Role of intra-adsorbate Coulomb correlations in energy transfer at metal surfaces

We present and discuss a theory of electronic friction for open-shell atomic or molecular adsorbates moving normal to a metallic surface. The theory applies to the case where the intra-adsorbate Coulomb interaction splits the positive-and negative-ion peaks in the spectral density of the adsorbate by an amount larger than their widths, and where one of them is much nearer the Fermi level than the other. We distinguish two limits: (i) the low-temperature friction regime where the friction is caused by the overlap of the adsorbate level's width and the Fermi level, and (ii) the high-temperature friction regime, where the friction is caused by thermally induced transitions. In regime (i) we find a large enhancement in the friction in many cases due to the Kondo effect, which can occur even at very high temperatures. In this region, the frictional force is highly temperature and velocity dependent. In region (ii), on the other hand, we typically find a reduction in the friction, sometimes substantial, from what is found in the traditional theory. Our results should be applicable to the description of desorption induced by hot electrons, which has been called DIMET when in region (ii).