Ultrasonic Measurement in Liquid Alkali Metals (Part 1). Ultrasonic Velocity and Absorption in Liquid Mixtures of K-Rb and Na-Cs (Part 2)

摘要

Ultrasonic absorption and velocity measurements have been made in high purity liquid sodium, potassium, rubidium, and cesium at temperatures from their melting points to 250C. Corresponding classical absorption values have also been computed over these ranges of temperature. It has been found that the measured absorption values exceed the classical values by 3% to 30%. These excess absorptions are attributed to structural relaxation. The ratio of bulk viscosity to shear viscosity was found to be approximately 2.3 in sodium and potassium, 3.4 in rubidium and 4 in cesium. Sound velocities are presented as linear functions of temperature. Both observed and classical absorptions are given as quadratic functions of temperature. Ultrasonic absorption and velocity measurements have been made in potassium-rubidium and sodium-cesium alloys at temperatures from 25C (or the liquidus point) to 250C. It has been found that the potassium-rubidium system behaves as an ideal liquid mixture. The ultrasonic measurements in sodium-cesium system suggest a substantial molecular association peak at 75 atomic percent sodium concentration is attributed to a molecular association of the form of 3Na + Cs = Na3Cs. (Author)