Relaxation Phenomena after Laser-Induced Photodetachment in Electronegative Rf Discharges

The response of a radio-frequency discharge in an electronegative gas to laser-induced photodetachment is considered. The discharge is described by a numerical fluid model, including the electron energy balance. The detachment event is simulated by transforming instantaneously all or part of the negative ions into electrons in the region of the discharge passed by the laser beam. In order to avoid severe restrictions on the computational time step, the evolution of the electron density and of the electric field is solved with a fully implicit numerical method. It turns out that the relaxation towards the periodic quasisteady state is mainly governed by a simultaneous increase of the production rate of negative ions and decrease of the ionization rate. The qualitative behavior of the calculated electron decay rate is in accordance with experimental observations.