Energy Transfer at Surfaces: Asymmetric Line Shapes and the Electron-Hole-Pair Mechanism

Rigorous expressions are derived for the line shape for an isolated vibrational mode of an atom or molecule adsorbed on a metallic surface in the presence of electron-hole damping. It is shown that this mechanism necessarily produces an asymmetric line shape with long tails. The experimental presence or absence of such a line shape should therefore play an important role in establishing whether or not electron-hole-pair production is an effective energy-transfer mechanism near metallic surfaces.