Infrared absorption of gaseous CH2BrOO detected with a step-scan Fourier-transform absorption spectrometer

Abstract

CH2BrOO radicals were produced upon irradiation, with an excimer laser at 248 nm, of a flowing mixture of CH2Br2 and O-2. A step-scan Fourier-transform spectrometer coupled with a multipass absorption cell was employed to record temporally resolved infrared (IR) absorption spectra of reaction intermediates. Transient absorption with origins at 1276.1, 1088.3, 961.0, and 884.9 cm (1) are assigned to nu(4) (CH2-wagging), nu(6) (O-O stretching), nu(7) (CH2-rocking mixed with C-O stretching), and nu(8) (C-O stretching mixed with CH2-rocking) modes of syn-CH2BrOO, respectively. The assignments were made according to the expected photochemistry and a comparison of observed vibrational wavenumbers, relative IR intensities, and rotational contours with those predicted with the B3LYP/aug-cc-pVTZ method. The rotational contours of nu(7) and nu(8) indicate that hot bands involving the torsional (nu(12)) mode are also present, with transitions 7(0)(1)12(nu)(nu) and 8(0)(1)12(nu)(nu), nu = 1-10. The most intense band (nu(4)) of anti-CH2BrOO near 1277 cm(-1) might have a small contribution to the observed spectra. Our work provides information for directly probing gaseous CH2BrOO with IR spectroscopy, in either the atmosphere or laboratory experiments. (C) 2014 AIP Publishing LLC.