Dynamic scaling and background relaxation in the ultrasonic spectra of the ethanol–dodecane critical mixture

• Published in: Chemical physics letters 2007-02, Vol.435 (4), p.263-267
• Main Authors: Mirzaev, S.Z., Iwanowski, I., Kaatze, U.
• Format: Article
• Language: English
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2006.12.070

Ultrasonic attenuation spectrum of an ethanol–dodecane mixture of critical composition and at low concentration of alcohol (inset). Ultrasonic attenuation spectroscopy of a noncritical ethanol–dodecane mixture revealed a low frequency relaxation term. Considering this term in the spectra for the mixture of critical composition the experimental scaling function agrees well with the predictions of the dynamic scaling theory. Dynamic light scattering and shear viscosity measurements yield the amplitudes ξ 0 = (0.37 ± 0.02) nm and Γ 0 = (6.4 ± 0.3) × 10 9 s −1 for the fluctuation correlation length and relaxation rate of concentration fluctuations, respectively. The adiabatic coupling constant results as small as ∣ g∣ = 0.13 ± 0.03 from the ultrasonic spectra and as g = 0.094 ± 0.01 from the pressure dependence of the critical temperature and the thermal expansion coefficient.