THEORETICAL-STUDY OF SPECTRAL DIFFERENCES IN THE XPS VALENCE BANDS OFPOLYETHYLENE LAMELLAE AND FILMS

With the aim of searching for conformational signatures, the XPS valen ce spectra of selected forms of the n-nonane compound, modeling the ex treme surface of polyethylene samples, are simulated at the second-ord er level of many-body Green's function theory, using the minimal STO-3 G basis set. Variations observed in the shape of spectral bands are an alyzed in terms of the combined influence of the pole strength factor together with the orbital relaxation, pair removal, and pair relaxatio n effects. Molecular orbital photoionization cross sections, line posi tions, and many-body effects exhibit evidence of the fundamental role played by directional orbitals: the origin of the striking conformatio nal signature exhibited in the inner valence band is attributed to alt erations of stabilizing interactions of hyperconjugation character and ultimately related to the large energetic dispersion of the C2s state s in an extended hydrocarbon.