Apparent Phase—Transition Effect in the NMR Spin—Spin Relaxation Time Caused by a Distribution of Correlation Times

It is shown that a broad distribution of correlation times produces an apparent-phase-transition effect in the NMR spin—spin relaxation time just before the onset of rigid-lattice behavior. NMR relaxation-time data for liquid water filling the pores of a charcoal adsorbent provide a sensitive test of the theory. The occurrence of the apparent phase transition for molecules adsorbed on the surfaces of solids provides a method of estimating the spread of activation energies for surface diffusion and thereby provides a new method for studying the heterogeneity of surfaces.