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

Abstract

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 *͑C-H͒ valence molecular orbital. A comparison has been made between the resonances observed in C 2 H 4 and CH 2 CHCN, in order to discuss the symmetry of the resonant state and also to analyze the substitution effect of the cyanogen group.

Excited state dynamics of acrylonitrile: Substituent effects at conical intersections interrogated via time-resolved photoelectron spectroscopy and ab initio simulation

“…Phys more detailed spectra in the literature. 9,10 The broad absorption band of AN was found to originate at 211 nm (5.88 eV) and was assigned to a ππ * state. Higher energy peaks were assigned to a vibrational progression.…”

“…7 The conjugated π system of α, β-enenitriles gives rise to several low-lying electronic states, resulting in a complex electronic structure that has been the subject of numerous spectroscopic characterization studies. 4,[8][9][10] In the first reported absorption spectrum of AN, the two overlapping absorption bands were observed to lie between 159 and 213 nm (5.8-7.8 eV) 8 and were assigned to n → π * and π → π * transitions. 4,8 Using electron energy loss spectroscopy and high resolution photoabsorption spectroscopy, these peaks were later reassigned to the π 2 (C= =C-C≡ ≡N) → π * 1 (C= =C-C≡ ≡N) transition (Ã 1 A ′ ) and the π 2 (C= =C-C≡ ≡N) → π * (C≡ ≡N) transition (B 1 (7.0-9.0 eV) was assigned to theC 1 A ′ (π 2 (C==C-C≡ ≡N) → π * 2 (C= =C-C≡ ≡N)) transition, while higher energy bands were attributed to a Rydberg series.…”

“…4,8 Using electron energy loss spectroscopy and high resolution photoabsorption spectroscopy, these peaks were later reassigned to the π 2 (C= =C-C≡ ≡N) → π * 1 (C= =C-C≡ ≡N) transition (Ã 1 A ′ ) and the π 2 (C= =C-C≡ ≡N) → π * (C≡ ≡N) transition (B 1 (7.0-9.0 eV) was assigned to theC 1 A ′ (π 2 (C==C-C≡ ≡N) → π * 2 (C= =C-C≡ ≡N)) transition, while higher energy bands were attributed to a Rydberg series. 9,10 To date, highresolution characterization of the electronic spectra has not been performed for CrN and MeAN, but low resolution UV-Vis spectra show similar broad overlapping bands in the 200-225 nm (5.5-6.2 eV) range. 7 The potential energy surfaces of the ground state and low lying excited states of AN have been extensively studied to characterize and enumerate the dissociative pathways associated with excitation at 193 nm.…”

Resonant Auger electron–photoion coincidence study of the fragmentation dynamics of an acrylonitrile molecule

“…According to the earlier studies [35,36,6,9,8] the orientation, localization and orbital type of these states are as follows:…”

“…This has been a stimulus for investigations of the ion-molecule chemistry of acrylonitrile and its fragments [1,2,3,4]. There is a number of experimental and theoretical studies concerning the inner-and valence-shell excitations [5,6,7,8,9,10] and the core-level photoemission of gaseous and adsorbed acrylonitrile [11,12,13,14,15,16] as well. In the case of solid acrylonitrile the non-radiative (electronic) decay channels at the nitrogen K-edge have been studied by resonant Auger electron spectroscopy (RAES) [17] and for the gas phase acrylonitrile have been published the mass spectrometric investigation results of ionization and appearance energies for all detected cations [18].…”