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  • 1
    Electronic Resource
    Electronic Resource
    Kinetics of intramolecular carbon atom exchange in ketene (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 4081-4093 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Intramolecular carbon atom exchange in highly vibrationally excited ketene was studied by monitoring the carbon monoxide fragments (12CO and 13CO ) from the photodissociation of 12CH213CO and 13CH212CO. Two experimental techniques were employed. In one set of experiments the IR transient absorptions of 12CO and 13CO were measured following pulsed excimer excitation of ketene 13C isotopomers, giving carbon atom exchange yields at 351 and 308 nm in a low pressure gas cell. In the other set of experiments, jet-cooled ketene 13C isotopomers were excited with tunable near-UV radiation, and the CO products were detected by monitoring their VUV laser-induced fluorescence. Carbon atom exchange yields were measured for energies extending from below the triplet decomposition threshold (CH2CO→CH2(X 3B1)+CO(X 1Σ+)) to about 4000 cm−1 above the singlet threshold (CH2CO→CH2(a 1A1)+CO(X 1Σ+)).The exchange yields range from 4 to 19%, and the energy dependence of the yield exhibits pronounced structure, with maxima at the triplet and singlet decomposition thresholds. Kinetic measurements of the appearance of the CO products were also performed. The time constant for the appearance of the exchanged CO (e.g., 13CO from 13CH212CO ) is significantly longer than that for the direct CO fragment (e.g., 12CO from 13CH212CO ). All the experimental observations are consistent with a simple reaction mechanism involving ketene isomerization, 13CH212CO(arrow-right-and-left)12CH213CO, and dissociation, 13CH212CO→13CH2+12CO and 12CH213CO→12CH2+13CO. The isomerization rate constant was determined by analyzing the CO kinetics and the carbon atom exchange yields in terms of the simple isomerization mechanism. A fit of the energy dependence of the isomerization rate constant to the results of tunneling-corrected Rice–Ramsberger–Kassel–Marcus (RRKM) calculations gave the threshold (28360±60 cm−1 ) for the isomerization process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460764
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  • 2
    Electronic Resource
    Electronic Resource
    Kinetic study of the reaction of HO2 with ozone (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 2122-2128 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction HO2+O3→OH+2O2 has been studied using a discharge-flow system with laser magnetic resonance detection. The rate constant for the reaction was determined directly by monitoring the first-order decay of isotopically labeled H18O2 in excess 16O3. The data give a curved Arrhenius plot over the temperature range 243〈T〈413 K: k(T)=(3.8±2.4) ×10−14 exp[−(820±190/T)] cm3 s−1. A more representative fit is obtained with a three parameter expression: k(T)=(3.2±5.8)×10−13 exp[−(1730±740)/T] + (1.2±0.5)×10−15 cm3 s1. The error limits are the 95% confidence limits on the coefficients while the accuracy of the measurements is estimated to be about ±20% at each temperature. An analysis of the OH radical product indicates that 16OH is formed predominately (75±10)%. The scrambling reactions H18O2+16O3→H16O2+18O18O16O (1c) and H18O2+16O2→H16O2+18O2 (8) were also examined and found to be slow. Their rate constants are k1c〈2×10−17 cm3 s−1 at 297 and 333 K and k8〈3×10−17 cm3 s−1 at 297 and 413 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453136
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  • 3
    Electronic Resource
    Electronic Resource
    Photodissociation of ketene: CH2(a˜ 1A1)(0,0,0) rotational state distributions (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 8890-8901 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ketene (CH2CO) cooled in a supersonic free jet is photodissociated by a tunable pulsed laser in the energy range from the threshold for production of CH2(a˜ 1A1)(0,0,0)+CO(X˜ 1Σ+) to 2900 cm−1 above. By scanning the 1CH2 probe laser wavelength, the CH2 laser-induced fluorescence spectrum is recorded and the 1CH2 product state distributions determined. The appearance thresholds and yield curves of individual 1CH2 rotational states are obtained by scanning the photolysis laser frequency with a fixed 1CH2 probe laser frequency. The yield curves, or photofragment excitation (PHOFEX) spectra, exhibit sharp steps spaced by the CO rotational term values. PHOFEX yield curves combined with the distribution data demonstrate that the ketene absorption cross section is constant within 10% over the 0–1000 cm−1 range of the PHOFEX spectra. PHOFEX curves up to 200 cm−1 and rotational state distributions for singlet methylene at 50, 100, and 170 cm−1 above its threshold are in good agreement with phase space theory (PST) calculations. The lowest energy methylene rotational states of + and − symmetry are formed in the ratio predicted by phase space theory at all energies. States of mixed singlet/triplet parentage are populated with equal probability for triplet characters ranging from 30% to 70%. For energies greater than 300 cm−1 above the threshold, the 1CH2 rotational distribution is substantially colder than the statistical distribution given by PST. These differences increase with excess energy above the singlet threshold. In this energy range, the dynamics of motion between the transition state and separated product fragments is in neither the adiabatic nor the statistical limit though the data do suggest that motion may well be adiabatic for molecules fragmenting to yield the lowest energy rotational states of ortho methylene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466692
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  • 4
