Cross-polarization dynamics and proton dipolar local field measurements in some organic compounds

Hartmann–Hahn inversion–recovery cross-polarization magic-angle spinning experiments were performed for all types of protonated carbons (CHn with n=1, 2 and 3). The resulting non-exponential decays were analyzed using both a simple memory function approach and density matrix calculations. Although the memory function approach provides a useful analytical description of the cross-polarization dynamics, the density matrix method is required to account better for the details of the spin dynamics. 13C-detected dipolar local fields of protons were measured using the wideline separation experiment. It was observed that the resulting local free induction decays may be quantitatively described by their local second moment. Moreover, the local spin diffusion process controlling the second stage of the cross-polarization dynamics is directly related to the strength of the local dipolar field of protons.