Photofragmentation laser-induced fluorescence of ozone: an in situ tool for precise mapping of ozone concentration in non-thermal plasmas

The absolute spatially resolved concentration of ozone has been determined in the near afterglow of a novel type of atmospheric multi-hollow barrier discharge using photofragmentation laser-induced fluorescence. The method consists of two steps: (i) photodissociation of O-3 to O(P-3) and O-2(X-3 Sigma(-)(g)) with considerable vibrational excitation; (ii) predissociation laser-induced fluorescence of the molecular fragment via the O-2 (B-3 Sigma(-)(u), v' = 0 <- X-3 Sigma(-)(g), v '' = 6) transition. Both processes happen during the same laser pulse, requiring the same excitation wavelength (approximate to 248 nm). The fluorescence signal has been calibrated by infrared absorption. The method allows in situ observation before the afterglow chemistry significantly affects the O-3 concentration, and is capable of revealing inhomogeneous ozone distributions in the reactor. (C) 2019 The Japan Society of Applied Physics