Use of polarization inversion for resolution of small dipolar couplings in SLF-2D NMR experiments – an application to liquid crystals

A density matrix description of the polarization inversion process is presented. Such a description enables the visualization of the role of the process in the suppression of zero-frequency peaks in SLF-2D NMR experiments based on the dipolar oscillations during cross-polarization. It is shown that during this process, a doubling of the amplitude of the oscillatory component occurs accompanied by a reduction of the initial intensity of the non-oscillatory component to zero. This significantly reduces the zero-frequency component and in the case of a liquid crystal studied, enables several small dipolar couplings to be resolved and interpreted in terms of the molecular structure and order.