Self-Diffusion and Nuclear Relaxation in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">He</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>

Direct spin-echo measurements of diffusion coefficient ($D$) and spin relaxation time (${T}_{1}$ and ${T}_{2}$) have been performed on ${\mathrm{He}}^{3}$, with an accuracy \ensuremath{\sim}2% in the range 0.5\ifmmode^\circ\else\textdegree\fi{}K to 4.2\ifmmode^\circ\else\textdegree\fi{}K and at pressures to 67 atmos in the liquid, the solid, and in dilute solutions of ${\mathrm{He}}^{3}$ in ${\mathrm{He}}^{4}$. Unactivated diffusion is observed to the lowest temperatures in the liquid, but not in the solid. By measurement of $D$ at 19 atmos we find an activation energy of 13.7\ifmmode^\circ\else\textdegree\fi{}K for the production of scatterers in He II. There is an extended discussion of experimental details.

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