NMR of Absorbed Systems. I. A Systematic Method of Analyzing NMR Relaxation-Time Data for a Continuous Distribution of Nuclear Correlation Times

Methods are outlined for the systematic analysis of NMR relaxation‐time data in terms of the continuous distribution of nuclear‐correlation‐time theories of Odajima and Resing. It is shown how unique values of the two significant parameters of these theories—the width parameter $\beta$ and the apparent rigid‐lattice second‐moment parameter ${\sigma }_0^2$ —can be obtained if a minimum occurs in the spin–lattice relaxation‐time data. While these parameters are only defined for the temperature where the minimum in the spin–lattice relaxation time occurs, it is possible, by seeking a form of the thermal activation law that enables reproduction of the temperature variations of the experimental data, to define further parameters related to the system—i.e., the thermal activation coefficients. The Resing theory, which takes into account an apparent phase transition effect that can occur in the spin–spin relaxation‐time data, is successfully applied by the method described, to NMR relaxation‐time data of water absorbed on both hair keratin and charcoal. The Eyring form of the thermal activation law is found to be appropriate in both instances.