Carbon-13 NOESY and equivalent protons: Methyl iodide dynamics

We have shown that proton-coupled carbon-13 2D NOESY experiments, performed on degenerate spin systems, can provide unique quantitative information about anisotropic reorientational motions and molecular geometry. Relevant theory for AX2 and AX3 spin systems is presented, assuming the dipole-dipole and random field relaxation mechanisms of 13C nucleus, and demonstrated on methyl iodide solution in chloroform. Agreement with experimental intensities of all the six independent peaks is very good in the whole range of mixing times (up to 45 s).