Pulsed NMR investigations on normal-fluid He-3 in restricted geometries

Spin echo experiments were performed on He-3 immersed in Pt powder (particl e size similar to 3 mu m, 40% packing) and 96.5% aerogel. At saturated vapo r pressure and fields of 29 and 70 mT the temperature (8-150 mK) and field gradient: (2-8 mT/cm) dependences of the transverse spin diffusion coeffici ent D-perpendicular to were investigated. Above similar to 80 mK D-perpendi cular to varied with T-2 and was the same for geometrically restricted and bulk He-3. However, at lower temperatures D-perpendicular to varied more we akly with temperature. At 10 mK, D-perpendicular to = 2x10(-4) (cm(2)/s) wa s measured for the Pt and 5 x 10(-4) for the aerogel sample, respectively. These results are compared with D-perpendicular to values obtained in a fie ld of 1 T on He-3 immersed in TmH2 powder of 10 Elm particle size. (C) 2000 Elsevier Science B.V. All rights reserved.