Electronic anisotropy in the Delta(5) -> Delta(1) 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 fea tures 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 th e 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 i s largest in the [(1) over bar 10] direction. Using expressions for the scr eened dipole-dipole interaction we have found that around 2 eV the local-fi eld effect is responsible for a part of the derivation effect. Another cont ribution comes from the joint-density-of-states for the bands at the (Y) ov er bar point of the surface Brillouin zone. (C) 1999 Elsevier Science B.V. All rights reserved.