Craig A Taatjes

• Sandia National Laboratories

Criegee intermediates are reactive intermediates that are implicated in transforming the composition of Earth’s troposphere and in the formation of secondary organic aerosol, impacting Earth’s radiation balance, air quality and human health. Yet, direct identification of their signatures in the field remains elusive. Here, from particulate and gas-...

Chlorinated organic compounds are prominently used for industrial production, but their vapors and emission byproducts can cause detrimental effects to human health and the environment. To accurately quantify organochlorine compounds, the absolute photoionization cross section of tetrachloroethylene, chlorobenzene, 1,2‐dichlorobenzene, and chloroac...

The absolute photoionization cross section of the monoterpenoid, alpha‐pinene (AP), is presented together with the relative photoionization cross sections of its dissociative fragments for the first time. Experiments are performed via multiplexed vacuum ultraviolet (VUV) synchrotron photoionization (PI) mass spectrometry in the 8.0–11.0 eV energy r...

Alkene ozonolysis generates short-lived Criegee intermediates that are a significant source of hydroxyl (OH) radicals. This study demonstrates that roaming of the separating OH radicals can yield alternate hydroxycarbonyl products, thereby reducing the OH yield. Specifically, hydroxybutanone has been detected as a stable product arising from roamin...

The mechanism for hydrocarbon ring growth in sooting environments is still the subject of considerable debate. The reaction of phenyl radical (C6H5) with propargyl radical (H2CCCH) provides an important prototype for radical-radical ring-growth pathways. We studied this reaction experimentally over the temperature range of 300-1000 K and pressure r...

Dimethyl ether (DME) oxidation is a model chemical system with a small number of prototypical reaction intermediates that also has practical importance for low-carbon transportation. Although it has been studied experimentally and theoretically, ambiguity remains in the relative importance of competing DME oxidation pathways in the low-temperature...

Radical-radical reactions contribute to molecular weight growth of polycyclic aromatic hydrocarbons (PAHs), but their role is not well understood. The phenyl (Ph, C6H5) + cyclopentadienyl (C5H5) reaction has not been studied but can serve as a surrogate reaction for many reactions of larger aryl-σ radicals with resonance-stabilized π-radicals. The...

Well-skipping radical-radical reactions can provide a chain-propagating pathway for formation of polycyclic radicals implicated in soot inception. Here we use controlled pyrolysis in a microreactor to isolate and examine the role of well-skipping channels in the phenyl (C6H5) + propargyl (C3H3) radical-radical reaction at temperatures of 800–1600 K...

A crucial chain‐branching step in autoignition is the decomposition of ketohydroperoxides (KHP) to form an oxy radical and OH. Other pathways compete with chain‐branching, such as “Korcek” dissociation of γ‐KHP to a carbonyl and an acid. Here we characterize the formation of a γ‐KHP and its decomposition to formic acid+acetone products from observa...

A crucial chain‐branching step in autoignition is the decomposition of ketohydroperoxides (KHP) to form an oxy radical and OH. Other pathways compete with chain‐branching, such as “Korcek” dissociation of γ‐KHP to a carbonyl and an acid. Here we characterize the formation of a γ‐KHP and its decomposition to formic acid + acetone products from obser...

The reactivity of carbonyl oxides has previously been shown to exhibit strong conformer and substituent dependencies. Through a combination of synchrotron-multiplexed photoionization mass spectrometry experiments (298 K and 4 Torr) and high-level theory [CCSD(T)-F12/cc-pVTZ-F12//B2PLYP-D3/cc-pVTZ with an added CCSDT(Q) correction], we explore the c...

Rapid molecular‐weight growth of hydrocarbons occurs in flames, in industrial synthesis, and potentially in cold astrochemical environments. A variety of high‐ and low‐temperature chemical mechanisms have been proposed and confirmed, but more facile pathways may be needed to explain observations. We provide laboratory confirmation in a controlled p...

Rapid molecular weight growth of hydrocarbons occurs in flames, in industrial synthesis, and potentially in cold astrochemical environments. A variety of high‐ and low‐temperature chemical mechanisms have been proposed and confirmed, but more facile pathways may be needed to explain observations. We provide laboratory confirmation in a controlled p...

The reactions of carbonyl oxide Criegee intermediates with acids proceed predominantly by an insertion mechanism. We characterise the products from one of the simplest reactions of carbonyl oxides with inorganic acids, CH2OO + hydrogen chloride, which occurs via a 1,2-insertion in the H–Cl bond. Reactions of both HCl and DCl isotopologues yield pro...

