Core level photoemission and theoretical studies of cyano organic compounds

The X-ray photoemission spectroscopy (XPS) study of the C1s core level of polyacrylonitrile (PAN), (CH₂CHCN)_x, reveals two components separated by 1.0 eV with the following intensity: 2 for the high binding energy (BE) component and 1 for the low one. To interpret the spectrum, the polymer is modelled by molecules where the nearest-neighbour's environment is respected and an ab initio calculation of the C1s vertical ionization energies (IE) in the series CH₃CN, CH₂CHCN, CH₃CH₂CN, CH₂CNCH₂CH₂CN, CH₃CHCNCH₃, CH₄ and CH₃CH₂CH₃ is performed. A ΔSCF level of approximation is chosen after a detailed study of the smallest CH₃CN molecule. In all the compounds studied the binding energy of the 1s level of a carbon atom increases as its distance from the nitrogen atom decreases. The use of this rule enables us to interpret the C1s XPS spectrum of polyacrylonitrile and CH₃CH₂CN together with those of two other cyano molecules: CNC₆H₄CN and CH₂CNCHCHCH₂CN.