A5074918602- Laser-Matter Interactions and Applications
- Advanced Chemical Physics Studies
- Mass Spectrometry Techniques and Applications
- Atomic and Molecular Physics
- Laser Design and Applications
- Laser-induced spectroscopy and plasma
- Spectroscopy and Quantum Chemical Studies
- Spectroscopy and Laser Applications
- Catalytic Processes in Materials Science
- Nuclear Physics and Applications
- Synthesis and Properties of Aromatic Compounds
- Astrophysics and Star Formation Studies
- Ion-surface interactions and analysis
- Quantum, superfluid, helium dynamics
- Advanced Fiber Laser Technologies
- Fullerene Chemistry and Applications
- Catalysis and Oxidation Reactions
- Diamond and Carbon-based Materials Research
- Advanced Combustion Engine Technologies
- Astro and Planetary Science
- Atmospheric chemistry and aerosols
- Photoreceptor and optogenetics research
- Quantum optics and atomic interactions
- Traumatic Ocular and Foreign Body Injuries
- Advanced X-ray Imaging Techniques
Kansas State University
2012-2020
Lawrence Berkeley National Laboratory
2017-2020
Deutsches Elektronen-Synchrotron DESY
2019
Hobart and William Smith Colleges
2019
University of Connecticut
2019
University of California, Berkeley
2019
Berkeley College
2019
Max Planck Institute for Nuclear Physics
2019
SLAC National Accelerator Laboratory
2019
A key question concerning the three-body fragmentation of polyatomic molecules is distinction sequential and concerted mechanisms, i.e., stepwise or simultaneous cleavage bonds. Using laser-driven OCS into O^{+}+C^{+}+S^{+} employing coincidence momentum imaging, we demonstrate a novel method that enables clear separation breakup. The accomplished by analyzing in native frame associated with each step taking advantage rotation intermediate molecular fragment, CO^{2+} CS^{2+}, before its...
The formation of the simplest polycyclic aromatic hydrocarbon (PAH), naphthalene (C10H8), was explored in a high-temperature chemical reactor under combustion-like conditions phenyl (C6H5)-vinylacetylene (C4H4) system. products were probed utilizing tunable vacuum ultraviolet light by scanning photoionization efficiency (PIE) curve at mass-to-charge m/ z = 128 (C10H8+) molecules entrained molecular beam. data fitting with PIE reference curves naphthalene, 4-phenylvinylacetylene (C6H5CCC2H3),...
The dissociation of an H$_2^+$ molecular-ion beam by linearly polarized, carrier-envelope-phase-tagged 5 fs pulses at 4$\times10^{14} $W/cm$^2$ with a central wavelength 730 nm was studied using coincidence 3D momentum imaging technique. Carrier-envelope-phase-dependent asymmetries in the emission direction H$^+$ fragments relative to laser polarization were observed. These are caused interference odd and even photon number pathways, where net-zero 1-photon predominantly contributes H$^+$+H...
Abstract An experimental route to identify and separate geometric isomers by means of coincident Coulomb explosion imaging is presented, allowing isomer-resolved photoionization studies on isomerically mixed samples. We demonstrate the technique cis/trans 1,2-dibromoethene (C 2 H Br ). The momentum correlation between bromine ions in a three-body fragmentation process induced 3 d inner-shell used cis trans structures isomers. experimentally determined correlations fragment-ion kinetic...
A synthetic route to racemic helicenes via a vinylacetylene mediated gas phase chemistry involving elementary reactions with aryl radicals is presented. In contrast traditional routes solution and ionic reaction intermediates, the synthesis involves targeted ring annulation free radical intermediates. Exploiting simplest helicene as benchmark, we show that of 4-phenanthrenyl ([C14H9]•) (C4H4) yields [4]-helicene (C18H12) along atomic hydrogen low-barrier mechanism through...
The three-ring polycyclic aromatic hydrocarbons (PAHs) 3H-benz[e]indene (C13H10) and 1H-benz[f]indene along with their naphthalene-based isomers 2-(prop-2-yn-1-yl)naphthalene (C13H10), 2-(prop-1-yn-1-yl)naphthalene 2-(propa-1,2-dien-1-yl)naphthalene were formed through a "directed synthesis"via high temperature chemical micro reactor under combustion-like conditions (1300 ± 35 K) the reactions of 2-naphthyl isomer (C10H7˙) allene (C3H4) methylacetylene (C3H4). distributions probed utilizing...
Synchrotron based mass spectrometry coupled with theoretical calculations provides insight into polycyclic aromatic hydrocarbon water interactions.
Laser-induced adiabatic alignment and mixed-field orientation of 2,6-difluoroiodobenzene (C6H3F2I) molecules are probed by Coulomb explosion imaging following either near-infrared strong-field ionization or extreme-ultraviolet multi-photon inner-shell using free-electron laser pulses. The resulting photoelectrons fragment ions captured a double-sided velocity map spectrometer projected onto two position-sensitive detectors. ion side the is equipped with pixel mass spectrometry camera,...
Abstract Polycyclic aromatic hydrocarbons (PAHs) represent the link between resonance‐stabilized free radicals and carbonaceous nanoparticles generated in incomplete combustion processes circumstellar envelopes of carbon rich asymptotic giant branch (AGB) stars. Although these PAHs resemble building blocks complex nanostructures, their fundamental formation mechanisms have remained elusive. By exploring reaction phenyl radical with biphenyl/naphthalene theoretically experimentally, we...
