A5069698484- Atmospheric chemistry and aerosols
- Catalysis and Oxidation Reactions
- Catalytic Processes in Materials Science
- Advanced Chemical Physics Studies
- Atmospheric Ozone and Climate
- Advanced Combustion Engine Technologies
- Spectroscopy and Laser Applications
- Analytical Chemistry and Chromatography
- Mass Spectrometry Techniques and Applications
- Chemical Thermodynamics and Molecular Structure
- Combustion and flame dynamics
- Free Radicals and Antioxidants
- Photochemistry and Electron Transfer Studies
- Water Quality Monitoring and Analysis
- Chemical Reaction Mechanisms
- CO2 Reduction Techniques and Catalysts
- Analytical Chemistry and Sensors
- Atmospheric and Environmental Gas Dynamics
- Various Chemistry Research Topics
- Heat transfer and supercritical fluids
- Inorganic and Organometallic Chemistry
- Spectroscopy and Quantum Chemical Studies
- Electrochemical Analysis and Applications
- Molecular Junctions and Nanostructures
- Oxidative Organic Chemistry Reactions
Sandia National Laboratories California
2015-2024
Orange (Poland)
2022
Robert Bosch (Germany)
2022
Laboratoire de Chimie Moléculaire et Thioorganique
2022
Bioanalytica (Switzerland)
2022
Lawrence Livermore National Security
2014-2020
Sandia National Laboratories
2014-2020
Joint Institute for Laboratory Astrophysics
2009-2012
University of Colorado Boulder
2012
University of Wisconsin–Madison
2002-2005
Rate coefficients are directly determined for the reactions of Criegee intermediates (CI) CH2 OO and CH3 CHOO with two simplest carboxylic acids, formic acid (HCOOH) acetic (CH3 COOH), employing complementary techniques: multiplexed photoionization mass spectrometry cavity-enhanced broadband ultraviolet absorption spectroscopy. The measured rate in excess 1×10(-10) cm(3) s(-1) , several orders magnitude larger than those suggested from many previous alkene ozonolysis experiments assumed...
Transient absorption probing of a Criegee intermediate acetaldehyde oxide reveals the UV spectra two possible conformers, <italic>syn</italic>- and <italic>anti</italic>-CH<sub>3</sub>CHOO, enables direct measurements conformer-dependent reactivity.
Oxidation of organic compounds in combustion and Earth's troposphere is mediated by reactive species formed the addition molecular oxygen (O2) to radicals. Among most crucial elusive these intermediates are hydroperoxyalkyl radicals, often denoted "QOOH." These their reactions with O2 responsible for radical chain branching that sustains autoignition implicated tropospheric autoxidation can form low-volatility, highly oxygenated aerosol precursors. We report direct observation kinetics...
We present the time-resolved UV absorption spectrum of B̃ ((1)A') ← X̃ electronic transition formaldehyde oxide, CH2OO, produced by reaction CH2I radicals with O2. In contrast to its photodissociation action spectrum, oxide extends longer wavelengths and exhibits resolved vibrational structure on low-energy side. Chemical kinetics measurements reactivity establish identity absorbing species as CH2OO. Separate initial radical concentration allow a determination absolute cross section value at...
Isoprene has the highest emission into Earth's atmosphere of any nonmethane hydrocarbon. Atmospheric processing alkenes, including isoprene, via ozonolysis leads to formation zwitterionic reactive intermediates, known as Criegee intermediates (CIs). Direct studies have revealed that reactions involving simple CIs can significantly impact tropospheric oxidizing capacity, enhance particulate formation, and degrade local air quality. Methyl vinyl ketone oxide (MVK-oxide) is a four-carbon,...
The rapid reaction of the smallest Criegee intermediate, CH2OO, with water dimers is dominant removal mechanism for CH2OO in Earth's atmosphere, but its products are not well understood. This was recently suggested as a significant source most abundant tropospheric organic acid, formic acid (HCOOH), which consistently underpredicted by atmospheric models. However, using time-resolved measurements kinetics UV absorption and product analysis photoionization mass spectrometry, we show that...
The branched C5 alcohol isopentanol (3-methylbutan-1-ol) has shown promise as a potential biofuel both because of new advanced biochemical routes for its production and combustion characteristics, in particular fuel homogeneous-charge compression ignition (HCCI) or related strategies. In the present work, fundamental autoignition chemistry is investigated by using technique pulsed-photolytic Cl-initiated oxidation analyzing reacting mixture time-resolved tunable synchrotron photoionization...
The reaction between CH3O2 and OH radicals has been shown to be fast play an appreciable role for the removal of radials in remote environments such as marine boundary layer. Two different experimental techniques have used here determine products this reaction. HO2 yield obtained from simultaneous time-resolved measurements absolute concentration CH3O2, OH, by cw-CRDS. possible formation a Criegee intermediate measured broadband cavity enhanced UV absorption. A ϕHO2 = (0.8 ± 0.2) upper limit...
Decomposition kinetics of stabilised CH2OO and CD2OO Criegee intermediates have been investigated as a function temperature (450-650 K) pressure (2-350 Torr) using flash photolysis coupled with time-resolved cavity-enhanced broadband UV absorption spectroscopy. was observed to be faster than under equivalent conditions. Production OH radicals following decomposition also monitored laser-induced fluorescence (LIF), results indicating direct production in the v = 0 1 states low yields. Master...
We report a combined experimental and quantum chemistry study of the initial reactions in low-temperature oxidation tetrahydrofuran (THF). Using synchrotron-based time-resolved VUV photoionization mass spectrometry, we probe numerous transient intermediates products at P = 10–2000 Torr T 400–700 K. A key reaction sequence, revealed by our experiments, is conversion THF-yl peroxy to hydroperoxy-THF-yl radicals (QOOH), followed second O2 addition subsequent decomposition dihydrofuranyl...
