ANISOTROPY OF THE PHOTOELECTRON MEAN FREE-PATH AND ITS INFLUENCE ON THE EXAFS AMPLITUDE

The anisotropy of the inelastic mean free path (MFP) for electrons with energies between approximately 10-1000 eV has been studied for the first time in ReO3, NaWO3 and TiO crystals. The MFP was calculated within the one-plasmon and local density approximations from the imaginary part of the complex energy-dependent exchange and correlation potential of the Hedin-Lundqvist type. It is shown that the MFP in compounds with a highly anisotropic electron density distribution, such as ReO3 and NaWO3, differs in various crystallographic directions from the MFP calculated for the averaged electron density. In particular, it was found that in the ReO3 crystal, the MFP values in [100] directions coincide with those for a spherically averaged cluster potential and are approximately 1 angstrom smaller than in [110] and [111] directions. This result explains the variation of the outer shell amplitudes in the Re L3-edge EXAFS in ReO3.