Abstract

The photolysis of aqueous C1O₂ has been studied with a new femtosecond transient absorption spectrometer, allowing absorbance changes as small as ΔA͌ 1 × 10^-4 to be recorded with a time resolution of 150 fs. ClO₂ was photolyzed at 390 nm and the ultrafast formation and decay of photoproducts were monitored from 230 nm to 78 nm, using either harmonics of the 780 nm pulses or a white light continuum. The main photolytic product, ClO + O, is formed with a quantum yield of 0.9, but disappears through a fast geminate recombination, producing vibrational excited C1O₂ in the electronic ground state. The hot ClO, subsequently cools down in 10 ps. In addition to ClO + O, Cl + O₂ is formed, with a quantum yield of 0.1 within the first 10 ps of the photolysis pulse, thus indicating the absence of the expected long-lived ClOO species. Using a simple model including the vibrational cooling of C1O₂ and the absorbance of aqueous Cl we are able to account for the experimental observations.

© 1997 Optical Society of America