Tables of rate constants extracted from <i>chemical kinetics and photochemical data for use in stratospheric modeling. Evaluation number 7</i>

DeMore, W. B.; Margitan, J. J.; Molina, Mario J.; Watson, Robert; Golden, D. M.; Hampson, R. F.; Kurylo, Michael J.; Howard, Carleton J.; Ravishankara, A. R.

doi:10.1002/kin.550171010

Cited by 1,319 publications

(2,650 citation statements)

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“…From Table 2 (Wallington and Hurley, 1992) and DeMore et al (1997). Again there is a nearly linear dependence of the relative rate constants R 2 on n. In this case the linear theory predicts R 2 =0.77, 0.52, and 0.25, as compared to the measured ratios R 2 =0.77, 0.48, 0.24.…”

Section: Enrichment Of Deuterium Through Methane Photochemistrymentioning

confidence: 78%

On the volatile inventory of Titan from isotopic abundances in nitrogen and methane

Lunine

Yung

Lorenz

1999

Planetary and Space Science

102

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We analyze recently published nitrogen and hydrogen isotopic data to constrain the initial volatile abundances on Saturn's giant moon Titan. The nitrogen data are interpreted in terms of a model of non-thermal escape processes that lead to enhancement in the heavier isotope. We show that these data do not, in fact, strongly constrain the abundance of nitrogen present in Titan's early atmosphere, and that a wide range of initial atmospheric masses (all larger than the present value) can yield the measured enhancement. The enrichment in deuterated methane is now much better determined than it was when Pinto et al. (1986. Nature 319, 388±390) ®rst proposed a photochemical mechanism to preferentially retain the deuterium. We develop a simple linear theory to provide a more reliable estimate of the relative dissociation rates of normal and deuterated methane. We utilize the improved data and models to compute initial methane reservoirs consistent with the observed enhancement. The result of this analysis agrees with an independent estimate for the initial methane abundance based solely on the present-day rate of photolysis and an assumption of steady state. This consistency in reservoir size is necessary but not su cient to infer that methane photolysis has proceeded steadily over the age of the solar system to produce large quantities of less volatile organics. Our analysis indicates an epoch of early atmospheric escape of nitrogen, followed by a later addition of methane by outgassing from the interior. The results also suggest that Titan's volatile inventory came in part or largely from a circum-Saturnian disk of material more reducing than the surrounding solar nebula. Many of the ambiguities inherent in the present analysis can be resolved through Cassini±Huygens data and a program of laboratory studies on isotopic and molecular exchange processes. The value of, and interest in, the Cassini±Huygens data can be greatly enhanced if such a program were undertaken prior to the prime phase of the mission. #

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Section: Enrichment Of Deuterium Through Methane Photochemistrymentioning

confidence: 78%

On the volatile inventory of Titan from isotopic abundances in nitrogen and methane

Lunine

Yung

Lorenz

1999

Planetary and Space Science

102

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“…The NO 2 photolysis frequency is the product of the temperature and wavelength dependent absorption cross section, σ NO 2 (λ, T ), multiplied by its quantum yield, φ NO 2 (λ, T ), and the intensity of radiation at a particular wavelength and position with respect to a lamp, F (λ, x). σ NO 2 (λ, T ) and φ NO 2 (λ, T ) are well established (DeMore et al, 1997;Voigt et al, 2002), as is F (λ) for blacklamps (Carter et al, 2005(Carter et al, , 1995. Assuming that the wavelength dependence of the radiation passing through a small volume element located a distance x away from the lamp is independent of x, F (λ, x) may be written as F (λ)F (x), and the NO 2 photolysis frequency may be written as function of both temperature and distance from the lamp:…”

