Ozone reaction with excitation function

The functional principle behind nitrogen oxides analysers is generally the reaction of nitric oxide with ozone to yield excited nitrogen dioxide and water. The transition of the excited molecule to the ground state is accompanied by the release of radiant energy, which is suitably measured ... 

The exact mechanism arises in the process of inverse pre-dissociation, as discussed in detail by Herzberg (1966). During an atom-molecule collision, the reactants interact with one another subject to the relevant potential energy surface. The lifetime of this excited intermediate is on the order of molecular vibrational periods, or 10 s. The lifetime is a complex function of the chemical reaction dynamics, which in turn depends on the number of available states. In this specific instance, there is a state dependence for the isotopically substimted species. Ozone of pure has a Cav symmetry and has half the rotational complement of the asymmetric isotopomers. As a result, it was suggested that the extended lifetime for the asymmetric species leads to a greater probability of stabilization. While these assumptions are valid for a gas phase molecular reaction, they do not sufficiently account for the totality of the experimental ozone isotopic observations. Reviews by Weston (1999) and Thiemens (1999) have detailed the physical-chemical reasons. 

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