The absolute photoionization cross section of vinyl alcohol was determined by multiplexed photoionization mass spectrometry of the Norrish type II photodissociation of butanal at 308 nm. The measured cross sections at 10.005 and 10.205 eV are 7.5 ± 1.9 and 8.1 ± 1.9 MB, respectively. A higher signal-to-noise ratio photoionization spectrum of vinyl...

Gas-phase reactions of the o-methylphenyl (o-CH3C6H4) radical with the C3H4 isomers allene (H2C[double bond, length as m-dash]C[double bond, length as m-dash]CH2) and propyne (HC[triple bond, length as m-dash]C-CH3) are studied at 600 K and 4 Torr (533 Pa) using VUV synchrotron photoionisation mass spectrometry, quantum chemical calculations and RR...

Ongoing progress in synthetic biology, metabolic engineering, and catalysis continues to produce a diverse array of advanced biofuels with complex molecular structure and functional groups. In order to integrate biofuels into existing combustion systems, and to optimize the design of next-generation combustion systems, understanding connections bet...

Methacrolein oxide (MACR-oxide) is a four-carbon, resonance-stabilized Criegee intermediate produced from isoprene ozonolysis, yet its reactivity is not well understood. This study identifies the functionalized hydroperoxide species, 1‑hydroperoxy-2-methylallyl formate (HPMAF), generated from the reaction of MACR-oxide with formic acid using multip...

div> Using VUV synchrotron photoionization mass spectrometry, quantum chemistry and RRKM kinetic modeling, our paper identifies the products formed when a substituted aromatic free radical (ortho- methylphenyl) reacts with two C3H4 isomers found in flames – propyne and allene. Both reactions form polycyclic aromatic hydrocarbons but profound stru...

We have used 308 nm photolysis of acetaldehyde to measure a photoionization spectrum of the formyl (HCO) radical between 8 and 11.5 eV using an 11 meV FWHM photoionization energy resolution. We have confirmed that the formyl radical is the carrier of the spectrum by generating an identical spectrum of the HCO product in the Cl + H2CO reaction. The...

Isoprene is the most abundant non-methane hydrocarbon emitted into the Earth's atmosphere. Ozonolysis is an important atmospheric sink for isoprene, which generates reactive carbonyl oxide species (R₁R₂C O⁺O⁻) known as Criegee intermediates. This study focuses on characterizing the catalyzed isomerization and adduct formation pathways for the react...

Oxiranes are a class of cyclic ethers formed in abundance during low‐temperature combustion of hydrocarbons and biofuels, either via chain‐propagating steps that occur from unimolecular decomposition of β‐hydroperoxyalkyl radicals (β‐̇QOOH) or from reactions of HȮO with alkenes. The cis‐ and trans‐isomers of 2,3‐dimethyloxirane are intermediates of...

Oxiranes are a class of cyclic ethers formed in abundance during low‐temperature combustion of hydrocarbons and biofuels, either via chain‐propagating steps that occur from unimolecular decomposition of β‐hydroperoxyalkyl radicals (β‐̇QOOH) or from reactions of HOȮ with alkenes. Ethyloxirane is one of four alkyl‐substituted cyclic ether isomers pro...

We studied the oxidation of neo-pentane by combining experiments, theoretical calculations, and mechanistic developments to elucidate the impact of the 3rd O2 addition reaction network on ignition delay time predictions. The experiments are based on photoionization mass spectrometry in jet-stirred and time-resolved flow reactors allowing for sensit...

In the context of tropospheric chemistry, Criegee intermediates denote carbonyl oxides with biradical/zwitterionic character (R1R2COO) that form during the ozonolysis of alkenes. First discovered almost 70 years ago, stabilised versions of Criegee intermediates formed via collisional removal of excess energy have interesting kinetic and mechanistic...

Significance Ozonolysis is an important sink of alkenes in Earth’s troposphere, leading to the formation of Criegee intermediates (CIs), whose reactions significantly impact tropospheric composition. The reactivity of the four-carbon unsaturated CIs derived from isoprene, the most abundant alkene, has remained unknown until now. Direct measurements...

Perfluorooctanoic acid, PFOA, is one of the many concerning pollutants in our atmosphere; it is highly resistant to environmental degradation processes, which enables it to accumulate biologically. With direct routes of this chemical to the environment decreasing, as a consequence of the industrial phase out of PFOA, it has become more important to...

