Femtosecond, two-photon, planar laser-induced fluorescence of carbon monoxide in flames.

Two-photon, planar laser-induced fluorescence (TP-PLIF) of carbon monoxide was performed in steady and driven flames using femtosecond (fs) laser pulses at 1 kHz. Excitation radiation at 230.1 nm (full-width at half-maximum bandwidth of 270  cm^-1) was used to pump many rovibrational two-photon transitions in the B¹∑⁺←X¹∑⁺ system. Visible fluorescence in the range 362-516 nm was captured using an image intensifier and high-speed camera. The signal dependence on excitation energy and wavelength is presented. Photolytic interferences from the ultraviolet laser were explored in a sooting diffusion flame. Using an excitation laser intensity of 10¹⁰  W/cm², negligible photolytic interferences were observed, and PLIF imaging of dynamic flame events was performed at 1 kHz.