${}^6\text{L}\text{i}$ spin-alignment echo (SAE) nuclear-magnetic-resonance (NMR) spectroscopy is used to monitor single-particle two-time correlation functions in ${\text{LiAlSi}}_2{\text{O}}_6$ glass. The method, here applied in the temperature range from 300 to 400 K, is sensitive to ultraslow Li hopping processes with rates $\left(1/{\tau }_{\text{SAE}}\right)$ down to 10 jumps/s. The use of a sample with natural ${}^6\text{L}\text{i}$ abundance allowed the measurement of pure NMR spin-alignment echoes which are damped with increasing mixing time exclusively by slow Li jumps, i.e., free of influences arising from, e.g., interfering spin-diffusion effects. The considerably stretched correlation functions reveal the presence of a broad distribution of jump rates. The results are comprehensively compared with those recently obtained from both ${}^7\text{L}\text{i}$ SAE and ${}^7\text{L}\text{i}$ spin-lattice relaxation NMR as well as from dc conductivity measurements. Interestingly, the activation energy of the latter, which are sensitive to long-range Li transport parameters, is in good agreement with that microscopically probed by ${}^6\text{L}\text{i}$ SAE NMR, here.

• Received 21 May 2008

DOI:https://doi.org/10.1103/PhysRevB.78.054303