Photochemistry of dibromine peroxide, BrOOBr

Abstract

The photochemistry of dibromine peroxide was investigated by means of mixed quantum-classical trajectory calculations on seven coupled potential energy surfaces. Photoexcited BrOOBr disintegratesrapidly, at a rate comparable with thermal decomposition. The rate constant is J = 9.7 × 10−2 s−1. The mechanism was investigated, and the final photolysis products are shown to be mainly 2Br + O2, though there is a minor channel leading to 2 BrO. Their formation involves an unusual intermolecular vibronic energy redistribution process. A hitherto unknown isomer of BrOOBr, the van der Waals complex O2 (a 1 ∆g ) · Br2 (X 1 Σ+g ) was found, which is more stable than the peroxide by 1.2 mHartree.