Study of Bulk Longitudinal Spin Relaxation in 3He-4He Liquid Mixtures

Longitudinal spin relaxation has been investigated in spin polarised liquid 3He-4He mixtures in cesium-coated glass cells. The contribution of wall relaxation is found to be either negligible or easy to separate, and bulk relaxation times can be derived from systematic studies. We report on relaxation measurements at saturated vapour pressure, for temperatures ranging from 1.1 to 3K. 3He densities vary from 0.07 to 11 mmol.cm−3 (3He concentrations between x3≃0.3 and 34%), so that both normal and superfluid 3He-4He solutions are studied. At fixed temperature, the longitudinal relaxation time is inversely proportional to the 3He number density over the whole range of investigated concentrations. In contrast, it is almost independent of temperature (changes do not exceed 10%). Comparison with published data and expected behaviours is discussed.