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

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