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1.
Br-atom atomic resonance absorption spectrometry (ARAS) has been developed and applied to measure thermal decomposition rate constants for CF3Br (+ Kr)→CF3+Br (+ Kr) over the temperature range, 1222–1624 K. The Br-atom curve-of-growth (145<λ<163 nm) was determined using this reaction. For [Br]≤1×1012 molecules cm−3, absorbance, (ABS)=1.410×10−13 [Br], yielding σ=1.419×10−14 cm2. The curve-of-growth was then used to convert (ABS) to Br-atom profiles which were then analyzed to give measured rate constants. These can be expressed in second-order by k1=8.147×10−9 exp(−24488 K/T) cm3 molecule−1 s−1 (±33%, 1222≤T≤1624 K). A unimolecular theoretical approach was used to rationalize the data. Theory indicates that the dissociation rates are closer to second- than to first-order, i.e., the magnitudes are 30–53% of the low-pressure-limit rate constants over 1222–1624 K and 123–757 torr. With the known, E0=ΔH00=70.1 kcal mole−1, the optimized theoretical fit to the ARAS data requires 〈ΔEdown=550 cm−1. These conclusions are consistent with recently published data and theory from Kiefer and Sathyanarayana. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 859–867, 1998  相似文献   

2.
The processes of vibrational relaxation and unimolecular dissociation of the perfluoromethyl halides CF3Cl, CF3Br, and CF3I have been studied in the shock tube with the laser-schlieren technique. Vibrational relaxation was resolved in pure CF3Cl and CF3Br (400–484 K and 400–500 K, respectively), and in the mixtures; 2% CF3Cl/Kr (500–1000 K), 10% CF3Cl/Kr (440–670 K), 4% CF3Br/Kr (450–850 K), and 2% CF3I/Kr (620–860 K). Relaxation in the pure gases is extremely rapid, but shows a well-resolved, accurately exponential decay which provides very precise relaxation times in close agreement with ultrasonic results. Relaxation times as short as 0.1 μs-atm can be resolved, showing the method has a resolution within a factor 2–3 of the best ultrasonic methods. Relaxation dilute in rare gas shows a complex double exponential behavior consistent with a two-stage series process. Rates of CF3(SINGLEBOND)X fission in these mixtures were measured over 1800–3000 K, P<0.55 atm, for CF3Cl; 1600–2500 K, P<0.55 atm, in CF3Br; and 1260–2100 K, P<0.34 atm, in CF3I. Rates for dissociation were derived from a full profile modeling using a secondary mechanism of six CF3 reactions. RRKM analysis showed all dissociations to lie near the low pressure limit. Using literature barriers, these rates are best fit with (ΔE)all=−270 cm−1 for CF3Cl, 〈ΔEdown=0.3 T for CF3Br, and 〈ΔEdown=800 cm−1 for CF3F. All these transfers are on the large side, similar to those found in other halogenated methanes. © 1997 John Wiley & Sons, Inc.  相似文献   

3.
The rate constants for the gas-phase reactions between methylethylether and hydroxyl radicals (OH) and methylethylether and chlorine atoms (Cl) have been determined over the temperature range 274–345 K using a relative rate technique. In this range the rate constants vary little with temperature and average values of kMEE+OH = (6.60−2.62+3.88) × 10−12 cm3 molecule−1 s−1 and kMEE+Cl= (34.9 ± 6.7) × 10−11 cm3 molecule−1 s−1 were obtained. The atmospheric lifetimes of methylethylether have been estimated with respect to removal by OH radicals and Cl atoms to be ca. 2 days and ca. 30–40 days, respectively. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 231–236, 1997.  相似文献   

