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  • 1
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    Kinetics and product studies of the BrO + ClO reaction - Implications for Antarctic chemistry (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Discharge flow-mass spectrometry and flash photolysis-UV spectrometry were used to investigate the reaction of ClO with BrO over the temperature range of 220-400 K and the pressure range of 1-760 Torr. Rate constants were determined for: (1) Br + ClOO, (2) Br + OClO, and (3) BrCl + O2. It is found that the rate constants for the overall reaction and each reaction branch are inversely dependent on temperature and independent of pressure. For temperatures found in the Antarctic stratosphere, the rate coefficients for the channels yielding ClOO and OClO are a factor of 2-3 larger than previously estimated.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 15; 887-890
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  • 2
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    A kinetics study of the homogeneous and heterogeneous components of the HCl + ClONO2 reaction (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The kinetics of the reaction HCl + ClONO2 to Cl2 + HNO3 were investigated at 298 K using a flow reactor with FTIR analysis to assess the importance of this reaction for stratospheric chemistry. The observed reaction was characteristic of a heterogeneous process; an upper limit of 5 x 10 to the -18th cu cm/molecule per s was obtained for the homogeneous gas phase rate constant. From calculations of the first order wall rate constant, estimates were made of the reaction rate on stratospheric aerosols. Because both HCl and ClONO2 need to be adsorbed on the particle surface, the reaction will be of negligible importance under most stratospheric conditions.
    Keywords: GEOPHYSICS
    Type: (ISSN 0094-8276); 13; 1351-135
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  • 3
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    Chemical kinetics and photochemical data for use in stratospheric modeling (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: As part of a series of evaluated sets, rate constants and photochemical cross sections compiled by the NASA Panel for Data Evaluation are provided. The primary application of the data is in the modeling of stratospheric processes, with particular emphasis on the ozone layer and its possible perturbation by anthropogenic and natural phenomena. Copies of this evaluation are available from the Jet Propulsion Laboratory.
    Keywords: GEOPHYSICS
    Type: NASA-CR-192795 , NAS 1.26:192795 , JPL-PUBL-92-20
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  • 4
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    Chemical kinetics and photochemical data for use in stratospheric modeling: Evaluation number 11 (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This is the eleventh in a series of evaluated sets of rate constants and photochemical cross sections compiled by the NASA Panel for Data Evaluation. The primary application of the data is in the modeling of stratospheric processes, with special emphasis on the ozone layer and its possible perturbation by anthropogenic and natural phenomena.
    Keywords: GEOPHYSICS
    Type: NASA-CR-198863 , JPL-PUBL-94-26 , NAS 1.26:198863
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  • 5
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    Stratospheric chemistry (1985)
    In:  CASI
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    Publication Date: 2019-08-13
    Description: Recent improvements in the data base for the currently identified reactions describing the chemistry of the major families of trace gas species, HO(x), NO(x), ClO(x), and hydrocarbons are assessed. The important coupling reactions between the families are introduced progressively. Chemical aspects such as heterogeneous reactions and reactions of sodium species, the importance of which are not yet completely established, are discussed. Recent attempts to reconcile some of the more unexpected kinetic behavior which has emerged from the extensive experimental studies of key reactions with current reaction rate theory are also examined. The uncertainties in the current kinetic and photochemical data base is given. The prospects for improvement of data for known reactions of atmospheric importance as well as for the identification of gaps in the chemical description of the atmosphere.
    Keywords: GEOPHYSICS
    Type: Atmospheric Ozone 1985. Assessment of our Understanding of the Processes Controlling its Present Distribution and Change, Volume 1; 32 p
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  • 6
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    Report on concentrations, lifetimes, and trends of CFCs, halons, and related species (1994)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The atmospheric lifetimes of molecules containing chlorine and bromine are the dominant parameters influencing their ability to promote enhanced ozone destruction in the stratosphere. The purpose of this report is to assess the present state of knowledge of the lifetimes of halocarbons using two complementary approaches. First, a time series of measurements of gas concentrations is used together with information on their emissions histories and a computational model of atmospheric circulation and chemistry to infer lifetimes through a mass balance approach. Second, an atmospheric chemical-dynamical model is used with detailed information on the chemistry and spectroscopy of the molecules of interest to calculate lifetimes. The lifetimes determined by these two methods are then compared. Attention is focused most closely on fully halogenated chlorine- and bromine-containing molecules, primarily the chlorofluorocarbons, and the halons, because of their ability to deliver chlorine and bromine to the stratosphere. Some attention will be given to those molecules containing hydrogen, which are subject to removal in the troposphere primarily by reaction with OH and by other processes.
    Keywords: GEOPHYSICS
    Type: NASA-RP-1339 , NAS 1.61:1339
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  • 7
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    Spatial variation of ozone depletion rates in the springtime Antarctic polar vortex (1990)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: An area-mapping technique, designed to filter out synoptic perturbations of the Antarctic polar vortex such as distortion or displacement away from the pole, was applied to the Nimbus-7 TOMS (Total Ozone Mapping Spectrometer) data. This procedure reveals the detailed morphology of the temporal evolution of column O3. The results for the austral spring of 1987 suggest the existence of a relatively stable collar region enclosing an interior that is undergoing large variations. A simplified photochemical model of O3 loss and the temporal evolution of the area-mapped polar O3 are used to constrain the chlorine monoxide (ClO) concentrations in the springtime Antarctic vortex. The O3 loss rates could be larger than deduced here because of underestimates of total O3 by TOMS near the terminator.
    Keywords: GEOPHYSICS
    Type: Science (ISSN 0036-8075); 248; 721-724
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  • 8
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    Rate of formation of the ClO dimer in the polar stratosphere - Implications for ozone loss (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The gas-phase recombination of chlorine monoxide (ClO) has been investigated under the conditions of pressure and temperature that prevail in the Antarctic stratosphere during the period of maximum ozone (O3) disappearance. Measured rate constants are less than one-half as great as the previously accepted values. One-dimensional model calculations based on the new rate data indicate that currently accepted chemical mechanisms can quantitatively account for the observed O3 losses in late spring (17 September to 7 October). A qualitative assessment indicates that the existing mechanisms can only account for at most one-half of the measured O3 depletion in the early spring (28 August to 17 September), indicating that there may be additional catalytic cycles, besides those currently recognized, that destroy O3.
    Keywords: GEOPHYSICS
    Type: Science (ISSN 0036-8075); 245; 1095-109
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  • 9
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    Kinetics of O3 destruction by ClO and BrO within the Antarctic vortex - An analysis based on in situ ER-2 data (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The kinetics of ozone destruction within the Antarctic polar vortex are studied via simultaneous in situ observations of ClO, BrO, O3, N2O, pressure, and temperature. It is found that the chlorine dimer mechanism rate, limited by the reaction ClO + ClO + M yields ClOOCl + M, contributes the most to the integrated rate of ozone destruction within the vortex on isentropic surfaces between altitudes of 14 and 18.3 km.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 11480-11
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  • 10
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    Hydrochloric acid and the chlorine budget of the lower statosphere (1994)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: Concentrations of HCl measurements in the lower stratosphere in 1993 by the ALIAS instrument on the ER-2 aircraft reveal that only 40% of inorganic chlorine (Cl(y), inferred from in situ measurements of organic chlorinated sources gases) is present as HCl, significantly lower than model predictions. Although the sum of measured HCl, ClO and ClONO2, the latter inferred from measurements of ClO and NO2 equals Cl(y) to within the incertainty of measurement, it is systematically less than Cl(y) by 30-50%. This discrepancy suggests that concentrations of ClONO2 may exceed those of HC; near 20 km altitude, consistent with a slower photolysis rate for ClONO2 than calculated using recommended cross sections. Comparison of profiles of HCl measured during 1992 and 1193 at mid-latitudes by balloon (BLISS and MARKIV), space shuttle (ATMOS), and satellite (HALOE) instruments with the aircraft data reveal an apparent pressure dependence to the HCl to Cl(y) ratio, consistent with a factor of 3-10 reduction in the photolysis rate for ClONO2 at ER-2 altitudes. However, the diurnal variation of ClO is well-simulated by models using the recommended photolysis rate, and simulations measurements of ClONO2 and HCl at mid-latitudes by ATMOS and MARKIV report HCl (HCL+ ClONO2) ratios greater than or equal to 50%. Premliminary measurements by ALIAS in the southern hemisphere report HCl/Cl(y) values of about 75%.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 23; p. 2575-2578
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