Theodore S Dibble

Theodore S Dibble
State University of New York College of Environmental Science and Forestry | SUNY-ESF · Department of Chemistry

PhD (Chemistry)

About

112
Publications
6,664
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2,201
Citations
Citations since 2017
21 Research Items
909 Citations
2017201820192020202120222023050100150
2017201820192020202120222023050100150
2017201820192020202120222023050100150
2017201820192020202120222023050100150
Additional affiliations
January 2011 - present
State University of New York College of Environmental Science and Forestry
Position
  • Halogen-initiated Oxidation of Hg(0)
January 2007 - present
Mississippi State University
Position
  • Cavity Ringdown Spectroscopy
August 1996 - present
State University of New York College of Environmental Science and Forestry
Position
  • Atmospheric Chemistry of Alkoxy Radicals

Publications

Publications (112)
Article
Mercury, a highly toxic metal, is emitted to the atmosphere mostly as gaseous Hg(0). Atmospheric Hg(0) enters ecosystems largely through uptake by vegetation, while Hg(II) largely enters ecosystems in oceans and in rainfall. Consequently, the redox chemistry of atmospheric mercury strongly influences its fate and its global biogeochemical cycling....
Preprint
Mercury, a highly toxic metal, is emitted to the atmosphere mostly as gaseous Hg(0). Atmospheric Hg(0) enters ecosystems largely through via uptake by vegetation, while Hg(II) largely enters ecosystems in oceans and via rainfall. Consequently, the redox chemistry of atmospheric mercury strongly influences its fate and its global biogeochemical cycl...
Article
Full-text available
We report on the first experimental determination of the absolute rate constant of the reaction of BrHg + NO in N2 bath gas using a laser photolysis-laser-induced fluorescence (LP-LIF) system. The rate constant of the reaction of BrHg + NO is determined to be 7.0-0.9+1.3 × 10-12 cm3 molecule-1 s-1 over 50-700 Torr and 315-353 K. The absence of a pr...
Article
We built a chemical kinetic model for the electron beam irradiation of methane and report simulation results with dose rates ranging from 2 to 200 kGy s–1 at 298 K and 1 atm pressure. The model contains 92 species and 778 gas-phase reactions. We report the time evolution of concentrations of stable products (including H2, C2H6, C3H8, C2H4, C3H6, C4...
Article
Reaction of Hg and NO2 significantly contributes to mercury removal in CO2 compression and purification unit. However, the reaction mechanism remains unclear and the product species is difficult to collect and identify experimentally. To gain insight into this reaction, we studied it using quantum chemical and kinetic calculations. A two-step react...
Article
Full-text available
We present a new chemical mechanism for Hg⁰/HgI/HgII atmospheric cycling, including recent laboratory and computational data, and implement it in the GEOS-Chem global atmospheric chemistry model for comparison to observations. Our mechanism includes the oxidation of Hg⁰ by Br and OH, subsequent oxidation of HgI by ozone and radicals, respeciation o...
Article
Full-text available
We present results of the first study of the reaction BrHgO• + CO → BrHg• + CO2, which constitutes a potentially important mercury reduction reaction in the atmosphere. We characterized the potential energy surface with CCSD(T)/CBS energies (with corrections for relativistic effects) at MP2 geometries. Master equation simulations were used to revea...
Article
Atomic bromine is known to dominate the oxidation of Hg(0) to Hg(II) via a two-step process in the atmosphere– formation of BrHg and subsequent reactions of BrHg with atmospheric radicals, particularly NO2. We report the first experimental determination of the rate constants for this reaction, which we measured versus temperature (313 – 373 K) and...
Article
In 2005, Calvert and Lindberg wrote that the use of laboratory-derived rate constants for OH + Hg(0) “…to determine the extent of Hg removal by OH in the troposphere will greatly over-estimate the importance of Hg removal by this reaction.” The HOHg• intermediate formed from OH + Hg will mostly fall apart in the atmosphere before it can react. By c...
