Iwanowski I, Sattarow A, Behrends R, Mirzaev S Z, Kaatze U
Drittes Physikalisches Institut, Georg-August-Universität, Friedrich Hund Platz 1, 37077 Göttingen, Germany.
J Chem Phys. 2006 Apr 14;124(14):144505. doi: 10.1063/1.2179073.
Acoustical attenuation spectrometry, dynamic light scattering, shear viscosity, density, and heat capacity measurements of the methanol/n-hexane mixture of critical composition have been performed. The critical part in the sonic attenuation coefficients nicely fits to the empirical scaling function of the Bhattacharjee-Ferrell [Phys. Rev. A 24, 1643 (1981)] dynamic scaling model if the theoretically predicted scaled half-attenuation frequency Omega(12) (BF)=2.1 is used. The relaxation rates of order parameter fluctuations, as resulting from the acoustical spectra, within the limits of experimental error agree with those from a combined evaluation of the light scattering and shear viscosity measurements. Both series of data display power law with amplitude Gamma(0)=44x10(9) s(-1). The amplitude of the fluctuation correlation length follows as xi(0)=0.33 nm from the light scattering data and as xi(0)=0.32 nm from the amplitude of the singular part of the heat capacity if the two-scale factor universality relation is used. The adiabatic coupling constant g=0.11 results from the amplitude of the critical contribution to the acoustical spectrum near the critical point, in conformity with g=0.12 as following from the variation of the critical temperature with pressure along the critical line and the thermal expansion coefficient.
对临界组成的甲醇/正己烷混合物进行了声衰减光谱、动态光散射、剪切粘度、密度和热容量测量。如果使用理论预测的标度化半衰减频率Ω(12)(BF)=2.1，则声衰减系数中的临界部分很好地符合Bhattacharjee-Ferrell[《物理评论A》24, 1643 (1981)]动态标度模型的经验标度函数。在实验误差范围内，由声谱得出的序参量涨落的弛豫率与光散射和剪切粘度测量的综合评估结果一致。这两组数据均显示出幂律，振幅Γ(0)=44×10^9 s^(-1)。如果使用双标度因子普适关系，涨落关联长度的振幅从光散射数据得出为ξ(0)=0.33 nm，从热容量奇异部分的振幅得出为ξ(0)=0.32 nm。绝热耦合常数g=0.11由临界点附近声谱的临界贡献的振幅得出，与沿临界线的临界温度随压力的变化以及热膨胀系数得出的g=0.12一致。
