摘要:

AbstractRate coefficients were calculated for vibrational relaxation and collision‐induced dissociation of ground state xenon fluoride in neon at temperatures between 300 and 1000 K for each of nine vibrational levels. These coefficients were calculated using a pairwise additive potential energy surface, which consists of a Morse function for the XeF interaction and Lennard–Jones functions for the NeXe and NeF interactions. Rate coefficients are provided for both temperature andv‐ dependences. The vibrational relaxation and dissociation processes occur by multiquanta transitions. Dissociation can take place from allv‐levels provided that the internal energy of the XeF molecule is close to the rotationless dissociation limit. The order of increase effectiveness of the various forms of energy in promoting dissociation in XeF was found to be translation–rotation‐vibration. At room temperature, neon atoms were found to be more efficient than helium atoms in the dissociation processes; helium atoms were found to be more efficient than neon atoms in the vibrational relaxation of XeF. Strong vibration–rotation coupling in both vibrational relaxation and in the dissociation processes is

ISSN:0538-8066    

DOI:10.1002/kin.550211102

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractEthers are being increasingly used as motor fuel additives to increase the octane number and to reduce CO emissions. Since their reaction with hydroxyl radicals (OH) is a major loss process for these oxygenated species in the atmoshpere, we have conducted a relative rate study of the kinetics of the reactions of OH radicals with a series of ethers and report the results of these measurements here. Experiments were performed under simulated atmospheric conditions; atmospheric pressure (≃ 740 torr) in synthetic air at 295 K. Using rate constants of 2.53 × 10−12, and 1.35 × 10−11cm3molecule−1s−1for the reaction of OH radicals withn‐butane and diethyl ether, the following rate constants were derived, in units of 10−11cm3molecule−1s−1: dimethylether, (0.232 ± 0.023); di‐n‐propylether, (1.97 ± 0.08); di‐n‐butylether, (2.74 ± 0.32); di‐n‐pentylether, (3.09 ± 0.26); methyl‐t‐butylether, (0.324 ± 0.008); methyl‐n‐butylether, (1.29 ± 0.03); ethyl‐n‐butylether, (2.27 ± 0.09); and ethyl‐t‐butylether, (0.883 ± 0.026). Quoted errors represent 2σ from the least squares analysis and do not include any systematic errors associated with uncertainties in the reference rate constants used to place our relative measurements on an absolute basis. The implications of these resul

ISSN:0538-8066    

DOI:10.1002/kin.550211103

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe kinetics of the gas‐phase thermal decomposition of 1,1,2,2‐tetrafluorocyclopropane (TFC) to 1,1‐difluoroethylene and CF2was studied in the temperature range of 507.0‐577.0 K and with a total pressure of 200 to 300 torr of a 1:100 mixture of reactant and C2H4. Also at 557.0 K experiments were made at different total pressures, in the range 2–20 torr with neat TFC and between 20–300 torr with the C2H4/TFC mixture, confirming that the reaction is in the high pressure limit. The reaction is first‐order and the rate constants fit the following Arrhenius relationship:\documentclass{article}\pagestyle{empty}\begin{document}$$\log \,k/(s^{ - 1}) = (14.02 \pm 0.16) - (45,150 \pm 200)/4.576T$$\end{document}From this value of the activation energy, the data for the decomposition of chemically activated TFC were revised. The new results yield a minimum energy of the activated molecule of 98 ± 4 kcal/mol and ΔH f°(TFC) = −155.4 ± 7 kcal/mol, while an analysis of the kinetic data yields ΔH f°

ISSN:0538-8066    

DOI:10.1002/kin.550211104

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe thermal reaction of CH2O with NO2has been investigated in the temperature range of 393–476 K by means of FTIR product analysis. Kinetic modeling of the measured CH2O, NO, CO, and CO2concentration time profiles under varying reaction conditions gave rise to the rate constants for the following key reactions:andThe error limits shown represent only the scatter (±1 σ) of the modeled values. In the modeling, the total rate constant for the CHO + NO2reaction,k2+k3, was not varied and the value reported by Gutman and co‐workers (ref. [8]) was used for the whole temperature range investigated here. The proposed reaction mechanism, employing these newly established rate constants, can quantitively account for nearly all measured product yields, including the [CO]/([CO] + [CO2]) ratios reported by earlier wo

