共查询到20条相似文献,搜索用时 46 毫秒
1.
UV spectra of SF5 and SF5O2 radicals in the gas phase at 295 K have been quantified using a pulse radiolysis UV absorption technique. The absorption spectrum of SF5 was quantified from 220 to 240 nm. The absorption cross section at 220 nm was (5.5 ± 1.7) × 10−19 cm2. When SF5 was produced in the presence of O2 an equilibrium between SF5, O2, and SF5O2 was established. The rate constant for the reaction of SF5 radicals with O2 was (8 ± 2) × 10−13 cm3 molecule−1 s−1. The decomposition rate constant for SF5O2 was (1.0 ± 0.5) × 105 s−1, giving an equilibrium constant of Keq = [SF5O2]/[SF5][O2] = (8.0 ± 4.5) × 10−18 cm3 molecule−1. The SF5 O2 bond strength is (13.7 ± 2.0) kcal mol−1. The SF5O2 spectrum was broad with no fine structure and similar to the UV spectra of alkyl peroxy radicals. The absorption cross section at 230 nm was found to (3.7 ± 0.9) × 10−18 cm2. The rate constant of the reaction of SF5O2 with NO was measured to (1.1 ± 0.3) × 10−11 cm3 molecule−1 s−1 by monitoring the kinetics of NO2 formation at 400 nm. The rate constant for the reaction of F atoms with SF4 was measured by two relative methods to be (1.3 ± 0.3) × 10−11 cm3 molecule−1 s−1. © 1994 John Wiley & Sons, Inc. 相似文献
2.
CS radicals have been produced by photodissociation of CS2 at 193 nm and their disappearance monitored by LIF. The vibrationally excited CS radicals rapidly relax to CS(ν = 0). At 298 K, the rate coefficients for CS(ν = 0) reactions with O2, O3 and NO2 are (2.9 ± 0.4) × 10?19, (3.0 ± 0.4) × 10?16 and (7.6 ± 1.1) × 10?17 cm3 molecule?1 s?1 respectively. The quenching of CS(A 1II)ν=0 by He has a rate coefficient of (1.3 ± 0.2) × 10?12 cm3 molecule?1 s?1. 相似文献
3.
S.D. Babenko V.A. Benderskii Ya.M. Zolotovitskii A.G. Krivenko 《Journal of Electroanalytical Chemistry》1977,76(3):347-365
A method of measuring the kinetics of currents arising at the electron photoemission from a metal into electrolyte solution when affected by the u.v. laser pulses for 10?8 s at the frequency of repetitions 10–25 Hz is described. Measurements have been taken in solutions without acceptors and in those containing N2O and NO2?, NO3? ions as electron acceptors. The rate constants of capture of the solvated electrons by N2O ((6±1)×09 mol?1 s?1) and NO2? ((4.5±1)×109 mol?1 s?1) and the diffusion coefficients of OH-radicals ((1.0±0.3)×10?5 cm2 s?1) and of NO ((1.2±0.3)×10?5 cm2 s?1) are found. The oxidation rate of NO32? has been shown to decrease from 40 cm s?1 in the range of potentials ?0.55 to ?1.0 V. The rate constant of bimolecular recombination of the solvated electrons ((1.3±0.4)×1010 mol?1 s?1) has been found from the dependence of the emitted charge on the light intensity. 相似文献
4.
The kinetics of the gas‐phase reactions of O3 with a series of selected terpenes has been investigated under flow‐tube conditions at a pressure of 100 mbar synthetic air at 295 ± 0.5 K. In the presence of a large excess of m‐xylene as an OH radical scavenger, rate coefficients k(O3+terpene) were obtained with a relative rate technique, (unit: cm3 molecule?1 s?1, errors represent 2σ): α‐pinene: (1.1 ± 0.2) × 10?16, 3Δ‐carene: (5.9 ± 1.0) × 10?17, limonene: (2.5 ± 0.3) × 10?16, myrcene: (4.8 ± 0.6) × 10?16, trans‐ocimene: (5.5 ± 0.8) × 10?16, terpinolene: (1.6 ± 0.4) × 10?15 and α‐terpinene: (1.5 ± 0.4) × 10?14. Absolute rate coefficients for the reaction of O3 with the used reference substances (2‐methyl‐2‐butene and 2,3‐dimethyl‐2‐butene) were measured in a stopped‐flow system at a pressure of 500 mbar synthetic air at 295 ± 2 K using FT‐IR spectroscopy, (unit: cm3 molecule?1 s?1, errors represent 2σ ): 2‐methyl‐2‐butene: (4.1 ± 0.5) × 10?16 and 2,3‐dimethyl‐2‐butene: (1.0 ± 0.2) × 10?15. In addition, OH radical yields were found to be 0.47 ± 0.04 for 2‐methyl‐2‐butene and 0.77 ± 0.04 for 2,3‐dimethyl‐2‐butene. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 394–403, 2002 相似文献
5.
