Electronic anisotropy in the D ªD edge region of Cu 110/

The normalized reflection difference Drrr between the w110x and the w001x directions of the Cu 110. surface is presented. Several features in the spectra, which are taken between 1.3 and 3 eV and includes the D5ªD1edge region, can be reproduced by approximating the difference between the surface tensorial components by the derivative of the bulk dielectric function. The data show that below the edge the effective electron mass is smaller for electron transport along the w110xchain direction than in thew001xdirection. The lifetime for electrons is largest in thew110xdirection. Using expressions for the screened dipole–dipole interaction we have found that around 2 eV the local-field effect is responsible for a part of the derivation effect. Another contribution comes from the joint-density-of-states for the bands at the Y point of the surface Brillouin zone. q1999 Elsevier Science B.V. All rights reserved.