A discharge-flow study of Cl₂O₃

The discharge-flow technique coupled with UV-absorption spectroscopy has been used to study the production of dichlorine trioxide, Cl₂O ₃, from the reaction between ClO and OClO radicals. The absorption cross section of Cl₂O₃ was determined to be (1.44 ± 0.10) × 10^-17 cm² molecule^-1 at λ_max = 267 nm (all errors reported are two standard deviations of the statistical error). The equilibrium constant for the process ClO + OClO + M ⇌ Cl₂O₃ + M was measured in the temperature range 243-298 K. A Second-Law analysis yielded values of Δ_rH^⊖ = -57.9 ± 2.1 kJ mol ^-1 and Δ_rS^⊖ = -132.6 ± 7.9 J K^-1 mol^-1. The rate coefficient for the formation of Cl₂O₃ was measured with helium as the third body at a concentration of ∼7.3 ± 10¹⁶ molecule cm^-3 over the temperature range 243-283 K. Analysis of these data employing the conventional form of the rate equation for the low-pressure limit, k ⁰(T) = k⁰(300)·(T/300)^-n, resulted in values of k⁰(300) = (2.83 ± 0.04) × 10^-32 cm⁶ molecule^-2 s^-1 and n = -4.32 ± 0.1. These spectroscopic, thermochemical and kinetic data are compared with previously reported values.