4.
The degradation and transformation of iodinated alkanes are crucial in the iodine chemical cycle in the marine boundary layer. In this study, MP2 and CCSD(T) methods were adopted to study the atmospheric transformation mechanism and degradation kinetic properties of CH3I and CH3CH2I mediated by ⋅OH radical. The results show that there are three reaction mechanisms including H-abstraction, I-substitution and I-abstraction. The H-abstraction channel producing ⋅CH2I and CH3C ⋅ HI radicals are the main degradation pathways of CH3I and CH3CH2I, respectively. By means of the variational transition state theory and small curvature tunnel correction method, the rate constants and branching ratios of each reaction are calculated in the temperature range of 200–600 K. The results show that the tunneling effect contributes more to the reaction at low temperatures. Theoretical reaction rate constants of CH3I and CH3CH2I with ⋅OH are calculated to be 1.42×10−13 and 4.44×10−13 cm3 molecule−1 s−1 at T=298 K, respectively, which are in good agreement with the experimental values. The atmospheric lifetimes of CH3I and CH3CH2I are evaluated to be 81.51 and 26.07 day, respectively. The subsequent evolution mechanism of ⋅CH2I and CH3C ⋅ HI in the presence of O2, NO and HO2 indicates that HCHO, CH3CHO, and I-atom are the main transformation end-products. This study provides a theoretical basis for insight into the diurnal conversion and environmental implications of iodinated alkanes.  相似文献   

5.
The relative rate technique has been used to measure the hydroxyl radical (OH) reaction rate constant of hexamethyldisiloxane (MM, (CH3)3Si-O-Si(CH3)3), octamethyltrisiloxane (MDM, (CH3)3Si-O-Si(CH3)2-O-Si(CH3)3), and decamethyltetrasiloxane (MD2M, (CH3)3Si-O-Si(CH3)2-O-Si(CH3)2-O-Si(Ch3)3). Hexamethyldisiloxane, octamethyltrisiloxane, and decamethyltetrasiloxane react with OH with bimolecular rate constants of 1.32 ± 0.05 × 10−12 cm3molecule−1s−1, 1.83 ± 0.09 × 10−12 cm3 molecule−1s−1, and 2.66 ± 0.13 × 10−12 cm3molecule−1s−1, respectively. Investigation of the OH + siloxane reaction products yielded trimethylsilanol, pentamethyldisiloxanol, heptamethyltetrasiloxanol, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and other compounds. Several of these products have not been reported before because these siloxanes and the proposed reaction mechanisms yielding these products are complicated. Some unusual cyclic siloxane products were observed and their formation pathways are discussed in light of current understanding of siloxane atmospheric chemistry. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 445–451, 1997.  相似文献   

6.
The rate constant for the reaction of CH3OCH2 radicals with O2 (reaction (1)) and the self reaction of CH3OCH2 radicals (reaction (5)) were measured using pulse radiolysis coupled with time resolved UV absorption spectroscopy. k1 was studied at 296K over the pressure range 0.025–1 bar and in the temperature range 296–473K at 18 bar total pressure. Reaction (1) is known to proceed through the following mechanism: CH3OCH2 + O2 ↔ CH3OCH2O2# → CH2OCH2O2H# → 2HCHO + OH (kprod) CH3OCH2 + O2 ↔ CH3OCH2O2# + M → CH3OCH2O2 + M (kRO2) k = kRO2 + kprod, where kRO2 is the rate constant for peroxy radical production and kprod is the rate constant for formaldehyde production. The k1 values obtained at 296K together with the available literature values for k1 determined at low pressures were fitted using a modified Lindemann mechanism and the following parameters were obtained: kRO2,0 = (9.4 ± 4.2) × 10−30 cm6 molecule−2 s−1, kRO2,∞ = (1.14 ± 0.04) × 10−11 cm3 molecule−1 s−1, and kprod,0 = (6.0 ± 0.5) × 10−12 cm3 molecule−1 s−1, where kRO2,0 and kRO2,∞ are the overall termolecular and bimolecular rate constants for formation of CH3OCH2O2 radicals and kprod,0 represents the bimolecular rate constant for the reaction of CH3OCH2 radicals with O2 to yield formaldehyde in the limit of low pressure. kRO2,∞ = (1.07 ± 0.08) × 10−11 exp(−(46 ± 27)/T) cm3 molecule−1 s−1 was determined at 18 bar total pressure over the temperature range 296–473K. At 1 bar total pressure and 296K, k5 = (4.1 ± 0.5) × 10−11 cm3 molecule−1 s−1 and at 18 bar total pressure over the temperature range 296–523K, k5 = (4.7 ± 0.6) × 10−11 cm3 molecule−1 s−1. As a part of this study the decay rate of CH3OCH2 radicals was used to study the thermal decomposition of CH3OCH2 radicals in the temperature range 573–666K at 18 bar total pressure. The observed decay rates of CH3OCH2 radicals were consistent with the literature value of k2 = 1.6 × 1013exp(−12800/T)s−1. The results are discussed in the context of dimethyl ether as an alternative diesel fuel. © 1997 John Wiley & Sons, Inc.  相似文献   

