High sensitivity nuclear quadrupole resonance approach for detection of modulation wave motion in incommensurate systems

In contrast to conventional NMR techniques that use magnetic field gradients (MFCs) to detect the diffusion of moving atoms, we have developed a highly sensitive approach for detecting electric field gradient (EFG) fluctuations seen by stationary atoms. These EFG fluctuations were observed in the quadrupole perturbed NMR behavior of a stationary nucleus (9 3Nb) in the incommensurate insulator barium sodium niobate and are attributed to motion of the modulation wave. We observed effective diffusion constants of order 10~13 cm2/s, which are 4 orders of magnitude smaller than those currently detectable with MFG NMR.