Dissociative electron attachment in nonplanar chlorocarbons with π∗/σ∗-coupled molecular orbitals

Abstract

Total absolute cross sections for the dissociative electron attachment (DEA) process are reported for a series of nonplanar ethylenic and phenylic compounds monosubstituted with (CH(2))(n)Cl groups, where n=1-4. Coupling between the local pi* molecular orbitals provided by the unsaturated moieties and the sigma* (C-Cl) orbital is thus examined as a function of the separation of these groups. In particular, the coupling is viewed from the perspective of the interacting temporary negative ions formed by short lived occupation of these orbitals and their decay into the DEA channel. A theoretical treatment of "remote" bond breaking, presented elsewhere, satisfactorily accounts for DEA in the chloroethylenic compounds presented here and emphasizes not only the delocalization of the coupled anionic wave functions but the importance of their relative phases. The dependence of the cross sections on the vertical attachment energies, measured by electron transmission spectroscopy, is also explored and compared to that found previously in chlorinated alkanes.

Elastic scattering of low-energy electrons by nitromethane

“…The LUMO + 3 corresponds to a σ * (a ) molecular orbital and is concentrated on the C-N bond. We also computed the canonical eigenvalues of the Fock operator and, using the empirical scaling relations for the LUMO (π * ) and LUMO + 1 (σ * ) orbitals from [35], we found for the LUMO and for the LUMO + 3, the values 0.39 and 4.60 eV for the vertical attachment energies (VAE), respectively, which are close to the present calculated π * and σ * resonance positions. We also computed the σ * VAE using another scaling relation from [36] for the LUMO, and obtained 4.61 eV.…”

“…Besides, the results obtained from the scaling relations of Refs. [35,36] suggest that the present calculations have located the σ * resonance at the right position. At the fixed nuclei approximation, there is no evidence of a σ * resonance at 2.4 eV.…”

“…6. Using the scaling relations of [35], the values for the π * and σ * VAE were 0.03 and 4.42 eV, respectively. In particular, the value of 0.03 eV for the π * orbital is much lower than the one previously obtained.…”

Stable negative ions and shape resonances in a series of organic molecules

“…Experience with many systems has also shown that the VOs of a closed shell neutral molecule describe the orderings and symmetries of low-lying shape resonances. [30][31][32][33][34][35][36] This is also true for the ordering of the ROHF states of the corresponding doublet openshell ions that are accessible.…”

Studies on the Processes of Electron Capture and Clustering of Benzyl Chloride by Ion Mobility Spectrometry

“…The theoretical explanation of the phenomenon may be based on the dependence of the cross-section for dissociative capture on the energy of electrons. The maximum cross-section for benzyl chloride is at about 0.8 eV [ 30 , 31 ]. This energy value is higher than the energy of electrons in nitrogen under the electric field in the IMS detector.…”