New Infrared Spectra of the Water-CO2 Complex: Determination of Four Intermolecular Modes and Test of a High-Level
A J Barclay1, A R W McKellar2, C Lauzin3
1Department of Physics and Astronomy, University of Calgary, 2500 University Drive North West, Calgary, Alberta T2N 1N4, Canada.
Abstract:
High resolution infrared spectra of water-CO2 dimers are further studied using tunable infrared sources to probe a pulsed slit jet supersonic expansion. The relatively weak transition of D2O-CO2 in the D2O ν1 fundamental region (≈2760 cm-1) is observed for the first time, as are various spectra of D2O-13CO2. Combination bands involving the intermolecular in plane geared bend (disrotatory) mode are observed for H2O-CO2 (≈1642, 2397 cm-1) in the H2O ν2 and CO2 ν3 regions, for HDO-CO2 (≈2761 cm-1) in the HDO ν3 region, and for D2O-CO2 (≈2386, 2705 and 2821 cm-1) in the CO2 ν3, D2O ν1, and D2O ν3 regions. A combination band involving the intermolecular in plane antigeared bend (conrotatory) mode is observed for D2O-13CO2 (≈2425 cm-1) in the CO2 ν3 region. And finally, a combination band involving the intermolecular twist (internal rotation) mode is observed for D2O-CO2 (≈2874 cm-1) in the D2O ν3 region. But this twist transition actually appears as two bands of similar intensity, separated by 2 cm-1, suggesting an "accidental" near-coincidence of the "real" combination state with a "dark" background state of the same symmetry. Intermolecular mode frequencies determined from the combination bands are in very good agreement with a recent theoretical calculation based on a high-level ab initio potential surface.
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