Evidence for orientational tunneling of co intercalated in c-60: A nuclear magnetic resonance study

We characterize the low-temperature dynamics of CO intercalated in C60 using NMR spectroscopy. CO in C60 is found to be dynamically inhomogeneous below 30 K: The 13CO line shapes reflect a dynamic disorder to static disorder transition, with only quantum tunneling among equivalent orientations in a local S6 symmetry potential remaining. The increased hindrance of the CO motion cannot be reconciled with common expectations of a homogeneous, thermally activated jumplike reorientation process, but is well accounted for in a model of orientational pinning due to asymmetric distortions of the cage potential.

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