Unseeded velocity measurement by ozone tagging velocimetry

Ozone tagging velocimetry is developed for unseeded velocity measurement of air flows. An ozone line is photochemically created by an ArF excimer laser. After a fixed time delay the ozone line is imaged with a KrF excimer laser sheet (248 nm) that photodissociates the ozone and produces vibrationally excited O2. The O2 is excited by the same 248-nm light through the Schumann–Runge band, B Σu-3(v′=0,2)←X Σg-3(v″=6,7). An intensified CCD camera records the O2 fluorescence from the initial and the final line positions to permit the velocity profile along the line to be determined.