Nature of Asymmetry in the Vibrational Line Shape of Single-Molecule Inelastic Electron Tunneling Spectroscopy with the STM

Probing Intermolecular Coupled Vibrations between Two Molecules

“…The asymmetry in the IETS line shapes is consistent with a previous study of asymmetric tunneling junctions [15]. The IETS spectrum taken with the CO-tip over the center of the surface CO is shown at the bottom of Fig.…”

“…In addition to the hindered translation (HT, ~2 meV) and hindered rotation (HR, ~20 meV) as reported before [5,12,15,17], another mode at 37.1 meV for the surface CO and 35.1 meV for the tip-CO was resolved. This energy is ~5 meV higher than that previously reported for the center of mass (CM) bouncing mode (Ag-CO stretch) [20,21] and our DFT calculations in Fig.…”

“…The HT and HR energies of CO on silver surfaces are lower than those on copper and gold surfaces [15] which can be correlated to the weaker binding [23] of CO on silver surfaces. All the vibrational modes for CO on the tip are red shifted from those of CO on the substrate, suggesting a weaker bonding of CO on the tip.…”

“…IETS, such as the propensity rules for mode intensity [13,14], spectral line shape [15,16] and spectroscopy with functionalized tip [14,17]. Therefore using a CO-tip to probe another nonplanar CO on the surface presents an ideal system for vibrational spectroscopy with STM-IETS to gain new insights into intermolecular interactions.…”

Detection and Characterization of Anharmonic Overtone Vibrations of Single Molecules on a Metal Surface

“…In addition, a small peak feature near zero bias appears. This has been reported before as a Zero Bias Conductance Dip and is also present with the tip positioned over the bare surface [31,32]. Isotope shifts for both vibration modes are readily apparent for the 13 Measurements of the new vibration mode for all three isotopes will yield clues needed for its identification.…”