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1.
The rate coefficients of the reactions of CN and NCO radicals with O2 and NO2 at 296 K: (1) CN + O2 → products; (2) CN + NO2 → products; (3) NCO + O2 → products and (4) NCO + NO2 → products have been measured with the laser photolysis-laser induced fluorescence technique. We obtained k1 = (2.1 ± 0.3) × 10?11 and k2 = (7.2 ± 1.0) × 10?11 cm3 molecule?t s?1 which agree well with published results. As no reaction was observed between NCO and O2 at 297 K, an upper limit of k3 < 4 × 10?17 cm3 molecule?1 S?1 was estimated. The reaction of NCO with NO2 has not been investigated previously. We measured k4 = (2.2 ± 0.3) × 10?11 cm3 molecule?1 s?1 at 296 K.  相似文献   

2.
Recent experimental results on the thermal decomposition of N2O5 in N2 are evaluated in terms of unimolecular rate theory. A theoretically consistent set of fall-off curves is constructed which allows to identify experimental errors or misinterpretations. Limiting rate constants k0 = [N2] 2.2 × 10?3 (T/300)?4.4 exp(?11,080/T) cm3/molec·s over the range of 220–300 K, k = 9.7 × 1014 (T/300)+0.1 exp(?11,080/T) s?1 over the range of 220–300 K, and broadening factors of the fall-off curve Fcent = exp(-T/250) + exp(?1050/T) over the range of 220–520 K have been derived. NO2 + NO3 recombination rate constants over the range of 200–300 K are krec,0 = [N2] 3.7 × 10?30 (T/300)?4.1 cm6/molec2·s and krec,∞ = 1.6 × 10?12 (T/300)+0.2 cm3/molec·s.  相似文献   

3.
A pulse radiolysis system was used to study the kinetics of the reaction of FC(O)O2 radicals with NO2. By monitoring the rate of the decay of NO2 using its absorption at 400 nm the reaction rate constant was determined to be (5.5 ± 0.6) × 10?12 cm3 molecule?1 s?1 at 296 K and 500–1000 mbar pressure of SF6 diluent. A long path length Fourier transform infrared spectrometer was used to investigate the thermal stability of the product FC(O)O2NO2. The rate of thermal decomposition of FC(O)O2NO2 was independent of the total pressure of N2 diluent over the range 100–700 torr and was fit by the expression k?3 = 6.0 × 1016 exp(?14150/T) s?1. The results are discussed in the context of the atmospheric chemistry of FCOx radicals. © 1995 John Wiley & Sons, Inc.  相似文献   

4.
The total rate constant for the reaction of Cl atoms with HO2NO2 was found to be less than 1.0 × 10?13 cm3 s?1 at 296 K by the discharge flow/resonance fluorescence technique. The reaction was also studied by the discharge flow/mass spectrometric technique. k1a + k1b was measured to be (3.4 ± 1.4) × 10?14 cm3 s?1 at 296 K. The reaction is too slow to be of any importance in stratospheric chemistry.  相似文献   

5.
Rate constants for the reaction O(3P) + SO2 + M have been determined over the temperature range of 299°–440°K, using a flash photolysis–NO2 chemiluminescence technique. For M?Ar, the Arrhenius expression was obtained. At room temperature k2Ar = (1.05 ± 0.21) × 10?33 cm6/molec2·sec. In addition, the rate constants k2 = (1.37 + 0.27) × 10?33 cm6/molec2·sec, k2 = (9.5 ± 3.0) ± 10?33 cm6/molec2·sec, k3 = (1.1 ± 0.2) ± 10?31 cm6/molec2·sec, and k3 = (2.6 ? 0.9) ± 10?31 cm6/molec2·sec were obtained at room temperature where k3M is the rate constant for the reaction O + NO + M → NO2 + M. The rate data are compared and discussed with literature values.  相似文献   