Preprint
We present a way for modelers to include the OH + Hg reaction while accounting quantitatively for the dissociation of HOHg•. We use high levels of quantum chemistry to establish the HO-Hg bond energy as 11.0 kcal/mole, and calculate the equilibrium constant for OH + Hg = HOHg•. Using the measured rate constant for association of OH with Hg, we dete...
Article
Models suggest BrHgONO to be the major Hg(II) species formed in the global oxidation of Hg(0), and BrHgONO undergoes rapid photolysis to produce the thermally stable radical BrHgO•. We previously used quantum chemistry to demonstrate that BrHgO• can, like OH radical, readily abstract hydrogen atoms from sp3-hybridized carbon atoms as well as add to...
Preprint
Full-text available
Models suggest BrHgONO to be the major Hg(II) species formed in the global oxidation of Hg(0), and BrHgONO undergoes rapid photolysis to produce the thermally stable radical BrHgO•. We previously used quantum chemistry to demonstrate that BrHgO• can, like OH radical, readily can abstract hydrogen atoms from sp<sup>3</sup>-hybridized carbon atoms as...
Article
Global models suggest BrHgONO to be the major Hg(II) species initially formed in atmospheric oxidation of Hg(0) in most of the atmosphere, but its atmospheric fate has not been previously investigated. In the present work, we use quantum chemistry to predict that BrHgONO photolysis to produce the thermally stable radical BrHgO•. Subsequently, BrHgO...
Article
Full-text available
Correction for ‘Comment on “Isomerization of the methoxy radical revisited: the impact of water dimers” by B. Bandyopadhyay et al. , Phys. Chem. Chem. Phys. , 2016, 18 , 27728 and “Isomerization of methoxy radical in the troposphere: competition between acidic, neutral and basic catalysts” by P. Kumar, B. Bandyopadhyay et al. , Phys. Chem. Chem. Ph...
Article
Full-text available
In two recent papers Bandyopadhyay and co-workers studied how atmospheric trace gases catalyze the isomerization of methoxy radical (CH3O•) to hydroxymethyl radical (•CH2OH). Their second paper extensively discussed the altitude dependence of this catalyzed isomerization. Unfortunately, they did not compare their computed isomerization rates with t...
Article
Full-text available
Photochemistry during the polar Spring leads to atmospheric mercury depletion events (AMDEs): Hg(0), which typically lives for months in the atmosphere, can experience losses of more than 90% in less than a day. These dramatic losses are known to be initiated largely by Br + Hg + M → BrHg• + M, but the fate of BrHg• is a matter of guesswork. It is...
Article
Full-text available
Mercury (Hg) is emitted to the atmosphere mainly as volatile elemental Hg⁰. Oxidation to water-soluble HgII plays a major role in Hg deposition to ecosystems. Here, we implement a new mechanism for atmospheric Hg⁰ ∕ HgII redox chemistry in the GEOS-Chem global model and examine the implications for the global atmospheric Hg budget and deposition pa...
Chapter
Full-text available
Alkoxy radicals represent a critical branching point in the atmospheric oxidation of volatile organic compounds. The competition among reaction with O2, isomerization reactions, and scission reactions influences ozone formation in polluted air. Reaction mechanisms are well understood, but major gaps exist in our knowledge of the branching ratios th...
Article
Full-text available
Mercury (Hg) is emitted to the atmosphere mainly as volatile elemental Hg⁰. Oxidation to water-soluble HgII controls Hg deposition to ecosystems. Here we implement a new mechanism for atmospheric Hg⁰ / HgII redox chemistry in the GEOS-Chem global model and examine the implications for the global atmospheric Hg budget and deposition patterns. Our si...
Article
Full-text available
We use computational chemistry to determine the rate constants and product yields for the reactions of BrHg˙ with the atmospherically abundant radicals NO2 and HOO. The reactants, products, and well-defined transition states are characterized using CCSD(T) with large basis sets. The potential energy profiles for the barrierless addition of HOO and...
Article
Mercury emissions to the atmosphere primarily consist of Hg(0), which tends not to enter ecosystems until it is oxidized. Atomic bromine initiates oxidation of Hg(0) via the BrHg• intermediate, but the further reactions of BrHg• are just beginning to be explored. Here we use quantum chemistry to determine that hydrogen abstraction from hydrocarbons...
