The UV absorption spectrum of dichlorine trioxide, Cl2O3 has been reco
rded in the wavelength range 220-340 nm and at 223 K using a recently
developed flash photolysis-kinetic UV absorption spectroscopy apparatu
s. Cl2O3 was generated in the reaction between ClO and OClO following
the partial photolysis of OClO. The spectrum obtained is smooth, and s
hows a peak at 267 nm, where sigma = 1.76 x 10-(17) cm(2) molecule(-1)
(base e). Results are broadly consistent with previous determinations
of the spectrum, although we report higher cross-sections in the long
-wavelength tail of the absorption. The discrepancies between these an
d previous measurements are discussed, together with the atmospheric i
mplications of this work.