OH radical measurement in a pulsed arc discharge plasma observed by a LIF method

Hydroxyl radicals generated by a pulsed arc discharge were measured by laser-induced fluorescence (LIF) with a tunable KrF excimer laser. It was shown that not only OH but excited O/sub 2/ (O/sub 2//sup */) and excited NO (NO/sup */) had absorption lines within a tunable range of the KrF laser, so that LIF signals of O/sub 2//sup */ and NO/sup */ were observed as well as OH signals. It was demonstrated that OH could be detected without disturbance by LIF signals of O/sub 2//sup */ or NO/sup */ through the A-X(3,0):P/sub 2/(8) excitation; OH density was measured under various conditions in the post-discharge region. The influences of humidity, discharge current, and O/sub 2/ concentration on OH density and OH decay rate were studied in H/sub 2/O/O/sub 2//N/sub 2/ mixture. The results provided some possible channels of OH production and reaction with other molecules in humid air. The absolute density of OH was estimated.