Elementary Processes and Kinetic Modeling for Hydrogen and Helium Plasmas

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.