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Complex research of elementary pair collision processes occurring when low-energy (0–70 eV) electrons pass through chalcogen (S, Se, Te) vapor has been carried out in the evaporation temperature intervals of those elements (T = 320÷700 K for sulfur, 420÷490 K for selenium, and 400÷600 K for tellurium). The vapor compositions of indicated elements are studied using the mass spectroscopy method. The radiation spectra are analyzed in the wavelength interval from 200 to 600 nm with the help of optical spectroscopy. Using highly monoenergetic electron beams, the total (integral) formation cross-sections for positive and negative S, Se, and Te ions are measured. It is found that, under the experimental conditions, the main components of chalcogen vapor are molecules containing 2 to 8 atoms. At the energies of bombarding electrons below 10 eV, the emission spectra mainly consist of bands of diatomic molecules, and, at higher energies (E > 15 eV), there appear separate atomic and ionic lines. At E = 50 eV, the lines of singly charged ions are the most intense ones. It is shown that the most effective reaction channel is the interaction of electrons with diatomic molecules of indicated elements, whereas other processes are mainly associated with the decay of polyatomic molecules. The excitation and ionization thresholds for interaction products are found by analyzing the energy dependences of process characteristics. Specific features are also observed in the energy dependences of the excitation and ionization functions. Doubly charged ions of diatomic sulfur molecules, as well as selenium and tellurium atoms, are revealed for the first time. The appearance of triply charged ions of diatomic sulfur molecules is also detected. The main contribution to the total (integral) effective ionization cross-section of both positive and negative ions is proved to be made by the interaction processes of electrons with diatomic molecules S2, Se2, and Te2. Besides the experimental research, a detailed theoretical study is carried out. Calculations with a theoretical analysis of their results are performed for the structural characteristics of homoatomic sulfur, Sn, selenium, Sen, and tellurium, Ten, molecules with n = 2÷8; namely, interatomic distances, ionization potentials, electron affinity energies, and dissociation energies. The energy characteristics are applied to calculate the appearance energies for singly and doubly charged ionic fragments of those molecules at the dissociative ionization. The obtained results are carefully compared with the available experimental and theoretical data.

The hydronium cation plays a crucial role in interstellar oxygen and water chemistry. While its spectroscopy was extensively investigated earlier, the collisional excitation of H 3 O + is not well studied yet.In this work we present state-to-state collisional data for rotational de-excitation of both ℎ -and -H 3 O + due to -H 2 impact. The cross sections are calculated within the close-coupling formalism using our recent, highly accurate rigid-rotor potential energy surface for this collision system. The corresponding thermal rate coefficients are calculated up to 100 K. For -H 3 O + the lowest 20 rotation-inversion states were considered in the calculations, while for ℎ -H 3 O + the lowest 11 states are involved (up to ≤ 5), so all levels with rotational energy below 420 K (292 cm −1 ) are studied.In order to analyse the impact of the new collisional rates on the excitation of H 3 O + in astrophysical environments radiative transfer calculations are also provided. The most relevant emission lines from an astrophysical point of view are studied, taking into account the transitions at 307, 365, 389 and 396 GHz. We show that our new collisional data have a non-negligible impact (from a few percents up to about a factor of 3) on the brightness and excitation temperatures of H 3 O + , justifying the revision of the physical conditions in the appropriate astrophysical observations. The calculated rate coefficients allow one to recalculate the column density of hydronium in interstellar clouds, which can lead to a better understanding of interstellar water and oxygen chemistry.

Elastic scattering of electrons by CF 3 radical has been studied theoretically in a wide energy range of 1-1000 eV in the framework of independent-atom model (IAM). The optical potential method is used for calculating the electron scattering amplitudes of the different atoms of the target molecule. The differential and integral cross sections are calculated for equilibrium internuclear distances of the ground state of the CF 3 radical in two approaches -IAM and additivity rule (IAM-AR) approximations. The calculated cross sections are compared with the experimental data for e + CF 3 and e + CF 3 H scattering and with other theoretical results. It is justified that the IAM performs slightly better for the differential cross sections, while the simpler IAM-AR approximation describes the integral cross sections better.