6.
The gas-phase reaction of the NO3 radical with NO2 was investigated, using a flash photolysis-visible absorption technique, over the total pressure range 25–400 Torr of nitrogen or oxygen diluent at 298 ± 2 K. The absolute rate constants determined (in units of 10?13 cm3 molecule?1 s?1) at 25, 100, and 400 Torr total pressure were, respectively, (4.0 ± 0.5), (7.0 ± 0.7), and (10 ± 2) for M = N2 and (4.5 ± 0.5), (8.0 ± 0.4), and (8.8 ± 2.0) for M = O2. These data show that the third-body efficiencies of N2 and O2 are identical, within the error limits, and that previous evaluations for M = N2 are applicable to the atmosphere. In addition, upper limits were determined for the rate constants of the reactions of the NO3 radical with methanol, ethanol, and propan-2-ol of ?6 × 10?16, ?9 × 10?16, and ?2.3 × 10?15 cm3 molecule?1 s?1, respectively, at 298 ± 2 K.  相似文献   

7.
The equilibrium constant, Keq of the reaction NO2 + NO3 + M 2 N2O5 + M has been determined for a small range of temperatures around room temperature in air at 740 torr by direct spectroscopical measurements of NO2, NO3, and N2O5. At 298 K, Keq was determined as (3.73 ± 0.61) × 10−11 cm3 molecule−1. Averaging this and 11 other independent evaluations of Keq yields Keq = (3.31 ± 0.82) × 10−11 cm3 molecule−1, where the uncertainty is given as one standard deviation. The kinetics of the O3/NO2/N2O5/NO3/ air system was studied in a static chamber at room temperature and 740 torr total pressure. Evidence of a unimolecular decay reaction of NO3, NO3 → NO + O2, was found and its rate coefficient was estimated as (1.6 ± 0.7) × 10−3 s−1 at 295 ± 2 K.  相似文献   

8.
Pulse radiolysis was used to study the kinetics of the reactions of CH3C(O)CH2O2 radicals with NO and NO2 at 295 K. By monitoring the rate of formation and decay of NO2 using its absorption at 400 and 450 nm the rate constants k(CH3C(O)CH2O2+NO)=(8±2)×10−12 and k(CH3C(O)CH2O2+NO2)=(6.4±0.6)×10−12 cm3 molecule−1 s−1 were determined. Long path length Fourier transform infrared spectrometers were used to investigate the IR spectrum and thermal stability of the peroxynitrate, CH3C(O)CH2O2NO2. A value of k−6≈3 s−1 was determined for the rate of thermal decomposition of CH3C(O)CH2O2NO2 in 700 torr total pressure of O2 diluent at 295 K. When combined with lower temperature studies (250–275 K) a decomposition rate of k−6=1.9×1016 exp (−10830/T) s−1 is determined. Density functional theory was used to calculate the IR spectrum of CH3C(O)CH2O2NO2. Finally, the rate constants for reactions of the CH3C(O)CH2 radical with NO and NO2 were determined to be k(CH3C(O)CH2+NO)=(2.6±0.3)×10−11 and k(CH3C(O)CH2+NO2)=(1.6±0.4)×10−11 cm3 molecule−1 s−1. The results are discussed in the context of the atmospheric chemistry of acetone and the long range atmospheric transport of NOx. © John Wiley & Sons, Inc. Int J Chem Kinet: 30: 475–489, 1998  相似文献   

9.
Far-infrared rotational transitions in ClO(X23/2, υ = 0) have been observed using laser magnetic resonance (LMR) with an optically pumped spectrometer. Five observed transitions at wavelengths between 444 and 713 µm have been compared with values predicted with spectroscopic constants from the literature. LMR detection of ClO has been used to study its reactions with NO and NO2 in a discharge flow system under pseudo-first-order conditions for ClO. The measured rate constants are k(ClO + NO) = (7.1 ± 1.4) × 10?12 exp[(270 ± 50)/T] cm3/molec·s for the temperature range of 202 < T < 393 K; k(ClO + NO2 + M) = (2.8 ± 0.6) × 10?33 exp[(1090 ± 80)/T] cm6/molec2·s (M = He, 250 < T < 387 K), (3.5 ± 0.6) × 10?33 exp[(1180 ± 80)/T] (M = O2, 250 < T < 416 K), and (2.09 ± 0.3) × 10?31 (M = N2, T = 297 K). All measurements were made at low pressures, between 0.6 and 6.6 torr. These results are compared with those from other studies.  相似文献   

