X-ray fluorescence measurements for O-containing [polyethylene oxide, polyvinyl alcohol, polyvinyl methyl ether], CO-containing [polyvinyl methyl ketone, polyethylene terephthalate], N-containing [poly-4-vinylpyridine (P4VP), polyaniline oligomer (PAO)], and S-containing [polyphenylene sulfide] substances are presented. Carbon K alpha X-ray emission spectra (XES) and X-ray photoelectron spectra (XPS) are compared with our DFT calculations performed with the Amsterdam density functional (ADF) program. The combined analysis of valence XPS and carbon K alpha XES allows us to determine the individual contributions from p sigma- and p pi-bonding molecular orbitals of the polymers. The Delta SCF calculations yield the accurate C1s core-electron binding energies (CEBEs) for all carbon sites of the organic compound. We calculate all CEBEs of the model molecules using the Delta E-KS approach. Our simulated C1s photoelectron and C Ka emission spectra are in good agreement with our measurements. We also obtain WD (work function and the other energies) values for the polymers and PAO from the difference between calculated (gas-phase) and measured (solid) CEBE values. (c) 2006 Wiley Periodicals, Inc.