Selective excitation by radiation damping field for a coupled nuclear spin system

A radiation damping field is an alternating field and could be utilized as an excitation source for NMR experiments. Here we report the excitation effect of radiation damping. For a long-range coupled 13C–12C–1H3 system in acetate, the 1H doublet is perturbed by the radiation damping field from the 1H signal of 12C–12C–1H3, and anti-phase single- and multiple-quantum coherences are excited. As a result, in the 13C spectrum the phase of the 13C–12C–1H3 quartet is strongly affected. The results of a theoretical analysis of the radiation damping effects based on the product operator formalism are also presented. The excitation effect of radiation damping suggests a useful indirect NMR detection method for measuring signals hidden in a huge signal.