10.
Mixtures of N2O, H2, O2, and trace amounts of NO and NO2 were photolyzed at 213.9 nm, at 245°–328°K, and at about 1 atm total pressure (mostly H2). HO2 radicals are produced from the photolysis and they react as follows: Reaction (1b) is unimportant under all of our reaction conditions. Reaction (1a) was studied in competition with reaction (3) from which it was found that k1a/k31/2 = 6.4 × 10?6 exp { z?(1400 ± 500)/RT} cm3/2/sec1/2. If k3 is taken to be 3.3 × 10?12 cm3/sec independent of temperature, k1a = 1.2 × 10?11 exp {?(1400 ± 500)/RT} cm3/sec. Reaction (2a) is negligible compared to reaction (2b) under all of our reaction conditions. The ratio k2b/k1 = 0.61 ± 0.15 at 245°K. Using the Arrhenius expression for k1a given above leads to k2b = 4.2 × 10?13 cm3/sec, which is assumed to be independent of temperature. The intermediate HO2NO2 is unstable and induces the dark oxidation of NO through reaction (?2b), which was found to have a rate coefficient k?2b = 6 × 1017 exp {?26,000/RT} sec?1 based on the value of k1a given above. The intermediate can also decompose via Reaction (10b) is at least partially heterogeneous.  相似文献   

11.
The kinetics of the atmospherically important gas-phase reactions of acenaphthene and acenaphthylene with OH and NO3 radicals, O3 and N2O5 have been investigated at 296 ± 2 K. In addition, rate constants have been determined for the reactions of OH and NO3 radicals with tetralin and styrene, and for the reactions of NO3 radicals and/or N2O5 with naphthalene, 1- and 2-methylnaphthalene, 2,3-dimethylnaphthalene, toluene, toluene-α,α,α-d3 and toluene-d8. The rate constants obtained (in cm3 molecule?1 s?1 units) at 296 ± 2 K were: for the reactions of O3; acenaphthene, <5 × 10?19 and acenaphthylene, ca. 5.5 × 10?16; for the OH radical reactions (determined using a relative rate method); acenaphthene, (1.03 ± 0.13) × 10?10; acenaphthylene, (1.10 ± 0.11) × 10?10; tetralin, (3.43 ± 0.06) × 10?11 and styrene, (5.87 ± 0.15) × 10?11; for the reactions of NO3 (also determined using a relative rate method); acenaphthene, (4.6 ± 2.6) × 10?13; acenaphthylene, (5.4 ± 0.8) × 10?12; tetralin, (8.6 ± 1.3) × 10?15; styrene, (1.51 ± 0.20) × 10?13; toluene, (7.8 ± 1.5) × 10?17; toluene-α,α,α-d3, (3.8 ± 0.9) × 10?17 and toluene-d8, (3.4 ± 1.9) × 10?17. The aromatic compounds which were observed to react with N2O5 and the rate constants derived were (in cm3 molecule?1 s?1 units): acenaphthene, 5.5 × 10?17; naphthalene, 1.1 × 10?17; 1-methylnaphthalene, 2.3 × 10?17; 2-methylnaphthalene, 3.6 × 10?17 and 2,3-dimethylnaphthalene, 5.3 × 10?17. These data for naphthylene and the alkylnaphthalenes are in good agreement with our previous absolute and relative N2O5 reaction rate constants, and show that the NO3 radical reactions with aromatic compounds proceed by overall H-atom abstraction from substituent-XH bonds (where X = C or O), or by NO3 radical addition to unsaturated substituent groups while the N2O5 reactions only occur for aromatic compounds containing two or more fused six-membered aromatic rings.  相似文献   

