Electronic anisotropy in the Δ5 → Δ1 edge region of Cu(110)

The normalized reflection difference Delta r/r between the [(1) over bar 00] and the [001] 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 Delta(5) --> Delta(1) edge 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 [(1) over bar 10] chain direction than in the [001] direction. The lifetime for electrons is largest in the [(1) over bar 10] direction. 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) over bar point of the surface Brillouin zone. (C) 1999 Elsevier Science B.V. All rights reserved.