Ionospheric chemistry

From a practical standpoint, much of the interest in the role of excited states in ionic interactions stems from their importance in ionospheric chemistry.Ih In addition, it has been realized more recently that certain ion-neutral interactions offer a comparatively easy means of populating electronically excited reaction products, which can produce chemiluminescence in the visible or UV region of the spectrum. Such systems are potential candidates for practical laser devices. Several charge-transfer processes have already been utilized in such devices, notably He+(I,He)I + and He2+(N2,2He)N2+.3 Interest in this field has stimulated new emphasis on fundamental studies of luminescence from ion-neutral interactions. 

E. Oran and T.R. Young, "Numerical Modeling of Ionospheric Chemistry and Transport Processes" Journal of Physical Chemistry, 81, 2463, (1977). 

Another reaction of minor importance to ionospheric chemistry is the reaction of Oj with NO. Previous studies have shown that the drift tube dependence and the temperature dependence up to 900 K are flat. The measurements up to 1400 K, continue this trend and show that neither translational, rotational, or vibrational energy has a large effect on the reactivity. 

We have briefly mentioned the use of data on IMR in plasma modeling and for the understanding of interstellar molecular synthesis as well as of ionospheric chemistry, and we also want to point out the applications of IMR in various methods of chemical ionization. The most recent one, developed in our laboratory, namely proton-transfer reaction mass spectrometry (PTR-MS), allows for on-line monitoring of volatile organic compounds at levels as low as a few parts per trillion and is therefore applicable for environmental, food, and medical research involving investigations of fast metabolic and enzymatic processes. 

A Review of Jovian Ionospheric Chemistry, Wesley T. Huntress, Jr. 

Clearly, further work is needed to more closely determine the actual values of qe(H3 ) over a range of temperatures, in view of the importance of even small qg(H3 ) values to diffuse interstellar chemistry (E.F. van Dishoeck in these Proceedings) and to Jovian ionospheric chemistry (A. Dalgarno in these Proceedings). However, experimental techniques have yet to be developed to do this. 

Another important problem in the atmospheric chemistiy models of Titan is the handling of the uncertainty of reaction branching ratios. This can be an important issue for the uncertainty analysis of many other reaction kinetic models. Chemical kinetic databases provide the uncertainty of rate coefficients independently of each other. Yet, for multichannel reactions using a direct method, it is easier to measure the overall rate coefficient than the rate coefficients of the constituent reaction steps. The branching ratios are then determined in other measurements. However, it is important to note that the branching ratios are correlated, since their sum has a unit value. Carrasco et al. (Carrasco and Pemot 2007 Plessis et al. 2010) demonstrated that the correlated branching ratios follow a Dirichlet distribution. The method was applied to the case of Titan ionospheric chemistry and used for the estimation of the effect of branching ratio correlations on the uncertainty of calculated concentrations. 

Carrasco, N., Dutuit, O., Thissen, R., Banaszkiewicz, M., Pemot, P. Uncertainty analysis of biinolecular reactions in Titan ionosphere chemistry model. Planetary Space Sci. 55, 141-157 (2007)... 

In this section, the wide diversity of teclmiques used to explore ion chemistry and ion structure will be outlined and a sampling of the applications of ion chemistry will be given in studies of lamps, lasers, plasma processing, ionospheres and interstellar clouds. 

Peter Warneck. Chemistry of the Natural Atmosphere. 1988 S. Pal Arya. Introduction to Micrometeorology. 1988 Michael C. Kelley. The Earth s Ionosphere. 1989 William R. Cotton and Richard A. Anthes. Storm and Cloud Dynamics. 1989... 

In this section, the chemical dynamics of meteor events are examined in greater detail. The present discussion addresses those processes that play an important role in the observations treated earlier. As iterated above, due to their high reactivity, high luminosity and low ionization potentials, the collision dynamics of metal atoms and ions play a prominent role in the ionospheric meteor phenomenology, and are therefore the focus of this section. There is a considerable body of literature on gas-phase metal chemistry in thermal equilibrium. During the past 15 years, these thermally... 

Air Force Geophysics Laboratory, Ionospheric Interactions Division. Hanscom AFB, Massachusetts 01731, Department of Chemistry. University of Maryland, Baltimore County Campus, Baltimore, Maryland 21228, and Department of Chemistry, University of California, Berkeley, California 94720. Received May 11, 1988... 

Eegley B. and Treiman A. H. (1992) Chemistry of atmosphere-surface interactions on Venus and Mars. In Venus and Mars Atmospheres, Ionospheres, and Solar Wind Interactions, Geophysical Monograph 66 (eds. J. G. Luhmann, M. Tatrallyay, and R. O. Pepin). American Geophysical Union, Washington, DC, pp. 7-71. 

The relevance of the above kind of electronic shape resonance to chemistry Is twofold. First, In environments such as plasmas, electrochemical cells, and the ionosphere, where free electrons are prevalent, the formation of such temporary anions can provide avenues for the free electrons to "cool down by transferring kinetic energy to the Internal (vibrational and/or electronic) degrees of freedom of the fragment. (6-14) Second, metastable states may play Important roles in quenching excited electronic... 

Previously, the conventional wisdom was that vibrational energy played a major role in reactivity and that rotational energy could largely be ignored. In the ionosphere, most of the chemistry involves only monatomic and diatomic ions and neutrals, and therefore very little vibrational excitation is present at temperatures below 900 K. Thus, the impact of both rotational and vibrational energy was not seriously considered in the high temperature regions of the ionosphere. A notable... 

As mentioned in the Introduction, much of the impetus for building the HTFA came from the desire to measure relevant ion-molecule reactions over the complete temperature range of the Earth s ionosphere. Figure 2 shows a simplified schematic of the ion chemistry of the upper ionosphere. While several ions are produced initially, the diatomic ions recombine with electrons rapidly and the slowly recombining O" " is left as the dominant ionic species. Reactions that convert O" " to diatomic ions, speed up recombination, and are therefore extremely important in controlling the plasma density of the ionosphere. In order of importance, the three most important neutrals are N2, O2, and NO and these are discussed first. The N" " atomic ion, not shown in Figure 2, is present in small concentrations. The reaction of N" " with O2 has been studied as a function of temperature as well as several reactions of diatomic ions of ionospheric importance and these are also discussed below. 

Figure 2. Simplified ion chemistry scheme for the E-region of Earth s ionosphere. The reaction of O with Nt...

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