Pressure Dependence of the Longitudinal Resonance Frequency of ³He Superfluid Phases in Aerogel

Pulsed NMR measurements have been performed on superfluid ³He within a 98% porosity aerogel over a pressure range of 8 to 26 bar. The aerogel sample is homogeneous and isotropic as indicated by in situ optical birefringence and, on similarly prepared samples, using SAXS characterization [1]. Two different superfluid phases are observed at low temperature. The two phases are identified as the same as the A and B-phases in pure ³He, from tip angle measurement and the NMR equations of Leggett [2]. The pressure and temperature dependence of the longitudinal resonance frequency of each phase is reported in this article.