Measurement of hydroxyl radicals in an atmospheric pressuredischarge plasma by using laser-induced fluorescence

摘要

Hydroxyl radicals were measured by laser-induced fluorescence(LIF) using a tunable KrF excimer laser in an atmospheric pressuredischarge plasma. In that LIF, all of the OH(A2Σ-X2Π(3,0)) branches were identifiedwithin a tunable range of the laser. A time evolution of OH densityshowed that OH density increased with humidity and oxygen concentration.This results indicates OH radicals were mainly produced by chemicalreactions of H₂O with O radicals. There could be another OHproduction process other than H₂O+O→2OH. OH generated bythe another reaction reached a peak at about 5 μs after discharge. Itmay have been a collisional dissociation of H₂O withelectrons. OH density augmented after 0.6-μs pulsed discharge forseveral tens μs, then decreasing exponentially. The OH lifetimeshortened with increasing pressure. This result implies OH were mainlydecreased by a reaction with NO₂ generated from O₂and N₂. Two-dimensional OH distribution was also measuredusing two-dimensional LIF (2-D LIF) technique. They showed OH radicalsproceeded uniformly along a discharge path, then decreasing withhorizontal diffusion