The photochemistry of liquid 1,4-dioxane at 184.9 nm and 147.0 nm

Abstract

Photodecomposition of 1,4-dioxane in a condensed phase at 184.9 nm proceeds with quantum yields as follows: φ(C 2H 4) = 0.55, φ(H 2) = 0.26 and φ(CO) = 0.03. Quantum yields at 147.0 nm are φ(C 2H 4) = 0.52, φ(H 2) = 0.28 and φ(CO) = 0.03. Quenching studies coupled with these quantum yield measurements in the liquid phase afford Stern—Volmer quenching constants in the range 17 – 36 M −1. Nitrous oxide and benzene are used as quenchers of the excited state leading to H 2 and C 2H 4 photolysis products following irradiation at 184.9 and 147.0 nm. The quantum yield for the production of N 2 at 184.9 nm has been determined to be ≈ 0.70. At 147.0 nm φ(N 2) ≈ 0.42 in 1,4-dioxane—N 2O solutions. The transfer of energy proceeds less efficiently in the higher excited state than in the ground state at 184.9 nm for N 2 production. At 147.0 nm experiments in solution using I 2 as a radical scavenger show that 51% of the initially produced hydrogen atoms are scavenged by 2 × 10 −2M I 2. Fluorescence quenching experiments employing C 6H 6 and N 2O show Stern—Volmer quenching constants of 28 and 38 M −1, respectively. The quenching results show that the excited state involved in fluorescence is the same as that involved in photodecomposition.