The reactions of the indenyl radicals with acetylene (C2 H2 ) and vinylacetylene (C4 H4 is studied in a hot chemical reactor coupled to synchrotron based vacuum ultraviolet ionization mass spectrometry. These experimental results are combined theory reveal that resonantly stabilized thermodynamically most stable 1-indenyl radical (C9 H7. always formed pyrolysis 1-, 2-, 6-, 7-bromoindenes at 1500 K. reacts yielding 1-ethynylindene plus atomic hydrogen, rather than adding second molecule...
Intermolecular processes offer unique decay mechanisms for complex systems to internally relax. Here, we report the observation of an intermolecular Coulombic channel in endohedral fullerene, a holmium nitride (Ho_{3}N) embedded within C_{80} between neighboring ions, and carbon cage. By measuring ions electrons coincidence after XUV photoabsorption, can isolate different channels, which are found be more prevalent relative intra-atomic Auger decay.
A unified low-temperature reaction mechanism on the formation of acenes, phenacenes, and helicenes-polycyclic aromatic hydrocarbons (PAHs) that are distinct via linear, zigzag, ortho-condensed arrangements fused benzene rings-is revealed. This is mediated through a barrierless, vinylacetylene gas-phase chemistry utilizing tetracene, [4]phenacene, [4]helicene as benchmarks contesting established ideas molecular mass growth processes to PAHs transpire at elevated temperatures. opens up an...
We report on the design and performance of a double-sided coincidence velocity map imaging spectrometer optimized for electron-ion ion-ion experiments studying inner-shell photoionization gas-phase molecules with soft X-ray synchrotron radiation. The apparatus employs two microchannel plate detectors equipped delay-line anodes coincident, time- position-resolved detection photoelectrons Auger electrons kinetic energies up to 300 eV one side photoions 25 per unit charge opposite side....
For the last decades, hydrogen-abstraction-acetylene-addition (HACA) mechanism has been widely invoked to rationalize high-temperature synthesis of PAHs as detected in carbonaceous meteorites (CM) and proposed exist interstellar medium (ISM). By unravelling chemistry 9-phenanthrenyl radical ([C14 H9 ]. ) with vinylacetylene (C4 H4 ), we present first compelling evidence a barrier-less pathway leading prototype tetracyclic PAH - triphenylene (C18 H12 via an unconventional hydrogen...
Charge asymmetric dissociation into ${\mathrm{C}}^{2+}+\mathrm{O}$ following ionization of a CO${}^{+}$ molecular-ion beam with intense ultrashort (7--40-fs) laser pulses is studied using coincidence three-dimensional momentum imaging method. The data suggest that allowing the molecule enough time to stretch within pulse such it ionizes beyond curve crossings and ${\mathrm{C}}^{+}+{\mathrm{O}}^{+}$ potentials enhances otherwise hard-to-reach charge channel.
The fragmentation dynamics of 2,6- and 3,5-difluoroiodobenzene after iodine 4d inner-shell photoionization with soft X-rays are studied using coincident electron ion momentum imaging. By analyzing the correlation between fluorine cations in three-fold coincidence events, we can distinguish two isomers experimentally. Classical Coulomb explosion simulations overall agreement experimentally determined fragment kinetic energies correlations point toward different mechanisms time scales. While...
The fragmentation dynamics of an endohedral fullerene, $\mathrm{S}{\mathrm{c}}_{3}\mathrm{N}@{\mathrm{C}}_{80}$, after absorption a soft-x-ray photon, has been studied with ion-ion-coincidence momentum-imaging technique. Molecular inner-shell ionization at 406.5 eV, targeting the Sc ($2p$) shell encapsulated $\mathrm{S}{\mathrm{c}}_{3}\mathrm{N}$ moiety and C ($1s$) ${\mathrm{C}}_{80}$ cage, leads to cage through evaporation ${\mathrm{C}}_{2}$, emission small molecular carbon ions...
Vacuum ultraviolet (VUV) single photon ionization mass spectrometry (SPI-MS) is a vacuum-based technique typically used for the analysis of gas phase and solid samples, but not liquids due to challenge in introducing volatile vacuum. Here we present first demonstration situ liquid by integrating System Analysis at Liquid Interface (SALVI) microfluidic reactor into VUV SPI-MS. Four representative organic compound (VOC) solutions were illustrate feasibility analysis. Our results show accurate...
Abstract A unified low‐temperature reaction mechanism on the formation of acenes, phenacenes, and helicenes—polycyclic aromatic hydrocarbons (PAHs) that are distinct via linear, zigzag, ortho ‐condensed arrangements fused benzene rings—is revealed. This is mediated through a barrierless, vinylacetylene gas‐phase chemistry utilizing tetracene, [4]phenacene, [4]helicene as benchmarks contesting established ideas molecular mass growth processes to PAHs transpire at elevated temperatures. opens...
We present a method for determining the detection efficiency of neutral atoms relative to keV ions. Excited D* are produced by D2 fragmentation in strong laser field. The fragments detected micro-channel plate detector either directly as neutrals or ions following field ionization and acceleration static electric Moreover, we propose new mechanism which detected. show that ratio yield can be related these species.