Article
Propane is the smallest molecule that can serve as a model of the chemistry of diesel autoignition. Diesel autoignition requires H-migration reactions of the type •OOCH2CH2CH2OOH → HOOCH2CH2C•HOOH. Previous studies of this type of H-migration reactions accounted for tunneling (through-barrier processes) using 1-D models of the reaction coordinate,...
Article
Full-text available
Quantum chemical calculations have been carried out to investigate the structures, vibrational frequencies, and thermochemistry of the products of BrHg• reactions with atmospherically abundant radicals Y• (Y = NO2, HO2, ClO, BrO, or IO). The coupled cluster method with single and double excitations (CCSD), combining with relativistic effective core...
Article
We have investigated the kinetics for the reaction CH3O• + NO2 in N2 bath gas. The rate constants are well-fit by the Troe expression over the temperature (250–335 K) and pressure range (30–700 Torr) investigated. The termolecular rate constant is given by cm6 molecule−2 s−1, and the rate constant at the high-pressure limit is given by cm3 molecule...
Article
Full-text available
A series of BrHgY compounds (Y= NO2, ClO, BrO, HOO, etc.) are expected to be formed in the Br-initiated oxidation of Hg(0) to Hg(II) in the atmosphere. These BrHgY compounds have not yet been reported in any experiment. This paper determines the potential to use proton-transfer reaction mass spectrometry (PTRMS) to detect these atmospherically impo...
Article
Relative rate studies were carried out to determine the temperature dependent rate constant ratio k1/k2a: CH3O• + O2 → HCHO + HO2• (R1) CH3O• + NO2 (+M) → CH 2ONO2 (+ M) (R2a) over the temperature range 250-333 K in an environmental chamber at 700 Torr using FTIR detection. Absolute rate constants k2 were determined using laser flash photolysis/las...
Article
Full-text available
Quantum calculations are used to determine the stability of reactive gaseous mercury (Hg(II)) compounds likely to be formed in the Br-initiated oxidation of gaseous elemental mercury (Hg(0)). Due to the absence of any evidence, current models neglect the possible reaction of BrHg with abundant radicals such as NO, NO2, HO2, ClO, or BrO. The present...
Article
Full-text available
Quantum calculations are used to determine the stability of reactive gaseous mercury (Hg(II)) compounds likely to be formed in the Br-initiated oxidation of gaseous elemental mercury (Hg(0)). Due to the absence of any evidence, current models neglect the possible reaction of BrHg• with abundant radicals such as NO, NO2, HO2, ClO, or BrO. The presen...
Article
The cis-trans isomerization of chemically activated 1-methylallyl is investigated using RRKM/Master Equation methods for a range of pressures and temperatures. This system is a prototype for a large range of allylic radicals formed from highly exothermic (∼35 kcal/mol) OH + alkene reactions. Energies, vibrational frequencies, anharmonic constants,...
Article
The methoxy radical is an intermediate in the atmospheric oxidation of methane, and the branching ratio (k(1a)/k(1b)) (CH(2)DO• + O(2) → CHDO + HO(2) (1a) and CH(2)DO• + O(2) → CH(2)O + DO(2) (1b)) strongly influences the HD/H(2) ratio in the atmosphere, which is widely used to investigate the global cycling of molecular hydrogen. By using the FT-I...
Article
Full-text available
The kinetics of three unimolecular reactions of the n-propylperoxy radical were studied by canonical variational transition state theory and multidimensional small curvature tunneling (SCT). The reactions studied were 1,5 and 1,4 H-migration, and HO(2) elimination. Benchmark calculations were carried out at the CCSD(T) level in order to determine w...
Article
Recent experimental work by Hakoda et al. attempted to determine the G-value of OH radical in electron-beam irradiation of humid N2 using the conversion of CO to CO2 to titrate OH. Kinetic modeling is used to simulate the experiment of Hakoda et al. in an attempt to determine the validity of their assumptions and the reason the observed G-value was...
