Water density and polarizability deduced from the refractive index determined by interferometric measurements up to 250 MPa

Abstract

The refractive index of water is precisely determined in the visible light range as a function of the pressure until 250 MPa by means of a new measurement device that uses a special pipe tee included in an interferometer set. This technique allows revisiting the Bradley-Tait and Sellmeier equations to make them dependent on the wavelength and the pressure, respectively. The Bradley-Tait equation for the pressure dependence of the water refractive index is completed by a wavelength-dependent factor. Also, in the considered pressure and wavelength ranges, it is shown that the Sellmeier coefficients can be straightforwardly linked to the pressure, allowing the determination of the refractive index of water for either any wavelength or pressure. A new simple model allows the determination of the density of water as a function of the measured refractive index. Finally, the polarizability of water as function of pressure and wavelength is calculated by means of the Lorentz-Lorenz equation.

Underwater Wireless Acousto-Optic Waveguide (UWAOW)

“…The curves are in agreement and overlap each other up to a SPL of 260 dB re 1 µPa @ 1 m. Above this value, the formulation presented by Buick et al 4 follows the one adopted by the IAPWS, whereas the rather complicated equation suggested by Weiss et al 26 exhibits a smaller change in refractive index. …”

“…The influence of optical wavelength, temperature and density on the refractive index of water has been extensively covered by a number of research groups. More recent publications include: Schiebener et al in 1990, 25 26 In chronological order, a comprehensive review on the refractive index of light water and steam is given by the widely cited paper of Schiebener et al 25 This formulation has also been adpted by the International Association for the Properties of Water and Steam (IAPWS) and thus it represents the widely referenced source when dealing with the refractive index of water. 27 In this work, the coefficients published in 1997 by the IAPWS with the updated ITS-90 Temperature scale, are considered to evaluate the refractive index as a function of different parameters.…”

“…A third relationship between refractive index and applied pressure was derived by Weiss et al in 2012. 26 It is obtained by combining the Bradley-Tait equation, that was used also by IAPWS, with the Sellmeier dispersion coefficients that are assumed to be pressure dependent. Expanding up to a second order polynomial with three coefficients, the equation can be written as a function of the applied pressure P and the optical wavelength λ op .…”

Protein biosensing with fluorescent microcapillaries

“…For the latter two values, we take 2.25 and 1.37 g/cm 3 as typical of proteins [63]. Accordingly, α n is estimated to be 5.1 x 10 −21 cm 3 , which is almost three orders of magnitude larger than that of water [64] and justifies the replacement of α ex by α n in Eq. (6).…”

Indicating pressure and environmental effects by means of the spectral shift with rhodamine B and fluorescein

“…30, ε(p) and d(p) (25 • C) for water were determined from the modified Tait-equation 31 and parameters given in the references. 30,32 For ethanol d(p) and ε(p) (25 • C) were obtained according to Refs. 33 and 34, respectively.…”