Abstract
Single-molecule vibrations of four isotopes of CO on Cu(001) and Cu(110) at 8 K have been measured by inelastic electron tunneling spectroscopy with the scanning tunneling microscope (STM-IETS). While the low energy hindered rotation exhibits strong intensity, the C-O stretch approaches the present detection limit of STM-IETS. By performing vibrational microscopy, the spatial distribution of the hindered rotation intensity is found to be more localized than the topographic depression in constant current images.