k1′ ) 7.14 10 -12 T 0.86 exp(-2370/T )c m 3 molecule -1 s -1 , accounting for less than 0.1% of the Cl2 yield at 298 K but increasing to about 46% at 1000 K. The new Cl2O + ClO products can be produced by the fragmentation of the two complexes; the rate constant for their formation was found to be pressure-independent and can be expressed by k2 ) 2.19 10 -14 T 0.70 exp(-1110/T )c m 3 molecule -1 s -1 covering the temperature range of 200-1000 K. Above room temperature, Cl2O formation becomes competitive; for example, its branching ratios, k2/kt, are predicted to be 0.19, 0.55, and 0.62 at 298, 500, and 1000 K, respectively. The predicted total rate constant agrees closely with available experimental results. The heat of formation of ClOOCl has been examined in detail using different reactions and computational methods. The results of these calculations converge to ¢fH°0(ClOOCl) ) 30 ( 2 kcal/mol.