Criegee intermediates, which are the result of ozonolysis of alkenes, play a key role in many chemical and physical processes in the Earth’s atmosphere. Their reactions with various atmospheric compounds are responsible for formation of hydroxyl radicals, atomic oxygen and hydrogen, sulfuric and nitric acids, and other chemically active radicals and molecules. In this work we have considered collisional-induced chemical reactions between three simple Criegee intermediate molecules: CH2OO, CH3CHOO, and (CH3)2COO with methane, which is a well-known active greenhouse gas. Methane concentration rapidly growths last decades that causes serious concern to the global scientific community. It was established that reactions between methane and Criegee Intermediates can follow through two main routes. One of them occurs over exchange of oxygen and hydrogen atoms upon collision and leads to the formation of methanol. Another one pass through the formation of an intermediate complex with a deep energy minimum, and produces OH radicals and a variety of other products, among which are acetone, acetaldehyde, formaldehyde, propaldehyde, methanol, water molecules, and others. In this work, the both kinds of the reactions have been studied, and the relative reaction rates of both pathways have been compared.

Benzene is one of the most common classes of industrial chemicals. As a rule, it enters the atmosphere as a result of man-made accidents and during the evaporation of solvents. Benzene and its derivatives are toxic and have a negative impact on the environment and the human body. Therefore, issues related to the transformation of benzene in the atmosphere are of increased interest. In this study, the structures and electronic energies of equilibrium configurations and transition complexes of the C6H6F and C6H6F+ systems are calculated using the density functional theory. It is shown that the interaction of benzene with atomic fluorine can proceed through two channels: the elimination of hydrogen with the formation of a phenyl radical and the addition of a fluorine atom with the formation of an ipso-fluorocyclohexadienyl radical. It is established that for the dissociation of the ipso-fluorocyclohexadienyl radical into fluorobenzene and atomic hydrogen, it is necessary to expend about 27 kcal/mol. This indicates a low probability of this process occurring at low temperatures. Under experimental conditions, when the temperature of fluorine atoms is about 1000 K, the ipso-fluorocyclohexadienyl radical decomposes to form fluorobenzene. In this case, the occurrence of secondary reactions is unlikely. The conclusions drawn from the analysis of the results of quantum chemical calculations are in close agreement with the experimental data.

Pentalene and its chemically active isomers benzocyclobutadiene and phenylacetylene play an important role in processes of creation and destruction of polyaromatic hydrocarbons (PAHs), which are the main element of soot microparticles, abundantly arising due to burning of organic fuels in internal combustion engines, power plants, and natural fires. They are one of the most dangerous anthropogenic air pollutants, causing serious negative impacts on human health. The probable dissociation mechanisms of pentalene and its isomers, as far as their cations and dications are considered. It is shown that the loss of electrons during ionization changes the aromatic/antiaromatic properties of pentalene and its isomers to the opposite ones. At low values of internal energy the main dissociation pathway for neutral molecules and cations is the acetylene elimination. At high values of internal energy H atom loss becomes the major reaction.

In recent years numerous satellite data on the yellow glow of the sodium layer (located at an altitude of 85–95 km from the Earth’s surface) have become available. Studies of optical activity at sodium D‑line frequencies are necessary for a better understanding of the plasma-chemical processes occurring in the mesosphere. It should be taken into account that these processes occur in a neutral environment, where molecular nitrogen is the main component. In this study the analytical numerical expressions for the elements of a 3 × 3 matrix of the interaction between Na(2Pj) and N2( X^1Σ _g^ + ) and the interaction potential between Na(2S1/2) and N2( X^1Σ _g^ + ) are obtained at medium and large interparticle distances that determine the collisional broadening of the radiation lines. The exchange, quadrupole–quadrupole, dispersion, and spin–orbit interactions are taken into account. The exchange interaction between the valence Na electron and N2( X^1Σ _g^ + ) molecule is described by the local Hellman pseudopotential. The effect of the overlap between Na(2S1/2,2Pj) and N2( X^1Σ _g^ + ) electron densities is taken into account in the evaluation of long-range quadrupole–quadrupole and dispersion interactions.

В настоящее время большое внимание исследователей уделяется многоуровневому моделированию сложных газофазных физико-химических процессов, протекающих в атмосфере, при горении и в плазмохимических установках. Одним из важнейших микроскопических процессов, определяющих перенос излучения в указанных системах, является уширение спектральных линий при столкновениях излучающих атомов с атомами в основном состоянии. В данной работе предложена формулировка единой франк-кондоновской теории уширения спектральных линий в газах в терминах теории медленных атомных столкновений и неадиабатических переходов. Это позволяет по виду адиабатических потенциальных кривых сталкивающихся атомов выбирать наиболее эффективные каналы приводящих к уширению столкновений и на этой основе применять достаточно простые модели, разработанные в теории неадиабатических переходов. В качестве примера использования такого подхода проведены расчеты центра и крыльев контура спектральной линии излучения Ar( 3 P 1 ) → Ar( 1 S 0 ) возбужденных атомов аргона в собственном газе.

