We have carried out the comparative analysis of the efficiencies of resonant and non-resonant mechanisms of electron capture by ions into Rydberg states of atoms, Xe(n), and the inelastic n → n′ transitions between the highly-excited states in the plasmas of rare gas mixtures, Rg/Xe, containing atomic, Xe$^{+}$, and molecular, RgXe$^{+}$ and Xe$_{2}^{+}$, ions (Rg = Ne, Ar and Kr, [Xe]≪[Rg]). The rate constants of resonant electron capture by Xe$^{+}$ ions in ternary collisions with rare gas atoms, Rg($^{1}S_{0}$), and dissociative recombination of heteronuclear, RgXe$^{+}$, and homonuclear, Xe$_{2}^{+}$, ions were evaluated on the basis of the original approach within the framework of the theory of non-adiabatic transitions between electronic terms of RgXe$^{+}+e$ system. For the alternative mechanism of the three-body electron capture by Xe$^{+}$ ions in collisions with Ne, Ar and Kr atoms the calculations of the rate constants were carried out in the impulse approximation by taking into account both short-range and polarization electron-atom interactions. The rate constants of the three-body electron capture by ions and n → n′ transitions in collisions with electrons were calculated on the basis of the well-known theoretical models. We have determined the ranges of plasma ionization degree and electronic and gas temperatures as well as the principal quantum number of Xe atom which correspond to situations when the resonant free-bound and bound-bound transitions of electron play a key role.

A theoretical description of the process of dissociative excitation of a molecular ion by electron impact in the case of effective population of a huge number of its vibrational-rotational levels is presented. Our consideration is based on the quantal version of the theory of non-adiabatic transitions between the electronic terms of a molecular ion combined with replacing the summation over vJ-levels by integration over v and J. Semianalytical formulas are derived for the integral contribution of the entire vibrational-rotational quasicontinuum to the cross sections, $\sigma_T^{\mathrm{de}}(\varepsilon)$, and the rate constants, $\alpha^{\mathrm{de}}(T, T_e)$ of the process under study in a plasma with temperatures $T_e$ and $T$ of its electronic and ionic components. The developed theory is used to study the processes of dissociative excitation of heteronuclear (HeXe$^{+}$ and ArXe$^{+}$) and homonuclear (Ar$_2^{+}$ and Xe$_2^{+}$) ions of inert gases. We demonstrate a strong dependence of the results on the ion dissociation energy and large differences in the behavior and characteristic values of $\sigma_T^{\mathrm{de}}(\varepsilon)$ and $\alpha^{\mathrm{de}}(T, T_e)$ for these systems in different ranges of electron energy, $\varepsilon$, and temperatures $T_e$ and $T$. The regions of dominance of the contributions of two competing channels are determined: direct dissociative excitation and dissociative recombination into total cross sections and the rate constants of destruction of rare gas molecular ions by electron impact. Analyzing behavior of the differential rate constants of dissociative excitation per unit range of electron energy in the final channel of reaction we demonstrate qualitative differences in the dynamics of this process for weakly bound and moderately bound molecular ions.