Remarkable reduction of rf power by ATANSEMA and DATANSEMA separated local field in solid-state NMR spectroscopy

We propose a novel approach to markedly reduce rf power for both 1H and observed nuclei during spin exchange for separated local field experiments. The rf power to satisfy the Hartmann-Hahn matching conditions during spin exchange for observed nuclei was arbitrarily reduced by alternating the directions of effective fields for 1H nuclei with unequal duration times and amplitudes. The proposed techniques were compared experimentally with those developed previously by the authors. The rf power for observed nuclei and average 1H were reduced by factors of 9 and 2, respectively, for 13C NMR signals of liquid crystalline 5CB.