    Electronic Resource
    Electronic Resource
    Photodissociation of ketene: Vibrationally excited CH2(a˜ 1A1) (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 8902-8906 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ketene (CH2CO) cooled in a supersonic free jet is photodissociated by a tunable pulsed laser in the energy range from 1460 to 2900 cm−1 above the threshold for singlet methylene CH2(a˜ 1A1) production. By scanning the 1CH2 probe laser wavelength, the CH2 laser-induced fluorescence (LIF) excitation spectrum is recorded and the 1CH2(0,1,0), (0,2,0), and (1,0,0) product state rotational distributions determined. As observed previously for the (0,0,0) state, the rotational state distributions of vibrationally excited methylene are in good agreement with phase space theory (PST) for excess energies less than 200 cm−1 above the appearance threshold of each vibrational state probed. For higher excess energies, 1CH2(0,1,0) and (0,2,0) rotational distributions like those for (0,0,0) are substantially colder than the statistical distribution given by PST. The quantum yields of vibrationally excited states are determined at several excess energies above the singlet threshold. These values are larger than predicted by PST and match values predicted by variational Rice–Ramsperger–Kassel–Marcus (RRKM) theory and by the separate statistical ensembles (SSE) method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466693
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  • 5
    Electronic Resource
    Electronic Resource
    Transition state vibrational level thresholds for the dissociation of triplet ketene (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 3202-3219 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Rate constants for the unimolecular dissociation of ketene (CH2CO) and deuterated ketene (CD2CO) have been measured at the threshold for the production of CH2 (X˜ 3B1) or CD2 (X˜ 3B1) and CO (X˜ 1Σ+) by photofragmentation in a cold jet. The rate constant increases in a stepwise manner as energy increases. This is in accord with the long-standing premise that the rate of a unimolecular reaction is controlled by flux through quantized transition-state thresholds at each energy level for vibrational motion orthogonal to the reaction coordinate. The first step in rate constant and/or photofragment excitation (PHOFEX) spectrum gives accurate values for the barrier to dissociation above the zero-point energy of the products, 1281±15 cm−1 for CH2CO and 1071±40 cm−1 for CD2CO. The measured rate constants are fit by Rice–Ramsperger–Kassel–Marcus (RRKM) theory. The vibrational frequencies at the transition state obtained from the fits are compared with ab initio results. Vibrational motions at the transition state orthogonal to the reaction coordinate are also revealed in CO product rotational distributions. Calculations using an impulsive model which includes vibrational motions at the transition state reproduce the experimental dependence of the PHOFEX spectra on the CO J state quite well. The small dependence of rate constant on jet temperature (4–30 K) indicates that the Ka quantum number for rotation about its symmetry axis is conserved in the energized ketene molecule. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468631
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  • 6
    Electronic Resource
    Electronic Resource
    Measurement of the Kinetics of Reactive Uptake by Submicron Sulfuric Acid Particles (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 2080-2087 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100007a043
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  • 7
    Electronic Resource
    Electronic Resource
    Oxidation of carbon disulfide by reaction with hydroxyl. 2. Yields of hydroperoxyl and sulfur dioxide in oxygen (1990)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 94 (1990), S. 2386-2393 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100369a037
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  • 8
    Electronic Resource
    Electronic Resource
    Oxidation of CS2 by reaction with OH. 1. Equilibrium constant for the reaction OH + CS2 .dblarw. CS2OH and the kinetics of the CS2OH + O2 reaction (1990)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 94 (1990), S. 2381-2386 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100369a036
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  • 9
    Electronic Resource
    Electronic Resource
    Kinetic studies of the reactions of mercaptooxy with nitrogen dioxide, nitric oxide, and oxygen (1987)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 91 (1987), S. 5749-5755 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100306a046
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  • 10
    Electronic Resource
    Electronic Resource
    Structures in the energy dependence of the rate constant for ketene isomerization (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 7846-7854 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The isomerization of highly vibrationally excited and rotationally cold ketene has been investigated by monitoring the 12CO and 13CO dissociation products following laser excitation of jet-cooled 12CH2 13CO, 13CH2 12CO, and 12CD2 13CO. The rate constants for the reactions 12CH2 13CO(arrow-right-and-left)13CH2 12CO and 12CD2 13CO(arrow-right-and-left)13CD2 12CO are reported as a function of energy with a resolution of 1 cm−1. The rate constants exhibit pronounced peaks as a function of energy near the reaction threshold. This structure is attributed to quasistable motion along the reaction coordinate in the vicinity of the isomerization transition state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464592
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