IODINE DISSOCIATION IN THE PHOTOCHEMISTRY OF N2O/I2 MIXTURES

A new kinetic scheme for the dissociation of I-2 by O-2(a) has been proposed by Azyazov et al. (J. Chem. Phys. 130, 104306/9 (2009)). In principle, the reactions initiated by UV photolysis of N2O/I-2 mixtures can be used to probe the chain propagation stage of this dissociation model, and provide additional validation. In the present study, 193 nm laser photolysis of N2O/I-2 mixtures was used to initiate secondary chemical reactions and to produce iodine atoms. Singlet oxygen was generated in this system by the fast reaction O(D-1)+N2O -> O-2(a)+N-2. Emission spectroscopy and laser induced fluorescence techniques were used to follow the time evolutions of I* and I-2. The photolysis of N2O/I-2 mixtures creates all of the species needed to sustain the chain propagation stage of I-2 dissociation process. However, it was found that the high pressures of N2O needed to generate sufficient concentrations of O-2(a) suppressed the I-2 dissociation process. Computational modeling indicated that suppression of the chain propagation reactions under the conditions examined was consistent with the revised dissociation model.