Alignment echo of spin-3/2 9Be nuclei:: Detection of ultraslow motion

It is demonstrated that the alignment echo of Be-9 is quite useful for detecting ultraslow atomic motions in the metallic glass Zr46.75Ti8.25Cu7.5Ni10Be27.5. The time scale of detectable atomic motion is between T-2 = 1.5 ms and T-1 of a few seconds. Similar to previous works of H-2 NMR, the Jeener-Broekaert sequence is used to create quadrupolar order for spin-3/2 nuclei upon nonselective excitations. Since the chemical and Knight shift distributions are not negligible for Be-9, the proper choice of the dephasing time between the first and the second pulses is essential for achieving pure quadrupolar order. It is demonstrated experimentally that slow atomic motions contribute significantly to the decay of the alignment echo near the glass transition temperature. (C) 1998 Academic Press.