On the Recombination Rate of Iodine Atoms in the Presence of Various Gases

Year: 1959 DOI: 10.7907/KAVE-WG75
The rate of iodine atom recombination in the presence of various gases has been studied by the flash photolysis technique. The temperature dependence of the rate constant has been determined for recombination in helium, hydrogen, benzene, and methyl iodide. The negative temperature dependences are fitted by the form, k∝1/Tn, where n(He) = 0.80, n(H₂ = 1.48, n(C₆H₆ = 2.53, and n(CH₃I = 3.24.

The iodine atom recombination rate constant was also measured at 50°C. for ethyl iodide, hydrogen iodide, carbon monoxide, and nitric oxide. The rate constants relative to helium at 50°C. are:

He 1.00 C₂H₅I 179.
H₂ 3.33 NI 21.1
C₆H₆ 61.1 CO 4.07
CH₃I 88.8 NO >1.4 x 10⁴

Nitric oxide appears to be a very efficient third body gas and only a lower limit on the rate constant could be established.

Calculations have been made for some possible mechanisms of iodine atom recombination. A classical three body collision model is proposed for atom recombinations. The classical equations of motion were programmed to be solved numerically on a digital computer and some trajectories were examined.