Elementary Processes and Kinetic Modeling for Hydrogen and Helium Plasmas

Abstract

Abstract:We report cross-sections and rate coefficients for excited states colliding with electrons, heavy particles and walls useful for the description of H 2 /He plasma kinetics under different conditions. In particular, the role of the rotational states in resonant vibrational excitations of the H 2 molecule by electron impact and the calculation of the related cross-sections are illustrated. The theoretical determination of the cross-section for the rovibrational energy exchange and dissociation of H 2 molecule, induced by He atom impact, by using the quasi-classical trajectory method is discussed. Recombination probabilities of H atoms on tungsten and graphite, relevant for the determination of the nascent vibrational distribution, are also presented. An example of a state-to-state plasma kinetic model for the description of shock waves operating in H 2 and He-H 2 mixtures is presented, emphasizing also the role of electronically-excited states in affecting the electron energy distribution function of free electrons. Finally, the thermodynamic properties and the electrical conductivity of non-ideal, high-density hydrogen plasma are finally discussed, in particular focusing on the pressure ionization phenomenon in high-pressure high-temperature plasmas.

Temperature and density dependent cooling function for H2 with updated H2/H collisional rates

“…The reaction rates included for the formation and destruction channels of H2 have been taken from Coppola et al (2011b) and Capitelli et al (2007). The collisional data with He are fully available for the whole H2 rovibrational manifold (F. Esposito, private communication and Celiberto et al 2017). The collisional data for the system H 2-H + have been included using the fits provided by Gerlich (1990); transitions up to (v = 0, j = 8) are therein reported.…”

Non-equilibrium plasma for ignition and combustion enhancement

“…If the particle density is sufficiently high, the radiative decay of the excited level competes with the collisional quenching. To correctly model this process and to properly account for the energy balance, the E − V processes of H 2 have been modeled by explicitly following the kinetics of vibrational levels of electronically excited states [63,64].…”

High-current H2+ beams from a filament-driven multicusp ion source

“…As was pointed out elsewhere, 23 higher electron energies favor excitation to singlet states over triplet states (which are predominantly from electron collisions below 20 eV). Triplet states feed the H + and H + 3 fractions by creating free H. 24 Having predominantly singlet excited states, thus, benefits H + 2 production. The size, shape, and position of the filament have an effect on the properties of the plasma.…”