A5087543122- Laser-Matter Interactions and Applications
- Mass Spectrometry Techniques and Applications
- Advanced Chemical Physics Studies
- Spectroscopy and Quantum Chemical Studies
- Atomic and Molecular Physics
- Ion-surface interactions and analysis
- Photochemistry and Electron Transfer Studies
- Molecular spectroscopy and chirality
- Laser Design and Applications
- Chemical Reactions and Isotopes
- Energetic Materials and Combustion
- Advanced Electron Microscopy Techniques and Applications
- Nuclear Physics and Applications
- Advanced X-ray Imaging Techniques
- Radioactive element chemistry and processing
- X-ray Spectroscopy and Fluorescence Analysis
- Molecular Spectroscopy and Structure
- Quantum, superfluid, helium dynamics
- Advanced Thermodynamics and Statistical Mechanics
- Fluorine in Organic Chemistry
- Analytical Chemistry and Sensors
- Radical Photochemical Reactions
- Forensic Fingerprint Detection Methods
- Laser-induced spectroscopy and plasma
- CO2 Reduction Techniques and Catalysts
Kansas State University
2018-2025
SLAC National Accelerator Laboratory
2024-2025
University of Science and Technology of China
2024
Roaming mechanisms, involving the brief generation of a neutral atom or molecule that stays in vicinity before reacting with remaining atoms precursor, are providing valuable insights into previously unexplained chemical reactions. Here, mechanistic details and femtosecond time-resolved dynamics H3+ formation from series alcohols varying primary carbon chain lengths obtained through combination strong-field laser excitation studies ab initio molecular calculations. For small alcohols, four...
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...
Coulomb explosion imaging (CEI) with x-ray free electron lasers has recently been shown to be a powerful method for obtaining detailed structural information of gas-phase planar ring molecules [R. Boll et al. Nat. Phys. 18, 423-428 (2022)]. In this Letter, we investigate the potential CEI driven by tabletop laser and extend approach differentiating three-dimensional (3D) structures. We study static patterns nonplanar organic that resemble structures typical products formed in ring-opening...
Abstract An essential problem in photochemistry is understanding the coupling of electronic and nuclear dynamics molecules, which manifests processes such as hydrogen migration. Measurements migration molecules that have more than two equivalent sites, however, produce data difficult to compare with calculations because initial site unknown. We demonstrate coincidence ion-imaging measurements a few deuterium-tagged isotopologues ethanol can determine contribution each initial-site...
The detailed understanding of electronic coherence in quantum systems requires measurements on the attosecond timescale. Attosecond x-ray pulses enable study core-excited molecular systems. Here we report coherent motion electrons 1,1-difluoroethylene ion following ionization <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>K</a:mi></a:math> shell two nonequivalent carbon sites with a subfemtosecond pulse. Using angular streaking technique to track Auger-Meitner...
A comparative study of bond rearrangement is reported for the double ionization three triatomic molecules: carbon dioxide, carbonyl sulfide, and water (${\mathrm{D}}_{2}\mathrm{O}$). Specifically, we formation molecular cation ${\mathrm{AC}}^{+}$ from edge atoms a dication ${\mathrm{ABC}}^{2+}$ following by intense, short (23 fs, 790 nm) laser pulses. The comparison made using branching ratio each molecule, thereby minimizing differences due to differing rates. highest water, which has bent...
The Coulomb explosion of tribromomethane (bromoform, CHBr3) induced by 28 fs near-infrared laser pulses is investigated three-dimensional coincidence ion momentum imaging. We focus on the fragmentation into three, four, and five ionic fragments measured in present different ways visualizing correlations. show that experimentally observed correlations for 4- 5-fold coincidences are well reproduced classical simulations contain information about structure parent molecule could be used to...
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...
We studied the fragmentation of planar formic acid (HCOOH) molecules following their double ionization by intense ultrashort laser pulses. Deuterium tagging (i.e., HCOOD) combined with coincidence momentum imaging measurements all fragment ions enabled determination role hydroxyl and carboxyl hydrogen atoms in breakup. Specifically, we observe a strong preference for (OD) group to remain intact...
The predissociation dynamics of the 6s (B2E) Rydberg state gas-phase CH3I were investigated by time-resolved Coulomb-explosion imaging using extreme ultraviolet (XUV) free-electron laser pulses. Inner-shell ionization at iodine 4d edge was utilized to provide a site-specific probe ensuing dynamics. combination velocity-map (VMI) spectrometer coupled with pixel mass spectrometry (PImMS) camera permitted three-dimensional ionic fragment momenta be recorded simultaneously for wide range charge...
