We report ab initio calculations of the x-ray absorption cross section for
the near edge x-ray absorption fine structure of C2H6, and C2H4, and C2H2 a
t the C K-edge, based on a full multiple scattering formalism. The angular
dependence of the electric dipole transition in the calculations as well as
the angular dependent experiments for the oriented molecules give a good o
pportunity to compare both. The resonance can be assigned to a sigma* shape
resonance. The multiple scattering formalism and the experiment agree well
and thereby support the existence of such features in the spectra.