The kinetics and mechanism of Cl-atom-initiated reactions of CHO? CHO were studied using the FTIR detection method to monitor the photolysis of Cl2–CHO? CHO mixtures in 700 torr of N2–O2 diluent at 298 ± 2 K. The observed product distribution in the [O2] pressure of 0–700 torr combined with relative rate measurements provide evidence that: (1) the primary step is Cl + CHO? CHO → HCl + CHO? CO with a rate constant of [3.8 ± 0.3(σ)] × 10?11 cm3 molecule?1 s?1; (2) the primary product CHO? CO unimolecularly dissociates to CHO and CO with an estimated lifetime of ≤ca. 1 × 10?7 s; (3) alternatively, the CHO? CO reacts with O2 leading to the formation of CO, CO2, and most likely the HO radical, but no stable products containing two carbon atoms; (4) the HO2 radical, formed in the secondary reaction CHO + O2 → HO2 + CO, reacts with the CHO? CHO with a rate constant ca. 5 × 10?16 cm3 molecule?1 s?1 to form HCOOH and a new transient product resembling that detected previously in the HO2 reaction with HCHO. 相似文献
6.
The kinetics of C2H5O2 and C2H5O2 radicals with NO have been studied at 298 K using the discharge flow technique coupled to laser induced fluorescence (LIF) and mass spectrometry analysis. The temporal profiles of C2H5O were monitored by LIF. The rate constant for C2H5O + NO → Products (2), measured in the presence of helium, has been found to be pressure dependent: k2 = (1.25±0.04) × 10?11, (1.66±0.06) × 10?11, (1.81±0.06) × 10?11 at P (He) = 0.55, 1 and 2 torr, respectively (units are cm3 molecule?1 s?1). The Lindemann-Hinshelwood analysis of these rate constant data and previous high pressure measurements indicates competition between association and disproportionation channels: C2H5O + NO + M → C2H5ONO + M (2a), C2H5O + NO → CH3CHO + HNO (2b). The following calculated average values were obtained for the low and high pressure limits of k2a and for k2b : k = (2.6±1.0) × 10?28 cm6 molecule?2 s?1, k = (3.1±0.8) × 10?11 cm3 molecule?1 s?1 and k2b ca. 8 × 10?12 cm3 molecule?1 s?1. The present value of k, obtained with He as the third body, is significantly lower than the value (2.0±1.0) × 10?27 cm6 molecule?2 s?1 recommended in air. The rate constant for the reaction C2H5O2 + NO → C2H5O + NO2 (3) has been measured at 1 torr of He from the simulation of experimental C2H5O profiles. The value obtained for k3 = (8.2±1.6) × 10?12 cm3 molecule?1 s?1 is in good agreement with previous studies using complementary methods. © 1995 John Wiley & Sons, Inc. 相似文献
7.
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
8.
Jan A. Herman Kazimiera Herman Terry B. McMahon 《Journal of the American Society for Mass Spectrometry》1991,2(3):220-225
Fourier transform ion cyclotron resonance mass spectrometry has been used to measure the reaction rates for ions derived from methylamine with dimethylamine or trimethylamine. The use of the selective ion ejection technique greatly simplifies the elucidation of the ion-molecule reaction channels. The rate constants for proton transfer from protonated metwlamine, CH3NH 3 + (m/z 32), to dimethylamine and trimethylamine are 16.1 ± 1.6 × 10?10 and 9.3 ± 0.9 × 10?10 cm3 molec?1s?1, respectively. The rate constants for charge transfer from methylamine molecular ion, CH3NH 2 + (m/z 31), to dimethylamine and trimethylamine are 9.3 ± 1.8 x 10?10 and 15.0 ± 5 × 10?10 cm3molec?1s?1, respectively. 相似文献
9.
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
10.
