Measurements of the Ultrasonic Attenuation in Superfluid ³ He- <i>A</i>

Abstract

The anisotropic attenuation of zero sound in superfluid 3He-A has been measured for eight frequencies in the range (24 ÷ 94) MHz at a pressure of 29.3 bar. The clapping resonance was studied at all frequencies and the re-entrance of the normal flapping resonance was observed for the first time at both 34.2 and 44.2 MHz. The results provide evidence for weak f-wave pairing effects and a measure of strong-coupling corrections to the energy gap away from Tc.