Absolute rate constant for the reaction of atomic hydrogen with acetylene over an extended pressure and temperature range
01 Feb 1976-Journal of Chemical Physics (American Institute of Physics)-Vol. 64, Iss: 3, pp 1150-1155
TL;DR: In this paper, a flash photolysis coupled with time resolved detection of H via resonance fluorescence has been used to obtain absolute rate parameters for the reaction of atomic hydrogen with acetylene.
Abstract: The technique of flash photolysis coupled with time resolved detection of H via resonance fluorescence has been used to obtain absolute rate parameters for the reaction of atomic hydrogen with acetylene, i.e., H+C2H2?C2H3* (1); C2H3*+M→C2H3+M (2). The rate constant for the reaction is strongly pressure dependent and was measured over the pressure range 10 to 700 torr. The reaction was also studied as a function of temperature over the range 193 to 400 °K and the high pressure limit of the rate constant at each temperature was used to obtain the Arrhenius expression k1= (9.63±0.60) ×10−12 exp(−2430±30/1.987T) cm3 molecule−1⋅sec−1. The present results are compared with those of previous studies.
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01 Jan 1984
TL;DR: In this article, a critical survey of reaction rate coefficient data important in describing high-temperature combustion of H2, CO, and small hydrocarbons up to C4 is presented.
Abstract: This chapter is a critical survey of reaction rate coefficient data important in describing high-temperature combustion of H2, CO, and small hydrocarbons up to C4. A recommended reaction mechanism and rate coefficient set is presented. The approximate temperature range for this mechanism is from 1200 to 2500 K, which therefore excludes detailed consideration of cool flames, low-temperature ignition, or reactions of organic peroxides or peroxy radicals. Low-temperature rate-coefficient data are presented, however, when they contribute to defining or understanding high-temperature rate coefficients. Because our current knowledge of reaction kinetics is incomplete, this mechanism is inadequate for very fuel-rich conditions (see Warnatz et al., 1982). For the most part, reactions are considered only when their rates may be important for modeling combustion processes. This criterion eliminates considering many reactions among minor species present at concentrations so low that reactions of these species cannot play an essential part in combustion processes. The philosophy in evaluating the rate-coefficient data was to be selective rather than exhaustive: Recent results obtained with experimental methods capable of measuring isolated elementary reaction rate parameters directly were preferred, while results obtained using computer simulations of complex reacting systems were considered only when sensitivity to a particular elementary reaction was demonstrated or when direct measurements are not available. Theoretical results were not considered.
547 citations
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228 citations
Cites methods from "Absolute rate constant for the reac..."
...However, because this expression may underestimate k1 (see Figure 3) [Payne and Stief, 1976; Sugawara et al., 1981; Knyazev and Slagle, 1996], we adopt an alternative expression for Model C (see Table 1 E08001 MOSES ET AL....
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References
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TL;DR: In this article, the authors measured the absorption coefficients of acetylene, propyne and 1-butyne using a photoelectric technique in the region 1050-2000 A. The photoionization curves and the Rydberg series yielded the same ionization potential: 11.41, 10.36, and 10.18 eV.
Abstract: Absorption coefficients of acetylene, propyne and 1‐butyne were measured by a photoelectric technique in the region 1050–2000 A. Two or three Rydberg series accompanied by vibrational bands were observed in the spectrum of these molecules. The photoionization curves and the Rydberg series yielded the same ionization potential: 11.41, 10.36, and 10.18 eV for acetylene, propyne and 1‐butyne, respectively.
184 citations
118 citations
TL;DR: In this paper, the relative importance of two primary processes in the photolyis of water were determined by time resolved detection (via resonance fluorescence) of H and O formed in processes 1 and 2 respectively.
Abstract: The relative importance of two primary processes in the photolyis of water: (1) H2O + h (nu) yields H + OH, and (2) H2O + h (nu) yields H2 + OD-1 were determined in a direct manner by time resolved detection (via resonance fluorescence) of H and O formed in processes 1 and 2 respectively. The initially formed OD-1 was deactivated to ground state OP-3 prior to detection via resonance fluorescence. The relative quantum yields for processes 1 and 2 are 0.89 and 0.11 for the wavelength interval 105 to 145nm and = to or greater than 0.99, and = to or less than 0.01 for the wavelength interval 145 to 185nm. Rate constants at 300 K for the reactions OD-1 + H2, + Ar, and + He are presented.
108 citations
TL;DR: In this paper, a detailed quantitative study of the photochemistry of CH4, C2H2, C 2H 2, C 2 H4 and C2 H6 is presented for the Jovian upper atmosphere composed of 90% H2, 10% He with a CH4 mixing ratio of 7×10−4.
Abstract: A detailed quantitative study of the photochemistry of CH4, C2H2, C2H4 and C2H6 which includes eddy and molecular diffusion is presented for the Jovian upper atmosphere composed of 90% H2, 10% He with a CH4 mixing ratio of 7×10−4. The densities of the following constituents are calculated: CH4, CH, 1CH2, CH3, C2H2, C2H3, C2H4, C2H5, C2H6, H. The C2H6 mixing ratio is ∼10−5 and the C2H2 concentration ∼109 cm−3 throughout the upper stratosphere and lower mesosphere. The concentration of C2H2 near the mesopause is sufficiently large to make it the most important radiator of infrared energy. C2H2 is also an efficient catalyst in the recombination of H atoms. In the region of photolysis approximately 20% of the dissociated CH4 molecules are irreversibly converted to heavier hydrocarbons. Density profiles of atomic hydrogen which are needed to interpret Lyman-α albedo measurements of Jupiter are calculated with H2 dissociation and ionization and CH4 dissociation as sources of H.
97 citations
TL;DR: In this paper, a wide-temperature-range study using ESR atom detection has been employed to measure the rate of the reaction H + CH4→H2 + CH3.
Abstract: A wide‐temperature‐range study using ESR atom detection has been employed to measure the rate of the reaction H + CH4→H2 + CH3. Over the temperature range 426°–747°K, we obtain a specific rate constant for the above reaction of k1 = 6.9 ± 0.6 × 1013exp[(−11 800 ± 200) / RT] expressed in units of cubic centimeters per mole per second. The value obtained in the present work is compared to a number of other results obtained by various workers. The activation energy we observe is considerably higher than previous values obtained in this temperature range. However, our results coupled with the heat of the reaction predict an activation energy for the reverse reaction which agrees well with experimental values. In addition, the pre‐exponential factor we obtain agrees with absolute rate theory predictions as well as with entropy considerations. We do not agree with literature results which give very low pre‐exponential factors suggesting steric factors of the order of 10−3–10−5 for this reaction.
67 citations