7.
Rate constants have been determined for the reactions of Cl atoms with the halogenated ethers CF3CH2OCHF2, CF3CHClOCHF2, and CF3CH2OCClF2 using a relative‐rate technique. Chlorine atoms were generated by continuous photolysis of Cl2 in a mixture containing the ether and CD4. Changes in the concentrations of these two species were measured via changes in their infrared absorption spectra observed with a Fourier transform infrared (FTIR) spectrometer. Relative‐rate constants were converted to absolute values using the previously measured rate constants for the reaction, Cl + CD4 → DCl + CD3. Experiments were carried out at 295, 323, and 363 K, yielding the following Arrhenius expressions for the rate constants within this range of temperature:Cl + CF3CH2OCHF2: k = (5.15 ± 0.7) × 10−12 exp(−1830 ± 410 K/T) cm3 molecule−1 s−1 Cl + CF3CHClOCHF2: k = (1.6 ± 0.2) × 10−11 exp(−2450 ± 250 K/T) cm3 molecule−1 s−1 Cl + CF3CH2OCClF2: k = (9.6 ± 0.4) × 10−12 exp(−2390 ± 190 K/T) cm3 molecule−1 s−1 The results are compared with those obtained previously for the reactions of Cl atoms with other halogenated methyl ethyl ethers. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 165–172, 2001  相似文献   

8.
Relative rate coefficients for the reaction of acetyl (CH3CO) radicals with O2 (k4) and Cl2 (k7) have been obtained at 298 K and 228 K as a function of total pressure, using FTIR/environmental chamber techniques. Measured values of k4/k7 were placed on an absolute basis using k7=2.8×10−11 exp(−47/T) cm3 molec−1 s−1. At 298 K, the value of k4 is constant ((7±2)×10−13 cm3 molec−1 s−1) at pressures from 0.1 to 2 torr, then increases to a high pressure limiting value of (3.2±0.6)×10−12 cm3 molec−1 s−1, which is approached at pressures above 300 torr. At 228 K, the low-pressure value of k4 increases by about 20–30%, while the high pressure value remains unchanged. Experiments designed to elucidate the products of reaction (4) as a function of pressure at 298 K indicate that the reaction occurs via a concerted mechanism in which CH3CO radicals combine with O2 to give an excited acetylperoxy radical (CH3COO2*) which is increasingly stabilized at high pressure at the expense of a low pressure decomposition channel. The yield of acetylperoxy radicals from reaction (4) decreases from >95% at pressures above 100 torr, to about 90% at 60 torr, and 50% at 6 torr. Indirect evidence for formation of OH radicals from the low pressure decomposition is presented, although the carbon-containing coproduct(s) of this channel could not be identified. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 655–663, 1997.  相似文献   

9.
Rate constants for the reactions of OH, NO3, and O3 with pinonaldehyde and the structurally related compounds 3-methylbutanal, 3-methylbutan-2-one, cyclobutyl-methylketone, and 2,2,3-trimethyl-cyclobutyl-1-ethanone have been measured at 300±5 K using on-line Fourier transform infrared spectroscopy. The rate constants obtained for the reactions with pinonaldehyde were: kOH=(9.1±1.8)×10−11 cm3 molecule−1 s−1, kNO3=(5.4±1.8)×10−14 cm3 molecule−1 s−1, and kO3=(8.9±1.4)×10−20 cm3 molecule−1 s−1. The results obtained indicate a chemical lifetime of pinonaldehyde in the troposphere of about two hours under typical daytime conditions, [OH]=1.6×106 molecule cm−3. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 527–533, 1997.  相似文献   