A great deal of attention is being paid by researchers to the multilevel modeling of complex gas-phase physicochemical processes occurring in the atmosphere, during combustion, and in plasma-chemical installations. One of the most important microscopic processes determining the transfer of radiation in these systems is the broadening of spectral lines in collisions of radiating atoms with atoms in the ground state. In this paper, we propose a formulation of the unified Franck-Condon theory of the broadening of spectral lines in gases in terms of the theory of slow atomic collisions and nonadiabatic transitions. This makes it possible to select the most efficient channels leading to the broadening of collisions based on the form of the adiabatic potential curves of the colliding atoms and, on this basis, apply fairly simple models developed in the theory of nonadiabatic transitions. As an example of using this approach, the center and wings of the of the spectral line contour of the Ar( 3 P 1 ) → Ar( 1 S 0 ) emission of excited argon atoms in their own gas are calculated.

Criegee intermediates, which are the products of the ozonolysis of alkenes, play a key role in many chemical and physical processes in the atmosphere. Their reactions with other atmospheric compounds are responsible for the formation of hydroxyl, methyl, hydrogen radicals, nitric and sulfuric acids, and others. Methane is an active greenhouse gas whose concentration has increased rapidly in the last several decades. In this work, we consider the interaction between these two important atmospheric compounds. We choose the three simple Criegee intermediate (CI) molecules: formaldehyde oxide (CH2OO), acetaldehyde oxide (CH3CHOO), and acetone oxide ((CH3)2COO). Some reactions between methane and these Cis have been studied earlier as possible pathways for deactivating methane as well as a source of methanol formation due to molecular collisions in the atmosphere. In the present study, we extend the consideration to the case when an intermediate energetically stable complex is formed after collision. We found that this complex could easily decompose to form an OH radical and another unstable fragment, which can quickly dissociate into CH3 radicals, atomic hydrogen, acetone, acetaldehyde, propaldehyde, methyl alcohol, water, and others, depending on the type of CI being reacted with. These compounds can actively interact with other atmospheric components and change their physical and chemical properties. In addition, CI with a methyl substituent is shown to have increased energy in transition states and minima, resulting in slower reaction rates.

The reaction of benzene with fluorine atoms may be of interest as a source of phenyl and ipso-fluorocyclohexadienyl radicals or as a method for fluorobenzene gas phase synthesis. The structures and electronic energies of the equilibrium configurations and transition complexes of the C6H6F system are calculated in the density functional approximation. It was found that the interaction of benzene with atomic fluorine can proceed via two channels: hydrogen abstraction with the phenyl radical formation, and hydrogen substitution with the ipso-fluorocyclohexadienyl radical as primary product. Then the dissociation of the ipso-fluorocyclohexadienyl radical leads to creation of fluorobenzene and atomic hydrogen. The initiation of this reaction requires the activation energy near 27 kcal/mol, which indicates the low probability of this process, occurring at temperatures close to the standard (298 K). The calculations of the fluorocyclohexadienyl isomers and their cations also indicate that the formation of fluorobenzene as a product of secondary reactions is unlikely. The conclusions are confirmed by experimental data.

Carbonyl oxides, or Criegee intermediates, play an important role in many physicochemical processes occurring in the Earth's atmosphere. Criegee intermediates are chemically active compounds that easily react with other atmospheric components, promoting the formation of OH and CH3 radicals, toxic compounds of nitrogen, and various acids. Traditionally, the literature considers reactions involving only those carbonyl oxides that are the most stable in the troposphere under the standard atmospheric conditions. In this study, it is shown that in the mesosphere and ionosphere, where the total concentration of molecules is low and the intensity of UV radiation and the number of free electrons are high, reactions involving electronically excited states of the Criegee intermediates CH3CHOO play a significant role. In this case, we should take into account the features of the decomposition of all isomers of the CH3CHOO molecule.

Determination of the physical mechanisms of energy transfer from tropospheric disturbances to the ionosphere is one of the fundamental problems of atmospheric physics. Both regular events (passage of the solar terminator) and irregular ones (meteorological storms, earthquakes, solar eclipses, etc.) lead to such disturbances. This paper presents the results of observations of tropospheric and ionospheric disturbances during the passage of the solar terminator, solar eclipse, and meteorological storm. Lidar sounding shows that during the development of these events, regions are formed in the troposphere with a noticeable increase in the amplitudes of variations in density, pressure, and temperature with periods corresponding to acoustic and internal gravity waves (AWs and IGWs, respectively). Simultaneous satellite measurements demonstrate the response of the ionosphere to tropospheric disturbances. Based on the observational data for each of the events, the characteristic periods and the time and spatial scales of variations are determined. It is found that the response time of the ionosphere to tropospheric disturbances is 30–40 min. As a result of numerical modeling using the AtmoSym software package, it is shown that nonlinear and dissipative processes in the thermosphere lead to the formation of sources of secondary waves with periods longer than those of the primary AWs and IGWs propagating vertically upward from the troposphere into the thermosphere. The influence of tropospheric disturbances on the operation of global navigation satellite systems is also discussed.