Article
Two classes of unimolecular reactions of peroxy radicals are key to autoignition, namely, intramolecular H-atom shift (which promotes autoignition) and concerted HO(2) elimination (which inhibits autoignition). Olefin groups are prominent functional groups in biodiesel fuels. This paper explores the effects of the presence of an olefin group and it...
Article
This work presents ab initio calculations on the triplet potential energy surface for the N + HOCO reaction and RRKM/Master Equation calculations of the fates of chemically activated species formed in that reaction and in the reaction H + HOCO. Ab initio calculations were carried out at CCSD(T)/aug-cc-pVTZ//CCSD/aug-cc-pVDZ. The fates of chemically...
Article
Formates are produced in the atmosphere as a result of the oxidation of a number of species, notably dialkyl ethers and vinyl ethers. This work describes experiments to define the oxidation mechanisms of isopropyl formate, HC(O)OCH(CH3)2, and tert-butyl formate, HC(O)OC(CH3)3. Product distributions are reported from both Cl- and OH-initiated oxidat...
Conference Paper
3-methylfuran (3MF) is a minor oxidation product of isoprene (2-methyl-1,3-butadiene) in chamber experiments. The source of 3MF may be heterogeneous, in which case its inclusion in models of the tropospheric chemistry of isoprene is a source of error. One radical mechanism suggested by Francisco-Mrquez et al. [ES&T 2005] is still regarded as a plau...
Conference Paper
Calculations on an alkoxy radical intermediate in the OH-initiated degradation of isoprene indicate that this radical forms two intramolecular hydrogen bonds. This creates the possibility for a unique reaction, the concerted transfer of two hydrogen atoms across those hydrogen bonds. This reaction leads to the production of hydroxyacetone and methy...
Article
Full-text available
A chemical kinetic model has been assembled based upon previous literature to assist in developing a better understanding of the mechanism behind the electron beam irradiation of humid air. Thermodynamic determination of the feasibility of particular product sets was used to eliminate certain reactions proposed previously, dynamical models were use...
Article
Full-text available
A chemical kinetic model has been assembled to assist in better understanding the mechanisms underlying hydroxyl radical production via electron beam irradiation of humid air. Thermodynamic determination of the feasibility of particular product sets was used to eliminate certain reactions proposed previously, dynamical models were used to guide the...
Article
Full-text available
An atmospheric argon microwave plasma jet with a plasma column 8 mm long and 1-2 mm wide is studied. Existence of hydroxyl (OH) radicals down to 28 mm away from the plasma orifice is evidenced by UV cavity ringdown spectroscopy. The measured OH (v(')=0, J(')=3.5) number density at 28 mm is 7.2x10(12) molecule/cm(3). The plasma gas flow velocity, al...
Article
Full-text available
Simultaneous measurements of absolute concentrations of H2O and OH radicals in an atmospheric AC discharge using continuous wave cavity ringdown spectroscopy (cw-CRDS) are reported. Formation of OH radicals and plasma temperatures are characterized by optical emission spectroscopy. The concentration of OH radical at the edge of the discharge plume...
Article
We employ a suite of optical techniques, visual imaging, optical emission spectroscopy (OES), and cavity ringdown spectroscopy (CRDS), to characterize a low power, low gas flow rates, atmospheric-pressure argon microwave induced plasma (MIP). A series of plasma images captured in a time resolution range of 10 mus-0.05 s shows that the converging po...
Article
We employ a suite of optical techniques, namely, visual imaging, optical emission spectroscopy and cavity ringdown spectroscopy (CRDS), to characterize a low power, low gas flow rates, atmospheric-pressure argon microwave induced plasma. The plasma is created by a microwave plasma torch, which is excited by a 2.45 GHz microwave with powers ranging...
Article
Identification and quantification of reactive plasma species in the downstream part of an atmospheric plasma jet remain less explored; and how far a reactive species can exist in the downstream and its formation mechanism remain little known. The objective of this work was to employ the UV-cavity ringdown spectroscopy technique to explore how far O...
