Dissociation of H 2 O 2 on water surfaces (ice and water droplets).

OH radicals are an important constituent of the atmosphere. Therefore, all reactions that act as a source of OH radicals are important. It is known that photo-dissociation of H 2 O 2 is an important source of OH radicals in the atmosphere. In the present study, using Born-Oppenheimer molecular dynamics simulations, we have shown that the H 2 O 2 molecule can dissociate thermally on water droplets, as well as on the surface of ice, to form OH radicals. Furthermore, the dissociation of H 2 O 2 was found to be very fast (less than 50 fs) on the ice surface compared with on the water droplets. We believe this route for the formation of OH radicals could be more critical than photo-dissociation, as it can take place both during the day and at night, but further studies with more sophisticated theoretical approaches or experiments are required to confirm this hypothesis.