Determination of the structure of wood from the self-diffusion probability densities of a fluid observed by position-exchange NMR spectroscopy

Abstract

Self-diffusion of a fluid absorbed in a solid matrix is restricted by the walls of the matrix. We demonstrate that the local self-diffusion probability densities (propagators) of fluid molecules can be measured by position-exchange nuclear magnetic resonance spectroscopy (POXSY), and analysis of the shape of the propagators reveals the local size-distributions of the voids in the matrix. We also show that, in the case of rectangular voids, size-distribution can be calculated in a long diffusion-time limit without any assumptions about the shape of the distribution. Pinus sylvestrispine wood was used as a sample material in the experiments, and the results show that this method gives detailed information about the structure of wood.