Simultaneous two-dimensional visualization of soot and OH in flames using laser-induced fluorescence

Two-dimensional visualization of soot has been realized in flames with the use of laser-induced fluorescence in C2 from laser-vaporized soot [LIF(C2)LVS]. Soot particles are heated to vaporization temperatures by the absorption of laser radiation. C2 radicals produced by this process are excited at wavelengths around 563 nm through the transition ν′ = 0 d3∏g←ν″ = 1 a3∏u, and the subsequent fluorescence at approximately 516 nm is detected. By frequency-doubling of the laser radiation, wavelengths around 281.5 nm are achieved, which can excite OH radicals to the ν′ = 1 A2Σ+ state from ν″ = 0 X2∏, with subsequent fluorescence at approximately 310 nm. With the use of both these excitation wavelengths, and a Cassegrainian split-mirror telescope as the imaging detection system in front of the charge-coupled device (CCD) camera, simultaneous two-dimensional single-shot images of soot and OH were obtained on a single CCD chip, thus enabling both sooting regions and reaction zones in flames to be monitored