Potential energy surface multiple reaction paths

In the previous sections it has been implicitly assumed that the unimolecular reaction is electronically adiabatic and, thus, occurs on a single potential energy surface. Electronically excited states (i.e., multiple potential energy surfaces) for unimolecular reactions was discussed in chapter 3 and it is assumed that the reader has read and is familiar with this material (Nikitin, 1974 Hirst, 1985 Steinfeld et al., 1989). Transitions between electronic states are particularly important for the unimolecular decomposition of ions. For example, the following two dissociation paths ... 

In 2009, Xu et al. completed a comprehensive study of the C2H5O potential energy surface, reporting on the decomposition and isomerization reactions of all three C2H5O radicals and reviewing the previous hterature. Multiple decomposition paths were found for all species, with a main channel accounting for >75% of reaction for each species at moderate to h h pressures and temperatures below about 800 K the secondary processes were predicted to increase in importance at higher temperatures and lower... 

Carpenter and Borden made two important conclusions that raise significant concerns about the traditional physical organic notions of reaction mechanisms. First, nonstatistical dynamics can occur even when intermediates exist in relatively deep potential energy wells, not just on flat caldera-like surfaces. Second, multiple products can be formed from crossing a single TS. The steepest descent path from a TS can only link to a single product, but reactions can follow nonsteepest descent paths that reach different products. 

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