Selective On-Resonance N.M.R. Irradiation of a Dipolar Double.

Abstract

Raman magnetic resonance where double-quantum transitions are observed without the need for multidimensional n.m.r. spectroscopy has been investigated further. Theoretical analysis of the on-resonance case where weak continuous-wave irradiation was applied at the frequency of a single-quantum transition was performed and guidelines for a consistent perturbation treatment were devised. Theoretical results agree well with experimental data obtained for a system of two dipolar coupled nuclei of spin oriented by a liquid crystal. The same approach is applicable to near-resonance experiments which are shown to be the optimal experimental scheme for Raman n.m.r. By using weak selective irradiation, a symmetric excitation–detection scheme can be realized for multiple-quantum n.m.r. experiments. Near- or on-resonance selective irradiation provides an efficient transfer of multiquantum coherence into observable coherences and could be used to study multiquantum relaxation processes.