| Abstract
| - The gas-phase electron transmission (ET) and dissociative electron attachment (DEA) spectra are reportedfor the series of (bromoalkyl)benzenes C6H5(CH2)nBr (n = 0−3), where the bromine atom is directly bondedto a benzene ring or separated from it by 1−3 CH2 groups, and the dihalo derivative 1-Br-4-Cl-benzene. Therelative DEA cross sections (essentially due to the Br- fragment) are reported, and the absolute cross sectionsare also evaluated. HF/6-31G and B3LYP/6-31G* calculations are employed to evaluate the virtual orbitalenergies (VOEs) for the optimized geometries of the neutral state molecules. The π* VOEs, scaled withempirical equations, satisfactorily reproduce the corresponding experimental vertical electron attachmentenergies (VAEs). According to the calculated localization properties, the LUMO (as well as the singly occupiedMO of the lowest lying anion state) of C6H5(CH2)3Br is largely localized on both the benzene ring and theC−Br bond, despite only a small π*/σ*C-Br interaction and in contrast to the chlorine analogue where theLUMO is predicted to possess essentially ring π* character. This would imply a less important role ofintramolecular electron transfer in the bromo derivative for production of the halogen negative fragmentthrough dissociation of the first resonant state. The VAEs calculated as the anion/neutral energy differencewith the 6-31+G* basis set which includes diffuse functions are relatively close to the experimental valuesbut do not parallel their sequence. In addition the SOMO of some compounds is not described as a valenceMO with large π* character but as a diffuse σ* MO.
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