Vibrational temperature and vibrational relaxation of molecular oxygen in the afterglow of pulsed positive corona discharge

摘要

The density of vibrationally excited O_2(v = 6) in the afterglow of a pulsed positive corona discharge is measured using time-resolved laser-induced predissociation fluorescence (LIPF). Discharge occurs in a 13 mm point-to-plane gap in humid air. It is shown that humidity accelerates the vibration-to-translation (V-T) energy transfer from O_2(v) to the ambient gas. This acceleration can be explained by the rapid vibration-to-vibration (V-V) process of O_2(v)-H_2O system and the extremely rapid V-T process of H_2O-H_2O system. It is shown that the vibrational temperature of O_2 in the secondary streamer channels is much higher than that in the primary streamer channels. Since the cross section of dissociative attachment, e + O_2 → O + O~-, drastically increases with the O_2 vibrational temperature especially for low electron energy (< 5 eV), the secondary streamer might produce abundant O and O~- in spite of its low electron energy (1-2 eV).