Ozonolysis of isoprene, one of the most abundant volatile organic compounds emitted into the Earth’s atmosphere, generates two four-carbon unsaturated Criegee intermediates, methyl vinyl ketone oxide (MVK-oxide) and methacrolein oxide (MACR-oxide). The extended conjugation between the vinyl substituent and carbonyl oxide groups of these Criegee int...

Product detection studies of the gas-phase oxidation of o-methylphenyl radicals and m-methylphenyl radicals are reported at ambient temperature (~298 K) and 4 Torr (533.3 Pa) using VUV synchrotron photoionisation mass spectrometry. It is shown that cyclopentadienone (c-C5H4=O) + CH3CO and o-quinone methide (C6H4OCH2) + OH are unique product pathway...

Photolytically initiated oxidation experiments were conducted on cyclohexane and tetrahydropyran using multiplexed photoionization mass spectrometry (MPIMS) to assess the impact of the ether functional group in the latter species on reaction mechanisms relevant to autoignition. Pseudo-first-order conditions, with [O2]0:[R]0 > 2000, were used to ens...

Ammonia and amines are emitted into the troposphere by various natural and anthropogenic sources, where they have a significant role in aerosol formation. Here, we explore the significance of their...

The reaction of perfluorooctanoic acid with the smallest carbonyl oxide Criegee intermediate, CH2OO, has been measured and is very rapid, with a rate coefficient of (4.9 ± 0.8) × 10-10 cm3 s-1, similar to that for reactions of Criegee intermediates with other organic acids. Evidence is shown for the formation of hydroperoxymethyl perfluorooctanoate...

Methanol is a benchmark for understanding tropospheric oxidation, but is underpredicted by up to 100% in atmospheric models. Recent work has suggested this discrepancy can be reconciled by the rapid reaction of hydroxyl and methylperoxy radicals with a methanol branching fraction of 30%. However, for fractions below 15%, methanol underprediction is...

Methyl vinyl ketone (MVK) and methacrolein (MACR) are important intermediate products in atmospheric degradation of volatile organic compounds, especially of isoprene. This work investigates the reactions of the smallest Criegee intermediate, CH2OO, with its co-products from isoprene ozonolysis, MVK and MACR, using multiplexed photoionization mass...

Multiplexed photoionization mass spectrometry (MPIMS) is utilized to examine reaction mechanisms of ̇QOOH radicals derived from cyclohexene, a primary intermediate in low-temperature oxidation of cyclohexane, in order to assess the influence of a single C=C bond in a cyclic hydrocarbon on reactions relevant to chain-branching. The experiments were...

Trace atmospheric concentrations of carboxylic acids have a potent effect upon the environment, where they modulate aqueous chemistry and perturb Earth’s radiative balance. Halogenated carboxylic acids are produced by the tropospheric oxidation of halocarbons and are considered persistent pollutants because of their weak tropospheric and aqueous si...

Acetic acid (CH3COOH) is one of the most abundant carboxylic acids in the troposphere. In the study, the tropospheric chemistry of CH3COOH is investigated using the 3-D global chemistry transport model, STOCHEM-CRI. The highest mixing ratios of surface CH3COOH are found in the tropics by as much as 1.6 ppb in South America. The model predicts the s...

The absolute photoionization spectrum of the hydroxyl (OH) radical from 12.513 to 14.213 eV was measured by multiplexed photoionization mass spectrometry with time-resolved radical kinetics. Tunable vacuum ultraviolet (VUV) synchrotron radiation was generated at the Advanced Light Source. OH radicals were generated from the reaction of O(¹D) + H2O...

Trace atmospheric concentrations of carboxylic acids have a potent effect upon the environment, where they mod- ulate aqueous chemistry and perturb Earth’s radiative balance.1 Halogenated carboxylic acids are produced by the tropospheric oxidation of halocarbons, and are considered persistent pollutants because of their weak tropospheric and aqueou...

Criegee intermediates (CIs), carbonyl oxides formed in ozonolysis of alkenes, play key roles in the troposphere. The decomposition of CIs can be a significant source of OH to the tropospheric oxidation cycle especially during nighttime and winter months. A variety of model-measurement studies have estimated surface-level stabilized Criegee intermed...

A comparison of two fuels demonstrates how analysis of ˙OH and HO 2 ˙ formation kinetics via the eigenvalues of a system of simplified kinetic equations can give mechanistic insights.

