On the possibility of negative ion concentration growth between pulses of discharge current in oxygen

We present a critical analysis of data available in literature on the degra dation of low-pressure oxygen plasma. Special attention is paid to two effe cts repeatedly observed in the initial stage of plasma degradation: a sharp growth in the flux of negative ions incident on the wall and an increase i n the probing current during the laser-induced photodetachment. Both these phenomena are attributed by various authors to an absolute growth in the ne gative ion concentration. Our analysis shows that the whole body of experim ental data cannot be explained based only on the influence of bulk plasmach emical reactions without taking into account special features of the transp ort processes in electronegative gases. An alternative mechanism is propose d which involves a two-stage degradation of the electronegative gas plasma accompanied by a change in the diffusion regime. (C) 2000 MAIK "Nauka/Inter periodica".