Alternative optical equation for dielectric liquids.

Abstract

A "statistically permanent" pair of molecules interacting by dispersion forces, as a unit element of a simple cubic "crystal" modeling a nonpolar liquid dielectric at a given thermal state, has been used to explain low and high pressure refractive index n measurements. It has been shown that the equation (epsilon-1)2epsilon+1 / 9epsilon=c(lambda)r exp r(2) / 1-T/T(l)[where epsilon identical withn(2), c(lambda)>or=1 close to a unity liquid constant for wavelength lambda, r =4pirhoalpha/3, rho is the number density, alpha is the mean polarizability of a free molecule, T(l) is the internal temperature = a/RV, a is the van der Waals constant identical with(27/64)(RT(c))(2)/p(c), and R is the universal gas constant] is more accurate than any already known optical equation of liquids. The small changes in Lorentz-Lorenz refraction L identical with(epsilon-1)V/(epsilon+2) according to ( partial differentialL/ partial differentialp)(T)<0 and ( partial differentialL/ partial differentialT)(p)>( partial differentialL/ partial differentialT)(V)>0 are expected and observed in all pressure ranges. The translational fluctuation parameter <x(-6)> of the right order of magnitude is obtained from n.