Low Resolution Electronic Spectrum of Crystalline para-Dimethoxybenzene with Application to Benzene

Abstract

The spectrum of a thin (0.37μ) crystal of para‐dimethoxybenzene for light incident on the 001 plane and polarized along the a and b crystallographic axes is given. From this, approximate spectra are determined for the two in‐plane directions of the molecule. Absorption at 2900 A is polarized predominately in a direction perpendicular to the line joining the substituents while absorption at 2350 A is parallel to this line. The 2600 and 2000 A absorptions in benzene are related respectively to the 2900 and 2350 A bands in dimethoxybenzene and consequently the benzene bands are found to arise from transition to upper states of species B_2u and B_1u respectively. The relation to conventional orbital theory is briefly discussed.