Y. Bedjanian et al., KINETICS AND MECHANISM OF THE IO+CLO REACTION, The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory, 101(22), 1997, pp. 4088-4096
The kinetics and mechanism of the reaction between IO and ClO radicals
have been studied by the mass spectrometric discharge-flow method at
T = 298 K and at total pressure around 1 Torr. The value of the overal
l rate constant k(1) = (1.1 +/- 0.2) x 10(-11) cm(3) molecule(-1) s(-1
) has been determined under pseudo-first-order conditions using an exc
ess of ClO over IO radicals. The quantitative detection of the reactio
n products OClO, Cl, and ICl allowed for the determination of the bran
ching ratios (0.55 +/- 0.03), (0.25 +/- 0.02), and (0.20 +/- 0.02) for
the channels producing I + OClO, I + Cl + O-2, and ICI + O-2, respect
ively. Ln addition, the rate coefficient (3.2 +/- 0.5) x 10(-13) cm(3)
molecule(-1) s(-1) has been measured at room temperature for the reac
tion I + Cl2O --> ICl + ClO. The kinetic data obtained allow for a red
etermination of the heat of formation of IO: Delta H-f(IO) = (27.7 +/-
1.2) kcal mol(-1) (based on the current value of Delta H-f(OClO) = (2
2.6 +/- 1.0) kcal mol(-1)). The data obtained indicate that the reacti
on IO + ClO, which could be involved in stratospheric ozone depletion
if iodine is present in the stratosphere, is much less important than
assumed in previous model calculations.