The kinetics of the gas-phase reactions of 1,4-benzodioxan, 2,3-dihydrobenzofuran, and 2,3-benzofuran with OH radicals and O3 have been studied at 298 ± 2 K and atmospheric pressure of air and the products have also been investigated. 1,4-Benzodioxan and 2,3-dihydrobenzofuran were chosen as volatile model compounds for dibenzo-p-dioxin and dibenzofuran, respectively. The rate constants, or upper limits thereof, for the O3 reactions were (in cm3 molecule?1 s?1 units): 1,4-benzodioxan, <1.2 × 10?20; 2,3-dihydrobenzofuran, <1 × 10?19; and 2,3-benzofuran, (1.83 ± 0.21) × 10?18. Using a relative rate method, the rate constants for the OH radical reactions (in cm3 molecule?1 s?1 units) were: 1,4-dibenzodioxan, (2.52 ± 0.38) × 10?11; 2,3-dihydrobenzofuran, (3.66 ± 0.56) × 10?11; and 2,3-benzofuran, (3.73 ± 0.74) × 10?11. Salicylaldehyde was observed as a product of the OH radical-initiated and O3 reactions of 2,3-benzofuran, with measured formation yields of 0.26 ± 0.05 and 0.13 ± 0.07, respectively. 相似文献
11.
The rate constants for proton transfer from H3+ ions to N2, O2, and CO have been measured as function of hydrogen buffer gas partial pressure. The rate constant for proton transfer from H3+ to N2 shows a very large pressure dependence, increasing from 1.0 × 10?9 cm3/s at low H2 partial pressures to 1.7 × 10?9 cm3/s at high H2 partial pressures. The rate constants for proton transfer from H3+ to O2 and CO are constant with partial pressure of H2; giving values of 6.4 × 10?10 cm3/s and 1.7 × 10?9 cm3/s, respectively. The roles of excess vibrational energy in H3+ ions and of equilibrium between forward and back reaction are discussed. Back reaction is observed only for the reaction of H3+ ions with O2, and an equilibrium constant of K = 2.0 ± 0.4 at 298 K has been determined. From these data the proton affinity of O2 is deduced to be 0.47 ± 0.11 kcal/mole higher than that of H2. 相似文献
12.
Jens Sehested 《国际化学动力学杂志》1994,26(10):1023-1039
The ultraviolet absorption spectrum of CF3CFClO2 and the kinetics of the self reactions of CF3CFCl and CF3CFClO2 radicals and the reactions of CF3CFClO2 with NO and NO2 have been studied in the gas phase at 295 K by pulse radiolysis/transient UV absorption spectroscopy. The UV absorption cross section of CF3CFCl radicals was measured to be (1.78 ± 0.22) × 10?18 cm2 molecule?1 at 220 nm. The UV spectrum of CF3CFClO2 radicals was quantified from 220 nm to 290 nm. The absorption cross section at 250 nm was determined to be (1.67 ± 0.21) × 10?18 cm2 molecule?1. The rate constants for the self reactions of CF3CFCl and CF3CFClO2 radicals were (2.6 ± 0.4) × 10?12 cm3 molecule?1 s?1 and (2.6 ± 0.5) × 10?12 cm3 molecule?1 s?1, respectively. The reactivity of CF3CFClO2 radicals towards NO and NO2 was determined to (1.5 ± 0.6) × 10?11 cm3 molecule?1 s?1 and (5.9 ± 0.5) × 10?12 cm3 molecule?1 s?1, respectively. Finally, the rate constant for the reaction of F atoms with CF3CFClH was determined to (8 ± 2) × 10?13 cm3 molecule?1 s?1. Results are discussed in the context of the atmospheric chemistry of HCFC-124, CF3CFClH. © 1994 John Wiley & Sons, Inc. 相似文献
13.
Rate constants for the reactions of O3 and OH radicals with acetylene, propyne, and 1-butyne have been determined at room temperature. The rate constants obtained at 294 ± 2 K for the reactions of O3 with acetylene, propyne, and 1-butyne were (7.8 ± 1.2) × 10?21 cm3/molecule · s, (1.43 ± 0.15) × 10?20 cm3/molecule · s, and (1.97 ± 0.26) × 10?20 cm3/molecule · s, respectively. The rate constants at 298 ± 2 K and atmospheric pressure for the reactions with the OH radical, relative to a rate constant for the reaction of OH radicals with cyclohexane of 7.57 × 10?12 cm3/molecule · s, were determined to be (8.8 ± 1.4) × 10?13 cm3/molecule · s, (6.21 ± 0.31) × 10?12 cm3/molecule · s, and (8.25 ± 0.23) × 10?12 cm3/molecule · s for acetylene, propyne, and 1-butyne, respectively. These data are discussed and compared with the available literature rate constants. 相似文献
14.
