The quantitative infrared and NIR spectrum of CH2I2 vapor: vibrational assignments and potential for atmospheric monitoring

Other literature type English OPEN
Johnson, T. J. ; Masiello, T. ; Sharpe, S. W. (2006)

Diiodomethane (CH<sub>2</sub>I<sub>2</sub>) 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 CH<sub>2</sub>I<sub>2</sub> has been acquired at 0.1 cm<sup>-1</sup> resolution. Two strong b<sub>2</sub> symmetry A-type bands at 584 and 1114 cm<sup>-1</sup> are observed, but are not resolved when broadened to 760 Torr with nitrogen and appear as B-type. In contrast, the b<sub>1</sub> symmetry C-type bands near 5953, 4426 and 3073 cm<sup>-1</sup> are resolved with rotational structure, including Q-branches with widths &le;1 cm<sup>-1</sup>. The quantitative infrared and near-infrared vapor-phase spectra (600&ndash;10 000 cm<sup>-1</sup>) 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 C<sub>2<i>v</i></sub> point group.
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