ONE-DIMENSIONAL SURFACE-STATES ON METAL-SURFACES

The unoccupied Shockley surface states of the Ni(110) surface have bee n investigated by inverse photoemission on the clean and the H covered surface. The H/Ni(110) adsorption system forms a two-dimensionally or dered (1 X 2) phase at low temperature and a one-dimensionally ordered ''streaky'' (1 X 2) phase at room temperature. On the two-dimensional ly ordered phase all surface states are down-shifted due to the attrac tive protonic potential of the adsorbed H. On the one-dimensionally or dered phase those surface states which propagate in the direction of t he perturbed periodicity, i.e. perpendicular to the atom rows of the r econstructed H/Ni(110) surface, are completely quenched. The surface s tates which propagate along the rows in the direction where the period icity is conserved are virtually unaffected by the disorder. This indi cates that they are confined to individual atom rows representing trul y one-dimensional surface states.