The molecular translation displacement probability (displacement profi
le) characterizes the average pathway of liquid molecules imbibed in a
microporous medium. Under the narrow pulsed field gradient approximat
ion, displacement profiles can be obtained by Fourier transform of the
spin-echo attenuation profiles measured as a function of the amplitud
e of the pulsed magnetic field gradient (Q-space NMR imaging). In the
present study, the molecular displacement profiles of water molecules
in cellulose fiber samples with different water contents were measured
as a function of the diffusion observation time (5-1200 ms). The time
course of the translational displacement profiles indicates the prese
nce of both free diffusing and restricted water in the fiber samples o
versaturated with water. This confirms the results from previous studi
es on the same system by using a population-weighted model. Water mole
cules in the appropriately saturated fiber samples exhibit essentially
restricted diffusion behavior when the diffusion observation time is
sufficiently long. The anisotropy of water diffusion in cellulose fibe
rs was also investigated by studying the fiber sheet sample using a te
trahedral gradient combination pattern consisting of six different com
binations of simultaneously applied orthogonal gradients (x, y, and z
gradients).