafast photochemical reactions determining their time-evolving relative populations are key steps toward understanding predicting outcomes. Yet, most contemporary studies struggle with clearly identifying quantifying competing molecular structures/species among the emerging products. Here, we show that mega-electronvolt electron diffraction in combination ab initio dynamics calculations offer a powerful route...
We investigated the ultrafast structural dynamics of cyclobutanone following photoexcitation at λ = 200 nm using gas-phase megaelectronvolt electron diffraction. Our investigation complements simulation studies same process within this special issue. It provides information about both electronic state population and through well-separable inelastic elastic scattering signatures. observe depopulation photoexcited S2 with n3s Rydberg character its signature a time constant (0.29 ± 0.2) ps...
The mechanical properties of DNA fundamentally constrain and enable the storage transmission genetic information its use in nanotechnology. Many depend on ionic environment due to highly charged backbone. In particular, both theoretical analyses direct single-molecule experiments have shown bending stiffness salt concentration. contrast, salt-dependence twist is much less explored. Here, we employ optimized multiplexed magnetic torque tweezers study torsional under varying conditions as a...
We extend covariance velocity map ion imaging to four particles, establishing cumulant mapping and allowing for measurements that provide insights usually associated with coincidence detection, but at much higher count rates. Without correction, a fourfold analysis is contaminated by the pairwise correlations of uncorrelated events, we have addressed this calculation full cumulant, which subtracts correlations. demonstrate approach on four-body breakup formaldehyde following strong field...
Directly imaging structural dynamics involving hydrogen atoms by ultrafast diffraction methods is complicated their low scattering cross sections. Here we demonstrate that megaelectronvolt electron sufficiently sensitive to follow in isolated molecules. In a study of the photodissociation gas phase ammonia, simultaneously observe signatures nuclear and corresponding electronic structure changes resulting from dissociation time-dependent diffraction. Both assignments are confirmed ab initio...
Conformational isomers or conformers of molecules play a decisive role in chemistry and biology. However, experimental methods to investigate chemical reaction dynamics are typically not conformer-sensitive. Here, we report on gas-phase megaelectronvolt ultrafast electron diffraction investigation {\alpha}-phellandrene undergoing an electrocyclic ring-opening reaction. We directly image the evolution specific set into product isomer predicted by Woodward-Hoffmann rules real space time. Our...
Filming atomic motion within molecules is an active pursuit of molecular physics and quantum chemistry. A promising method laser-induced Coulomb Explosion Imaging (CEI) where a laser pulse rapidly ionizes many electrons from molecule, causing the remaining ions to undergo repulsion. The ion momenta are used reconstruct geometry which tracked over time (i.e., filmed) by ionizing at adjustable delay with respect start interatomic motion. Results distorted, however, ultrafast during pulse. We...
Abstract Electrocyclic reactions are characterized by the concerted formation and cleavage of both σ π bonds through a cyclic structure. This structure is known as pericyclic transition state for thermal minimum in excited photochemical reactions. However, geometry has yet to be observed experimentally. We use combination ultrafast electron diffraction wavepacket simulations image structural dynamics electrocyclic ring-opening reaction molecule α-terpinene. The motion into dominated...
The absolute photoabsorption cross sections of norbornadiene (NBD) and quadricyclane (QC), two isomers with chemical formula C7H8 that are attracting much interest for solar energy storage applications, have been measured from threshold up to 10.8 eV using the Fourier transform spectrometer at SOLEIL synchrotron radiation facility. absorption spectrum NBD exhibits some sharp structure associated transitions into Rydberg states, superimposed on several broad bands attributable valence...
The combination of computer simulations and two powerful experimental methods for following molecular change on femtosecond timescales offers an unprecedented view how a photoexcited molecule breaks apart.
We present results from an experimental ion imaging study into the fragmentation dynamics of 1-iodopropane and 2-iodopropane following interaction with extreme ultraviolet intense femtosecond laser pulses a photon energy 95 eV. Using covariance analysis, range observed pathways resulting polycations can be isolated interrogated in detail at relatively high count rates (∼12 ions shot-1). By incorporating recently developed native frames analysis approach three-dimensional procedure,...
Recent developments in X-ray free-electron lasers have enabled a novel site-selective probe of coupled nuclear and electronic dynamics photoexcited molecules, time-resolved photoelectron spectroscopy (TRXPS). We present results from joint experimental theoretical TRXPS study the well-characterized ultraviolet photodissociation CS2, prototypical system for understanding non-adiabatic dynamics. These demonstrate that sulfur 2p binding energy is sensitive to changes structure following...
Abstract Structural imaging of transient excited-state species is a key goal molecular physics, promising to unveil rich information about the dynamics underpinning photochemical transformations. However, separating electronic and nuclear contributions spectroscopic observables challenging, typically requires application high-level theory. Here, we employ site-selective ionisation via ultrashort soft X-ray pulses time-resolved Coulomb explosion interrogate structural ultraviolet...
The photodissociation dynamics of strong-field ionized methyl iodide were probed using intense extreme ultraviolet (XUV) radiation produced by the SPring-8 Angstrom Compact free electron LAser.
We present the first vacuum ultraviolet time-resolved photoelectron spectroscopy (VUV-TRPES) study of photoisomerization dynamics in paradigmatic molecule cis-stilbene. A key reaction intermediate its dynamics, known as phantom state, has often been invoked but never directly detected gas phase. report direct spectral signatures state isolated cis-stilbene, observed and characterized through a combination VUV-TRPES ab initio multiple spawning (AIMS) nonadiabatic simulations channel-resolved...
We demonstrate the applicability of covariance analysis to three-dimensional velocity-map imaging experiments using a fast time stamping detector. Studying photofragmentation strong-field doubly ionized D2O molecules, we show that combining high count rate measurements with yields same level information typically limited "gold standard" true, low coincidence experiments, when averaging over large ensemble events. This increases effective data acquisition by approximately 2 orders magnitude,...
Polyatomic molecules in strong laser fields can undergo substantial nuclear motion within tens of femtoseconds. Ion imaging methods based on dissociation or Coulomb explosion therefore have difficulty faithfully recording the geometry dependence field ionization that initiates process. Here we compare strong-field double and subsequent water (both H$_2$O D$_2$O) 10-fs 40-fs 800-nm pulses. We find pulses turn off before internuclear occurs, whereas rapid take place during process for The...
We investigate the role of nuclear motion and strong-field-induced electronic couplings during double ionization deuterated water using momentum-resolved coincidence spectroscopy. By examining three-body dicationic dissociation channel, ${\mathrm{D}}^{+}/{\mathrm{D}}^{+}/\mathrm{O}$, for both few- multicycle laser pulses, strong evidence intrapulse dynamics is observed. The extracted angle- energy-resolved yields are compared to classical trajectory simulations occurring from different...
Multipath holographic interference in strong-field quantum tunnel ionization is key to revealing subangstrom attosecond dynamics for molecular movies. This critical subcycle motion often obscured by longer timescale effects such as ring-shaped patterns that appear above-threshold (ATI). In the present work, we overcome this problem combining two techniques theory and experimental analysis: unit-cell averaging time-filtering data simulations. Together these suppress ATI rings enable an...
We demonstrate compression and shaping of few cycle pulses from a high average power ytterbium laser system. The commercial 20 W, 100 kHz Yb system are spectrally broadened in two-stages using cascaded, gas-filled, stretched hollow-core fibers then compressed shaped an acousto-optic modulator-based pulse-shaper. pulse-shaper allows for compression, characterization, all one system, producing ∼10 fs with 30 μ J energy.
Dimeric complexes composed of d