SURFACE VIBRATIONS OF OXYGEN AND SULFUR IN THE P(2X2) AND C(2X2) STRUCTURES ON NI(100)

Vibrational excitations of oxygen and sulphur chemisorbed on Ni(100) in the consecutive p(2 × 2) and c(2 × 2) structures have been investigated by high-resolution electron energy loss spectroscopy (EELS). Vibrational losses due to localized modes are observed at 53 and 39 meV for the p(2 × 2)O and c(2 × 2)O structures respectively and at 46 and 44 meV for the corresponding p(2 × 2)S and c(2 × 2)S structures. The large difference in Vibrational excitation energies for the two oxygen structures as compared to those for sulphur is attributed to differences in the shape of the chemisorption potential well. © 1979.