Dynamic scaling of the critical ultrasonic attenuation in binary liquids: Evidence from broadband spectrometry

Between 200 kHz and 500 MHz, the ultrasonic attenuation spectrum of the eth anol/dodecane mixture of critical composition has been measured at various temperatures near the critical one. The measured broadband spectra are eval uated in light of the Ferrell-Bhattacharjee dynamic scaling theory. The exp erimental findings largely fit the theoretical spectral function if suitabl e crossover corrections are made using dynamic lightscattering data. The me asured scaling function follows the predictions of the recent Folk-Moser re normalization-group theory even better. Combining our ultrasonic attenuatio n coefficient: data with density data from the literature, the asymptotic c ritical behavior of the thermal expansion coefficient and of the specific h eat has been determined and found consistent with the two-scale factor univ ersality. The sonic attenuation data have also been evaluated to yield the adiabatic coupling constant g of the dynamic scaling theory, The unusually small absolute value [g] =0.1 resulted, in fairly good agreement with \g\ = 0.13 as following from thermodynamic data PACS number(s): 62.60.+v, 64.60. Ht, 43.35.+d.