Angular resolved UPS of the c(2×2) overlayer of selenium on Ni (001) using polarised and unpolarised HeI radiation
The c(2×2) Se overlayer on Ni(001) was studied by angular resolved UPS using unpolarised and polarised HeI (21.2 eV) radiation. The polariser was designed in such a way that s-, p- and unpolarised light could be used without breaking vacuum. A good correlation between the photoelectron spectra and the surface Brillouin zone of the c(2×2) Se overlayer was found. The p z- and the degenerate p x-, p y-derived Se levels are well separated at the M̄ point lying at 3.8 eV(p z and 5.2 eV (p x, p y), respectively. The bands show dispersion and cross between M and overlineГ so that at overlineГ the p x-, p y -derived levels lie closer to the Fermi edge.