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(MFG's) to detect the diffusion of moving atoms, we have developed a highlysensitive approach for detecting electric field gradient (EFG) fluctuationsseen by stationary atoms. These EFG fluctuations were observed in the quadrupoleperturbed NMR behavior of a stationary nucleus (93Nb)in the incommensurate insulator barium sodium niobate and are attributed tomotion of the modulation wave. We observed effective diffusion constants oforder 10-13cm2/s, which are 4 orders of magnitude smaller than those currently detectable with MFG NMR. © 1995 The American Physical Society.