Horsewill, A.J. and S.M.M. Abu-Khumra, Dynamic Tunneling Polarization as a Quantum Rotor Analogue of Dynamic Nuclear Polarization and the NMR Solid Effect. Phys. Rev. Lett., 2011. 107(12): p. 127602.
http://link.aps.org/doi/10.1103/PhysRevLett.107.127602
The populations of the tunneling states of CH3 are manipulated by rf irradiation of weakly allowed sideband transitions within the manifold of tunneling-magnetic levels. Substantial positive and negative CH3 tunneling polarizations are observed, providing a quantum rotor analogue of dynamic nuclear polarization and the solid effect in NMR. The field-cycling NMR technique used in the experiments employs level crossings between tunneling and Zeeman systems to report on the tunneling polarization. The tunneling lifetimes are measured and the field dependence investigated.