Abstract
The full-width half-maxima (FWHM) of the 6 meV parallel frustrated translation mode of CO chemisorbed on Pt(111) (Eads =1.5 eV) have been measured using high-resolution helium atom scattering over the temperature range 50–200 K for four different isotopomers and the results are compared with earlier measurements on CO/Cu(001), which has a much lower adsorption energy of 0.7 eV. The FWHM is independent of the temperature and isotopomer and corresponds to a vibrational lifetime of 1.37±0.22 ps. The observed lifetime is attributed to both phononic and electronic frictional damping and is used, in conjunction with quasi-elastic helium scattering measurements, to estimate the diffusion barrier to be Ebarr ∼ 130 meV.
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