Instantaneous imaging of ozone in a gliding arc discharge using photofragmentation laser-induced fluorescence

Ozone vapor, O-3, is here visualized in a gliding arc discharge using photofragmentation laser-induced fluorescence. Ozone is imaged by first photodissociating the O-3 molecule into an O radical and a vibrationally hot O-2 fragment by a pump photon. Thereafter, the vibrationally excited O-2 molecule absorbs a second (probe) photon that further transits the O-2-molecule to an excited electronic state, and hence, fluorescence from the deexcitation process in the molecule can be detected. Both the photodissociation and excitation processes are achieved within one 248 nm KrF excimer laser pulse that is formed into a laser sheet and the fluorescence is imaged using an intensified CCD camera. The laser-induced signal in the vicinity of the plasma column formed by the gliding arc is confirmed to stem from O-3 rather than plasma produced vibrationally hot O-2. While both these products can be produced in plasmas a second laser pulse at 266 nm was utilized to separate the pump-from the probe-processes. Such arrangement allowed lifetime studies of vibrationally hot O-2, which under these conditions were several orders of magnitude shorter than the lifetime of plasma-produced ozone.