Magnetic exchange splitting of one layer of cobalt deposited on top of the (111) surface of copper

We have measured angle-resolved photoemission spectra for one and two ordered layers of Co deposited on top of a Cu(111) surface using synchrotron radiation ($25l~h\ensuremath{\nu}l~80$ eV). The spectrum at normal emission for one monolayer of Co presents the same exchange-splitting-induced three-peak structure that the spectrum of Co(0001). The magnetic-exchange-splitting values at the $\overline{\ensuremath{\Gamma}}$ and $\overline{K}$ points of the two-dimensional Brillouin zone are 0.7 and 0.5 eV, respectively.