Vol 42, No 4 (2023)

The problem of global climate change has become one of the most important challenges to humanity in the 21st century. The main reason is the appearance in the atmosphere of an excessive concentration of greenhouse gases, which absorb the thermal radiation of the Earth and partially return it to the Earth’s surface. The accumulation of greenhouse gases in the atmosphere leads to a rapid increase in the global average air temperature and, as a result, climate change. It is well known that greenhouse gases have a high transparency in the visible spectral range and high absorption in the infrared range. In this paper, we propose a new technique for recording the CO2 and CH4 spectra. An experimental setup based on dynamic Fourier spectrometer is developed. It allows to record IR absorption spectra in the wavelength range of 1.0 to 1.7 μm with a 10 cm–1 spectral resolution. Long-term recording of the atmospheric transmittance in the conditions of urban development is carried out. Based on the obtained data, the CO2 and CH4 integral and volumetric concentrations are monitored. It is shown that the carbon dioxide and methane volumetric concentrations time dependences accurately reflects the traffic congestion degree on that day. Reduction of volume concentrations in the evening hours is explained by the increase of the optical path and the additional capture of air masses outside the heavy traffic area.

In order to study the potential energy surfaces (PESs) of systems containing ethylene, hydrogen, and oxygen atoms, quantum chemical calculations are carried out using the hybrid B3LYP method of the density functional theory (DFT) and the composite CBS-QB3 method. An enthalpy diagram reflecting the PES of this reaction system is constructed. It is shown that the addition of a hydrogen atom to ethylene with the formation of an ethyl radical occurs through the formation of a van der Waals complex. The diagram of enthalpies of monomolecular reactions of decomposition and isomerization of the ethoxyl radical is presented in detail, and a conclusion is made about the probability of their occurrence. The global PES minimum of the system describing the sequential addition of hydrogen and oxygen atoms to ethylene is the hydroxyethyl radical. Intermediates CHCH2OH and CH2OCH2 are localized on the PES of the C2H4 + O system and possible pathways for their further transformation are analyzed. The data obtained make it possible to estimate the ranking of individual elementary reactions in the processes of combustion and oxidation of hydrocarbons and the probabilities of various directions for the transformation of chemical species in the studied systems

The results of experimental studies on the effect of gas-dispersed parameters of the flow of an air suspension of aluminum particles—the average particle diameter d32 and excess air coefficient α—on the flame propagation velocity are presented. The dependences of the apparent flame propagation velocity, uf, on the coefficient of excess air α for ASD-1-grade aluminum powder with d32 = 17.4 µm and ASD-4-grade aluminum powder with d32 = 7.4 µm are obtained. It is established that the number of maxima and their location on the dependence graph uf(α) depend on the particle combustion mode, which in turn is determined by the particle size. For both powder grades, there is a maximum on the dependence graph uf(α) in the rich region (α ≈ 0.2). For aluminum particles with d32 = 17.4 µm, the flame propagation velocity decreases monotonically with increasing α. For particles with d32 = 7.4 µm, whose combustion occurs in the kinetic mode, there is a second maximum in the region of stoichiometric air suspension compositions (α ≈ 1.0). The number and location of maxima and their variation depending on the average diameter d32 allows us to draw certain conclusions about the combustion mechanism of aluminum particles.

The results of the radiation characteristics of shock-heated air measurements in the vacuum-ultraviolet region are presented. The experiments are carried out in the STS shock tube of the Institute of Mechanics, Moscow State University at shock-wave velocities of 7.3 to 10.7 km/s and initial pressures in the low-pressure chamber of 0.125, 0.2, and 0.25 Torr. An analytical model of the radiation process is constructed, which takes into account the absorption of radiation during its passage through the air . Processing the experimental dependences of the radiation intensity on time for the main radiation lines using this model made it possible to propose a radiation method for determining the electron temperature of a shock-heated gas. The presented data are compared with the experimental data of other authors.

As applied to experimental measurements of the parameters of the neutral component in the Earth’s ionosphere, the propagation of quasi-harmonic pulses of acoustic gravity waves (AGWs) of limited duration in an isothermal atmosphere is analyzed. A criterion for weak distortions of impulse signals during their propagation over long distances is obtained. The reflection and refraction of such pulses by atmospheric layers with a parabolic dependence of the equilibrium temperature in them on height are also considered. It is shown that, under certain conditions, AGW pulses can propagate without distortion over long distances.

The method of resonance fluorescence (RF) of chlorine atoms in a flow reactor in the temperature range of 273 to 366 K is used to measure the rate constant of the reactions of a chlorine atom with hydrogen sulfide, the value of which decreased as temperature in the reactor increased. This behavior of the rate constant could be explained by the fact that this reaction occurs on the surface of the reactor. However, experiments carried out under different conditions of the diffusion of reagents to the surface of the reactor showed that the reaction of the chlorine atom with hydrogen sulfide proceeds in the volume.