Article
Extensive studies on atmospheric microwave induced plasma or microwave plasma torch have been reported in literature. One of the well-known phenomena created in such a plasma is the existence of a converging point in the plasma plume. It is widely published in literature that this converging point divides a plasma plume into two distinctive regions...
Article
AC glow discharges were generated in atmospheric pressure by applying high voltage AC in the range of 3500-15000 V to a pair of stainless steel electrodes separated by an air gap. The discharges were characterized by optical emission spectroscopy (OES) and continuous wave cavity ringdown spectroscopy (cw-CRDS). The electronic (Tex), vibrational (Tv...
Article
Quantum chemical calculations have obtained significant and useful information about chemical reactions relevant to atmospheric chemistry. This article reviews two problems for which it would seem that such calculations could readily provide a great deal of helpful information, but for which that potential has not been fully realized. The first is...
Article
Previous studies of 1,4-hydroxycarbonyls derived from alkanes have suggested that they can cyclize to saturated furans, which can subsequently eliminate water to form the corresponding dihydrofurans. CBS-QB3 and G3 studies of 5-hydroxy-2-pentanone and 2-hydroxypentanal show that both steps have activation barriers far too large for these reactions...
Article
The beta-hydroxyethylperoxy (I) and beta-hydroxyethoxy (III) radicals are prototypes of species that can undergo hydrogen atom transfer across their intramolecular hydrogen bonds. These reactions may play an important role in both the atmosphere and in combustion systems. We have used density functional theory and composite electronic structure met...
Article
Cavity ringdown spectroscopy (CRDS) is a sensitive absorption spectral technique and capable of measuring absolution concentration of species in a variety of environments. In recent years, CRDS has been increasingly applied for plasma diagnostics. Through measurements of high resolution spectral linewidths of selected species, plasma gas kinetic te...
Article
Many molecules or transient radicals have well-documented absorption cross-sections in the ultraviolet (UV) region, but their absorption cross-sections in the near-infrared (NIR) region are much less often known and are difficult to measure. We propose a method to determine the unknown NIR absorption cross-sections using the known absorption cross-...
Article
Full-text available
The hydroperoxy radical (HO2) plays a critical role in Earth's atmospheric chemistry as a component of many important reactions. The self-reaction of hydroperoxy radicals in the gas phase is strongly affected by the presence of water vapor. In this work, we explore the potential energy surfaces of hydroperoxy radicals hydrogen bonded to one or two...
Article
Full-text available
Quantum mechanical calculations were used to determine the structure and energetics of peroxy radicals (P1 and P2) and alkoxy radicals (A1-A3) formed in the atmospheric degradation of 2-methyl-3-buten-2-ol. At the level of theory employed (B3LYP/6-31G(d,p)) low energy conformers were identified with zero, one, or two hydrogen bonds. The beta C-C sc...
Article
The laser-induced fluorescence (LIF) excitation spectra of the 4-methylcyclohexoxy and d11-cyclohexoxy radicals have been measured for the first time. LIF intensity was used as a probe in direct kinetic studies of the reaction of O(2) with trans-4-methylcyclohexoxy and d11-cyclohexoxy radicals from 228 to 301 K. Measured rate constants near room te...
Article
Calculations are carried out on the A state of HO2, CH3O2, and CH3CH2O2 and 10 isomers and conformers of the isoprene-OH-O2 peroxy radicals derived from OH addition to isoprene (2-methyl-1,3-butadiene). In addition to calculating vertical and adiabatic excitation energies, we consider the effect of excitation on molecular structure, and examine the...
Article
The first overtones of the asymmetric CH stretch of 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene and 1,3-butadiene were observed in gas phase. The absorption was monitored by means of continuous wave Cavity Ring Down Spectroscopy (cw CRDS) at room temperature. A near infrared diode laser was employed as a light source. The absorpti...
Article
Quantum mechanical calculations were used to determine the structure and stability of second-generation peroxy and alkoxy radicals formed in the atmospheric degradation of isoprene (2-methyl-1,3-butadiene). Certain of these radicals exhibit a novel hydrogen bonding motif, consisting of two intramolecular hydrogen bonds. The hydrogen bonds are donat...
