Ab Initio Studies of ClO_x Reactions. 2. Unimolecular Decomposition of s-ClO_3 and the Bimolecular O + OClO Reaction

摘要

The unimolecular decomposition of symmetric ClO_3 has been investigated at the G2M(CC2)//PW91PW91/6-311+G(3df) level of theory. The results show that the main dissociation products are ~3O + OClO instead of the commonly assumed ClO + O_2. The rate constants at high- and low-pressure limits were predicted to be K_2~∞ = 1.5 * 10~(20)T~(-1.1) exp(-18360/T)s~(-1) and k_2~0 = 3.76 * 10~(25)T~(-3.28) exp(-13890/T) cm~3 mol~(-1) s~(-1) in the temperature range 500-25000 K. For the bimolecular processes, the sum of the predicted abstraction (k_3) and association (k_(-2)) values can reasonably explain the experimental nonzero intercepts of the strong pressure-dependent rate constants, with the predicted total rate constants agreeing closely with the experimental values. The association and abstraction rate constants in the temperature range 200-500 K can be represented respectively by k_(-2) = 40.1T~(-6.16) exp(-403/T) for 1 Torr He and k_3 = 1.0 * 10~(-16)/T~(1.44) exp(-469/T) cm~3 molecule~(-1) s~(-1). The abstraction rate constant for 500-2500 K can be expressed by k_3 = 8.69 * 10~(-17)T~(1.45) exp(-441/T) cm~3 molecule~(-1) s~(-1).