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OH detection and spectroscopy by DFWM in flames; comparison with CARS

This paper presents a study of OH detection by degenerate four-wave mixing (DFWM) in a premixed laminar CH4-air flame, at pressures varying from 1 to 7 bar. The P and Q branches of the A 2 Sigma +-X 2 Pi electronic transition are observed. A spectroscopic study is performed and saturation and pressure effects on the lineshapes and concentration profiles are presented. A preliminary comparison between CARS and DFWM is given.