Article
Quantum mechanical calculations have previously shown that certain second-generation alkoxy radicals formed in the atmospheric degradation of isoprene (2-methyl-1,3-butadiene) will undergo a novel reaction pathway: the simultaneous jumping of two H-atoms across the hydrogen bonds with a barrier of only similar to5 kcal/mol. The alkenoxy radical pro...
Article
The laser-induced fluorescence (LIF) excitation spectrum of cyclohexoxy radical has been measured for the first time. The dominant vibrational progression is consistent with computations, at CIS/6-31+G(d), of the C−O stretch frequency of the axial conformer of cyclohexoxy radical. LIF intensity was used as a probe in direct kinetic studies of the r...
Article
The laser induced fluorescence spectrum of the $\tilde{B}$ state of 4-methyl cyclohexoxy radical was obtained at 228 K and 50 Torr $N_{2}$. The spectrum appears to arise only from the trans isomer, and is very similar to that observed from cyclohexoxy radical, itself. Thermodynamic arguments indicate the spectrum must arise almost solely from the d...
Article
Oxygenated organic compounds (ethers, esters, and ketones) are increasingly being used as replacements for hydrocarbons as solvents and fuel additives. The reaction pathways of alkoxy radical intermediates in the degradation of organic compounds may have a substantial effect on the extent of formation of ozone in polluted air, so alkoxy radicals co...
Article
This paper presents quantum chemical studies of the unimolecular isomerization (1,5 H-shift) and decomposition (β C−C scission) reactions of a series of six oxygenated alkoxy radicals and 1-butoxy radical. The goal is to better understand the effects of ether, carbonyl, and ester functional groups on the reactivity of alkoxy radicals relevant to at...
Article
Smog chamber/FTIR techniques were used to study the relative reactivity of OH radicals with methanol, ethanol, phenol, C2H4, C2H2, and p-xylene in 750Torr of air diluent at 296±2K. Experiments were performed with, and without, 500–8000μgm−3 (4000–50000μm2cm−3 surface area per volume) of NaCl, (NH4)2SO4 or NH4NO3 aerosol. In contrast to the recent f...
Article
Full-text available
Several recent papers have suggested that aerosol particles at atmospherically relevant concentrations can catalyze the OH-initiated degradation of selected volatile organic compounds (VOCs). If the degradation of many VOCs were to be affected in this manner, there could be large effects (locally or regionally) on the production of tropospheric ozo...
Article
This paper employs quantum chemical methods to investigate gaps in our understanding of the fates of radical intermediates in the OH-initiated degradation of isoprene. We employ two density functional theory (DFT) approaches:  the well-known B3LYP functional and the recently constructed MPW1K functional. The Complete Basis Set method CBS-QB3 is use...
Article
Quantum mechanical calculations using B3LYP functional and the CBS-QB3 approach are used to determine the critical points on the potential energy surface for the reaction of OH with O2, and RRKM-Master Equation calculations are used to follow the time history of the intermediates. The HOCH2OO radical is bound by 35.8 kcal/mole and the barrier for t...
Article
Kinetic studies of the reactions of 3-pentoxy with NO and O2 have been performed using laser-induced fluorescence detection of 3-pentoxy radicals. Experiments were carried out at a total pressure of 50 Torr at subambient temperatures. Arrhenius expressions are obtained for the reactions of 3-pentoxy with NO (kNO) and O2 (kO2): kNO = (5.6 ± 1.6) × 1...
Article
The atmospheric degradation pathways of the atmospherically important terpenes alpha-pinene and beta-pinene are studied using density functional theory. We employ the correlation functional of Lee, Yang, and Parr and the three-parameter HF exchange functional of Becke (B3LYP) together with the 6-31G(d) basis set. The C-C bond scission reactions of...
Article
The atmospheric degradation pathways of the atmospherically important terpenes a-pinene and beta -pinene are studied using density functional theory. We employ the correlation functional of Lee, Yang, and Parr and the three-parameter HF exchange functional of Becke (B3LYP) together with the 6-31G(d) basis set. The C-C bond scission reactions of the...
