Femtosecond, two-photon, laser-induced fluorescence (TP-LIF) measurement of CO in high-pressure flames

Quantitative, kiloherz-rate measurement of carbon monoxide mole fractions by femtosecond two-photon, laser-induced fluorescence (TP-LIF) was demonstrated in high-pressure, luminous flames over a range of fuel-air ratios. Femtosecond excitation at 230.1 nm was used to pump CO two-photon rovibrational X-1 Sigma(+)-> B-1 Sigma(+) transitions in the Hopfield-Birge system and avoid photolytic interferences with excitation irradiance similar to 1.7 x 10(10) W/cm(2). The effects of excitation wavelength, detection scheme, and potential sources of de-excitation were also assessed to optimize the signal-to-background and signal-to-noise ratios and achieve excellent agreement with theoretically predicted CO mole fractions at low and high pressure. (C) 2018 Optical Society of America