Nuclear Spin Relaxation in Liquid Helium 3

Abstract

The longitudinal relaxation time of liquid ${\mathrm{He}}^3$ has been measured as a function of temperature above 1°K and of magnetic field below 13 kgauss in a number of sample containers. At a temperature of 2.0°K and in a magnetic field of 10 kgauss the longitudinal relaxation time, $T_1$, varied with the sample container from 60 seconds to 400 seconds. The transverse relaxation time, $T_2$, was measured by a new method and was approximately 30 seconds at a field of 10 kgauss in all sample containers. $T_1$ was determined as a function of magnetic field at 2.0°K in a single sample container; the values increased from less than 50 seconds in approximately zero field to 400 seconds at 13 kgauss. An impurity relaxation model is proposed to explain the $T_1$ results. By assuming both wall relaxation and a bulk relaxation given by the Bloembergen, Purcell, and Pound theory, the dependence of $T_1$ on pressure and temperature can be quantitatively understood. The low values of $T_2$ are inconsistent with the Bloembergen, Purcell, and Pound theory and may be due to the presence of paramagnetic impurities in suspension in the bulk liquid.