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Empty level structure and dissociative electron attachment cross section in (bromoalkyl)benzenes.
1Dipartimento di Chimica "G. Ciamician", Università di Bologna, via Selmi 2, 40126 Bologna, Italy, and Centro Interdipartimentale di Ricerca in Scienze Ambientali (CIRSA), Università di Bologna, via S. Alberto 163, 48100 Ravenna, Italy.
The Journal of Physical Chemistry. A
|July 13, 2006
Summary
Electron attachment to bromoalkylbenzenes reveals how electron energy relates to molecular structure. Computational methods accurately predict electron attachment energies, aiding in understanding fragmentation pathways.
Area of Science:
- Physical Chemistry
- Quantum Chemistry
- Spectroscopy
Background:
- Electron transmission (ET) and dissociative electron attachment (DEA) are key techniques for probing molecular electronic structures.
- Understanding electron interactions with organic molecules is crucial for various chemical and physical processes.
Purpose of the Study:
- To investigate the gas-phase electron attachment spectra of (bromoalkyl)benzenes (C6H5(CH2)nBr, n=0-3) and 1-Br-4-Cl-benzene.
- To correlate experimental electron attachment energies with calculated virtual orbital energies and electron localization.
Main Methods:
- Experimental measurement of gas-phase electron transmission (ET) and dissociative electron attachment (DEA) spectra.
- Computational calculations using Hartree-Fock (HF)/6-31G and B3LYP/6-31G* for virtual orbital energies (VOEs).
- Calculation of anion/neutral energy differences using the 6-31+G* basis set.
Main Results:
- Relative and absolute DEA cross sections for Br- fragment formation were determined.
- Scaled pi* VOEs correlated well with experimental vertical electron attachment energies (VAEs).
- LUMO localization in C6H5(CH2)3Br involves both the benzene ring and C-Br bond, differing from its chlorine analogue.
Conclusions:
- Empirical scaling of calculated VOEs provides a reliable method for predicting experimental VAEs.
- Molecular structure significantly influences electron localization and dissociation pathways in bromoalkylbenzenes.
- The study provides insights into the mechanisms of electron-induced fragmentation in halogenated aromatic compounds.