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.

The intense precipitation of energetic electrons from the Earth’s radiation belt (ERB) is one of the most important sources of ionization in the ionosphere and atmosphere. A large-scale statistical analysis is carried out of the data from continuous low-orbit satellite observations of solar-cycle variations in the flux enhancements of the ERB electrons with energy >30 keV at an altitude of 850 km, acquired from the NOAA/POES and MetOp satellites in the interval from 1998 to 2022. The basic features of artificial failures in the satellite database with high-time resolution measurements in the interval from 2014 to 2022 are found and described. Appropriate data correction is carried out. It is shown that the average annual number of days with electron flux enhancements increases rapidly within three years after the solar-cycle maximum and reaches its greatest value near the middle of the declining phase of solar activity. Then the frequency of event occurrence begins to decrease noticeably within an 8-year interval, including the minimum, rising, and maximum phases of the solar cycle. The minimum level is achieved at the maximum solar activity.

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.

There are many reasons for natural gas (methane) leaks in gas distribution networks. One of the most important tasks of gas distribution organizations is to promptly identify and eliminate gas leaks before they cause emergency situations. Eliminating gas leaks as soon as possible will minimize the negative impact on the environment. This paper proposes a new original method for detecting emergency gas emissions into the atmosphere and leaks on gas pipeline systems. The technique involves the simultaneous use of both experimental and calculated data to determine the concentration and characteristic sizes of gas emissions. The methodology is tested at laboratory conditions using a propane cylinder and a gas burner. The Scorpion monophotonic sensor is used as the recording equipment. As a result of processing the experimental data and mathematical modeling using computational fluid dynamics methods, the dependence of the propane concentration on the distance to the burner is constructed and the characteristic dimensions of the gas cloud are determined.

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 настоящей работе впервые прямым способом в мезоскопическом масштабе длин решена «флуктуационная теорема». Получено аналитическое выражение для парной корреляционной функции критического состояния флюида, параметром которой является дисперсия плотности, легко восстанавливаемая из оптических экспериментов. Сравнение нашего результата с парной корреляционной функцией Орнштейна—Цернике позволило определить поправку Фишера η = 0,25, повышающую сходимость. Показано, что полученные результаты дают надежную теоретическую основу для оптической диагностики статистического состояния критических флюидов. In this paper we have solved the «fluctuation theorem» on the mesoscopic length scale for the first time in a direct way. An analytical expression for the pair correlation function of the critical state of fluid was obtained, where the density variance is the parameter that could be easily defined by optical measurements. By comparison of our result with the Ornstein—Zernike pair correlation function we have got the Fisher index η= 0.25 to increase the convergence. It was shown that the obtained results provide a reliable theoretical basis for optical diagnostics of the critical state of fluids.

An Erratum to this paper has been published: https://doi.org/10.1134/S1990793124340050

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.

The features of the resonant and anomalous structure of the associative ionization (AI) spectra for the case of the dipole-dipole interaction of Rydberg atoms are analyzed using the stochastic approach. The use of this approach makes it possible to quantitatively describe the AI reaction with the formation of a positively charged molecular ion. It is found that the efficiency of asymmetric ionization processes for Auger transitions can exceed that of symmetric ones by orders of magnitude. The important role of this phenomenon for the development of modern applied quantum research and the concept about ionization processes occurring in the ionosphere is discussed. The obtained results can be used to solve a number of fundamental problems of ionospheric plasma physics. This especially concerns the time delay effect of signals of global navigation satellite systems (GNSS), which significantly affects the stability of GNSS operation and remote sensing of the Earth’s surface.

Currently, the developers of global navigation satellite systems (GNSS) are making significant efforts to solve a number of fundamental problems. However, ignorimg by researchers the entire set of nonequilibrium physical and chemical processes occurring in the ionosphere, which affect the propagation of satellite signals, often does not allow to have a progress in their solution. In this paper, we discuss the main chemical reactions that occur in the lower ionosphere of the Earth with the participation of the Rydberg states of O 2 , N 2 , and NO molecules. An explanation of the physical reason for the time delay of the satellite signal, leading to errors in GNSS positioning, is given. A quantum approach is proposed, through which the transition from the traditional idea of the propagation of radio waves to the movement of the corresponding photons is carried out. In this case, the effective delay time in resonant photon scattering is determined by the characteristic lifetime of the intermediate autoionization states of vibrationally excited Rydberg complexes. The value of the lifetime is defined by the presence of a strong nonadiabatic coupling of the electronic and nuclear motions in the intermediate states of the complex, which does not depend on the strength of the external field created by the GNSS transmitter.

