Bimodal dependence of light scattering/fluctuations on the concentration of aqueous solutions

Resumo

Two concentration ranges (from 10⁻⁵ to 10⁻⁹ and from 10⁻¹³ to 10⁻¹⁸ M) corresponding to enhanced fluctuations of Rayleigh and Raman scattering of second-harmonic (527 nm) pulses of YVO₄:Nd³⁺ laser are found for aqueous solutions of antioxidant potassium phenosan. A correlation is revealed between the rise in elastic Rayleigh scattering intensity and its fluctuations and the shift of the center of OH Raman band of water toward the ice component characteristic frequency (3200 cm⁻¹). The development of phase-equilibrium instabilities is analyzed based on the model of fluctuations of the number of hydrogen bonds on the assumption of formation/destruction of ordered hydration layer of phenosan molecules in water.