Cross Relaxation in Dilute Paramagnetic Systems

The theory of cross relaxation developed by Bloembergen, Shapiro, Pershan, and Artman is applied to the case of highly diluted paramagnetic salts. We find that the second moment for cross relaxation between two diluted paramagnetic species may be far greater than the sum of the second moments of individual lines which would be obtained from ordinary line width measurements. We can thus explain the dominance of cross relaxation in cases where the separation between the interacting resonances is up to twenty times the sum of the diluted linewidths.