SOUND-TRANSMISSION PHENOMENA AND PHASE-SEPARATION KINETICS AT THE SUPERFLUID NORMAL INTERFACE OF LIQUID HE-3-HE-4 MIXTURES

The transmission and reflection of sound at the interface between He-3-dilute and He-3-concentrated phases of a liquid He-3-He-4 mixture are studied. The effect of phase separation on sound phenomena is involved in terms of the effective growth coefficient calculated under assumptions of the existence of phase equilibrium at the interface. At low temperatures the phase-separation kinetics is governed by the processes associated with the excitation and propagation of second sound modes to compensate the difference in He-3 concentration of adjacent phases. The growth coefficient is found to vanish at the maximum concentration point on the separation line of the He-3-dilute phase. Accordingly, the behavior of the sound transmission coefficient as a function of separation pressure displays a small smooth maximum at the pressure of the maximum concentration point and the reflection of the second sound wave from the normal He-3-concentrated phase reaches its maximum value at the same pressure.