The reaction ClO+ClO→products has been studied by a molecular modulation technique as a function of temperature from 268 to 338 K using pressures from 2 to 700 Torr. The reaction is found to have a strong pressure dependence and to be second order under the conditions used. The data have been interpreted in terms of three pressure-independent channels and a fourth, pressure-dependent channel in which the ClO dimer is formed. The termolecular rate constant for the formation of the dimer is kter=(6.0+0.37-0.34)¿10-32 (T/300.0)-2.1¿0.7cm6 molecule-2 s-1

The title reaction is then discussed in the light of the large ozone depletions seen in the Antarctic spring. A catalytic cycle involving the ClO dimer is presented which may account for these observations.