The face dependence of the effective electron mean free path derived from spherical-wave corrections in photoelectron diffraction of W(110) and W(100) surfaces

Spherical-wave corrections can be of importance in a single-scattering calculation of the angular anisotropy of the photoemission from W(110) and W(100) 4f core levels. More precisely, for photon energies of approx 65 eV, these corrections are sufficiently large to show the necessity, when using an isotropic electron mean free path lambda sub ee , to vary it according to the face under study. This leads to an effective electron mean free path lambda sub ee of 8 A for W(110) and 5 A for W(100). When this variation is allowed, the plane-wave approximation leads to results for W(110) which are in as good agreement with experiments as those for W(100). In particular, the influence of the hydrogen-induced reconstruction on the azimuthal patterns of W(110) is now very well reproduced. 17 ref.--AA