Optical Constants Of Water Research Articles

Comparison between transmittance equations of optical cell for calculating optical constants of liquid materials

A method for determining the optical constants of liquid materials by using transmittances of optical cell filled with liquid materials was introduced, and three equations for calculating the transmittance of optical cell were comparatively investigated. The transmittance spectrograms at normal incidence of optical cell filled with water at different thicknesses were measured in spectral range 2–2.5μm, and optical constants of water were calculated based on the measured spectrum, which are used to validate these equations. The results show that the method in this work can effectively calculate the optical constants of liquid materials. Considered the multiple transmission through the glass, the equations have a better ability to calculate the total transmittance of optical cell filled with liquid material compared with omitting the multiple transmission.

Comparison of three methods for determining optical constants of liquid materials based on transmittance spectrum of optical cell

Two methods for calculating the equivalent or effective transmittance of net liquid materials by using transmittances of optical cell were introduced, and three double-thickness transmittance methods (DTTs) to determine the optical constants of liquid materials were comparatively investigated. The transmittance spectrograms at normal incidence of optical cell with water at different thicknesses were measured in spectral range 2–2.5μm, and the optical constants of water were calculated by three methods, which are used to validate these methods with the existing data of reference. The results show that DTTs can not accurately calculate the optical constants of liquid materials by using the equivalent or effective transmittance data of liquid materials, and DTTs using the transmittance spectrum of optical cell filled with liquid materials can effectively calculate the optical constants of liquid materials.

Infrared absorption spectra of liquid water and deuterated water by Car-Parrinello molecular dynamics

Infrared (IR) absorption spectra plays a key role in the study of thermodynamic and dynamic properties of liquid water. Car-Parrinello molecular dynamics simulations within the framework of density-functional theory are used to study the IR absorption, dielectric function and optical properties of liquid water and deuterated water. Using the energy minimization model to obtain the input structure, we calculate the molecular dipole moment of water and deuterated water at ambient temperature, and then obtain the IR absorption spectra by Fourier transforming the autocorrelated function of dipole moment. As the numerical analysis indicates, the calculated results fit well with previous literature experiments. The absorption peak represents the stretching mode of oxygen-hydrogen covalent bond and shows a slight red shift. The dielectric functions and optical constants of water and deuterated water at the temperature of 303 K are extracted from IR absorption spectrum.

Spectral radiation characteristics of water sprays

In this paper an analysis is presented to predict the spectral absorption, extinction and scattering coefficients of water sprays using Mie theory for spherical, homogeneous particles. The spectral absorption and extinction efficiencies are calculated for different mean droplet diameters and different droplet size distributions. To generalize the results and account for the spectral dependence of the optical constants of water, the efficiency factor for extinction in the small particle size limit of the Mie theory is used for scaling. The results of calculations for different size water droplet spray distributions are discussed. The results reported can be used in radiative transfer submodels of computational fluid dynamics simulation of fire suppression using water sprays/mists.

Bleaching of a polydisperse aqueous aerosol by laser radiation

The bleaching of a polydisperse aqueous aerosol by cw 10.6 μ wavelength laser radiation and diffusive evaporation of the water droplets were investigated using a numerical solution to a set of equations. The spatial and temporal dependences and the parameters characterizing the bleaching process were found. The parameters of the bleaching process were analyzed as a function of the radiation energy flux density, initial temperature of the droplets, evaporation coefficient and optical constants of water, and initial aerosol dropletsize distribution function. The efficiency of the bleaching process was investigated and the results compared with experiment.

Optical constants of water in the infrared

The results of our earlier studies of reflection and absorption in various spectral regions are reviewed and then used to provide values of the complex index of refraction of water at 27°C in the spectral range 5000–10 cm−1, corresponding to wavelengths in the range 2 μm to 1 mm. Values of n, k, and the Lambert absorption coefficient a, which are presented graphically and in tabular form, should prove useful in studies of the scattering of infrared radiation by water droplets in the atmosphere and in studies of radiative heat balance at water surfaces.

Optical Constants of Water in the 200-nm to 200-μm Wavelength Region

Extinction coefficients k(lambda) for water at 25 degrees C were determined through a broad spectral region by manually smoothing a point by point graph of k(lambda) vs wavelength lambda that was plotted for data obtained from a review of the scientific literature on the optical constants of water. Absorption bands representing k(lambda) were postulated where data were not available in the vacuum uv and soft x-ray regions. A subtractive Kramers-Kronig analysis of the combined postulated and smoothed portions of the k(lambda) spectrum provided the index of refraction n(lambda) for the spectral region 200 nm </= lambda </= 200 microm.

Optical Constants of Water in the Infrared

The infrared reflectance of water in the region 5000–300 cm−1 has been measured at near-normal incidence and at an incidence angle of 53°. On the basis of the measured values of spectral reflectance and the existing data on spectral transmittance, we have obtained values for the real and imaginary parts of the refractive index of water. The resulting values, which are presented in both graphical and tabular form, are compared with recent determinations by other investigators.