Liquid water optical constants

Bertie JE, Lan Z. 1996. Infrared intensities of liquids. XX The intensity of the OH stretching band of liquid water revisited, and the best current values of the optical constants of H20(I) at 25 °C between 15,000 and 1 cm . Appl Spectrosc 50 1047-1057. 

Appendix 1. Calculation of Fourier Amplitudes b -i for Librators Appendix 2. Transformation of Integral for Spectral Function of Precessors Appendix 3. Optical Constants of Liquid Water... 

It is now well understood that the static dielectric constant of liquid water is highly correlated with the mean dipole moment in the liquid, and that a dipole moment near 2.6 D is necessary to reproduce water s dielectric constant of s = 78 T5,i85,i96 holds for both polarizable and nonpolarizable models. Polarizable models, however, do a better job of modeling the frequency-dependent dielectric constant than do nonpolarizable models. Certain features of the dielectric spectrum are inaccessible to nonpolarizable models, including a peak that depends on translation-induced polarization response, and an optical dielectric constant that differs from unity. The dipole moment of 2.6 D should be considered as an optimal value for typical (i.e.. 

The radiative transfer model in Madronich (1987) permits the proper treatment of several cloud layers, each with height-dependent liquid water contents. The extinction coefficient of cloud water is parameterized as a function of the cloud water computed by the three-dimensional model based on a parametrization given by Slingo (1989). For the Madronich scheme used in WRF/Chem, the effective radius of the cloud droplets follows Jones et al. (1994). For aerosol particles, a constant extinction profile with an optical depth of 0.2 is applied. 

These equations are used to subtract the contribution of reflections on the interfaces of such a strongly absorbing medium as liquid water, when one wishes to calculate the optical constant k and at the same time n. It is also used (37) in the calculation of these optical constants n and k when the measured value log(/o(i )//(f )) is that obtained using another set-up,... 

Figure 5. (A2) Various spectral quantities related to liquid water in the mid-IR region. Experimental values of log(/Q(i )//(i )) are shown in the case of an absorption set-np with a 1 p,m thick sample and of an ATR cell with an immersed portion of the crystal about 3 cm long (41). The optical constants n and k are also displayed together with the imaginary dielectric constants e".

According to Twomey (1977) an increase of cloud droplet concentration involves an increase of the albedo if other factors (liquid water content, thickness of cloud) remain constant. Thus, for a cloud thickness of 0.1 km (liquid water content 0.3 g m"3) the albedo is raised from 0.25 to 0.43 when the drop concentration is increased by a factor of eight. For a cloud with a thickness of 1 km the corresponding albedo increase is from 0.82 to 0.90. However, an increase in the optical thickness of a cloud also leads to a higher absorption of the infrared radiation emitted by the Earth s surface. 

On the basis of a definite analogy between e tx and F-centers we may expect the appearance under certain conditions of (e tr)2- particles of the type of F -centers. From the polaron model (57) it follows that the bipolaron (two electrons localized in a common polarization well) can not exist. In accordance with the work of Vinetskii and Giterman (63), in some cases the formation of the bipolarons becomes energetically possible in the result of interaction of the polarization wells of two separate polarons. However, the saving in energy for such bipolaron states is not large and hence they will not be stable in liquids under room temperature. Actually, up to the present time a series of attempts have been made to detect (e aq)2 in the irradiated liquid water but these attempts were not successful. The polaron theory (57) predicts that F -centers (two electrons in the anionic vacancy) may be stable. For this it is necessary that the ratio e/n2 (e and n2 are the static and optical dielectric constants, n—refraction index) should be more than 1.5. Evidently, in the glassy systems under consideration this requirement is fulfilled. 

Fig. 3. Bulk absorbance of hexagonal ice at lOOK(left) and the bulk absorbance of liquid water (right). (Reprinted with permission from Bettie JE, Labbe HJ, Whally E. (1969) / Chem Phys 50 4501 Querry MR, Wieliczka DM, Segelstein D. In Handbook of Optical Constants of Solids II, Academic Press Boston, MA, 1991.)...

The close similarity of the liquid water profile in Fig. 7 with the 13 mbar spectrum of H2O on NaCl(OOl) in Fig. 8 is good evidence that the thin film is liquid-like. Use of the optical constants of liquid water and the Beer-Lambert relation has enabled the determination of the coverage values as listed on Fig. 8 and the construction of the isotherm in Fig. 9. (A monolayer, (9 = 1, corresponds to each Na" Cl" surface ion pair covered, on average, by an H2O molecule.) In order to provide a context with an ambient environment, the water pressure needed to produce a monolayer on NaCl(lOO) corresponds to 40% relative humidity [77,78], a rather arid condition. In addition, the pristine appearing surfaces of the salt crystals in Fig. 2, photographed at 50% RH, were coated with several water layers. 

There are numerous properties of materials which can be used as measures of composition, e.g. preferential adsorption of components (as in chromatography), absorption of electromagnetic waves (infra-red, ultra-violet, etc.), refractive index, pH, density, etc. In many cases, however, the property will not give a unique result if there are more than two components, e.g. there may be a number of different compositions of a particular ternary liquid mixture which will have the same refractive index or will exhibit the same infra-red radiation absorption characteristics. Other difficulties can make a particular physical property unsuitable as a measure of composition for a particular system, e.g. the dielectric constant cannot be used if water is present as the dielectric constant of water is very much greater than that of most other liquids. Instruments containing optical systems (e.g. refractometers) and/or electromechanical feedback systems (e.g. some infra-red analysers) can be sensitive to mechanical vibration. In cases where it is not practicable to measure composition directly, then indirect or inferential means of obtaining a measurement which itself is a function of composition may be employed (e.g. the use of boiling temperature in a distillation column as a measure of the liquid composition—see Section 7.3.1). 

The absorption spectrum of the solvated electron depends not only on the nature of the solvent but also on parameters that modify the structure and properties of the solvent, such as pressure and temperature. The optical absorption band shifts to higher energies (shorter wavelengths) with increasing pressure up to 2000 bar the shift is larger in primary alcohols than in water and it correlates with the increase in liquid density rather than with the rise in dielectric constant. A rise in the temperature induces a red shift of the solvated electron absorption spectrum. Thus, the absorption maximum in water is located around 692 nm at 274 K and 810 nm at 380... 

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