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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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(3P1) → Ar(1S0) emission of excited argon atoms in their own gas are calculated. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The diagnostics of nonequilibrium two-temperature plasma parameters in the D and E layers of the lower ionosphere are required to improve the operation of satellite navigation systems, flight tests with the use of gas-discharge devices, and remote sensing of the Earth's surface. Together with the main neutral atmospheric molecules of nitrogen and oxygen, excited states of oxygen atoms play an important role in the exchange reactions. This work is devoted to calculating the concentration of atomic oxygen generated during photodissociation in the E layer of the Earth's ionosphere (at altitudes from 90 to 105 km). The calculation results are in a good agreement with the existing experimental and theoretical data. The role of direct dissociation of oxygen molecules under the action of fast electrons is discussed; it is shown that the process is not dominant. [ABSTRACT FROM AUTHOR]

Phenylacetylene and its chemically active isomer pentalene play an important role in the formation and destruction of polyaromatic hydrocarbons—the main components of the soot microparticles formed during the combustion of fossil fuel, which are the most dangerous anthropogenic aerosol air pollutants for human health. The probable mechanisms of the decay of phenylacetylene and its isomers upon ionization by electron impact are considered. It is shown that the loss of electrons during ionization changes the aromatic/antiaromatic properties of phenylacetylene and its isomers to the opposite properties. [ABSTRACT FROM AUTHOR]

The example of the lowest 1S resonance of the H– anion demonstrates that the resonance energy and its width calculated by way of finding the optimal point using the method of the complex absorbing potential has a systematic error, whose magnitude depends on the parameters of the absorbing potential and on the approximation used to solve the Schrödinger equation. It is shown that the accuracy of the calculation of resonance parameters can be improved if you replace finding the optimal point with averaging over the trajectory closure interval. [ABSTRACT FROM AUTHOR]

The search for ways to predict earthquakes, including predicting the point in time when they will occur and their possible coordinates and energy, is a global scientific problem. Researchers have discovered a number of natural phenomena that can be considered their precursors. Changes that occur in Earth's ionosphere due to the emissions of radioactive radon in the compression regions are also related to earthquakes. They lead to the creation of an additional glow of heavy dust particles in a wide range of wavelengths (including the microwave and infrared ranges). The physical origin of this phenomenon is that sufficiently fast alpha particles interact with neutral air molecules and cause their ionization. The resulting ions charge heavy dust particles in the air with sufficient electric field strength to ionize the air. At the same time, these processes are accompanied by the neutralization of charged dust particles by air ions due to the recombination process. The published experimental data on the size of the region in which heavy dust particles glow and the observed times of glowing make it possible to estimate the typical sizes of these particles. [ABSTRACT FROM AUTHOR]

This paper presents the results of the analysis of a numerical experiment on the generation of acoustic gravity waves (AGWs) in the lower atmosphere and their propagation into the upper atmosphere. The observed variations in atmospheric pressure during the passage of a solar eclipse on March 20, 2015, over Kaliningrad (54° N, 20° E) are considered the be a wave source. The calculation results showed that the passage of a solar eclipse is accompanied in the lower atmosphere by an increase in wave activity in the AGW range with periods of ~4–20 min. In the upper atmosphere, at altitudes of ~200 km, disturbances are formed due to the dissipation of AGWs coming from the lower atmosphere; these disturbances propagate with characteristic periods of ~50 min. The propagation direction of these disturbances was opposite to the propagation direction of the solar eclipse region along the Earth's surface. The results of the numerical experiment are in qualitative agreement with the results of observations of ionospheric disturbances during the solar eclipse on March 20, 2015. [ABSTRACT FROM AUTHOR]

The ground and 10 lowest excited adiabatic electronic states of the Na2 dimer are calculated using the pseudopotential method. The use of the basis [7s6p5d4f] of atomic orbitals makes it possible to extend the range of available internuclear distances up to 1.7–50 Å. It is found that the theoretical values of the Te and De constants are in a good agreement with the experimental ones. Herein you will find the sample calculations of the radial non-adiabatic coupling matrix elements enable to transform the basis of the adiabatic states to quasidiabatic one. It is found also that the Le Roy modified radius scales down the left boundary of an asymptotic range for the electronic state with the (3s + 5p) dissociation limit and for the higher states. [ABSTRACT FROM AUTHOR]

Recently it has been theoretically predicted and experimentally confirmed that at altitudes of 80-110 km from the Earth's surface the signals of the global navigation satellite systems (GNSS) are delayed as a result of a multiple resonance scattering by the Rydberg complexes. The attenuation of GNSS signals occurs mainly in the lower atmosphere layers, where the greatest effect is achieved through interaction with charged aerosol layers. A thunderstorm conditions are of particular interest whereby the presence of strong electric fields and hydration of aerosols can lead to the detachment of OH radicals from water clusters. Since the spectrum of radiation and absorption of these radicals for rotational transitions is part of the microwave range, they are expected to make an additional resonance contribution to the delay of radio signals thus necessitating a detailed study of the electronic structure of the OH radical. This paper offers the ab initio calculations of the dipole moment function for the ground X2Π state of the OH molecule using the dipole length approach and the finite-field method. The comparison with the experiment shows that in extended model spaces the approximation of the dipole length leads to more accurate values of the dipole moment than the finite-field method. [ABSTRACT FROM AUTHOR]

Ab initio calculations of the adiabatic potential curves and matrix elements of radial nonadiabatic coupling of the N2 molecule for the states related to dissociation limits I-V were performed. The most important spectral characteristics of the adiabatic states agreed well with the available experimental and theoretical data. The diabatic states were constructed. The diabatic quantum defects and radial matrix elements of the configuration interaction of the dissociative and Rydberg configurations whose states converge to the ground state X2Σg+ and the first electronically excited state A2Πu of the N2+ ion were calculated. The possibility of using the results for calculating the cross sections and rate constants of dissociative recombination and associative ionization within the framework of the multichannel quantum defect theory was discussed. [ABSTRACT FROM AUTHOR]

A method was developed for calculating the vibronic potential energy surfaces (PESs) of atmospheric complexes consisting of orbitally degenerate Rydberg nitrogen and oxygen molecules and the molecules of a neutral medium in the ground electronic state. The degenerate states are formed as a result of L-mixing in the D and E layers of the atmosphere during the periods of increased solar activity. The complexes are populated in the nonequilibrium two-temperature plasma and are responsible for the incoherent additional background radiation in the decimeter (microwave) and terahertz (IR) bands at an altitude of 80-110 km from the Earth's surface. To describe the interaction ofa weakly bound electron with a singly charged molecular ion and a neutral molecule ofa gas medium, the formalism of the multichannel quantum defect (MCD) theory was used. Quantum-chemical calculations of the dependences of the scattering lengths, polarizabilities, and quadru-pole moments of the main atmospheric molecules N2 and 02 on the interatomic distance were performed. The specific features of the behavior of vibronic PESs of Rydberg complexes for large values of the principal quantum number (n⪢) were analyzed. The vibronic PESs of orbitally degenerate states were constructed. They are necessary for determining the positions and shape of the vibronic minima of the L-mixing cross sections of the N2 and 02 Rydberg molecules in the D and E layers of the Earth's atmosphere, where the delay times of satellite positioning signals should be minimum. The possibility of "quantum chaos" appearing in the Rydberg complexes at sufficiently large n values and angular momenta of the weakly bound electron was noted. [ABSTRACT FROM AUTHOR]