The initial oxidation products of methyl butyrate (MB) and ethyl butyrate (EB) are studied using a time- and energy-resolved photoionization mass spectrometer. Reactions are initiated with Cl• radicals in an excess of oxygen at a temperature of 550 K and a pressure of 6 Torr. Ethyl crotonate is the sole isomeric product that is observed from concer...

Following measurements in the winter of 2012, formic acid (HCOOH) and nitric acid (HNO3) were measured using a chemical ionisation mass spectrometer (CIMS) during the Summer Clean Air for London (ClearfLo) campaign in London, 2012. Consequently, the seasonal dependence of formic acid sources could be better understood. A mean formic acid concentrat...

The rapid reaction of the smallest Criegee intermediate, CH2OO, with water dimers is the dominant removal mechanism for CH2OO in the Earth’s atmosphere, but its products are not well understood. This reaction was recently suggested as a significant source of the most abundant tropospheric organic acid, formic acid (HCOOH), which is consistently und...

The reactions of Criegee intermediates with NO2 have been proposed as a potentially significant source of the important nighttime oxidant NO3, particularly in urban environments where concentrations of ozone, alkenes and NOx are high. However, previous efforts to characterize the yield of NO3 from these reactions have been inconclusive, with many s...

Product formation, in particular ketohydroperoxide formation and decomposition, were investigated in time-resolved, Cl-atom initiated neopentane oxidation experiments in the temperature range 550 K – 675 K using a photoionization time-of-flight mass spectrometer. Ionization light was provided either by the Advanced Light Source tunable synchrotron...

The carbonyl oxide intermediates in the ozonolysis of alkenes, often known as Criegee intermediates, are potentially important reactants in Earth's atmosphere. For decades, careful analysis of ozonolysis systems was employed to derive an understanding of the formation and reactions of these species. Recently it has proved possible to synthesize at...

Hydroxyacetone (CH3C(O)CH2OH) is observed as a stable end product from the (CH3)2COO Criegee intermediate, acetone oxide, in a flow tube coupled with multiplexed photoionization mass spectrometer detection. In the experiment, the two isomers at m/z = 74 are distinguished by their different photoionization energies and reaction times. Hydroxyacetone...

The Criegee intermediate acetone oxide, (CH3)2COO, is formed by laser photolysis of 2,2-diiodopropane in the presence of O2 and characterized by synchrotron photoionization mass spectrometry and by cavity ringdown ultraviolet absorption spectroscopy. The rate coefficient of the reaction of the Criegee intermediate with SO2 was measured using photoi...

The pulsed photolytic chlorine-initiated oxidation of diethyl ketone [DEK; (CH3CH2)2C=O], 2,2,4,4-d4-DEK [d4-DEK; (CH3CD2)2C=O] and 1,1,1,5,5,5-d6-DEK [d6-DEK; (CD3CH2)2C=O] is studied at 8 Torr and 1 – 2 atm and from 400 – 625 K. Cl atoms produced by laser photolysis react with diethyl ketone to form either primary (3-pentan-on-1-yl, RP) or second...

This work provides new temperature-dependent mole fractions of elusive intermediates relevant to the low-temperature oxidation of dimethyl ether (DME). It extends the previous study of Moshammer et al. [J. Phys. Chem. A 119 (2015) 7361-7374] in which a combination of a jet-stirred reactor and molecular beam mass spectrometry with single-photon ioni...

We report a combined experimental and quantum chemistry study of the initial reactions in low-temperature oxidation of tetrahydrofuran (THF). Using synchrotron-based time-resolved VUV photoionization mass spectrometry, we probe numerous transient intermediates and products at P = 10-2000 Torr and T = 400-700 K. A key reaction sequence, revealed by...

Multiplexed photoionization mass spectrometry (MPIMS) is used to determine branching fractions of conjugate alkenes from R + O2 oxidation reactions for cyclohexane (c-C6H12) and tetrahydropyran (c-C5H10O), a lignocellulosic-derived oxygenated biofuel. Because conjugate alkene formation is coincident with the formation of HO2, the results reveal the...

Cl-initiated oxidation reactions of three small-chain methyl esters, methyl propanoate (CH3CH2COOCH3; MP), methyl butanoate (CH3CH2CH2COOCH3; MB), and methyl valerate (CH3CH2CH2CH2COOCH3; MV) are studied at 1 or 8 Torr and 550 and 650 K. Products are monitored as a function of mass, time, and photoionization energy using multiplexed photoionization...

