Modeling Multiparticle Coherences in Solid-State Nuclear Spin Systems Using Infinite-Range Interaction

Using the exactly solvable model known in statistical physics as the infinite-range interaction model (the van der Waals model), we obtain expressions for the hierarchy of multispin multiquantum time correlation functions for a solid-state paramagnetic nuclear spin system with magnetic dipole-dipole interaction between nuclei. These functions are observed experimentally using contemporary multiquantum NMR spectroscopy methods. We write the complete set of orthogonal multispin operators explicitly and find the time dependence for amplitudes of multiparticle time correlation functions. The proposed model describes the behavior of multiparticle correlation functions well, at least for not very large numbers n of expansion harmonics. The theoretical results agree well with the experimental data obtained for hexamethylbenzol.