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Measuring the Concentration of Minor Species from the Modulation Dip of the Nonresonant Background of Broad-Band CARS Spectra

Volume 47, Number 6 (June 1993) Page 710-714

Hahn, J.W.; Park, S.N.; Lee, E.S.; Rhee, C.; Kang, K.T.; Chung, S.H.; Choi, C.Y.; Huh, Y.D.

A new technique for measuring the concentration of species from the modulation dip of the nonresonant background of broad-band CARS spectra has been proposed. To reduce the mode noise superimposed on the CARS spectra, we used a modeless laser generating amplified spontaneous emission as the Stokes beam of the broad-band CARS. The modulation dip induced by a minor species, CO in Ar, was numerically calculated and fitted as a function of CO concentration and temperature. We applied this technique in measuring CO concentration in a static cell and also the profile of CO concentration in a CH4/air premixed flame of a counterflow burner.