The quantitative infrared and NIR spectrum of CH2I2 vapor: vibrational assignments and potential for atmospheric monitoring T. J. Johnson, T. Masiello, and S. W. Sharpe Pacific Northwest National Laboratory, Richland, WA 99354, USA
Abstract. Diiodomethane (CH2I2) has recently become a molecule of
significant atmospheric interest as it can contribute to coastal IO
formation. As part of the PNNL database of gas-phase infrared spectra, the
quantitative absorption spectrum of CH2I2 has been acquired at 0.1 cm-1
resolution. Two strong b2 symmetry A-type bands at 584 and
1114 cm-1 are observed, but are not resolved when broadened to 760 Torr
with nitrogen and appear as B-type. In contrast, the b1 symmetry C-type
bands near 5953, 4426 and 3073 cm-1 are resolved with rotational
structure, including Q-branches with widths ≤1 cm-1. The
quantitative infrared and near-infrared vapor-phase spectra (600–10 000 cm-1)
are reported for the first time. Some bands are discussed in
terms of their potential for atmospheric monitoring and theoretical
detection limits on a selected basis. FT-Raman spectra and ab initio calculations are
used to complete vibrational assignments in the C2v point group.
Citation: Johnson, T. J., Masiello, T., and Sharpe, S. W.: The quantitative infrared and NIR spectrum of CH2I2 vapor: vibrational assignments and potential for atmospheric monitoring, Atmos. Chem. Phys., 6, 2581-2591, doi:10.5194/acp-6-2581-2006, 2006.