Full-hemispherical angle-scanned x-ray photoelectron diffraction has been used to investigate the molecular orientation and librational motion of ${\mathrm{C}}_{60}$ molecules adsorbed on the Cu(110) surface. The molecules are found to face the substrate surface in an unusual bonding configuration, rotating their symmetry axes by a few degrees away from the high-symmetry directions of the Cu(110) substrate. Despite the asymmetric molecular orientation, the ${\mathrm{C}}_{60}$ molecules are immobile, i.e., they show no librational motion, up to temperatures well above the ${\mathrm{C}}_{60}$ sublimation temperature.

• Received 16 April 1999

DOI:https://doi.org/10.1103/PhysRevB.60.4517