Superfluid 3He in narrow cylinders

Superfluid 3He has been confined to the interior of very long 2 micicron diameter cylinders and studied with continuous wave nuclear magnetic resonance. An external static magnetic field was placed both along and perpendicular to the cylinder axes, and the radio-frequency field was oriented in order to study both longitudinal and transverse resonance modes. With the static magnetic field along the cylinder axes the longitudinal resonance shows one well-defined resonance at a frequency which is roughly .8 times the bulk longitudinal frequency. The transverse spectrum has two peaks whose shift frequencies are roughly .6 and .9 times that of bulk liquid. In both longitudinal and transverse modes the ratios of frequencies in confined liquid to that in bulk liquid are temperature dependent. With the magnetic field perpendicular to the cylinder axes the transverse resonance shows one peak between the Larmor frequency and that of bulk liquid, but its temperature dependence cannot be characterized in any simple fashion. There is also a continuum of absorption around the Larmor frequency, and a negatively shifted line, both of which are more prominent in low magnetic fields. The longitudinal resonance was not studied in a perpendicular field. The observed frequencies have been used to deduce the mean square projections of the l-- vector along the cylinders' principal axes averaged over a cross section of the cylinder. The l-- vector describes the order parameter of superfluid 3He-A. The experiments also revealed a transition from the A phase to the B phase in the cylinders which is raised above the bulk liquid's transition temperature by about 12 mu K