Quantum Influences in the Diffusive Motion of Pyrrole on Cu(111).

Classical diffusion—quantum barrier: On Cu(111), pyrrole diffuses in channels, hopping between adjacent bridge sites over a barrier above hollow sites. The motion of the center of mass can be described classically; however, the activation barrier arises from the quantum character of internal vibrational modes that are largely unexcited during the motion. The unique helium spin‐echo experiment is indicated by the green sphere and arrows. [ABSTRACT FROM AUTHOR]