Kinetic equations whose solution requires the cross sections of elastic and inelastic electron scattering on atoms and molecules are used to solve numerous problems in plasma physics. To construct cross sections, modern calculations of the characteristics of resonant electron scattering are required, which are based on the use of methods operating with a complex Hamiltonian. The complex absorbing potential (CAP) method is used for a similar class of problems, but is characterized by unstable estimates of the resonance parameters. In this study, for a single-channel problem with an explicit parameterization of the scattering matrix, we analyze the features of the CAP method. It is shown that, depending on the choice of the initial conditions, there are two types of CAP-trajectories with real limits as the complex scaling factor tends to zero. The trajectories of the first type are characterized by the presence of the optimal point, and the trajectories of the second type are characterized by the presence of a closed section in the vicinity of the resonance. It is also shown that for finite values of the scaling factor, the CAP trajectory does not pass through resonance. These conclusions are qualitatively confirmed by the results of the independent application of the CAP method to the calculations of model and many-electron systems.

Determination of the physical mechanisms of the energy transfer of tropospheric disturbances to the ionosphere is one of the fundamental problems of atmospheric physics. This article presents the observational results of tropospheric and ionospheric disturbances during the passages of the solar terminator and solar eclipse. Lidar observations showed the occurrence of tropospheric regions with noticeably increased amplitudes of density, pressure, and temperature variations with periods corresponding to acoustic and internal gravity waves, which were generated in the troposphere during the development of these events. Simultaneous satellite measurements demonstrate the response of the ionosphere to these tropospheric disturbances. Based on the experimental data, we determine the typical periods and spatial scales of variations. It is shown that the response time of the ionosphere to tropospheric disturbances is 30–40 min.

Criegee intermediates, or carbonyl oxides, are formed during the ozonolysis of alkenes, which are typical anthropogenic air pollutants. They play an important role in a variety of chemical reactions occurring both in the near-surface layer and in the upper layers of the Earth’s atmosphere. In the lower troposphere, Criegee intermediates have time to lose their internal vibrational energy due to collisions with nitrogen molecules and interact with other components of the atmosphere in their original form. The products of such reactions are, for example, sulfuric and nitric acids. In the stratosphere and mesosphere, Criegee intermediates decompose into chemically active fragments that participate in a variety of secondary reactions. In this study, we consider the processes of decomposition of the methylcarbonyloxide isomer anti -CH 3 CHOO in the upper atmosphere. It is shown that the main decay products are atomic oxygen, methane, CO, CO 2 , and OH radicals. The formation of more complex chemically active fragments is also possible.

The increase in the concentration of methane in the atmosphere as a result of anthropogenic activity, melting of permafrost, and decomposition of gas hydrates on the seabed has attracted close attention of the scientific community in recent decades due to the potentially dangerous effect of methane on the ozone layer and the Earth’s climate. According to various estimates, the greenhouse effect from methane is dozens of times stronger than the similar effect from carbon dioxide; therefore, the processes of methane transfer to the upper layers of the Earth’s atmosphere, as well as its lifetime and interaction with other substances present in the stratosphere, mesosphere and ionosphere are of great scientific interest. In this study, we consider the chemical reactions occurring during collisions of methane molecules with methyl carbonyl oxide CH3CHOO in the upper atmosphere. It is shown that this process initiates the formation of the OH radical and starts a cascade of chemical reactions, the products of which are CH3, atomic hydrogen, acetone, acetaldehyde, propaldehyde, methyl alcohol, and water. These compounds are able to actively influence the composition of the atmosphere and its physicochemical properties.

The measurements of Montenbrook et al. to determine the water surface level of the Walchensee alpine lake in Bavaria (Germany) are a vivid example of the manifestation of the peculiarities of the relationship between the GPS satellite system as a source and remote sensing of the Earth’s surface. The experiments were conducted in 2007 in the framework the GORS (GPS Occultation, Reflectometry and Scatterometry) program. The authors described the observed features in detail but did not provide their physical justification. In this study, it is shown that the observed effects are caused by the resonant interaction of electromagnetic waves with a medium containing Rydberg molecular complexes. They are the main reason for the delay of satellite constellation signals at altitudes of 60 to 110 km.