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Journal Article

# The Recombination of Atoms. II. Causes of Variation in the Observed Rate Constant for Iodine Atoms

Margaret I. Christie, Anna J. Harrison, R. G. W. Norrish and G. Porter
Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences
Vol. 231, No. 1187 (Sep. 20, 1955), pp. 446-457
Stable URL: http://www.jstor.org/stable/99799
Page Count: 12
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## Abstract

A re-investigation of the recombination of iodine atoms in presence of the inert gases over a wider range of experimental conditions has shown that the simple termolecular rate law -d(I)/dt = k(I)2 (M) is not obeyed. For each of the inert gases k, the experimentally determined termolecular rate constant, increases with the ratio (I2)/(M), where (I2) and (M) are the concentrations of iodine molecules and inert gas molecules respectively. The dependence of k on (I2)/(M) was obscured in previous work by the fact that a thermal effect, which results in a lowering of the apparent value of k as recombination proceeds, increases as (I2)/(M) increases and compensated for the real increase in k with (I2)/(M). Except at low (I2)/(M) values, k is a linear function of (I2)/(M), the gradient being the same for all five inert gases. A rapid termolecular reaction I+I+I2 = I2+I2 with a rate constant k = 470 × 10-32 ml.2 mol.-2 s-1 is postulated to explain the linear relationships. By extrapolation the values of kM the third-order rate constants for the five inert gases are $\matrix\format\c\kern.8em&\c\kern.8em&\c\kern.8em&\c\kern.8em&\c\kern.8em&\ c \\ M & \text{He} & \text{Ne} & \text{A} & \text{Kr} & \text{Xe} \\ 10^{32}k_{M}(\text{ml}.^{2}\text{mol}.^{-2}\text{s}^{-1}) & 0\cdot 67 & 0\cdot 92 & 1\cdot 84 & 2\cdot 25 & 2\cdot 99 \endmatrix$

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