Researchers led by Prof. FU Bina and Prof. ZHANG Donghui from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences, in collaboration with Prof. HAN Yongchang from Dalian University of Technology and Prof. Joel M. Bowman from Emory University have discovered a novel collision-induced roaming mechanism in an important combustion reaction. The results were published in Chemical Science.

 

Roaming is a novel mechanism in reaction dynamics. It describes an unusual pathway, which can be quite different from the conventional minimum-energy path, leading to products. While roaming has been reported or suggested in a number of unimolecular reactions, it has been rarely reported for bimolecular reactions.

 

3D polar plot for the product translational energy and angular distributions via the collision-induced roaming mechanism and the complex-mediated roaming mechanism. (Image by FU Yanlin)

 

Here, scientists report a high-level computational study of roaming dynamics in the important bimolecular combustion reaction H + C ₂H ₄→H ₂ + C ₂H ₃, using a new, high-level machine learning based potential energy surface.

 

In addition to the complex-mediated roaming mechanism, a noncomplex forming roaming mechanism is found. It can be described as a direct inelastic collision where the departing H atom roams and then abstracts an H atom. Scientists denoted this as “collision-induced” roaming.

 

These two roaming mechanisms have different angular distributions; however, both produce highly internally excited C ₂H ₃. The roaming pathway leads to remarkably different dynamics as compared with the direct abstraction pathway. A clear signature of the roaming mechanism is highly internally excited C ₂H ₃, which could be observed experimentally.

 

This work was supported by the National Natural Science Foundation of China, the Ministry of Science and Technology of China and the Chinese Academy of Sciences. (Tex and image by FU Yanlin)