10.
The gas-phase reaction of ozone with vinylcyclohexane and methylene cyclohexane has been investigated at ambient T and p=1 atm of air in the presence of sufficient cyclo-hexane or 2-propanol added to scavenge OH. The reaction rate constants, in units of 10−18 cm3 molecule−1 s−1, are 7.52±0.97 for vinylcyclohexane (T=292±2 K) and 10.6±1.9 for methylene cyclohexane (T=293±2 K). Carbonyl reaction products were cyclohexyl meth-anal (0.62±0.03) and formaldehyde (0.47±0.04) from vinylcyclohexane and cyclohexanone (0.55±0.10) and formaldehyde (0.60±0.05) from methylene cyclohexane, where the yields given in parentheses are expressed as carbonyl formed, ppb/reacted ozone, ppb. The sum of the yields of the primary carbonyls is close to the value of 1.0 that is consistent with the simple mechanisms: O3+cyclo(C6H11)−CH(DOUBLEBOND)CH2→α(HCHO+cyclo(C6H11)CHOO)+(1−α)(HCHOO+cyclo(C6H11)CHO) for vinylcyclohexane and O3+(CH2)5C(DOUBLEBOND)CH2→α(HCHO +(CH2)5COO)+(1−α)(HCHOO+(CH2)5C(DOUBLEBOND)O) for methylene cyclohexane. The coefficients α are 0.43±0.10 for vinylcyclohexane and 0.52±0.05 for methylene cyclohexane, i.e., (formaldehyde+the substituted biradical) and (HCHOO+cyclohexyl methanal or cyclo-hexanone) are formed in ca. equal yields. Reaction rate constants, carbonyl yields, and reaction mechanisms are compared to those for alkene structural homologues. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 855–860, 1997  相似文献   

11.
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   

12.
Real-time kinetic measurements are reported for the Cl + CH3CO → CH2CO + HCl reaction. The experiments utilize infrared spectroscopy to determine the time dependence of the ketene formed via this reaction and of the CO produced from the subsequent rapid reaction between chlorine atoms and ketene. The reaction is investigated over a pressure range of 10–200 torr and a temperature range of 215–353 K. Within experimental error the rate constant under these conditions is k5a = (1.8 ± 0.5) × 10−10 cm3 s−1. We have also examined the Cl + CH2CO reaction and found it to have a rate constant of k6 = (2.5 ± 0.5) × 10−10 cm3 s−1 independent of temperature. © John Wiley & Sons, Inc. Int J Chem Kinet 29: 421–429, 1997.  相似文献   

13.
Ab initio calculations have been used to characterize the transition states for halogen abstraction by CH3 in reactions with CF4, CF3Cl, CF3Br, and CF3I (1–4). Geometries and frequencies were obtained at the HF/6-31G(d) and MP2=full/6-31G(d) levels of theory. Energy barriers were computed via the Gaussian-2 methodology, and the results were employed in transition state theory analyses to obtain the rate constants over 298–2500 K. There is good accord with literature measurements in the approximate temperature range 360–500 K for reactions (2–4), and the computed activation energies are accurate to within ±6 kJ mol−1. Recommended rate constant expressions for use in combustion modeling are k;1=1.6×10−19 (T/K)2.41 exp(−13150 K/T), k2=8.4×10−20(T/K)2.34 exp(−5000 K/T), k3=4.6×10−19 (T/K)2.05 exp(−3990 K/T), and k4=8.3×10−19 (T/K)2.18 exp(−1870 K/T) cm3 molecule−1 s−1. The results are discussed in the context of flame suppression chemistry. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 179–184, 1998.  相似文献   