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.

В рамках стохастического подхода выполнен анализ особенностей резонансной и аномальной структур спектров ассоциативной ионизации (АИ) для случая дипольно-дипольного взаимодействия ридберговских атомов. Использование такого подхода позволяет количественно описать реакцию АИ с образованием положительно заряженного молекулярного иона. Обнаружено, что эффективность несимметричных процессов ионизации для оже-переходов может на порядки превышать эффективность симметричных. Обсуждена важная роль этого явления для развития современных квантовых прикладных исследований и представлений о процессах ионизации, протекающих в ионосфере. Полученные результаты могут быть использованы для решения ряда принципиальных проблем физики плазмы ионосферы. Особенно это касается эффекта "временной задержки" сигналов глобальных навигационных спутниковых систем (ГНСС), что, в свою очередь, существенно влияет на устойчивость работы ГНСС и дистанционное зондирование поверхности Земли.

В настоящее время разработчиками глобальных навигационных спутниковых систем (ГНСС) прилагаются значительные усилия для решения ряда фундаментальных проблем. Однако игнорирование исследователями целой совокупности протекающих в ионосфере неравновесных физико-химических процессов, которые влияют на распространение спутниковых сигналов, зачастую не позволяют продвинуться в их решении. В данной работе обсуждены основные химические реакции, протекающие в нижней ионосфере Земли с участием ридберговских состояний молекул O 2 , N 2 и NO. Дано объяснение физической причины временнóй задержки спутникового сигнала, приводящей к ошибкам позиционирования ГНСС. Предложен квантовый подход, посредством которого осуществляется переход от традиционного представления о распространении радиоволн к движению соответствующих фотонов. В этом случае эффективное время задержки при резонансном рассеянии фотона определяется характерным временем жизни промежуточных автоионизационных состояний колебательно-возбужденных ридберговских комплексов. Величина времени жизни обусловлена наличием сильной неадиабатической связи электронного и ядерного движений в промежуточных состояниях комплекса, которая не зависит от напряженности внешнего поля, создаваемого передатчиком ГНСС.

The intense precipitation of energetic electrons (with an energy of tens of keV) from the Earth's radiation belt (ERB) is one of the most important sources of ionization in the ionosphere and atmosphere. In this paper, we analyze the spatial distribution of electron fluxes with energies greater than 30 keV at an altitude of 850 km using the maximum amount of statistical data available today. It is found that the region of electron precipitation from the outer zone of the ERB is shifting over North America to the pole, and over Siberia to the equator. Moreover, in the region of the Brazilian magnetic anomaly (BMA), the intensity of the energetic electron fluxes and its area in the 24th solar cycle decreases compared to the 23rd cycle. Based on the analysis of the distribution of quasi-trapped electrons under the radiation belt at low latitudes confirms the mechanism of their rapid radial transfer from the outer zone of the ERB to the Earth. The results obtained are mainly related to the change in the configuration of the Earth's magnetic field, as well as to the decrease in solar and geomagnetic activity in the 24th solar cycle.

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.

The process of formation of complexly charged thunderclouds with layers of positive and negative ions and large ion clusters that appear in the troposphere under the action of cosmic rays is considered. To calculate the ion concentrations, a kinetic model has been developed that includes 34 components and 102 reactions. The calculation is carried out using the KINET software package. It is shown that at altitudes from 5 to 35 km, the ionization of air under the action of cosmic rays leads to the formation of a weakly ionized plasma consisting mainly of ions O_2^ - , O_2^ + , and O_4^ + . Under conditions of minimal magnetic rigidity, the maxima of ion concentrations O_2^ - and O_4^ + are observed at altitudes from 15 to 20 km. It has been established that in the surface layer from 0 to 5 km, air ionization caused by γ radiation is much weaker than the ionization by cosmic rays.

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.