Endophytic fungi are ubiquitous plant endosymbionts that establish complex and poorly understood relationships with their host organisms. Many endophytic fungi are known to produce a wide spectrum of volatile organic compounds (VOCs) with potential energy applications, which have been described as "mycodiesel". Many of these mycodiesel hydrocarbons...

Mechanism for the biosynthesis of sesquiterpenes: α-, and β-caryophyllene, humulen, α-selinene, α-guaiene, and τ-gurjunene. Generally, FPP is ionized to generate an allylic cation, and then through a 11,1 closure to form humulyl cation and a subsequent deprotonation to yield α-caryophyllene, or through a 11,1 closure to form humulyl cation, another...

Mechanism for the biosynthesis of sesquiterpenes β-chamigrene and thujopsene. Chamigrene biosynthesis could begin with the ionization and subsequent allylic rearrangement of the diphosphate moiety of FPP, allowing for the formation of nerodidyl diphosphate (NPP, cisoid conformation). Reionization of the ciscoid conformation of NPP and subsequent in...

Mechanism for the biosynthesis of monoterpenes: α-, and β-pinene, α-limonene, 2-careen, β-ocimene, and τ-terpinene. The biosynthesis of pinene can be rationalized by postulating that GPP ionizes to a stable allylic cation, followed by collapse to linalyl diphosphate (LPP). The reionization of the LPP cisoid conformer followed by intramolecular elec...

Terpene profiles of TPS in the cluster 2. (DOCX)

Terpene profiles of TPS in the cluster 3. (DOCX)

Terpene profiles of TPS in the cluster 4. (DOCX)

Terpene profiles of TPS in non-clustered group. (DOCX)

Terpene profiles of TPS in the cluster 5. (DOCX)

Compound profile of the control strain lacking TPS. (DOCX)

GC spectrum of terpene standards. (DOCX)

Chain-branching reactions represent a general motif in chemistry, encountered in atmospheric chemistry, combustion, polymerization, and photochemistry; the nature and amount of radicals generated by chain-branching are decisive for the reaction progress, its energy signature, and the time towards its completion. In this study, experimental evidence...

Gas-phase product detection studies of o-hydroxyphenyl radical and O2 are reported at 373, 500, and 600 K, at 4 Torr (533.3 Pa), using VUV time-resolved synchrotron photoionisation mass spectrometry. The dominant products are assigned as o-benzoquinone (C6H4O2, m/z 108) and cyclopentadienone (C5H4O, m/z 80). It is concluded that cyclopentadienone f...

Soot formation in combustion is a complex process in which polycyclic aromatic hydrocarbons (PAHs) are believed to play a critical role. Recent works concluded that three consecutive additions of acetylene (C2H2) to propargyl (C3H3) create a facile route to the PAH indene (C9H8). However, the isomeric forms of C5H5 and C7H7 intermediates in this re...

Carbonyl oxides, also known as Criegee intermediates, are key intermediates in both gas phase ozonolysis of unsaturated hydrocarbons in the troposphere and solution phase organic synthesis via ozonolysis. Although the study of Criegee intermediates in both arenas has a long history, direct studies in the gas phase have only recently become possible...

The reaction of O((3)P) + propyne (C3H4) was investigated at 298 K and 4 Torr using time-resolved multiplexed photoionization mass spectrometry and a synchrotron-generated tunable vacuum ultraviolet light source. The time-resolved mass spectra of the observed products suggest five major channels under our conditions: C2H3 + HCO, CH3 + HCCO, H + CH3...

The present paper describes further development of the multi-scale informatics approach to kinetic model formulation of Burke et al. (Burke, M. P.; Klippenstein, S. J.; Harding, L. B. Proc. Combust. Inst. 2013, 34, 547-555.) that directly incorporates elementary kinetic theories as a means to provide reliable, physics-based extrapolation of kinetic...

We present a microwave discharge flow tube coupled with a double imaging electron/ion coincidence device and vacuum ultraviolet (VUV) synchrotron radiation. The system has been applied to the study of the photoelectron spectroscopy of the well-known radicals OH and OD. The coincidence imaging scheme provides a high selectivity and yields the spectr...

The low-temperature oxidation of three cyclic ketones, cyclopentanone (CPO; C5H8[double bond, length as m-dash]O), cyclohexanone (CHO; C6H10[double bond, length as m-dash]O), and 2-methyl-cyclopentanone (2-Me-CPO; CH3-C5H7[double bond, length as m-dash]O), is studied between 550 and 700 K and at 4 or 8 Torr total pressure. Initial fuel radicals R a...