14.
15.
A detailed chemical kinetic model for ethanol oxidation has been developed and validated against a variety of experimental data sets. Laminar flame speed data (obtained from a constant volume bomb and counterflow twin‐flame), ignition delay data behind a reflected shock wave, and ethanol oxidation product profiles from a jet‐stirred and turbulent flow reactor were used in this computational study. Good agreement was found in modeling of the data sets obtained from the five different experimental systems. The computational results show that high temperature ethanol oxidation exhibits strong sensitivity to the fall‐off kinetics of ethanol decomposition, branching ratio selection for C2H5OH + OH ↔ Products, and reactions involving the hydroperoxyl (HO2) radical. The multichanneled ethanol decomposition process is analyzed by RRKM/Master Equation theory, and the results are compared with those obtained from earlier studies. The ten‐parameter Troe form is used to define the C2H5OH(+M) ↔ CH3 + CH2OH(+M) rate expression as k = 5.94E23 T−1.68 exp(−45880 K/T) (s−1) ko = 2.88E85 T−18.9 exp(−55317 K/T) (cm3/mol/sec) Fcent = 0.5 exp(−T/200 K) + 0.5 exp(−T/890 K) + exp(−4600 K/T) and the C2H5OH(+M) ↔ C2H4 + H2O(+M) rate expression as k = 2.79E13 T0.09 exp(−33284 K/T) (s−1) ko = 2.57E83 T−18.85 exp(−43509 K/T) (cm3/mol/sec) F cent = 0.3 exp(−T/350 K) + 0.7 exp(−T/800 K) + exp(−3800 K/T) with an applied energy transfer per collision value of <ΔEdown> = 500 cm−1. An empirical branching ratio estimation procedure is presented which determines the temperature dependent branching ratios of the three distinct sites of hydrogen abstraction from ethanol. The calculated branching ratios for C2H5OH + OH, C2H5OH + O, C2H5OH + H, and C2H5OH + CH3 are compared to experimental data. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 183–220, 1999  相似文献   

16.
A discharge flow reactor coupled to a laser-induced fluorescence (LIF) detector and a mass spectrometer was used to study the kinetics of the reactions CH3O+Br→products (1) and CH3O+BrO→products (2). From the kinetic analysis of CH3O by LIF in the presence of an excess of Br or BrO, the following rate constants were obtained at 298 K: k1=(7.0±0.4)×10−11 cm3 molecule−1 s−1 and k2=(3.8±0.4)×10−11 cm3 molecule−1 s−1. The data obtained are useful for the interpretation of other laboratory studies of the reactions of CH3O2 with Br and BrO. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 249–255, 1998.  相似文献   

17.
Using a relative rate method, rate constants have been measured for the gas-phase reactions of the OH radical with the dibasic esters dimethyl succinate [CH3OC(O)CH2CH2C(O)OCH3], dimethyl glutarate [CH3OC(O)CH2CH2CH2C(O)OCH3], and dimethyl adipate [CH3OC(O)CH2CH2CH2CH2C(O)OCH3] at 298±3 K. The rate constants obtained were (in units of 10−12 cm3 molecule−1 s−1): dimethyl succinate, 1.4±0.6; dimethyl glutarate, 3.3±1.1; and dimethyl adipate, 8.4±2.5, where the indicated errors include the estimated overall uncertainty of ±25% in the rate constant for cyclohexane, the reference compound. The calculated tropospheric lifetimes of these dibasic esters due to gas-phase reaction with the OH radical range from 1.4 days for dimethyl adipate to 8.3 days for dimethyl succinate for a 24 h average OH radical concentration of 1.0×106 molecule cm−3. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 471–474, 1998  相似文献   

18.
Three-membered ring (3MR) forming processes of X(SINGLE BOND)CH2(SINGLE BOND)CH2(SINGLE BOND)F and CH2(SINGLE BOND)C((SINGLE BOND)Y)(SINGLE BOND)CH2(SINGLE BOND)F (X(DOUBLE BOND)CH2, O, or S and Y(DOUBLE BOND)0 or S) through a gas phase neighboring group mechanism (SNi) are studied theoretically using the ab initio molecular orbital method with the 6–31+G* basis set. When electron correlation effects are considered, the activation (ΔG) and reaction energies (ΔG0) are lowered by ca. 10 kcal mol−1, indicating the importance of the electron correlation effect in these reactions. The contribution of entropy of activation (−TΔS) at 298 K to ΔG is very small, and the reactions are enthalpy controlled. The ΔG and ΔG0 values for these ring closure processes largely depend on the stabilities of the reactants and the heteroatom acting as a nucleophilic center. The Bell–Evans–Polanyi principle applies well to all these reaction series. © 1997 John Wiley & Sons, Inc. J Comput Chem 18 : 1773–1784, 1997  相似文献   

