Observation of CH₃ Tunneling Manifold by Level-Crossing NMR

Rotational tunneling spectra of strongly hindered CH₃ torsional oscillator pairs which do not interact among themselves are reported. These results are obtained by applying the Zeeman-tunneling level matching method in the proton spin rotating frame. Two noninteracting CH₃ particle manifolds explain the observed CH₃ multiquantum transitions driven by intramolecular and/or intermolecular dipole-dipole interactions to first or second order. Level matching resonances indicating that two methyl groups simultaneously undergo a symmetry breaking transition are observed. The dependencies of level-crossing transitions on Zeeman-tunneling mixing time and tilt angle are reported.