Electronic and vibrational excitation of acrylonitrile by low and intermediate energy electrons

Electronic and vibrational excitation of acrylonitrile induced by 3-50 eV energy electrons has been investigated by the electron energy loss spectroscopy. Electronic excitation spectra have been recorded for 30 and 50 eV impact energies at a 10° scattering angle in the energy loss range from 5.5 to 11.5 eV, corresponding to the excitation of electrons belonging to the outermost-valence-shell molecular orbitals. We have reviewed the assignment of the valence excited states occurring in the 5.5-9 eV energy loss region. The vibrational patterns associated with the two lowest-energy singlet valence excited states have also been re-examined. Moreover, we have proceeded for the first time to the analysis and attribution of several Rydberg series converging to the ionic ground state and to its two lowest-energy electronic excited states. The study of the excitation function of the C-H stretching modes of acrylonitrile in the 3-11 eV electron impact energy range has shown evidence of a broad shape resonance built on the electronic ground state of the molecule and centered at 5.85 eV. This resonance contributes to a preferential excitation of the C-H stretching modes suggesting that the charge distribution of the additional electron is very likely that of a σ* (C-H) valence molecular orbital. A comparison has been made between the resonances observed in C2H4 and CH2CHCN, in order to discuss the symmetry of the resonant state and also to analyze the substitution effect of the cyanogen group. © 1995 American Institute of Physics.