CURVED-WAVE CORRECTIONS TO THE ELECTRON-SCATTERING DEBYE-WALLER FACTOR

The influence of atomic movement on the electron scattering is calculated in a curved-wave theory. The contribution in the angular momentum representation of the Green function can be split off into the Debye-Waller factor for the plane-wave scattering and a curved-wave correction. The additional term can be used to correct the expressions for the fine structure in the x-ray absorption spectra or for the angle resolved photoelectron diffraction. The results are applicable to all approximative expressions for these properties. As a main result due to the thermal movement of the atoms the elements of the t-matrix, t(iota), have to be replaced by t(iota)TD = t(iota) + k2-sigma-10(2)t(iota) where t is a modified t-matrix. t and t have a different k-dependence. The consequence is a shift in the peaks of the absolute value of the Fourier-transformed spectrum. For nickel we get a shift up to 0.1 au in the single scattering expression for the first nearest neighbour.