Molecular tunneling measured by dipole-dipole–driven nuclear magnetic resonance

In low-field nuclear magnetic resonance in solids, transitions are not driven directly by the oscillating field, but by the dipole-dipole interactions modulated by the applied oscillating field. This results in strong {Δ}m=2 transitions due to oscillating internal field gradients. Tunnel sidebands, symmetry forbidden in ordinary NMR, become strongly allowed. Tunnel frequencies of rotating molecular groups are measured in a previously inaccessible frequency range.