Vibrational excitation and negative ion production in radio frequency parallel plate H2 plasmas

A theoretical study of the vibrational kinetics and attachment in low pressure hydrogen plasmas produced by Radio Frequency (RF) discharges is performed. In particular we study the influence of gas/surface kinetic processes such as the vibrational deactivation and the atomic recombination of molecules. The production of vibrationally excited molecules by the surface recombination of atoms is also considered. The study is realized by means of a self-consistent one dimensional kinetic model, and a parallel plate RF discharge test case is implemented. Results show that surface processes are able to affect the vibrational distribution function (vdf) and the negative ion (H-) density. The effect of vibrational exothermicity of H atom recombination is also discussed as a way to reduce the gap between theory and experimental results. Moreover, it is shown that the H- ion heating by the electric field strongly affects the detachment rate: this effect is specially important for negative ions produced through Rydberg states in this kind of discharges.