The kinetics of the gas-phase reactions of the OH radical with (C2H5O)3PO and (CH3O)2P(S)Cl and of the reactions of NO3 radicals and O3 with (CH3O)2P(S)Cl have been studied at room temperature. Using a relative rate technique, the rate constants determined for the reactions of the OH radical with (C2H5O)3PO and (CH3O)2P(S)Cl at 296 ± 2 K and 740 torr total pressure of air were (5.53 ± 0.35) × 10?11 and (5.96 ± 0.38) × 10?11 cm3 molecule?1 s?1, respectively. Upper limits to the rate constants for the NO3 radical and O3 reactions with (CH3O)2P(S)Cl of <3 × 10?14 cm3 molecule?1 s?1 and <2 × 10?19 cm3 molecule?1 s?1, respectively, were obtained. These data are compared and discussed with previous literature data for organophosphorus compounds. 相似文献
15.
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
16.
Rate constants for the removal of Cl atoms in the reaction Cl + O3 → ClO + O2 were measured by the flash photolysis resonance fluorescence technique over the temperature range 213–298 K. The rate constant is given by the Arrhenius expression (2.94 ± 0.49) × 10?11 exp[?(298 ± 39)/T] in units of cm3 molecule?1 s?1. Comparison with recent results from other laboratories are presented. 相似文献
17.
The reaction rate constant of the addition of atomic fluorine to excess PF3 was determined by fast flow ESR measurements to be (8.6 ± 0.6) × 1012 cm3 mole?1 s?1 at 300 K. The stoichiometry of the overall reaction of F with PF3 was 2:1. Finite difference calculations simulating several reaction mechanisms suggest that the reaction occurs in two consecutive addition steps, F + PF3 = PF4 and F + PF4 = PF5. Assuming this mechanism is correct, the rate constant for the second reaction would be approximately (1.2 ± 0.2) × 1013 cm3 mole?1 s?1. 相似文献
18.
The decay of prompt fluorescence in crystalline naphthalene at 300 K, excited by a picosecond 266 nm pulse, has been studied as a function of excitation intensity. Experimental decay curves can be fitted only when the exponential distribution in depth of excitation and the radial (gaussian) intensity profile of the excitation are both taken into account. From an analysis of the decay at early time (?5 ns) a best fit value of the singlet—singlet annihilation rate constant is found γSS = (4 ± 1) × 10?10 cm3 s?1. If the reaction is diffusion-limited, this rate implies an average singlet diffusivity DS = (2 ± 1) × 10?4 cm2 s?1. 相似文献
19.
Ernesto C. Tuazon Pilar Martin Sara M. Aschmann Janet Arey Roger Atkinson 《国际化学动力学杂志》2011,43(11):631-638
Rate constants for the reactions of 2‐methoxy‐6‐(trifluoromethyl)pyridine, diethylamine, and 1,1,3,3,3‐pentamethyldisiloxan‐1‐ol with OH radicals have been measured at 298 ± 2 K using a relative rate method. The measured rate constants (cm3 molecule?1 s?1) are (1.54 ± 0.21) × 10?12 for 2‐methoxy‐6‐(trifluoromethyl)pyridine, (1.19 ± 0.25) × 10?10 for diethylamine, and (1.76 ± 0.38) × 10?12 for 1,1,3,3,3‐pentamethyldisiloxan‐1‐ol, where the indicated errors are the estimated overall uncertainties including those in the rate constants for the reference compounds. No reaction of 2‐methoxy‐6‐(trifluoromethyl)pyridine with gaseous nitric acid was observed, and an upper limit to the rate constant for the reaction of 1,1,3,3,3‐pentamethyldisiloxan‐1‐ol with O3 of <7 × 10? 20 cm3 molecule?1 s?1 was determined. Using a 12‐h average daytime OH radical concentration of 2 × 106 molecule cm?3, the lifetimes of the volatile organic compounds studied here with respect to reaction with OH radicals are 7.5 days for 2‐methoxy‐6‐(trifluoromethyl)pyridine, 1.2 h for diethylamine, and 6.6 days for 1,1,3,3,3‐pentamethyldisiloxan‐1‐ol. Likely reaction mechanisms are discussed. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 631–638, 2011 相似文献
20.
Yoshihiko Hatano Masayoshi Ohno Noriyuki Kouchi Hitoshi Koizumi Atsushi Yokoyama Goro Isoyama Hideo Kitamura Taizo Sasaki 《Chemical physics letters》1981,84(3):454-457
An attempt has been made 'o measure the rate constant for the de-excitation of a state-specified excimer using the pulse character of synchrotron radiation. The rate constants have been obtained for de-excitation of a vibrationally relaxed excimer Xe2*(Ou+; low v) by SF6 and N2 as 9 × 10?10 and 7 × 10?12 cm3 molecule?1 s?1 respectively. 相似文献