Modeling of wave driven molecular (H2, N2, N2-Ar) discharges as atomic sources

Microwave H₂, N₂, and N₂-Ar discharges driven by traveling surface waves are investigated as sources of ground state N(⁴S), H(1s) atoms. The dissociation kinetics is discussed in the framework of theoretical models based on a self-consistent treatment of the main discharge balances, wave electrodynamics and plasma-wall interactions. It is shown that the number density of hydrogen H(1s) atoms depends heavily on the wall conditions at low pressure conditions. The kinetics of N(⁴S) and metastable N(²D) and N(²P) atoms and of the molecular N₂(A³Σ_u⁺) metastable state in a pure N₂ discharge are shown to be strongly coupled. One possible way to control and to enhance nitrogen dissociation is the use of an N₂-Ar mixture. The increase in dissociation degree of N₂ molecules at high Ar fractional concentration can be attributed to dissociative recombination between electrons and N₂⁺ positive ions. The predicted results for the atomic density are compared with emission spectroscopy data.