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International audienc

A binary n-pentanol-nitromethane solution in the homogeneous state near the critical stratification point is acoustically studied in a frequency range of 5÷2800 MHz. The experiment confirmed the existence of the anomalous ultrasound attenuation, which can be analyzed in terms of the effective ultrasound absorption. On the basis of experimental data, the regular and fluctuation components of the effective ultrasound absorption coefficient of the solution are resolved. It is shown that the fluctuation part of the effective absorption coefficient can be described in the framework of the Ferrell-Bhattacharjee theory of heat capacity relaxation. On the basis of this theory with the use of the obtained experimental data, the crossover scaling function is determined, and its parameters and Ω 1/2 are found. K e y w o r d s: binary solutions, critical stratification point, ultrasound absorption coefficient, crossover function.

The propagation velocity and the absorption coefficient of ultrasound in a frequency range of 5-2800 MHz in a n-pentanol-nitromethane solution in a vicinity of its critical stratification point from the homogeneous state side have been studied. The research make it possible to reveal the influence of concentration fluctuations on the sound propagation velocity. Three regions of dynamical parameters are analyzed: the mean-field (FL ≪ 1), fluctuation (FL ≫ 1), and transition (crossover, FL = 1) ones. On the basis of experimental data, the temperature dependence of the concentration fluctuation relaxation time () is studied, and its magnitude 0 is determined. The contribution to the fluctuation part of the sound absorption coefficient at high frequencies (> 300 MHz), which is connected with the sound scattering by concentration fluctuations near the critical stratification point is estimated.

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