12.
The kinetics of the gas-phase reaction of Cl atoms with CF3I have been studied relative to the reaction of Cl atoms with CH4 over the temperature range 271–363 K. Using k(Cl + CH4) = 9.6 × 10?12 exp(?2680/RT) cm3 molecule?1 s?1, we derive k(Cl + CF3I) = 6.25 × 10?11 exp(?2970/RT) in which Ea has units of cal mol?1. CF3 radicals are produced from the reaction of Cl with CF3I in a yield which was indistinguishable from 100%. Other relative rate constant ratios measured at 296 K during these experiments were k(Cl + C2F5I)/k(Cl + CF3I) = 11.0 ± 0.6 and k(Cl + C2F5I)/k(Cl + C2H5Cl) = 0.49 ± 0.02. The reaction of CF3 radicals with Cl2 was studied relative to that with O2 at pressures from 4 to 700 torr of N2 diluent. By using the published absolute rate constants for k(CF3 + O2) at 1–10 torr to calibrate the pressure dependence of these relative rate constants, values of the low- and high-pressure limiting rate constants have been determined at 296 K using a Troe expression: k0(CF3 + O2) = (4.8 ± 1.2) × 10?29 cm6 molecule?2 s?1; k(CF3 + O2) = (3.95 ± 0.25) × 10?12 cm3 molecule?1 s?1; Fc = 0.46. The value of the rate constant k(CF3 + Cl2) was determined to be (3.5 ± 0.4) × 10?14 cm3 molecule?1 s?1 at 296 K. The reaction of Cl atoms with CF3I is a convenient way to prepare CF3 radicals for laboratory study. © 1995 John Wiley & Sons, Inc.  相似文献   

13.
The bimolecular reactions in the title were measured behind shock waves by monitoring the O-atom production in COS? O2? Ar and CS2? O2? Ar mixtures over the temperature range between 1400 and 2200 K. A value of the rate constant for S + O2 → SO + O was evaluated to be (3.8 ± 0.7) × 1012 cm3 mol?1 s?1 between 1900 and 2200 K. This was connected with the data at lower temperatures to give an expression k2 = 1010.85 T0.52 cm3 mol?1 s?1 between 250 and 2200 K. An expression of the rate constant for CS2 + O2 → CS + SO2 was obtained to be k21 = 1012.0 exp(?32 kcal mol?1/RT) cm3 mol?1 s?1 with an error factor of 2 between 1500 and 2100 K.  相似文献   

14.
The kinetics of reactions of HCCl with NO and NO2 were investigated over the temperature ranges 298–572 k and 298–476 k, respectively, using laser‐induced fluorescence spectroscopy to measure total rate constants and time‐resolved infrared diode laser absorption spectroscopy to probe reaction products. Both reactions are fast, with k(HCCl + NO) = (2.75 ± 0.2) × 10?11 cm3 molecule?1 s?1 and k(HCCl + NO2) = (1.10 ± 0.2) × 10?10 cm3 molecule?1 s?1 at 296 K. Both rate constants displayed only a slight temperature dependence. Detection of products in the HCCl + NO reaction at 296 K indicates that HCNO + Cl is the major product with a branching ratio of ? = 0.68 ± 0.06, and NCO + HCl is a minor channel with ? = 0.24 ± 0.04. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 12–17, 2002  相似文献   

15.
Rate constants for the reaction HO2 + NO2(+ M) = HO2NO2(+ M) have been obtained from direct observations of the HO2 radical using the technique of molecular modulation ultraviolet spectrometry. HO2 was generated by periodic photolysis of Cl2 in the presence of excess H2 and O2, and k1 was determined from the measured concentrations and lifetime of HO2 with NO2 present. k1 increased with pressure in the range of 40–600 Torr, and a simple energy transfer model gave the following limiting second- and third-order rate constants at 283 K: k1 = 1.5 ± 0.5 × 10?12 cm3/molec·sec and k1III = 2.5 ± 0.5 × 10?31 cm6/molec·sec. The ultraviolet absorption spectrum of peroxynitric acid was also recorded in the range of 195–265 nm; it showed a broad feature with a maximum at 200 nm, σmax = 4.4 × 10?18 cm2.  相似文献   