19.
The rate constant for the reaction of the hydroxyl radical with 1,1,1,3,3-pentafluorobutane (HFC-365mfc) has been determined over the temperature range 278–323K using a relative rate technique. The results provide a value of k(OH+CF3CH2CF2CH3)=2.0×10−12exp(−1750±400/T) cm3 molecule−1 s−1 based on k(OH+CH3CCl3)=1.8×10−12 exp (−1550±150/T) cm3 molecule−1 s−1 for the rate constant of the reference reaction. Assuming the major atmospheric removal process is via reaction with OH in the troposphere, the rate constant data from this work gives an estimate of 10.8 years for the tropospheric lifetime of HFC-365mfc. The overall atmospheric lifetime obtained by taking into account a minor contribution from degradation in the stratosphere, is estimated to be 10.2 years. The rate constant for the reaction of Cl atoms with 1,1,1,3,3-pentafluorobutane was also determined at 298±2 K using the relative rate method, k(Cl+CF3CH2CF2CH3)=(1.1±0.3)×10−15 cm3 molecule−1 s−1. The chlorine initiated photooxidation of CF3CH2CF2CH3 was investigated from 273–330 K and as a function of O2 pressure at 1 atmosphere total pressure using Fourier transform infrared spectroscopy. Under all conditions the major carbon-containing products were CF2O and CO2, with smaller amounts of CF3O3CF3. In order to ascertain the relative importance of hydrogen abstraction from the (SINGLE BOND)CH2(SINGLE BOND) and (SINGLE BOND)CH3 groups in CF3CH2CF2CH3, rate constants for the reaction of OH radicals and Cl atoms with the structurally similar compounds CF3CH2CCl2F and CF3CH2CF3 were also determined at 298 K k(OH+CF3CH2CCl2F)=(8±3)×10−16 cm3 molecule−1 s−1; k(OH+CF3CH2CF3)=(3.5±1.5)×10−16 cm3 molecule−1 s−1; k(Cl+CF3CH2CCl2F)=(3.5±1.5)×10−17 cm3 molecule−1 s−1]; k(Cl+CF3CH2CF3)<1×10−17 cm3 molecule−1 s−1. The results indicate that the most probable site for H-atom abstraction from CF3CH2CF2CH3 is the methyl group and that the formation of carbonyl compounds containing more than a single carbon atom will be negligible under atmospheric conditions, carbonyl difluoride and carbon dioxide being the main degradation products. Finally, accurate infrared absorption cross-sections have been measured for CF3CH2CF2CH3, and jointly used with the calculated overall atmospheric lifetime of 10.2 years, in the NCAR chemical-radiative model, to determine the radiative forcing of climate by this CFC alternative. The steady-state Halocarbon Global Warming Potential, relative to CFC-11, is 0.17. The Global Warming Potentials relative to CO2 are found to be 2210, 790, and 250, for integration time-horizons of 20, 100, and 500 years, respectively. © 1997 John Wiley & Sons, Inc.  相似文献   

20.
CH3NH2 thermal decomposition is shown to provide a suitable NH2 radical source for spectroscopic and kinetic shock tube studies. Using this precursor, the absorption coefficient of the NH2 radical at a detection wavelength of 16739.90 cm−1 has been determined. In the temperature range 1600–2000K the low‐pressure absorption coefficient is described by the polynominal equation: kNH2=3.953×1010/T 3+7.295×105/T 2−1.549×103/T [atm−1 cm−1] The uncertainty of the determined absorption coefficient is estimated to be ±10%. The rate of the thermal decomposition reaction CH3NH2+M → CH3+NH2+M is determined over the temperature range 1550–1900 K and at pressures near 1.6 atm. The rate coefficient was found to be: k1=2.51×1016 exp(−28430/T) [cm3 mol−1 s−1] The uncertainty of the determined rate coefficients is estimated to be ±20%. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 323–330, 1999  相似文献   

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