NECESSITY OF SELF-ENERGY CORRECTIONS IN LEED THEORY FOR XE(111) - COMPARISON BETWEEN THEORETICAL AND EXPERIMENTAL SPIN-POLARIZED LEED DATA

An essential problem in calculating the electronic structure of solids is that created by many-body interactions. They cause self-energy cor rections which in insulators and semiconductors range up to the width of the fundamental band gap. Angular-dependent intensity and asymmetry profiles measured in spin-polarized low-energy electron diffraction ( SPLEED) from Xe(111) clearly show the necessity of the self-energy cor rection if compared to standard SPLEED calculations. Effects due to th e self-energy correction have to be clearly distinguished from effects due to the inner potential. The real part of the inner potential affe cts the energy and, by refraction at the surface potential barrier, th e angles of the incident and the diffracted beams, whereas the self-en ergy correction is equivalent to a change of the energy of the primary beam only. This qualitative difference is proved in our SPLEED invest igations and is used to determine the self-energy correction and the i nner potential from angular-dependent profiles. For the self-energy co rrection we found a value of Delta E=3.0+/-1.5 eV and for the real (im aginary) part of the inner potential V-Or=3.0+/-1.5 eV (V-Oi=2.0+/-0.5 eV).