Formation of Excited Singlet States in the Nanosecond Pulse Radiolysis and Nanosecond Flash Photolysis of Aromatic Molecules in Liquid and Solid Solutions

Abstract

The absorption spectra of the excited singlet states of naphthalene and 1:2 benzanthracene have been observed in the nanosecond pulse radiolysis and flash photolysis of these solutes in cyclohexane, benzene, and polystyrene. The effect of xenon, piperylene, and excimer formation on the absorption spectra provides evidence for the assignment of these spectra to excited singlet states. The spectra are very similar both in shape and intensity to the triplet spectra; hence, little growth of the triplet state is observed as the excited singlet state decays. An extinction coefficient at 560 mμ for the 1:2 benzanthracene excited singlet is measured as ε560 = 9700M−1·cm−1. Using the photolysis data it is shown that approximately equal yields of excited singlet and triplet states are initially formed in the radiolysis of these systems. Large yields of ions are also formed in the pulse radiolysis of 1:2 benzanthracene in polystyrene and polymethyl-methacrylate.