PARTIALLY OCCUPIED SURFACE-STATE AT THE FERMI-LEVEL OF LA(0001)

A partially occupied surface state at the Fermi level of a well-ordere d La(0001) film grown on W(110) is observed by photoemission and inver se photoemission, which provide direct pictures of the occupied and un occupied part, respectively. The occupied part of the surface state gi ves rise to an intense direct recombination line in the N4,5O2,3O2,3 A uger-electron spectrum. The surface state is found to be sensitive to O2 adsorption and disordering of the surface induced by Ar-ion bombard ment. The present results support a view that such surface states occu r generally on close-packed surfaces of the rare-earth metals.