PHOTOELECTRON DIFFRACTION FROM CORE LEVELS AND PLASMON-LOSS PEAKS OF ALUMINUM

Photoelectron diffraction has been measured from a (001) single-crystal surface of aluminum. Anisotropies of the photocurrent of 73% and 65% have been observed in azimuthal scans of 2s and 1s core-level intensities comprising the [011] direction. Azimuthal intensity scans have also been measured for the plasmon-loss peaks accompanying the 2s core lines. The forward-scattering- related intensity maxima along 011 directions are reduced with increasing plasmon number n. This suggests that defocusing effects due to multiple photoelectron scattering along rows of atoms are important. The rate at which the forward-scattering maxima are suppressed with increasing n indicates a defocusing length of the order of 45 in Al, which is longer than what had been previously calculated for the case of Cu. Furthermore, the invariance with n of diffraction features away from the [011] direction gives support to the idea that photoelectrons and Kikuchi electrons exhibit essentially the same diffraction effects. © 1990 The American Physical Society.