ABSTRACT
This chapter presents applications and results of the Redfield theory. It describes some features of dipolar relaxation in systems consisting of more than two spins and deals with relaxation effects originating from other interactions involving spin 1/2 nuclei. An interesting complication of the Solomon-like description arises in a spin system consisting of more than two spins with mutual dipolar interactions. The unperturbed Hamiltonian consists of the Zeeman interactions between all the spins and the magnetic field and, possibly, scalar spin-spin couplings. The cross-correlation spectral densities do influence relaxation properties in multispin systems, at least under certain conditions. The nuclear magnetic resonance (NMR) spectrum of such a spin system consists of three groups of signals, each group being a symmetric doublet of doublets. Spin-inversion refers to changing the sign of all the magnetic quantum numbers. Spin decoupling in a heteronuclear spin system can simplify the picture, but caution is recommended in case of magnetic equivalence.