Reactions of hydroxybutyl radicals with O2 were investigated by a combination quantum-chemical calculations and experimental measurements product formation. In pulsed-photolytic Cl-initiated oxidation n-butanol, the time-resolved isomer-specific concentrations probed using multiplexed tunable synchrotron photoionization mass spectrometry (MPIMS). The interpretation data is underpinned potential energy surfaces for reactions four isomers (1-hydroxybut-1-yl, 1-hydroxybut-2-yl,...
Abstract Rate coefficients are directly determined for the reactions of Criegee intermediates (CI) CH 2 OO and 3 CHOO with two simplest carboxylic acids, formic acid (HCOOH) acetic (CH COOH), employing complementary techniques: multiplexed photoionization mass spectrometry cavity‐enhanced broadband ultraviolet absorption spectroscopy. The measured rate in excess 1×10 −10 cm s −1 , several orders magnitude larger than those suggested from many previous alkene ozonolysis experiments assumed...
Abstract Methanol is a benchmark for understanding tropospheric oxidation, but underpredicted by up to 100% in atmospheric models. Recent work has suggested this discrepancy can be reconciled the rapid reaction of hydroxyl and methylperoxy radicals with methanol branching fraction 30%. However, fractions below 15%, underprediction exacerbated. Theoretical investigations are challenging because intersystem crossing between singlet triplet surfaces – ∼45% products obtained via pre-product...
Low-temperature propane oxidation was studied at P = 4 Torr and T 530, 600, 670 K by time-resolved multiplexed photoionization mass spectrometry (MPIMS), which probes the reactants, intermediates, products with isomeric selectivity using tunable synchrotron vacuum UV ionizing radiation. The is initiated pulsed laser photolysis of oxalyl chloride, (COCl)2, 248 nm, rapidly generates a ∼1:1 mixture 1-propyl (n-propyl) 2-propyl (i-propyl) radicals via fast Cl + reaction. At all three...
The present paper describes further development of the multiscale informatics approach to kinetic model formulation Burke et al. (Burke, M. P.; Klippenstein, S. J.; Harding, L. B. Proc. Combust. Inst. 2013, 34, 547-555) that directly incorporates elementary theories as a means provide reliable, physics-based extrapolation models unexplored conditions. Here, we extend and generalize strategy treat systems considerable complexity-involving multiwell reactions, potentially missing...
We present a combined experimental and theoretical investigation of the autoignition chemistry prototypical cyclic hydrocarbon, cyclopentane. Experiments using high-pressure photolysis reactor coupled to time-resolved synchrotron VUV photoionization mass spectrometry directly probe short-lived radical intermediates products in cyclopentane oxidation reactions. detect key peroxy ROO OOQOOH, as well several hydroperoxides, formed by second O2 addition. Automated quantum chemical calculations...
The kinetics of the unimolecular decomposition stabilized Criegee intermediate syn-CH3CHOO has been investigated at temperatures between 297 and 331 K pressures 12 300 Torr using laser flash photolysis CH3CHI2/O2/N2 gas mixtures coupled with time-resolved broadband UV absorption spectroscopy. Fits to experimental results Master Equation Solver for Multi-Energy well Reactions (MESMER) indicate that barrier height is 67.2 ± 1.3 kJ mol-1 there a strong tunneling component reaction under...
Alkene ozonolysis generates short-lived Criegee intermediates that are a significant source of hydroxyl (OH) radicals. This study demonstrates roaming the separating OH radicals can yield alternate hydroxycarbonyl products, thereby reducing yield. Specifically, hydroxybutanone has been detected as stable product arising from in unimolecular decay methyl-ethyl-substituted intermediate (MECI) under thermal flow cell conditions. The dynamical features this novel multistage dissociation plus...
We investigate the gas-phase photochemistry of enolone tautomer acetylacetone (pentane-2,4-dione) following S2(ππ*) ← S0 excitation at λ = 266 and 248 nm, using three complementary time-resolved spectroscopic methods. Contrary to earlier reports, which claimed study one-photon found OH CH3 as only important products, we detect 15 unique primary photoproducts demonstrate that five them, including CH3, arise solely by multiphoton excitation. assign products six photochemical channels show most...
Abstract Oxiranes are a class of cyclic ethers formed in abundance during low‐temperature combustion hydrocarbons and biofuels, either via chain‐propagating steps that occur from unimolecular decomposition β ‐hydroperoxyalkyl radicals ( ‐̇QOOH) or reactions HOȮ with alkenes. Ethyloxirane is one four alkyl‐substituted ether isomers produced as an intermediate n ‐butane oxidation. While rate coefficients for ‐̇QOOH → ethyloxirane + ȮH reported extensively, subsequent reaction mechanisms the...
Low-temperature (LT) engine applications have several potential benefits, including reduced emissions and increased efficiency. Attaining these benefits requires accurate kinetic modeling of LT chain branching, which depends heavily on ketohydroperoxide (KHP) decomposition. For diethyl ether (DEE), a promising biofuel, current estimates the KHP decomposition rate constant are largely based empirical fits to data. In this study, we investigate most important isomer in DEE oxidation by...
In continuation of the authors' earlier work on substances having a carbonyl bridge, it has been found that tetraphenylcyclopentadienone can be used as one components in diene synthesis. Products are described resulting from addition maleic anhydride, maleic, fumaric, and acetylene dicarboxylic esters, benzoyl phenylacetylene. some instances primary products containing bridge could isolated. Tetraphenylbenzene derivatives result secondary reactions. Benzalacetophenone, dibenzoyl-ethylene...