Electro-Negativity Related Phenomena in Radio-Frequency Driven He/O_2 Atmospheric Pressure Plasmas

摘要

Numerical simulations of a capacitively-coupled radio-frequency driven atmospheric pressure plasma in helium with 0.5% oxygen admixture are presented. Apart from neutral reactive oxygen species, the discharge can produce high number densities of different singly-charged negative atomic and molecular oxygen ions, which are, in contrast to the neutral species, confined in the plasma bulk region. The formation of the individual negative oxygen ions is of fundamental interest as well as of technological relevance, since it is correlated to the formation of the corresponding reactive neutrals. The numerical simulation reveals a high electro-negativity, which leads to complex transient phenomena, like violation of the plasma bulk quasi-neutrality, subsequent electrical field enhancements, and related modification of the spatio-temporal excitation and ionization dynamics.