Insights into NMR relaxation and susceptibility representation

In this study, an analysis of the relaxation rate constant and the susceptibility definitions point out the most feasible setup to detect the non-exponential relaxation effects of longitudinal magnetization. The dipole–dipole interaction was considered the primary source of relaxation due to homonuclear or heteronuclear species. Some representative molecule systems were explored, such as Glycerol (alcohol), Butyltriethylammonium bis(Trifluoromethanesulfonyl)imide (ionic liquid), and Fluoroaniline (fluorines). Considering some physical and stoichiometric properties of these three molecule systems and applying the susceptibility representation, it can be concluded that the relaxation effects due to the dipole–dipole interaction of homonuclear species prevail against the heteronuclear species. Furthermore, the same analysis points out a range of frequency values in which the dipole–dipole interaction of heteronuclear species is favorable, even if the homonuclear one is available.