Hydroxyl tagging velocimetry method optimization: signal intensity and spectroscopy.
The previously demonstrated nonintrusive time-of-flight molecular velocity tagging method, hydroxyl tagging velocimetry (HTV), has shown the capability of operating both at room temperature and in flames. Well-characterized jets of either air (nonreacting cases) or hydrogen-air diffusion flames (reacting cases) are employed. A 7 x 7 OH line grid is generated first through the single-photon photodissociation of H2O by a approximately 193 nm pulsed narrowband ArF excimer laser and is subsequently revealed by a read laser sheet through fluorescence caused by A2sigma+(v' = 3) <-- X2pi(i)(v'' = 0), A2sigma+(v' = 1) <-- X2pi(i)(v'' = 0), or A2sigma+(v' = 0) < or = X2pi(i)(v'' = 0) pumping at approximately 248, approximately 282, or approximately 308 nm, respectively. A detailed discussion of the spectroscopy and relative signal intensity of these various read techniques is presented, and the implications for optimal HTV performance are discussed.