QUANTITATIVE IR SPECTRA AND VIBRATIONAL ASSIGNMENTS OF CH$_2$I$_2$, AN ATMOSPHERIC AEROSOL PRECURSOR
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Date
2006
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Ohio State University
Abstract
\maketitle As part of the Northwest Infrared (NWIR) database of quantitative infrared spectra, we have recently completed quantitative spectra of diiodomethane, CH$_2$I$_2$. Photolysis of this molecule in the presence of ozone, O$_3$, has been suggested as an immediate precursor to new particle formation over the oceans, particularly in coastal areas. Combined with the quantitative medium (0.1 cm$^{-1}$) resolution vapor-phase IR spectra, liquid-phase IR and FT-Raman spectra, as well as \it{ab initio} \rm calculations have been used to update and extend the vibrational assignments of earlier workers. Two strong b$_2$ symmetry A-type bands at 584 and 1114 cm$^{-1}$ are observed, but are not resolved at 760 Torr and appear as B-type. In contrast, the b$_1$ symmetry C-type bands near 5953, 4426 and 3073 cm$^{-1}$ are resolved with rotational structure, including Q-branches with widths $<$ 1 cm$^{-1}$. Potential use of these bands for atmospheric monitoring will be discussed.
Description
Author Institution: Pacific Northwest National Laboratory, P.O. Box 999, MSIN K8-88, Richland, WA 99354