Article
This Letter reports the, first kinetic study of 2-butoxy radicals to employ direct monitoring of the radical. The reactions of 2-butoxy with Oz and NO are investigated using laser-induced fluorescence (LIF). The Arrhenius expressions for the reactions of 2-butoxy with NO (k(1)) and O-2 (k(2)) in the temperature range 223-311 K have been determined...
Article
Fluorescence excitation spectra of tert-pentoxy [CH3CH2C(O·)(CH3)2] and 3-pentoxy radicals were observed for the first time. The radicals were produced by laser photolysis of the corresponding pentyl nitrites at 355 nm and studied in the wavelength range 345−400 nm. For tert-pentoxy, 12 vibronic bands were labeled in three progressions. One dominan...
Article
The laser induced fluorescence (LIF) excitation spectra of 3-pentoxy and tert-pentoxy radicals are obtained for the first time. The experiments were carried out in the wavelength range 345-400nm by laser photolysis or corresponding pentyl nitrites at 355nm. For 3-pentoxy, 15 vibronic bands were labled in three progressions with initial vibrational...
Article
Isoprene is one of the most important non-methane organic compounds in tropospheric chemistry, yet its atmospheric degradation pathways remain incompletely understood. The uncertain fates of alkoxy radicals formed in the first stages of the OH-initiated degradation of isoprene contribute significantly to our ignorance. This paper examines the C-C b...
Article
Laser-induced fluorescence (LIF) excitation spectra of t-C4H9O (tert-butoxy) and 2-C4H9O (2-butoxy) radicals were investigated in the wavelength range 335−400 nm. The radicals were formed by laser photolysis of the corresponding butyl nitrites at 355 nm. For tert-butoxy, 16 vibronic bands in two progressions were labeled. The dominant progression c...
Article
Atmospheric degradation of fluorinated ether compounds, which are being considered as replacements for the current generation of freon substitutes, and is expected to produce the CH2FO and CHF2O radicals, and the latter radical is believed to be formed in the course of flame suppression by halons. In the present study, the molecular structures of t...
Article
The structure of HOCH2CH2O has been studied at the B3LYP/6-31G(d,p) level of theory. Two conformers were found, the more stable of which possesses an intramolecular hydrogen bond. The activation energy for carbon–carbon bond fission was studied using the complete basis set approaches CBS-4 and CBS-q, and modified versions thereof. The low activatio...
Article
Laser-induced fluorescence (LIF) spectroscopy of tert-butoxy and 2-butoxy radicals formed by laser photolysis was investigated in the wavelength range 330-385 nm. For tert-butoxy, 13 vibronic bands corresponding to the C-O stretching vibration were assigned to two progressions, $\nu_{C-O}$ is $520\pm 10 cm^{-1}$. Numerous bands remain unassigned. F...
Article
Full-text available
Time-of-flight measurements were made of neutral helium atom beams extracted from a repetitive, pulsed, positive-point corona discharge. Two strong neutral peaks, one fast and one slow, were observed, accompanied by a prompt photon peak and a fast ion peak. All peaks were correlated with the pulsing of the discharge. The two types of atoms appear t...
Article
Published kinetic results for the FNO3 system suggest that some reactions of FO2 + NO and FO + NO2 may proceed through an FOONO intermediate. This molecule, an isomer of fluorine nitrate, FONO2, has received no experimental and essentially no theoretical study. The present work employs the quadratic configuration interaction method to investigate t...
Article
We present results of density functional calculations on ClOO using the local density approximation (LDA) and the Becke–Lee–Yang–Parr functional (BLYP). The accuracy of computed geometries and vibrational frequencies appears comparable to that achieved with very high quality single‐determinant methods [QCISD(T)].
Article
The reaction between CF3O and NO has been studied by laser flash photolysis/transient diode laser absorption over the range 213 K less than or equal to T less than or equal to 353 K. CF3O was generated by the 193 nm photolysis of(CF3O)(2). The dominant dissociation pathway is O-O bond fission (Phi congruent to 0.85), but C-O bond breaking occurs to...