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We study how the efficiencies of resonant electron–ion recombination processes in rare-gas-mixture plasmas depend on the deviation of the electron-energy distribution functions from the Maxwellian distribution. Our calculations demonstrate that nonequilibrium distributions commonly encountered in the experiment may lead to strong increases or decreases of the respective rate constants of three-body and dissociative recombination processes. The dependences of the results on the electronic temperature and on the principal quantum number of the Rydberg state in the final channels of the reactions are analyzed. [ABSTRACT FROM AUTHOR]

We have developed a semiclassical approach to the description of resonant dissociative excitation of a molecular ion induced by collisions with plasma free electrons and accompanied by the non-adiabatic transitions between its different electronic terms. It is based on the quasistatic treatment of nuclear particles relative motion in a molecular ion combined with the approximation of a quasicontinuum for rovibrational states. We have derived the semianalytic expressions for the Boltzmann-averaged cross sections, , and rate constants, αde(T, Te), of this process. The resulting expressions for and αde(T, Te) with explicit dependencies on the electron energy, ɛ, the gas, T, and electron, Te, temperatures are valid when the thermal energy kBT exceeds the value of the lowest vibrational quantum, ℏωe, of a molecular ion. The theory developed is applied to studying the resonant dissociative excitation of homo-nuclear , and ions as well as the hetero-nuclear rare gas ions RgXe+ (Rg = Ne, Ar, and Kr) with significantly different values of the dissociation energy. The efficiencies of the electron-impact dissociative excitation process and dissociative recombination leading to the population of the Rydberg states are compared. Our results of calculations are in good agreement with the available experimental data. [ABSTRACT FROM AUTHOR]

Resonant mechanisms of electron–ion recombination accompanied by the formation of Rydberg atoms in a plasma containing atomic and molecular ions are investigated. An analytical approach is developed for the description of three-particle electron capture into a Rydberg state as a result of resonant energy transfer from a free electron to the electronic shell of a quasimolecular ion formed during the collision of an atomic ion with a buffer gas atom. An efficient method is proposed to calculate dissociative recombination rates under thermal excitation of all rotational–vibrational (rovibrational) levels of the molecular ion. The dependence of the cross sections and the rate constants of the processes on the principal quantum number is established, and the relative role of these processes is determined in a wide range of temperatures of the electron, Te, and gas, T, components of the plasma. Conditions are found under which integral contributions of the continuous spectrum of the molecule and of the whole rovibrational quasicontinuum to the total rate of resonant electron capture are dominant. A specific analysis is carried out by an example of Ne + Xe+ + e and Ar + Xe+ + e heteronuclear systems with significantly different dissociation energies (D0 = 33 and 171 meV) of the ground electronic term of the RgXe+ (Rg = Ne and Ar) ion. It is shown that the capture rate constants essentially depend on the binding energy |εn| of the resulting Xe(n) atom, the temperatures T and Te, and the relationship between D0 and the thermal energy kBT. [ABSTRACT FROM AUTHOR]

A comparative analysis of efficiencies of the resonant and nonresonant mechanisms of electron capture by ions into Rydberg states of Xe(n) atoms and inelastic n → n' transitions between highly excited levels in the inert Rg/Xe gas mixture plasma that contains atomic (Xe+) and molecular (RgXe+ and Xe ) ions (Rg = Ne, Ar, and Kr, [Xe] [Rg]) is carried out. The rate constants of resonant electron capture by Xe+ ions in triple collisions with Rg() atoms of an inert gas and dissociative recombination of heteronuclear (RgXe+) and homonuclear (Xe ) ions are calculated based on our approach developed within the framework of the theory of nonadiabatic transitions between electron terms of the RgXe+ + e system. For the alternative mechanism of three-particle electron capture by Xe+ ions in collisions with Ne, Ar, and Kr atoms, the rate constants are calculated in the impulse approximation with account for the short-range and polarization electron–atom interactions. The rate constants of three-particle electron capture by ions and n → n' transitions in collisions with electrons are calculated using known theoretical models. Ranges of plasma ionization degrees, plasma electron and gas temperatures, and principle quantum number of Xe atom where resonant free–bound and bound–bound electron transitions play a key role are established. [ABSTRACT FROM AUTHOR]

We study various physical mechanisms of electron-ion recombination accompanied by the formation of Rydberg atoms in plasmas containing atomic and molecular ions. Analytical approach to the description of resonant mechanism of ternary electron capture associated with the non-adiabatic energy transfer from free electron to the electronic shell of a quasimolecular ion is developed. Similar technique is used for the evaluation of the integral contribution of all rovibrational states of a bound molecular ion to the Boltzmann-averaged cross section and rate constant of dissociative recombination (DR). Simple expressions for cross sections and rate constants of non-resonant electron capture to Rydberg states in ternary electron-ion-atom collisions are derived in the impulse approximation. We perform a comparative analysis of the efficiencies of resonant and non-resonant three-body recombination of electrons with atomic ions and DR of molecular ions in plasmas of rare gas mixtures, Rg/Xe, with small relative concentration of xenon ([Xe] ≪ [Rg], Rg = He, Ne, Ar, Kr). It is shown that in a wide range of plasma parameters the resonant recombination mechanisms are predominant. The behavior and magnitudes of the recombination rate constants turn out to be quite different for heteronuclear ions with small (HeXe+ and NeXe+, D0 = 13.1 and 33 meV) and moderate (ArXe+ and KrXe+, D0 = 171 and 400 meV) values of the dissociation energy. [ABSTRACT FROM AUTHOR]