Overtones of H vibrations at Ni(111): Formation of delocalized states - art. no. 233403

Vibrational states of H adsorbed on Ni(111) have been investigated by means of electron-energy-loss spectroscopy. In addition to the symmetric (upsilo n (s)) and asymmetric (upsilon (as)) fundamental modes, the corresponding o vertone structures are clearly detected. The overtone of upsilon (as), the predominantly parallel-polarized mode, exhibits a doublet structure, which is interpreted to result from the delocalization of the excited vibrational states. It is shown that the doublet corresponds to the "bonding" and "ant ibonding" orbitals, analogous to the linear combination of atomic orbitals for simple molecules.