Laser-induced photodetachment of negative oxygen ions in the spatial afterglow of an atmospheric pressure plasma jet

Abstract Negative ions are an important constituent of the spatial afterglow atmospheric pressure plasmas, where fundamental plasma-substrate interactions take place that vital for applications such as biomedicine, material synthesis, and ambient air treatment. In this work, we use laser-induced photodetachment to liberate electrons from negative in region plasma jet interacting with argon-oxygen mixture, microwave cavity resonance spectroscopy detect photodetached electrons. This diagnostic technique allows determination electron density effective collision frequency before, during after laser pulse was shot through measurement volume nanosecond time resolution. From a saturation study, it is concluded O − dominant ion afterglow. Moreover, decay found be dominantly driven by (re)formation dissociative attachment 2 . As consequence, identified species process responsible formation our experiment.