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 wit h 98.2% open volume porosity. A homogeneous superfluid phase is observ ed at pressures, P > 12 bar, accompanied by a sharp onset of frequency shifts showing little or no textural broadening; a result quite unexp ected for He-3 confined in random porous media. The transition tempera tures 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 grea ter than 40 degrees the resonance frequency drops abruptly to the norm al state value. This lip angle dependence is not consistent with eithe r the bulk He-3-A or He-3-B superfluid phases.