Vibrational lifetimes and friction in adsorbate motion determined from quasi-elastic scattering

Barbara A.J. Lechner, Holly Hedgeland, Andrew P. Jardine, William Allison, B. J. Hinch, John Ellis

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


The vibrational excitation of molecules adsorbed on a surface is typically probed by spectroscopic techniques such as infrared or Raman spectroscopy. In the present article we demonstrate an alternative method to determine vibrational lifetimes of adsorbate molecules using quasi-elastic helium atom scattering (QHAS). As a probe of diffusive motion of molecules on surfaces QHAS is well established. Here, we demonstrate that QHAS can also be used to probe the vibrational lifetime of a molecule in its adsorption well. Measurements of cyclopentadienyl, C5H5, on Cu(111) allow us to distinguish two substrate phonon modes as well as two molecular vibrational modes, perpendicular and parallel to the surface. We further find that the dephasing of the vibrational motion corresponds to the friction determined in previous diffusion measurements.

Original languageEnglish (US)
Pages (from-to)21819-21823
Number of pages5
JournalPhysical Chemistry Chemical Physics
Issue number34
StatePublished - Jul 7 2015

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry


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