Ultrasonic spectroscopy of liquids. Extending the frequency range of the variable sample length pulse technique

Abstract

A method is described that allows the ultrasonic absorption coefficient U of liquids to be precisely measured between about 1 and 100 MHz. The automatic measuring procedure can be performed easily and comparatively fast. At high a values t h e accuracy of the method is clearly superior to the more time-consuming resonator technique, which is applied in this frequency range. This accuracy is achieved by careful construction and adjustment of the specimen cell, by semiempirical consideration of diffraction effects within the sample, and by precise calibration of the set-up by a specially designed below cut-off piston attenuator. The short measuring time is enabled by the particular mode of operation also described in this paper.

Chair–chair conformational flexibility, pseudorotation, and exocyclic group isomerization of monosaccharides in water

“…Reference measurements have been performed with liquids of carefully adjusted sound velocity c s and density in order to appropriately correct the measured quality factor for intrinsic cell losses. [29][30][31][32][33][34][35] We used water/methanol mixtures and aqueous solutions of urea with well-known absorption coefficient as reference liquids. At frequencies above 3 MHz, absolute ␣ measurements have been performed by transmitting pulse-modulated sonic waves through a cell of variable sample length l. Four cells have been employed that mainly differed from one another by their dimensions and by the type of piezoelectric transducers used as a transmitter and a receiver.…”

“…37 Since the transducer area is finite, diffraction effects may affect the cell transfer function at frequencies below 30 MHz. These effects have been taken into account using a semiempirical correction term, 34 obtained from calibration measurements in which suitable reference liquids were used.…”

Relaxation rate and scaling function of the critical system 3-methylpentane-nitroethane-cyclohexane

“…Here F * denotes the ratio ͓A͑T c ͒c͑T c ͔͒ / ͓A͑T͒c͑T͔͒ which, in a limited temperature range near T c , is frequently assumed independent of T. Hence measurements of the sonic attenuation coefficient as a function of frequency and temperature T offer a favorable method to determine F͑⍀͒. 50 Measurements in that frequency range aimed predominantly at the noncritical background contribution to ␣. At those frequencies resonator methods are appropriate in which the pathway of interaction of the ultrasonic waves with the sample is virtually increased by multiple reflections.…”

Molecular Interactions in Poly(ethylene glycol)–Water Mixtures at Various Temperatures: Density and Isentropic Compressibility Study

“…[21,22] At frequencies between 3 MHz and 2 GHz absolute a measurements have been performed by transmitting pulse-modulated waves at varying sample thicknesses. [23][24][25] Altogether, seven different cells have been used, each one matched to a special frequency range. From the overlaps of the frequency ranges of different cells and different methods and from repeated measurements the following errors have been estimated for the attenuation coefficient: Da/a = 0.1, n < 12 MHz; Da/a = 0.03, 12 MHz n 150 MHz; Da/a = 0.01, 150 MHz n < 500 MHz; Da/a = 0.04, n !…”