Experimental and theoretical study of the XPS core levels of gas phase acetonitrile, acrylonitrile and propionitrile: model molecules for polyacrylonitrile

The gas phase molecules acetonitrile, propionitrile and acrylonitrile have been studied by high resolution X-ray photoelectron spectroscopy. The information obtained from these model molecules is used for the interpretation of the related polyacrylonitrile (PAN) spectrum. In order to solve a controversy in the assignment of the chemically shifted atoms in the C1s region, calculations of the shifts of the model molecules are presented at different levels of accuracy including double zeta and triple zeta basis sets, namely frozen orbital, self consistent field (ΔSCF), multi configurational self consistent field (ΔMCSCF) and Møller-Plesset second order perturbation (ΔMP2) calculations. The binding energies of the model molecules for PAN, proprionitrile, are extrapolated to give an estimation of the polymer chemical shifts.