Pulsed laser excitation of OH(A–X), NH2 (A–X), and CO2 (10.6-µm vibrational hot band) has been detected optoacoustically in flames. Detection sensitivities approaching 1 part in 109, 105, and 105, respectively, were obtained for these species. The form and characteristics of the pressure wave were examined, using OH in flames excited by dye laser and SF6 in a cold flow excited by a CO2 laser, to optimize the laser beam and microphone geometry and understand the influence of the microphone frequency response. Attempts to detect H2O using the vibrational overtone bands near 590 nm were successful in the vapor near 310 K but failed in the hot flame gases.
© 1983 Optical Society of America
Gregory P. Smith, Mark J. Dyer, and David R. Crosley, "Pulsed laser optoacoustic detection of flame species," Appl. Opt. 22, 3995-4003 (1983)