Charge carrier dynamics in a pulsed inductive RF discharge in oxygen

We report on the spatio-temporal behaviour of negative oxygen ions in a pulsed inductively coupled RF excited oxygen discharge in the gaseous electronics conference cell. The temporal behaviour of the positive and negative charge carriers in the afterglow of the discharge allows identification of the dominant loss processes of negative ions. The results are in good agreement with model calculations. The negative ions are trapped for a long time in the bulk plasma without diffusion to the walls. Negative ions can diffuse to the walls only after complete decay of the electron component and formation of an ion–ion plasma. We can identify a high fraction of negative oxygen molecular ions that are generated during this phase in collisions of negative atomic oxygen ions with metastable oxygen molecules. Such a high fraction of molecular negative ions has not been observed so far in continuous discharges.