Many-body Perturbation Study of Electron Correlation Effects on Nmr Parameters*

NMR is routinely used as an indispensable research tool in present-day chemical laboratories because a wide variety of parameters can be extracted from the response of an ensemble of nuclear spins to a resonant excitation. Among them, the chemical shift in nuclear magnetic shielding and the electroncoupled nuclear spin-spin coupling are direct measures of the change in chemical environment around the nuclei concerned. Consequently, the accumulation of shift and coupling data allows us to use the shift and nuclear spinspin coupling as empirical parameters in rapid identification of the molecular species present. Theoretically, they can be expressed as a sum of firstand second-order properties, thus reflecting the details of the static and dynamic electronic structure of molecules. In this review, we wish to report on electron correlation effects on these magnetic properties. Diagrammatic many-body perturbation theory (MBPT) (1,2) is employed to analyze the effects since the method is most unbiased, allowing us to make order-by-order evaluation of the correlation effects.