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This study focuses on the role of CO2 and CO electronically excited states in the kinetics of CO2 cold non-equilibrium plasma discharges by means of a state-to-state OD kinetic model based on the simultaneous and self-consistent solution of the electron Boltzmann equation and the master equations describing the vibrationally and electronically excited state kinetics and the plasma composition. A new CO2 dissociation model based on the use of the Biagi electron impact excitation cross sections, considered as fully dissociative, of several CO2 electronic excited states, in the energy range from 6.5 to 25 eV, is tested and compared with the results obtained by using the Phelps database in typical glow and microwave discharge conditions. Moreover, a refinement of the kinetics of the CO a 3 Π excited state is proposed by including new production and loss terms and the effect of the change of its time evolution density on the eedf, the electron temperature, the CO2 and CO vibrational distribution functions, electron impact and vibrational induced dissociation rates is investigated. Finally, the contribution of the CO a 3 Π state to CO2 dissociation is examined in terms of production and recombination (or back-reaction) processes both in microwave and glow discharge conditions. [ABSTRACT FROM AUTHOR]

Recent experiments by Groen et al (2019 Plasma Sources Sci. Technol. 28 075016) on CO2 activation at high translational temperature (3500 < Tg < 5500 K) are analyzed with a self-consistent code describing the vibrational kinetics of reacting CO2 together with CO and O2 and the corresponding electron Boltzmann equation. The kinetics results are compared with the corresponding thermodynamics values. This comparison shows that the major components of the mixture, i.e. CO and O can be described by the thermodynamic approach, while the other minor components present large deviation from equilibrium. A qualitative agreement is found between experimental and theoretical values of electron density, E/N and electron temperature in both diffuse and contracted regimes. The theoretical vibrational distributions as well as the corresponding electron energy distribution functions present non-equilibrium effects even at the considered high translational temperature. [ABSTRACT FROM AUTHOR]

A Boltzmann equation, in the presence of superelastic vibrational and electronic collisions and of electron-electron Coulomb collisions, has been solved in CO2 plasma in discharge and post discharge conditions. Superelastic vibrational collisions play an important role in affecting the electron energy distribution function (eedf) in a wide range of the reduced electric field E/N and of vibrational temperatures characterizing the vibrational modes of CO2. An important result is the dependence of fractional power losses and of the relevant rate coefficients on the vibrational temperatures of the system. Superelastic electronic collisions, on the other hand, are the main processes affecting eedf and related quantities in the post discharge conditions (i.e., E/N=O). In particular at low vibrational temperatures, the superelastic electronic collisions form an important plateau in the eedf, largely influencing the rate coefficients and the fractional power transfer. [ABSTRACT FROM AUTHOR]

Different models for relaxation dynamics of electrons and phonons in a thin metal film heated by femto-pico second laser pulses have been discussed. The traditional two-temperature approach reveals to be inaccurate due to deviations of electrons and phonons from Fermi-Dirac and Bose-Einstein distributions, respectively. Coupled Boltzmann kinetic equations have been adapted for the quantum statistics to study the energy distribution of electrons and phonons in metals. Theoretical details have been discussed and a new solution method has been proposed overcoming numerical problems and improving stability, allowing the study of the dynamics until the complete relaxation. Numerical results have been compared with photoemission spectroscopy experimental data. [ABSTRACT FROM AUTHOR]

A theoretical investigation of the electron and phonon time-dependent distributions in an Ag film subjected to a femtosecond laser pulse has been carried out. A system of two coupled time-dependent Boltzmann equations, describing electron and phonon dynamics, has been numerically solved. In the electron Boltzmann equation, electron–electron and electron–phonon collision integrals are considered together with a source term for laser perturbation. In the phonon Boltzmann equation, only electron–phonon collisions are considered, neglecting laser perturbation and phonon–phonon collisions. Screening of the interactions has been accounted for in both the electron–electron and the electron–phonon collisions. The results show the simultaneous electron and phonon time-dependent distributions from the initial non-equilibrium behaviour up to the establishment of a new final equilibrium condition. [ABSTRACT FROM AUTHOR]

A new set of electron-vibrational (e-V) processes linking the first 10 vibrational levels of the symmetric mode of CO2 is derived by using a decoupled vibrational model and inserted in the Boltzmann equation for the electron energy distribution function (eedf). The new eedf and dissociation rates are in satisfactory agreement with the corresponding ones obtained by using the e-V cross sections reported in the database of Hake and Phelps (H-P). Large differences are, on the contrary, found when the experimental dissociation cross sections of Cosby and Helm are inserted in the Boltzman equation. Comparison of the corresponding rates with those obtained by using the low-energy threshold energy, reported in the H-P database, shows differences up to orders of magnitude, which decrease with the increasing of the reduced electric field. In all cases, we show the importance of superelastic vibrational collisions in affecting eedf and dissociation rates either in the direct electron impact mechanism or in the pure vibrational mechanism.