We have measured phason hopping in isotopic powder samples of decagonal Al-Co-Ni quasicrystals, by time-of-flight quasielastic neutron scattering. The three isotopic samples were based on ${}^{\mathrm{nat}}\mathrm{Ni},$ and 99.5% enriched ${}^{58}\mathrm{Ni}$ and ${}^{60}\mathrm{Ni}.$ Two characteristic jump times have been observed. The anomalous temperature dependence observed in the icosahedral phases i-Al-Cu-Fe and Al-Mn-Pd is confirmed.

• Received 5 January 1999

DOI:https://doi.org/10.1103/PhysRevB.60.270