At temperatures above 380 K the unimolecular decomposition
of H3NSO3 into SO3 + NH3 competed efficiently with the
association reaction, and the SO3 decays were not simple
exponentials (see Figure 2). For these conditions the SO3 decay
and H3NSO3 appearance were modeled to extract the rate
coefficient for decomposition of H3NSO3. The kinetics were
modeled with the following mechanism