Critical Divergence of Ultrasonic Absorption in Critical Binary Mixtures of Triethylamine-Water

Ultrasonic attenuation of critical binary mixtures triethylamine-water has been measured over the frequencies 15–95 MHz and at temperatures 12.5–18.0°C. The total sound absorption \((ε,ω)\) can be well expressed by three terms, \((ε,ω){=}crit.(ε,ω)+bg(ε,ω)+σ(T)\), where ε =( T c - T )/ T c is the reduced temperature, ω is the angular frequency of the sound. The first term is the critical relaxation, the second the background relaxation, and the last the classical contribution. The reduced absorption per wavelength (αλ) * vs the reduced frequency ω * follows the theoretical universal function over a wide range of ω * (=1×10 0 ∼3×10 3 ). From numerical analysis of \(crit.(ε,ω)\) based on the Kawasaki mode-mode coupling theory, the characteristic frequency of order-parameter fluctuations is expressed by f D ( ε )= f 0 ε 3ν with ν=0.65 and a relaxation parameter is written by Q ( ε )= Q 0 ε -α with α=0.084 for ε >6×10 -3 and α=0.49 for ε <6×10 -3 . Discussions are given on the validity of hyper scaling relation and of correlation functions in the binary system studied.