Effect of halo-substitution on the lowest-lying empty π * orbitals in benzene derivatives: Electron transmission and dissociative attachment spectra

Abstract

The electron transmission (ET) and dissociative attachment (DA) spectra of the 4-haloanisoles X-C 6H 4-OCH 3 (X = F, Cl, Br, I) and 4-halopyridines X-C 5H 4N (X = Cl, Br) are reported. The ET spectra indicate that the two lowest-lying π-anion states (deriving from the benzene 2E 2u anion state) are almost equally stabilized by Cl, Br and I substituents. Except for fluorine, in both the anisole and pyridine derivatives the DA spectra display a peak in the fragment halogen anion yield close in energy to the lowest lying π * resonance observed in the ET spectra, regardless of its symmetry.