MEASUREMENTS OF LINE STRENGTHS IN THE HO2 NU-1 OVERTONE BAND AT 1.5-MU-M USING AN INGAASP LASER

We report the first observation of resolved rotational-vibrational overtone (2-nu-1) absorptions of the hydroperoxyl radical (HO2) in the 1.5-mu-m region, using two-tone frequency modulation spectroscopy (TTFMS) with an InGaAsP laser diode and White-cell optics. Photolysis of Cl2/H2/O2 mixtures was used to produce the HO2, and the concentration was determined by modulated-photolysis UV absorption spectroscopy. The line center absorption cross sections for the strongest lines ranged between 1.3 x 10(-20) and 10 x 10(-20) cm2 molecule-1 under Doppler-limited conditions. For the strongest line this corresponds to an integrated line strength S of 1.6 x 10(-21) cm2 molecule-1 cm-1, a line strength of the same order of magnitude as lines previously observed in the relatively weak nu-1 fundamental.