ISSN:0538-8066    

DOI:10.1002/kin.550211105

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe rate ofV→R,Tenergy relaxation following pulsed ir laser excitation is measured by employing an optoacoustic single pulse method. Under present experimental conditions the operation of convolution applies. The experimental optoacoustic waveform can be viewed as the convolution of the kinetic relaxation waveform with an optoacoustic waveform obtained under very fast energy relaxation conditions. A discrete Fourier transform deconvolution method is applied to optoacoustic measurements on SF6in argon to obtain the time constant, τ, for energy transfer. The present method gives τP= 182 ± 15 μs torr, in good agreement with other methods. These results were obtained without requiring either a theoretical description of the pressure waveform or an assumed laser irradiation geometry. For convolution to apply, the differential equation describing the pressure pulse must be linear under the conditions of the experiment. The linearity of the system can usually be tested experimen

ISSN:0538-8066    

DOI:10.1002/kin.550211106

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe high temperature kinetics of NH in the pyrolysis of isocyanic acid (HNCO) have been studied in reflected shock wave experiments. Time histories of the NH(X3Σ−) radical were measured using a cw, narrow‐linewidth laser absorption diagnostic at 336 nm. The second‐order rate coefficients of the reactions:were determined to be:\documentclass{article}\pagestyle{empty}\begin{document}$$k_{1{\rm a}} = 9.84\,\, \times \,\,10^{15} \,\,\exp (- 43000/T,{\rm K})\,\,\,\,\,\,(f = 0.65,F = 1.50)\,\,\,\,\,\,T = 1830 - 3340\,\,{\rm K,}$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$k_{\rm 2} = 5.1\,\, \times \,\,10^{13} \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(f = 0.7,F = 1.3)\,\,\,\,\,\,T = 2070 - 2730\,\,{\rm K,}$$\end{document}\documentclass{article}\pagestyle{empty}\begin{document}$$k_{\rm 3} = 2.65\,\, \times \,\,10^{14} \,\,\,\exp (- 38000/T,{\rm K})\,\,\,\,\,\,(f = 0.5,F = 1.4)\,\,\,\,\,\,T = 3140 - 3320\,\,{\rm K,}$$\end{document}cm3−mol−1−s−1, wherefandFdefine the lower and upper uncertainty limits, respectively. The data fork1aare somewhat better fit by:\documentclass{article}\pagestyle{empty}\begin{document}$$k_{{\rm 1a}} = 3.26\,\, \times \,\,10^{35} T^{ - 5.11} \,\,\exp (- 55300/T,{\rm K})\,\,\,{\rm cm}^{\rm 3} {\rm - mol}^{{\rm - 1}} {\rm - s}^{{\rm - 1}} .$

ISSN:0538-8066    

DOI:10.1002/kin.550211107

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe relative rate technique has been used to determine rate constants for the reaction of bromine atoms with a variety of organic compounds. Decay rates of the organic species were measured relative toi‐butane or acetaldehyde or both. Using rate constants of 1.74 × 10−15and 3.5 × 10−12cm3molecule−1s−1for the reaction of Br withi−butane and acetaldehyde respectively, the following rate constants were derived, in units of cm3molecule−1s−1: 2, 3−dimethylbutane, (6.40 ± 0.77) × 10−15; cyclopentane, (1.16 ± 0.18) × 10−15, ethene, (≤2.3 × 10−13); propene, (3.85 ± 0.41) × 10−12;trans‐2‐butene, (9.50 ± 0.76) × 10−12, acetylene, (5.15 ± 0.19) × 10−15; and propionaldehyde, (9.73 ± 0.91) × 10−12. Quoted errors represent 2σ and do not include possible systematic errors due to errors in the reference rate constants. Experiments were performed at 295 ± 2 K and atmospheric pressure of synthetic air or nitrogen. The results are discussed with respect to the mechanisms of these reactions and their utility in serving as

ISSN:0538-8066    

DOI:10.1002/kin.550211108

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractFourier transform infrared spectroscopy was used to identify and quantify products of the self reaction of ethylperoxy radicals, C2H5O2, formed in the photolysis of Cl2/C2H6mixtures in 700 torr total pressure of synthetic air at 295 K. From these measurements, branching ratios for the reaction channelsofk1a/(k1a+k1b) = 0.68 andk1c/(k1a+k1b+k1c) ⩽ 0.06 were established. Additionally, using the relative rate technique, the rate constant for the reaction of Cl atoms with C2H5OOH was determined to be (1.07 ± 0.07) × 10−10× cm3molecule−1s−1. Results are discussed with respect to the previous kinetic and mechanistic studies of C2H5

ISSN:0538-8066    

DOI:10.1002/kin.550211109

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550211101

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY