O3, reactions

Like the previous reaction, multiple pathways in the HO2 - - O3 reaction arise because of the participation of identical atoms. However, in this case the two... 

The HO2 + O3 reaction is an important contributor to the catalytic loss of ozone in the lower stratosphere through the cycle... 

Irradiation of the UDMH + Oq Reaction Products. One experiment was conducted in which the UDMH + O3 reaction products (with UDMH in slight excess) were irradiated by sunlight. The results are shown in Table I and Figure 1. It can be seen that rapid consumption of UDMH, the nitrosamine, and HONO occurred, with N-nitrodimethylamine (also dimethyInitramine) and additional formaldehyde being formed. The formation of nitramine upon irradiation of the nitrosamine is consistent with results of previous studies in our laboratories (9,10), and probably occurs as shown ... 

The sudden consumption of the remaining UDMH, and the increased relative importance of N-nitrosamine formation at -30 minutes into the photolysis can be rationalized by assuming that at that time the [NO I/ENO] ratio, and thus the photostationary state [O3], has become sufficiently high that O3 may be reacting with the hydrazine directly, and that reaction (3) begins to dominate over reaction (10). This results in higher rates of UDMH consumption by the OH radicals formed in the UDMH + O3 reaction (1), and by the OH radicals generated by the reaction of NO... 

Our results shed some light on the mechanism for the conversion of sulfides to SO2 and MSA in the atmosphere and in chamber experiments. If the NO2 (or an O3) reaction dominates, then CH3S will be converted to CH3SO ... 

This relates the detector signal to the intensity (I) of light produced, the efficiency of light collection (G), and the PMT sensitivity (A). The intensity of light produced is expressed as the product of the NO concentration, the flow rate, and a series of fractions (fraction of N02 formed in the excited state, fraction of NO2 decaying radiatively, and the fraction of NO-O3 reaction occurring within view of the detector). 

Over the past 10-20 years the kinetic data base for reaction of OH radicals with atmospheric pollutants has improved dramatically to a point where uncertainties in koH are typically in the range 10-20%. Critically evaluated data for OH radical reactions of atmospheric importance are available in several excellent reviews [8,15,22,24,25]. Likewise there are also extensive databases available for NO3 [8,13] and O3 reactions [8]. 

The halogen release mechanism is autocatalytic and has become known as the Bromine explosion . The Br2 produced in reaction (2.74) is rapidly photolysed, producing bromine atoms that can be oxidised to BrO by O3 (reaction (2.76))... 

Ozonolysis of pinenes contributes to OH radical and SOA formation. The latter has been speculated to be responsible for the formation of "blue haze". Hence, it is of vital importance to quantitatively understand the roles of ozonolysis of a- and jS-pinenes on both OH and SOA formation in the troposphere. The O3 reaction with both pinenes follows the Criegee mechanism, similar to that of iso-prene. The initial step proceeds through cycloaddition of O3 to the C=C double bond of each pinene, forming a primary ozonide (POZ). The available reaction energy is retained as the internal energy of the product, resulting in formation... 

The primary tropospheric oxidants are OH, O3, and NO3, with "OH and O3 reactions with hydrocarbons dominating primarily during daytime hours, and NO3 reactions dominating at night. Rate constants for the reactions of many different aromatic compounds with each of the aforementioned oxidants have been determined through laboratory experiments [16]. The rate constant data as well as atmospheric lifetimes for the reactions of toluene, m-xylene, p-xylene, m-ethyl-toluene, and 1,2,4-trimethylbenzene appear in Table 14.1. Only these particular aromatic compoimds will be discussed in this review paper, since much of the computational chemistry efforts have focused on these compounds. When considering typical atmospheric concentrations of the major atmospheric oxidants, OH, O3, and NO3 of 1.5 x 10, 7 x 10, and 4.8 x 10, molecules cm , respectively [17], combined with the rate constants, it is clear that the major atmospheric loss process for these selected aromatic compounds is reaction with the hydroxyl... 

An induction period with respect to olefin consumption is also observed in the photochemical laboratory experiments, thus indicating the buildup of an intermediate. When illumination is terminated in these experiments, the excess rate over the total of the O and O3 reactions disappears. These and other results suggest that the intermediate formed is photolyzed and contributes to the concentration of the major species of concern. 

Bodenstein et al. studied the CI2-O3 reaction at 35° and 50 °C. The reaction was preceded by an induction period which varied inversely with [O3]. After the induction period, the rate law... 

This chapter demonstrates the important role chemical dynamics play in the phenomenology of meteors and the associated ionospheric consequences. Although considerable work has been done to derive the important parameters of the relevant molecular and atomic collisions under extreme conditions, there are still many poorly known cross sections that are required to properly model the macroscopic observables based on microscopic processes. The current state of knowledge is best for low energy metal ion collisions, where the extensive work of the Armentrout group at the University of Utah (see Sec. 3.3.2) has made the most valuable and extensive contribution. A missing component are cross sections for Me+ -t- O3 reactions which could be an efficient source of metal oxide ions that dissociatively... 

In the previous discussion of O-atom and O3 reactions, the hydroxyl radical is a prominent product. As will be seen later, OH radicals are also produced in the photolyses of aldehydes and nitrous acid. The resulting OH chain mechanism for propylene is summarized below ... 

T he role of olefin-ozone (O3) reactions in generating aerosols from organic vapors and the influence of oxygen (O2) and water vapor on aerosol production in these reactions have been studied here. Kinetic data were examined to try to derive a mechanism for forming aerosols from organic vapors. 

One should add that the gas phase mixing ratio of O3 is important for these cycles, because the production of XO, and therefore the loss of Ojc (via XO + HO2 and XO + NO2), is promoted by O3 (reaction (3)). If O3 mixing ratios are small, halogen activation is slowed down as shown by Wagner et al. (2002) and von Glasow et al. (2002a). 

Atkinson has also produced evaluations for tropospheric modelling but of the species dealt with (OH, NO3 and O3 reactions with organic compounds) only the reactions of OH are directly relevant to combustion [64, 65]. 

Since the NO reaction above is 1000 times faster than the O3 reaction, at an O3 concentration of 60 ppbv the rates of these two reactions will be comparable when the NO concentration is 60 pptv. At NO concentrations lower than this, there will be NO, production, and at levels higher than 60 pptv there will be NO , destruction. Stedman and Shetter (1983) suggest that this reaction sequence could account for a small production of NO in regions of the globe with low NOj concentrations, and a major sink for it in areas heavily impacted by anthropogenic NO emissions. However, this mechanism remains highly speculative. 

We can use the O/O3 reaction described in the last section as an illustration of the factors affecting rate ... 

In NOJ, cycle 2, which is important in the lower stratosphere, the nitrate radical NO3 is formed from the N02 -I- O3 reaction... 

The 03-depletion cycle might involve photolysis of Br2) followed by the Br + O3 reaction and... 

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