Dynamics and density estimation of hydroxyl radicals in a pulsed corona discharge

Hydroxyl radicals generated by a pulsed corona discharge are measured by laser-induced fluorescence (LIF) with a tunable KrF excimer laser. The discharge with 35 kV voltage and 100 ns pulse current occurs between needle and plate electrodes in H2O/O-2/N-2 mixture at atmospheric pressure. The density and decay profile of OH radicals are studied. OH radicals decay with time after the discharge with a time constant of about 30-60 mus. The OH density is estimated to be about 7 x 10(14) cm(-3) in H2O(2.4%)/N-2 mixture 10 mus after the discharge. The OH density is approximately proportional to the energy dissipated in the discharge. The O-2 content influences the OH production. When the O-2 content is varied in H2O(2.4%)/O-2/N-2 mixture, the OH density is maximum at an O-2 content of 2%. The spatial distribution of OH density shows that OH radicals are produced in the streamers under positive discharge.