The 3 nu(1)+nu(2) combination band of HOCl: Assignments, perturbations, and line intensities

The high-resolution spectra (0.012 cm(-1)) of the 3 nu(1) + nu(2) combination band of hypochlorous acid HO35(37)Cl in the near infrared (similar to 11 478 cm(-1)) have been measured using a titanium:sapphire intracavity laser absorption (ICLA) spectrometer. Line assignments, absolute intensities, and the total band intensity for both isotopomers are reported. In the course of the band analysis two K-a branches (K-a = 2,3) were found to be perturbed via low-order Fermi-type (anharmonic) resonances by a dark perturber which has been identified to be the 2 nu(1) + 2 nu(2) + 3 nu(3) state. The data are compared with intensity predictions from simple empirical models and discussed with regard to detection limits for this molecule in the near infrared spectral region of the atmosphere. (C) 1997 Academic Press.