16.
An upper limit for the reaction rate of CO with the nitrate radical NO3 has been determined equal to 4 × 10?19 cm+3 molec?1 s?1 at 295 ± 2 K. In the experiment the isotopic species C13O16 and C13O18 mixed at 1–2 ppmv level in synthetic air have been reacted with NO3 and the reaction followed using long path infrared absorption FT spectroscopy. The result is of interest in the studies on the role played by NO3 in nighttime tropospheric chemistry.  相似文献   

17.
The reaction NO + O3 → NO2 + O2 has been studied in a 220-m3 spherical stainless steel reactor under stopped-flow conditions below 0.1 mtorr total pressure. Under the conditions used, the mixing time of the reactants was negligible compared with the chemical reaction time. The pseudo-first-order decay of the chemiluminescence owing to the reaction of ozone with a large excess of nitric oxide was measured with an infrared sensitive photomultiplier. One hundred twenty-nine decays at 18 different temperatures in the range of 283–443 K were evaluated. A weighted least-squares fit to the Arrhenius equation yielded k = (4.3 ± 0.6) × 10?12 exp[-(1598 ± 50)/T] cm3/molecule sec (two standard deviations in brackets). The Arrhenius plot showed no curvature within experimental accuracy. Comparison with recent results of Birks and co-workers, however, suggests that a nonlinear fit, as proposed by these authors, is more appropriate over an extended temperature range.  相似文献   

18.
The reactions of CCl3 with O(3P) and O2 and those of CCl3O2 with NO have been studied at 295 K using discharge flow methods with helium as the bath gas. The rate coefficient for the reaction of CCl3 with O was found to be (4.2 ± 0.6) × 10?11 cm3/s and that for CCl3O2 with NO was (18.6 ± 2.8) × 10?12 cm3/s with both coefficients independent of [He]. For reaction between CCl3 and O2 the rate coefficient was found to increase from 1.51 7times; 10?14 cm3/s to 7.88 × 10?14 cm3/s as the [He] increased from 3.5 × 1016 cm?3 to 2.7 × 1017 cm?3. There was no evidence for a direct two-body reaction, and it is concluded that the only product of this reaction is CCl3O2. Examination of these results for CCl3 + O2 in terms of current simplified falloff treatment suggests that the high-pressure limit for this reaction is ~ 2.5 × 10?12 cm3/s, which may be compared with a direct measurement of the high-pressure limit of 5 × 10?12 cm3/s. A value of (5.8 ± 0.6) × 10?31 cm6/s has been obtained for k0, the coefficient in the low-pressure region. This value is compared with corresponding values found earlier for the (CH3, O2) and (CF3, O2) systems and with estimates based on unimolecular rate theory.  相似文献   

19.
Kinetics for the reactions of OBrO with NO, O3, OClO, and ClO at 240–350 K were investigated using the technique of discharge flow coupled with mass spectrometry. The Arrhenius expression for the OBrO reaction with NO was determined to be k1 = (2.37 ± 0.96) × 10?13 exp[(607 ± 63)/T] cm3 molecule?1 s?1. The reactions of OBrO with O3, OClO, and ClO are slow chemical processes at 240–350 K. Upper limit rate constants for the OBrO reactions with O3, OClO, and ClO at 240–350 K were estimated to be k2 < 5.0 × 10?15 cm3 molecule?1 s?1, k3 < 6.0 × 10?14 cm3 molecule?1 s?1, and k4 < 1.5 × 10?13 cm3 molecule?1 s?1, respectively. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 430–437, 2002  相似文献   

20.
The third order rate coefficients for the addition reaction of Cl with NO2, Cl + NO2 + M → ClNO2 (ClONO) + M; k1, were measured to be k1(He) = (7.5 ± 1.1) × 10?31 cm6 molecule?2 s?1 and k1(N2) = (16.6 ± 3.0) × 10?31 cm6 molecule?2 s?1 at 298 K using the flash photolysis-resonance fluorescence method. The pressure range of the study was 15 to 500 torr He and 19 to 200 torr N2. The temperature dependence of the third order rate coefficients were also measured between 240 and 350 K. The 298 K results are compared with those from previous low pressure studies.  相似文献   

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