Spin-polarized 3He-4He solutions: Longitudinal spin diffusion and nonlinear spin dynamics.

Pulsed-NMR techniques have been used to investigate longitudinal spin diffusion and nonlinear spin dynamics in dilute, spin-polarised 3 He- 4 He solutions between 4 and 400 mK. Solutions with 3 He concentrations x 3 =3.5×10 -4 and 19.4×10 -4 were forcibly polarised to as much as 65% and 25%, respectively, with a 9.2-T magnetic field. A technique for measuring the coefficient of longitudinal spin diffusion D ∥ is described, and the results of the technique are compared with recent theoretical calculations