NUCLEAR-MAGNETIC-RESONANCE OF HE-3 SUPERFLUID CONFINED IN HIGH-POROSITY AEROGEL

We report pulsed nuclear magnetic resonance (NMR) measurements of the transverse frequency and magnetization of He-3 confined in aerogel with 98.2% open volume porosity. A homogeneous superfluid phase is observed at pressures, P > 12 bar, accompanied by a sharp onset of frequency shifts showing little or no textural broadening; a result quite unexpected for He-3 confined in random porous media. The transition temperatures and order parameter are both significantly suppressed from their bulk values and the magnetization data indicate this low temperature phase is an equal-spin pairing superfluid. For NMR tipping angles greater than 40 degrees the resonance frequency drops abruptly to the normal state value. This lip angle dependence is not consistent with either the bulk He-3-A or He-3-B superfluid phases.