Magnetic Perturbation of the Lowest Triplet States of Aromatic Molecules by Dissolved Oxygen

Abstract

THE absorption spectrum of benzene in the region 2795–3650 A. has been measured by Miss Pitts¹. She observed a shoulder at approximately 2900 A. which has been tentatively assigned by Pariser² as a transition to a ³ E _1u state. Since it had been shown that oxygen dissolved in benzene absorbs strongly in this region³, the spectrum has been re-investigated using pure benzene saturated with air or with nitrogen. A Beckman Model DU spectrophotometer with 5-cm. silica cells was used, and the results obtained are shown in Fig. 1. No shoulder around 2900 A. can be detected, although in most other respects the curve for air-saturated benzene is in reasonably good agreement with that of Miss Pitts. The absorption spectrum of the pure compound at room temperature therefore seems to provide no evidence for a triplet-level of benzene at about 34,000 cm.⁻¹.