1-D and 2-D NMR of broad-line solids: an application to quasicrystals

Nuclear magnetic resonance (NMR) techniques for measuring one-dimensional a bsorption spectra and too-dimensional exchange spectra of solids with extre mely inhomogeneously broadened lines are discussed. Among various "broad-li ne" solids, quasicrystals represent alloys of metallic elements, the struct ures of which include "forbidden" symmetry elements. NMR absorption lines o f quasicrystals exhibit a strong electric-quadrupole-induced inhomogeneous broadening that originates from the lack of translational periodicity of th e otherwise perfectly long-range-ordered quasiperiodic lattice. Recording a n NMR spectrum of a quasicrystalline sample requires a magnetic field-sweep technique. The two-dimensional exchange experiment on quasicrystals can be performed on selectively excited portions of the NMR spectrum only. Due to the off-resonance effects in a selective excitation. the use of a simple t hree-pulse stimulated-echo exchange sequence is preferred. The Al-27 spectr a of the Al-Pd-Mn and Al-Pd-Re families show interesting features like temp erature-dependent frequency shifts and exchange effects due to atomic motio n.