Laser scattering in water and aqueous solutions of salts

An automated laser polarimetric scatterometer, operating at a wavelength of 532nm, has been developed for measuring the total scattering matrix of liquid samples in a cylindrical geometry. The optical scheme of the polarimeter combines an electro-optic modulator with a rotary quarter-wave plate. The results of experiments involving distilled water and NaCl aqueous solutions are reported. The measured angular dependencies of the elements of the scattering matrix are compared with numerical computations based on the T-matrix method. The experimental scattering matrix data can be interpreted as a scattering on an ensemble of stochastic micron-scale clusters composed of polydisperse air bubbles having effective radii of 70-100 nm. The fractal dimension of such clusters was evaluated as 2.5-2.8. Their concentration increases with salt addition from 10(3) cm(-3) in distilled water to 10(6) cm(-3) in 0.8 M aqueous solution of NaCl.