Simultaneous imaging of H and OH in flames using a single broadband femtosecond laser source

Atomic hydrogen (H) and hydroxyl radical (OH) are two key intermediate species in the combustion of hydrocarbon fuels. For example, spatial temporal distribution H is useful to better understand ignition/extinction processes, whereas OH profiles can yield flame structure reaction zone different flames conditions. In present study, simultaneous laser-induced fluorescence (LIF) measurements obtained using a single ultrashort femtosecond-duration laser pulse near ?=307.7 nm for 3pLIF H. Measurements performed CH4-air C2H4-air stabilized over Hencken burner. Recently developed three-photon LIF (3pLIF) technique used H, same excitation simultaneously excite A2?+?X2? (0,0) transition. Red-shifting wavelength 307.7 as opposed commonly two-photon 205 deep-ultra-violet (DUV) pulses enables reduction absorption losses energy when transmitting through thick optical windows high-pressure vessels, example. Furthermore, efficiency fs generation scheme commercial parametric devices approximately factor higher compared 292 this number densities have been reported range equivalence ratios CH4/air C2H4/air established Simultaneous imaging premixed Bunsen presented. Prospective improvements increasing signal-to-noise hence potential kHz-rate single-shot also discussed.