Polarized absorption spectra of some aromatic radical anions in stretched polyethylene films

Six different aromatic radical anions were generated in stretched polyethylene films by ⁶⁰Co γ-ray irradiation at 77 K, and the polarized absorption spectra were observed at 77 K; the long and short molecular axis polarized components were determined by invoking the stepwise reduction procedure. The parent compounds are biphenyl, 4,4′-bipyridyl, phenathrene, benzo[c]-cinnoline, 1,2,3,4-dibenzanthracene and 1,2,3,4-dibenzophenazine. The restricted Hartree-Fock SCF m.o. CI calculations are in good agreement with the observed results. The spectral variations brought about by nitrogen atoms are interpreted in terms of a simple aza-perturbation treatment.