The photon spectrum from free-electron laser (FEL) light sources offers valuable information in time-resolved experiments and machine optimization the spectral temporal domains. We have developed a compact single-shot spectrometer to diagnose soft X-ray spectra. consists of an array off-axis Fresnel zone plates (FZP) that act as transmission-imaging gratings, Ce:YAG scintillator, microscope objective image scintillation target onto two-dimensional imaging detector. This operates segmented...
Site-selective probing of iodine 4d orbitals at 13.1 nm was used to characterize the photolysis CH2I2 and CH2BrI initiated 202.5 nm. Time-dependent fragment ion momenta were recorded using Coulomb explosion imaging mass spectrometry determine structural dynamics dissociating molecules. Correlations between these momenta, as well onset times electron transfer reactions them, indicate that each molecule can undergo neutral three-body photolysis. For CH2I2, evolution simultaneously...
The UV-photodissociation of methyl iodide (CH 3 I) and other competing processes are studies by time-resolved Coulomb explosion imaging.
We investigate the fragmentation and isomerization of toluene molecules induced by strong-field ionization with a femtosecond near-infrared laser pulse.
An ultrafast electron diffraction study of the structural dynamics cis , -1,3-cyclooctadiene has identified a ring stretching distortion as new reaction coordinate molecule transitions from excited state back to ground state.
We investigate the two- and three-body fragmentation of tribromomethane (bromoform, CHBr3) resulting from multiple ionization by 28-femtosecond near-infrared laser pulses with a peak intensity 6 × 1014 W cm-2. The analysis focuses on channels consisting exclusively ionic fragments, which are measured coincidence momentum imaging. dominant two-body channel is found to be Br+ + CHBr2+. Weaker HBr+ CBr2+, CHBr+ Br2+, CHBr2+ CHBr22+ channels, some require bond rearrangement prior or during...
We have studied the fragmentation of brominated cyclic hydrocarbons bromocyclo-propane, bromocyclo-butane, and bromocyclo-pentane upon Br(3d) C(1s) inner-shell ionization using coincidence ion momentum imaging. observe a substantial yield CH3+ fragments, whose formation requires intramolecular hydrogen (or proton) migration, that increases with molecular size, which contrasts prior observations migration in linear hydrocarbon molecules. Furthermore, by inspecting fragment correlations...
<title>Abstract</title> Photoinduced transformations of organic ring molecules play a crucial role in numerous physical, chemical and biological processes, ranging from biosynthesis vitamin D to optical switching molecular electronics. Although the development plethora ultrafast techniques such as time-resolved photoelectron spectroscopy, electron x-ray diffraction transient absorption has recently enabled detailed investigations electronic nuclear dynamics several conversion reactions,...
In molecular systems, the ultrafast motion of electrons initiates process chemical change. Tracking this electronic across molecules requires coupling attosecond time resolution to atomic-scale spatial sensitivity. work, we employ a pair x-ray pulses from an free-electron laser follow electron resulting sudden removal prototypical aromatic system, para-aminophenol. X-ray absorption enables tracking with atomic-site specificity. Our measurements are compared state-of-the-art computational...
We present a time-resolved measurement of the photodissociation and photoisomerization dynamics bromoform (CHBr3) in mono- di-cationic states produced by near-infrared (NIR) strong-field ionization. The dissociation process is probed NIR-induced Coulomb explosion imaging. find that for channels involving production HBr Br2 fragments, which require formation new bonds, appears to be delayed with respect primary C–Br bond channel. Ab initio molecular simulations support observed delay....
We describe the design and performance of a magnetic bottle electron spectrometer (MBES) for high-energy spectroscopy. Our features 2 m long drift tube electrostatic retardation lens, achieving sub-electronvolt (eV) kinetic energy resolution high (several hundred eV) electrons with close to 4π collection solid angle. A segmented anode detector enables simultaneous photoelectron spectra in efficiency modes. This versatile instrument is installed at time-resolved molecular optical sciences...
The photon spectrum from free-electron laser (FEL) light sources offers valuable information in time-resolved experiments and machine optimization the spectral temporal domains. We have developed a compact single-shot spectrometer to diagnose soft X-ray spectra. consists of an array off-axis Fresnel zone plates (FZP) that act as transmission-imaging gratings, Ce-YAG scintillator, microscope objective image scintillation target onto two-dimensional imaging detector. This operates energy range...
We present results of classical Coulomb explosion simulations to demonstrate that imaging can serve as a robust method for differentiating molecular structures and following structural changes in pump-probe experiments by tracking the motion individual atoms within molecule.