Calculation of spectral density for translational nuclear spin diffusion

Abstract In the case of nuclear spin relaxation by translational motion of equal nuclei the spectral density is calculated for isotropic and lattice diffusion. For lattice diffusion the treatment is valid not only if the mean time between flights is much greater than the Larmor period (cf. Torrey), but also for shorter correlation times. In the case of isotropic diffusion a Gaussian probability distribution of the displacements is assumed. The results have been compared with those of Torrey's models and showed only small differences.