Recent advances in the chemistry of electronically excited atoms
About: This article is published in Chemical Reviews.The article was published on 1970-08-01. It has received 357 citations till now.
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TL;DR: In this paper, a non-equilibrium discharge in nitrogen-oxygen mixtures is developed, which almost wholly describes chemical transformations of particles in the cold (200 K
Abstract: A kinetic scheme for non-equilibrium discharge in nitrogen-oxygen mixtures is developed, which almost wholly describes chemical transformations of particles in the cold (200 K
1,558 citations
TL;DR: In this article, it was shown that an artificial increase of the mixing ratio of the oxides of nitrogen in the stratosphere by about 1×10−8 may lead to observable changes in the atmospheric ozone level.
Abstract: The distribution of the compounds NO, NO2, NO3, N2O5, and HNO3 has been calculated for different choices of relevant parameters, the values of which are uncertain. An appreciable part of the NO and NO2 is converted to NO3, N2O5, HNO3 and possibly HNO2 is the ozone layer. Reactions of odd oxygen with NO and NO2 may be the dominating reassociation processes for odd-oxygen particles in the region below 45 km which is very important for the global ozone budget. Several processes may lead to the presence of significant amounts of nitrogen oxides, nitrous acid, and nitric acid in the stratosphere. Reported variations during the solar cycle of ozone concentrations above 30 km (Dutsch, 1969) can be explained by corresponding variations in the stratospheric odd nitrogen oxide content. An artificial increase of the mixing ratio of the oxides of nitrogen in the stratosphere by about 1×10−8 may lead to observable changes in the atmospheric ozone level. Chains of reactions involving the constituents OH, H2O2, and HO2 also lead to the catalytic destruction of odd oxygen. The presence of nitric acid with a mixing ratio of about 3×10−9 in the ozone layer (Murcray et al., 1968; Rhine et al., 1969) indicates much larger OH and HO2 concentrations than can be explained solely by the reaction O(1D) + H2O → 2 OH. The reaction N2O5 + H2O → 2HNO3 followed by O + HNO3 → OH + NO3 may also be an important source of OH if the rate constants given by Jaffe and Ford (1967) are adopted. It is difficult to explain the measured nitric acid concentrations between 20 and 30 km with the reaction HO2 + NO + M → HNO3 + M. Laboratory data (Asquith and Tyler, 1969) indicate that the reaction H2O2 + NO2 → HNO3 + OH (Nicolet, 1970α) is unimportant in the atmosphere.
551 citations
TL;DR: This review is concerned with the theoretical and computational modeling of bimolecular reactions, especially with generally applicable methods for kinetics (i.e., overall rates as opposed to detailed dynamics), and includes a basic theoretical framework that can be used for gas-phase thermal reactions, gas- phase microcanonical and state-selected reactions, and condensed-phase chemical reactions.
Abstract: A review of the theoretical and computational modeling of bimolecular reactions is given. The review is divided into several sections which are as follows: gas-phase thermal reactions; gas-phase state-selected reactions and product state distributions; and condensed-phase bimolecular reactions. The section on gas-phase thermal reactions covers the enthalpies and free energies of reaction, kinetics, saddle points and potential energy surfaces, rate theory for simple barrier reactions and bimolecular reactions over potential wells. The section on gas-phase state-selected reactions focuses on electronically adiabatic reactions and electronically nonadiabatic reactions. Finally, the section on condensed-phase bimolecular reactions covers reactions in liquids, reactions on surfaces and in solids and tunneling at low temperature.
534 citations
TL;DR: In this article, a self-consistent kinetic model was developed to study dc flowing glow discharges in N/sub 2/O/Sub 2/ mixtures, which includes the calculation of electron energy distribution functions and electron rate coefficients coupled with detailed vibrational kinetics of N/ sub 2/ molecules, chemical kinetics taking into account of neutral, excited and charged species, interaction of N and O atoms at the discharge tube wall, and the thermal balance of the discharge.
Abstract: A self-consistent kinetic model is developed to study dc flowing glow discharges in N/sub 2//O/sub 2/ mixtures. This model includes the calculation of electron energy distribution functions and electron rate coefficients coupled with detailed vibrational kinetics of N/sub 2/ molecules, chemical kinetics taking into account a large set of neutral, excited and charged species, interaction of N and O atoms at the discharge tube wall, and the thermal balance of the discharge. The results of this model agree reasonably well with the measurements of the electronic density, the gas temperature, the reduced electric field, the vibrational temperature of N/sub 2/ and the concentration of O, N atoms, NO molecules, N/sub 2/(C), N/sub 2//sup +/(B), and NO(/spl gamma/) excited states. The comparison was performed in a N/sub 2/-O/sub 2/ discharge at pressure p=2 Torr, for discharge currents I=15, 30, and 80 mA, a flow rate Q=100 sccm, and O/sub 2/ percentages ranging from 0 up to 100%,. >
350 citations
TL;DR: In this article, a simple general method for obtaining selection rules for the ro-vibronic states of reactant and product molecules connected in a reactive collision is discussed, neglecting only the coupling with nuclear spin, rather stringent restrictions are found to occur in systems involving three and more identical nuclei.
Abstract: A simple general method for obtaining selection rules for the ro-vibronic states of reactant and product molecules connected in a reactive collision is discussed. Neglecting only the coupling with nuclear spin, rather stringent restrictions are found to occur in systems involving three and more identical nuclei. Several radical and ion molecule reactions of current interest are used to illustrate this finding. Even more restrictive selection rules are found when assuming weak coupling (‘ incomplete exchange of identical nuclei ’) in the intermediate reaction complex. These include the well-known selection rules for inelastic collisions of molecules with several identical nuclei, but less trivial examples with chemical reaction are also presented. The symmetry corrections and nuclear spin statistics in statistical theories of scattering (including the prior distributions for the information-theoretic approach) are derived. Further applications are discussed briefly.
292 citations