Effect of metastable oxygen molecules in high density power-modulated oxygen discharges

Abstract

O2 M (A 3S u 1 1C 3D u1c 1 S u 2 ) was included in the simulation. This chemistry was necessary to capture the experimentally observed increase in the O2 negative ion density in the afterglow of the pulsed discharge. As the electron temperature drops in the afterglow, the rate coefficient of electron attachment with O2 M increases several fold. The wall recombination probability of oxygen atoms affected the O2 density drastically. For the conditions studied, the maximum O2 density in the afterglow increased with pressure, decreased with power, and showed a maximum with pulse period. The time in the afterglow at which the peak O2 density occurred decreased with pressure and power, and was independent of the pulse period. Knowing the temporal evolution of O2 in the afterglow may be important for applications requiring extraction of negative ions out of the discharge. © 2000 American Institute of Physics.@S0021-8979~00!07512-5#