Photodissociation dynamics of ClOOCl at 248.4 and 308.4 nm

Abstract

The dynamics of ClOOCl photodissociation at 248.4 and 308.4 nm was studied with photofragment translational spectroscopy. At 248.4 nm photoexcitation, the observed products are Cl, O₂, ClO and O. Product translational energy distributions P(E) and anisotropy parameters β were deduced from the measured time-of-flight spectra of the Cl, O₂, and ClO photoproducts. The photodissociation mechanisms have been discussed and compared with available theoretical results. Synchronous and fast sequential breaking of the two Cl–O bonds may both contribute to the dissociation. The relative product yields for [ClO] ∶ [Cl] was measured to be 0.15 ± 0.04 ∶ 1. The relative amounts of [O] ∶ [O₂] products were estimated to be 0.12 ∶ 1. The branching ratios among the Cl + O₂ + Cl ∶ ClO + ClO ∶ ClO + Cl + O product channels were estimated to be 0.82 ∶ 0.08 ∶ 0.10. At 308.4 nm excitation, time-of-flight spectra of the O₂ and ClO photoproducts were recorded while there was interference from Cl₂ impurity in detecting the Cl product. Nonetheless, the observed ClO yield relative to the O₂ yield at 308.4 nm is 1.5 times that at 248.4 nm. The branching ratio between the Cl + O₂ + Cl ∶ ClO + ClO product channels was estimated to be 0.81 ∶ 0.19 at 308.4 nm. This result suggests that the ClO product may contribute a noticeable yield in the photolysis of ClOOCl at the atmospherically important wavelengths above 300 nm.