Harmonic peaks in 1D NMR spectra induced by radiation damping fields

It is found experimentally that there exist some harmonic peaks in one-dimensional NMR spectra of solution samples with two dominant solvents. Theoretical analysis indicates that such harmonic peaks result from the interaction between two radiation damping fields induced by the dominant solvents. Using a homo-nuclear decoupling pulse as a radiation damping field, a novel detection approach is proposed to investigate these harmonic peaks without interferences caused by the nonlinear amplification of the receiver. The results presented herein give a new insight into the radiation damping effects in samples with solvent mixtures (e.g. natural products) at high fields.