Section: Radiation Modelmentioning

confidence: 97%

Design of and initial results from a Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC)

et al. 2007

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Abstract. The design of a Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC) is described and initial results obtained from HIRAC are presented. The ability of HIRAC to perform in-situ laser-induced fluorescence detection of OH and HO 2 radicals with the Fluorescence Assay by Gas Expansion (FAGE) technique establishes it as internationally unique for a chamber of its size and pressure/temperature variable capabilities. In addition to the FAGE technique, HIRAC features a suite of analytical instrumentation, including: a multipass FTIR system; a conventional gas chromatography (GC) instrument and a GC instrument for formaldehyde detection; NO/NO 2 , CO, O 3 , and H 2 O vapour analysers. Ray tracing simulations and NO 2 actinometry have been utilized to develop a detailed model of the radiation field within HIRAC. Comparisons between the analysers and the FTIR coupled to HIRAC have been performed, and HIRAC has also been used to investigate pressure dependent kinetics of the chlorine atom reaction with ethene and the reaction of O 3 and t-2-butene. The results obtained are in good agreement with literature recommendations and Master Chemical Mechanism predictions. HIRAC thereby offers a highly instrumented platform with the potential for: (1) high precision kinetics investigations over a range of atmospheric conditions; (2) detailed mechanism development, significantly enhanced according to its capability for measuring radicals; and (3) field instrument intercomparison, calibration, development, and investigations of instrument response at a range of atmospheric conditions.Correspondence to: P. W. Seakins

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“…Reaction rates have been up-dated (DeMore et al, 1994). An efficient calculation of photolysis rates has been included (Landgraf and Crutzen, 1998).…”

Section: Model Descriptionmentioning

confidence: 99%

Results of an interactively coupled atmospheric chemistry – general circulation model: Comparison with observations

et al. 2001

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Abstract.The coupled climate-chemistry model ECHAM4.L39(DLR)/CHEM is presented which enables a simultaneous treatment of meteorology and atmospheric chemistry and their feedbacks. This is the first model which interactively combines a general circulation model with a chemical model, employing most of the important reactions and species necessary to describe the stratospheric and upper tropospheric ozone chemistry, and which is computationally fast enough to allow long-term integrations with currently available computer resources. This is possible as the model time-step used for the chemistry can be chosen as large as the integration time-step for the dynamics. Vertically the atmosphere is discretized by 39 levels from the surface up to the top layer which is centered at 10 hPa, with a relatively high vertical resolution of approximately 700 m near the extra-tropical tropopause. We present the results of a control simulation representing recent conditions (1990) and compare it to available observations. The focus is on investigations of stratospheric dynamics and chemistry relevant to describe the stratospheric ozone layer.ECHAM4.L39(DLR)/CHEM reproduces main features of stratospheric dynamics in the arctic vortex region, including stratospheric warming events. This constitutes a major improvement compared to earlier model versions. However, apparent shortcomings in antarctic circulation and temperatures persist. The seasonal and interannual variability of the ozone layer is simulated in accordance with observations. Activation and deactivation of chlorine in the polar stratospheric vortices and their inter-hemispheric differences are reproduced. Considering methane oxidation as part of the dynamic-chemistry feedback results in an improved representation of the spatial distribution of stratospheric water vapour concentrations.The current model constitutes a powerful tool to investigate, for instance, the combined direct and indirect effects of anthropogenic trace gas emissions. Key words. Atmospheric composition and structure (mid-Correspondence to: M. Dameris (martin.dameris@dlr.de) dle atmosphere -composition and chemistry) -Meteorology and atmospheric dynamics (general circulation; middle atmosphere dynamics)

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Tables of rate constants extracted from chemical kinetics and photochemical data for use in stratospheric modeling. Evaluation number 7

Cited by 1,319 publications

References 0 publications

On the volatile inventory of Titan from isotopic abundances in nitrogen and methane

On the volatile inventory of Titan from isotopic abundances in nitrogen and methane

Design of and initial results from a Highly Instrumented Reactor for Atmospheric Chemistry (HIRAC)

Results of an interactively coupled atmospheric chemistry – general circulation model: Comparison with observations

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