Surface vibrational excitations of O in the p(2 × 2)O and c(2 × 2)O structures on Ni(100)

Surface vibrational excitations of O chemisorbed on the clean Ni(100) surface have been investigated by high-resolution electron energy loss spectroscopy (EELS). The observed vibrational losses in the Ni(100) p(2 × 2)O and Ni(100) c(2 × 2)O surface structures are 53.0 ± 0.5 and 39.5 ± 0.5 meV respectively. The unexpectedly large change in the vibrational excitation energy is attributed to a low potential barrier for oxygen dissolution into the Ni substrate.