X-RAY-INDUCED ELECTRON YIELD SPECTRUM OF THIN-FILMS OF 1,3-TRANS-BUTADIENE AND 1,3,5-TRANS-HEXATRIENE

The electron yield spectrum, also commonly referred to as near-edge X-ray absorption spectra (NEXAFS), of 1,3-trans-butadiene and 1,3,5-trans-hexatriene in the 280 330 eV photon-energy region are reported. The spectra were obtained by measuring the total yield of electrons as a function of photon energy. The results for butadiene are compared with earlier inner shell electron energy loss (ISEELS) data. A reassignment of the C1s --> pi* transitions was made using multiconfiguration self consistent field (MCSCF) calculations and recent X-ray photoelectron measurements of the C1s line in butadiene. It was found that even the first core excited states are strongly influenced by electron correlation. The first structure in the electron-yield spectrum was assigned to transitions from Is orbitals on the non-equivalent carbon atoms to the first corresponding states of pi symmetry. The electron-yield spectrum of 1,3,5-trans-hexatriene was assigned in analogy with the results for 1,3-trans-butadiene. The vibrational fine structure was revealed in the spectra of both molecules.