Rayleighndash;Brillouin light scattering from multicomponent mixtures: The Landaundash;Placzek ratio

摘要

In onehyphen;component fluids Rayleighndash;Brillouin light scattering can be used to determine the equation of state of the fluid: A combination of the Brillouin shift and the Landaundash;Placzek ratio yields the isothermal compressibility. The same technique has been applied to multicomponent mixtures. We derive an expression for the Landaundash;Placzek ratio in a multicomponent mixture and show that it contains additional terms compared to the onehyphen;component case due to concentration fluctuations in the mixture. When we apply the expression to recent experiments on a fivehyphen;component mixture of hydrocarbons, we show that the additional contribution cannot be neglected.