Electronic damping of adsorbate motion: CO vibration on the Cu(100) surface
Research output: Contribution to journal › Article › Scientific › peer-review
|Number of pages||6|
|Journal||Physical Review B|
|Publication status||Published - 1986|
|Publication type||A1 Journal article-refereed|
Cluster calculations have been applied to treat the electronic damping of adsorbate vibrations at a metal surface. Based on the broadening of the discrete one-electron energy levels of a finite cluster, buildup of a self-consistent quasicontinuum of electron energies at the Fermi level is shown to be possible. This is relevant to the description of the continuous low-energy spectrum of electron-hole pairs and application of a recent theoretical formulation. Using this approach we are able to evaluate the rate of electron-hole pair excitations induced by the vibrational motion, which lead to shorter lifetimes of the vibrational excitations, i.e., broadening of the vibrational levels, compared to those of a free molecule. For the linewidth of the C" he Cu(100) surface a value of 0.5 meV is obtained, corresponding to the lifetime of 1.3×10-12 s, in agreement with a recent experiment. The mechanism behind the electron-hole pair excitations is found to be localized charge oscillations between the molecular 2 resonance and the substrate, induced by the vibration. Cluster-size effects for this process were extensively examined and found to be negligible for the numerical result, which we obtain. For the CCu vibration mode our calculations predict electronic damping which is one order of magnitude less effective. We expect our approach to be applicable for the studies of adsorption-site effects and also for the evaluation of the electronic damping of other adsorbate motions.