First- and Zero-sound Velocity and Fermi Liquid Parameter F~8_2 m Liquid sHe Defcormined by a Path Length Modulation Technique

摘要

We have, measured the velocity of jirtt. and zrro-.iound in liquid~3 He at 12.6 MHz over the prcsnuiv tvnyc of 0.6' to lj.fi bar ustny a path length modulation technique Ihut we. have recently dcvetopctl. From them' measurements, the pressure, dependent tinhe of tlw Fermi liquid pammctcr was calculated and found to , larger at low presiurv than previously rcjmrtcd, These new values of F-j: indicate that tramvt'.rse zero-sound in a profmijatintj mtuie at all prexaures. The nvw values are. imjmtant for the interpretation of the frequencies ofonier parameter collective modes in the super-fluid phoney The new acoustic technique permits measurement in tvgimes of very high attenuation with a scwstlwiti in plmc velocity of altout 10 pirn achieved by a Icdlwk orraruiemetU. The stmnil wlwtl.y ii> thus measured continuously throughout the highly attenuattna crossover (wr as m/iine, even at the lowed pressures.