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.