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 Ψ(ε, ω) can be well expressed by three terms, Ψ(ε, ω)=Ψcrit.(ε, ω)+Ψbg(ε, ω)+σ(T), where ε=(Tc−T)⁄Tc 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*(=1×100∼3×103). From numerical analysis of Ψcrit.(ε, ω) based on the Kawasaki mode-mode coupling theory, the characteristic frequency of order-parameter fluctuations is expressed by fD(ε)=f0ε3ν with ν=0.65 and a relaxation parameter is written by Q(ε)=Q0ε−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. © 1979, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.