Effect of water on dynamics of HOCO radical

The activated HOCO* is one of the most important intermediates in combustion and atmospheric processes and could become thermally stabilized through the collision with the third species. In this work, the effect of a single water molecule on an energized HOCO* radical for the collision of HOCO + H₂O has been investigated by using direct dynamics methodology. The properties of the stationary points on the potential energy surface have been characterized at M06-2X/aug-cc-pVDZ level of theory. Interesting dynamical features and detailed atomic level mechanisms are presented. It is found that the water molecule is not involved in the chemical reaction, but it can substantially decrease the activation barrier when compared with the water-free system. Energy distributions of products indicate that H₂O can transfer the vibrational energy of the energized HOCO to its own rotational energy and thus serves as an efficient third body.