Measurements of nitrogen-broadening coefficients in the ν 3 band of the hydroperoxyl radical using a continuous wave quantum cascade laser

Abstract: Mid-infrared absorption spectroscopy was applied to the detection of the hydroperoxyl radical (HO2) in pulsed laser photolysis combined with a laser absorption kinetics reactor. The transition of the ν 3 vibrational band assigned to the O–O stretch mode around 1065cm−1 was probed with a thermoelectrically cooled, continuous wave, mid-infrared, distributed feedback quantum cascade laser (QCL). The HO2 was generated through 355nm photolysis of Cl2/1,4-c-C6H8/O2 mixtures. The mid-infrared absorption spectrum of the HO2 radical was recorded between 1064 and 1065.5cm−1. The absorption line shapes were well represented by the Voigt profile. The nitrogen-broadening coefficients of the HO2 radical at 295K were determined for four absorption lines around 1065cm−1. Mid-infrared absorption detection using a QCL as a spectroscopic light source is a powerful method in spectroscopic and kinetics studies of the HO2 radical. [ABSTRACT FROM AUTHOR]