Afterglow in Pulsed Microwave Atmospheric Pressure Discharge

Abstract

The plasma state can persist even after the external source of ionization is removed by releasing the electrostatic potential energy between opposite charges and the energy stored in the atoms or molecules of high atomic or rovibronic energy state. The released internal energy contribute to generation of excited species and subsequent radiative de-excitation. Such afterglow plasmas have found several applications such as trace element analysis (in particular in the form of flowing-afterglow mass spectroscopy) and for remote sterilization or cleaning. In microwave pulsed plasma at atmospheric pressure, afterglow can be intense due to enhanced densities of atomic ions, molecular ions, and excited species via high energy electrons generated by the microwave fields. The temporal and spatial dynamics of the afterglow are studied and the results are utilized to maximize the power coupling efficiency.