Substrate reconstruction and electronic surface states: Ag(001)

We present the result of a combined ab initio theoretical study and ultravi olet photoemission spectroscopy experiment of the electronic surface states of the clean and of the oxygen covered, unreconstructed and missing-row re constructed, Ag(001) surface. For the clean and for the unreconstructed oxy gen covered surface, theory and experiment find an electronic surface state at about 0.4 eV below the Fermi energy (EF) at the B point of the surface Brillouin zone. At the same point, theory predicts the existence of an empt y state at +3 eV. Upon reconstruction, the photoemission signal of the fill ed state is strongly reduced and, according to calculations, the state shif ts in energy above EF The surface interband transition (SIT) between the tw o states exists thus only for the unreconstructed surfaces and nearly match es the surface plasmon energy. Our investigation confirms therefore the cor relation between the presence of this SIT and the anomaly of the surface pl asmon dispersion curve of unreconstructed Ag(001). (C) 2001 Elsevier Scienc e B.V. All rights reserved.