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Old and new problems in the physics of multicusp magnetic sources for the production of negative H -/Dions are presented and discussed. We emphasize particularly, in this kind of plasmas, both the vibrational and electron non equilibrium energy distributions, the role of Rydberg states in enhancing the negative ion production, the production of vibrationally excited states by the Eley-Rideal mechanism, and the enhancement of negative ion concentrations in pulsed discharges. In appendix I recent cross sections calculations for elementary processes and the theoretical determination of hydrogen recombination probability on graphite surface are illustrated. In appendix II two types of sources are modeled: the first one is a classical negative ion source in which the plasma is generated by thermoemitted electrons; in the second one, electrons already present in the mixture are accelerated by an RF field to sufficiently high energy to ionize the gas molecules.

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The modeling of atmospheric gas, interacting with the space vehicles in re-entry conditions in planetary exploration missions, requires large set of scattering data for all those elementary processes occurring in the system. A fundamental aspect of re-entry problems is represented by the strong nonequilibrium conditions met in the atmospheric plasma close to the surface of the thermal shield, where numerous interconnected relaxation processes determine the evolution of the gaseous system towards the equilibrium conditions. A central role is played by the vibrational exchanges of energy, so that collisional processes involving vibrationally excited molecules assume a particular importance. In the present paper, theoretical calculations of complete sets of vibrationally state-resolved cross sections and rate coefficients are reviewed, focusing on the relevant classes of collisional processes: resonant and non-resonant electronimpact excitation of molecules, atom-diatom and molecule-molecule collisions as well as gas-surface interaction. In particular, collisional processes involving atomic and molecular species, relevant to Earth (N 2 ,O 2 ,NO), Mars (CO 2 ,CO,N 2) and Jupiter (H 2 ,He) atmospheres are considered.