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The processes of continuous photoabsorption by weakly bound NeAr+ molecular ions at room and elevated temperatures have been theoretically investigated. A comparative analysis of the relative contributions of four types of phototransitions (photodissociation, bound-bound transitions, free-free transitions and photoassociation) with different initial and final states of internuclear motion to the total absorption coefficient at room and elevated temperatures was made. It is shown that it is possible to describe under certain assumptions the above contributions under quasi-equilibrium conditions without resorting to direct calculation of photoabsorption coefficients for each of the channels. It is demonstrated that the relative efficiencies of different types of phototransitions in the NeAr+ ion radically differ from previous results for homonuclear noble gas ions and for ArXe+ and KrXe+ ions. The dependences of these contributions on the wavelength of the incident radiation and on the gas temperature of the plasma were investigated. It was found that there are well-defined regions corresponding to the predominance of a particular channel of phototransitions within the wavelength range where efficient absorption occurs. The presented results are of interest for the construction of kinetic models of pumping and excitation relaxation in gas lasers based on active media containing Ne/Ar mixtures. [ABSTRACT FROM AUTHOR]

We report investigation of the resonant process of electron impact induced charge transfer in the inert gas systems Ar + Xe+ and Kr + Xe+. Along with this, the reaction of the formation of charge-transfer ions XeRg+ in triple collisions Rg + Xe+ + e, occurring due to nonadiabatic transitions, is studied. These processes are compared with the efficiency of dissociative electron impact excitation of ArXe+ and KrXe+ ions, accompanied by the formation of Ar+ and Kr+ ions, under conditions of plasma equilibrium in nuclear motion. [ABSTRACT FROM AUTHOR]

Studies of radiative transitions between ground and charge transfer excited terms of heteronuclear rare-gas (ArXe)+ and (KrXe)+ ions with small and moderate dissociation energies ( D 0 ArXe + = 179 and D 0 KrXe + = 389 meV) are reported. Potential energy curves and dipole transition matrix elements are evaluated using ab initio calculations based on the CASSCF method followed by the NEVPT2 treatment and perturbative description of relativistic effects as implemented in the ORCA suite. We develop an efficient approach for the calculations of Boltzmann-averaged cross sections, rate constants, and absorption and emission coefficients associated with the integral contributions of bound–bound and bound–free transitions from a manifold of rovibrational states of the (RgXe)+ ion. A similar approach is used for the description of the free–free and free–bound transitions between different electronic terms of a quasimolecular (RgXe)+ ion temporarily formed during a collision of Ar or Kr atoms with Xe+ ions. Our method is based on the quantal version of the theory of non-adiabatic transitions in molecular and quasimolecular systems combined with the approximation of a quasicontinuum for rovibrational energy levels. This allowed us to obtain a semianalytic expression for the integral absorption properties particularly relevant at elevated temperatures. We perform a comprehensive analysis of the identified radiative processes in local thermodynamic equilibrium plasmas of rare gas Rg/Xe mixtures containing both atomic, Xe+, and molecular, RgXe+, ions and determine their role in the formation of the absorption and emission spectra in a wide range of wavelengths and gas temperatures. The results obtained are in good agreement with the available experimental data. [ABSTRACT FROM AUTHOR]

A number of optical and kinetic properties of heavy heteronuclear ions of inert gases ArXe+ and KrXe+ formed in the plasma of inert gas mixtures is investigated. Various types of nonadiabatic phototransitions between the ground and excited electronic terms of such ions, which are accompanied by charge exchange, are considered. The contributions of bound–free (photodissociation) and bound–bound phototransitions to the total photoabsorption coefficient under the conditions of thermal excitation of the entire vibration–rotation quasi-continuum are analyzed. We report on the results of calculation of the effective cross sections and rate constants of these processes of continuous absorption of electromagnetic radiation of the visible and UV ranges by ArXe+ and KrXe+ ions at different temperatures of the ionic plasma component. The resonant mechanism of dissociation of ArXe+ and KrXe+ ions by an electron impact in the processes of dissociative recombination and direct dissociative excitation is also considered. Analysis performed in this work extends the physical pattern of radiation-induced and collisional processes in the plasmas of Rg/Xe inert gas mixtures (Rg = Ar, Kr) excited by an electron beam, in gas discharges, and during optical pumping. The results of this study can be used for constructing kinetic models of active media of gas and plasma lasers, radiation sources of the UV range, excimer laser tubes, and microplasma cell arrays. [ABSTRACT FROM AUTHOR]

The electronic states of ArXe+ and KrXe+ molecular ions are theoretical studied. Electronic terms and oscillator strengths of transitions from the ground term are calculated using the multireference quantum chemical approach. Relative efficiencies of transitions are determined. The results are compared with existing theoretical data. [ABSTRACT FROM AUTHOR]

Specific features of the cross sections and rate constants of the electron-impact dissociative excitation of molecular ions are studied in a wide range of gas and electron temperatures. It is found that an increase in the gas temperature results in a significant change in the dependence of the cross sections on the incident electron energy. The efficiencies of dissociative recombination with Rydberg state population and the dissociative excitation of ions are compared. [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]

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]