Subdivision of phase space for anisotropically interacting water molecules

Epifanov, S.Yu.; Vigasin, A. A.

doi:10.1080/00268979709482591

Cited by 5 publications

(6 citation statements)

References 15 publications

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“…It has also been shown that the relative contribution of bound and quasi‐bound dimers to the continuum should vary with temperature and wavenumber [ Vigasin , 2010; Ptashnik et al , 2011], leading to an even more complicated temperature dependence. In fact, the area of strong temperature dependence in Figure 9 corresponds well to the temperature region 250–350 K, predicted by theory [ Epifanov and Vigasin , 1997; Vigasin , 2003] to be transitional between the dominance of bound and quasi‐bound dimers in water vapor. According to statistical partitioning of water molecule pairs [ Vigasin , 1991, 2003], the contribution of free pair collisions (which are partly responsible for the far wings of water monomers) is expected to be very small at close to standard temperature conditions.…”

Section: Discussionsupporting

confidence: 80%

“…On the other hand, recent ab initio calculations by Scribano and Leforestier [2007] and Lee et al [2008] have presented evidence that true ‐ bound water dimers may contribute 20%–40% of the self‐continuum in the midinfrared and far‐infrared, at close to atmospheric conditions. The development of the statistical approach to the partitioning of pair states in phase space for polyatomic molecules [ Vigasin , 1991, 2003; Epifanov and Vigasin , 1997] and its verification from classical trajectory calculations [ Lokshtanov et al , 2005] provide evidence that quasi ‐ bound water dimers (i.e., those with total energy higher than dissociation threshold), sometimes defined as a part of collision ‐ induced absorption , are also expected to contribute significantly to the self‐continuum at standard temperature and pressure [ Ptashnik et al , 2011].…”

Section: Introductionmentioning

confidence: 99%

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Water vapor self-continuum absorption in near-infrared windows derived from laboratory measurements

et al. 2011

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[1] In most near-infrared atmospheric windows, absorption of solar radiation is dominated by the water vapor self-continuum, and yet there is a paucity of measurements in these windows. We report new laboratory measurements of the self-continuum absorption at temperatures between 293 and 472 K and pressures from 0.015 to 5 atm in four near-infrared windows between 1 and 4 mm (10000-2500 cm −1 ); the measurements are made over a wider range of wavenumbers, temperatures, and pressures than any previous measurements. They show that the self-continuum in these windows is typically one order of magnitude stronger than given in representations of the continuum widely used in climate and weather prediction models. These results are also not consistent with current theories attributing the self-continuum within windows to the far wings of strong spectral lines in the nearby water vapor absorption bands; we suggest that they are more consistent with water dimers being the major contributor to the continuum. The calculated global average clear-sky atmospheric absorption of solar radiation is increased by ∼0.75 W/m 2 (which is about 1% of the total clear-sky absorption) by using these new measurements as compared to calculations with the MT_CKD-2.5 self-continuum model.

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Section: Discussionsupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Water vapor self-continuum absorption in near-infrared windows derived from laboratory measurements

et al. 2011

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“…A third potential contributor to the continuum is metastable complexes, molecular interactions that can affect absorption properties but do not result in the formation of bound complexes. It is thought that the number of these interactions may be large at atmospheric conditions [ Epifanov and Vigasin , 1997] with the band width being affected by the duration of the molecular interaction. This third process will not be considered further in this work due to uncertainties in the absorption cross sections.…”

Section: Introductionmentioning

confidence: 99%

Atmospheric water vapor complexes and the continuum

Daniel

Solomon

Kjaergaard

et al. 2004

Geophysical Research Letters

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[1] Estimates of absorption optical depths for the bound complexes H 2 O-H 2 O and the sum of H 2 O-N 2 , H 2 O-O 2 , and H 2 O-Ar at visible and near-infrared wavelengths are compared to the same quantities calculated from a frequently used water continuum parameterization (MT_CKD) and from a theoretical far wing water vapor lineshape theory. The temperature dependences of some of these optical depths are also compared. The comparisons suggest qualitatively that water complexes may contribute to the continuum at these wavelengths, and show that the temperature dependence of the continuum might provide insight into the role of the complexes in the atmosphere. Because of the dearth of laboratory measurements of the continuum at these wavelengths, and because the current estimates for the equilibrium constants of these water vapor complexes remain highly uncertain, more observations are needed before the importance of water complexes can be accurately quantified.

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“…Recently, Ptashnik et al (2011a) suggested that this could be explained by the fact that the theoretical spectra accounted only for truly bound dimers. In addition to these bound dimers, it was proposed by Vigasin (1985Vigasin ( , 1991Vigasin ( , 2003Vigasin ( , 2010 and Epifanov and Vigasin (1997), by a statistical partitioning of molecular pairs in phase space, that shorter-lived quasi-bound dimers should be of equal importance in atmospheric conditions. A simplified calculation (Ptashnik et al 2011a) indicated that these quasi-bound dimers might explain the additional spectral features in the observed near-room temperature spectra of the continuum.…”

Section: Post-2000mentioning

confidence: 98%