Non-adiabatic processes of molecular systems are quite common phenomena in the nature, but they are very difficult research topics both experimentally and theoretically. DICP scientists and their collaborators have made important progress in the studies of the non-adiabatic kinetics of the Cl + H2 reaction, thus solving a problem of great controversy in the field of chemical kinetics. The results were published in the journal of Science appearing on 24th October, and was cited by the Chemical & Engineering News of 27th October.

The reactivity of the spin-orbital excited states of the chlorine atom is a hot topic in research work. Previously, researchers have found experimentally that even under very high collision energies, the reactivity of the spin-orbital excited states of the chlorine atom is much higher than that of the ground state, and these findings are in conflict with the most precise theoretical derivations. Accordingly, this discrepancy constitutes a great challenge to the effectiveness of the Born-Oppenheimer approximation.

The DICP research team, headed by Prof. YANG Xueming, determined the relative differential cross sections of the ground state and the excited states of the Cl + H2 reaction by means of a Rydberg state hydrogen time of flight mass spectrometer ¨C cross molecular beam installation, and found that under low collision energies, the reactivity of the spin-orbital excited state of the chlorine atom was comparative to that of the ground state, and this implied that the Born-Oppenheimer approximation is not effective in this reaction at low collision energies. However, as the collision energy was increased, the reactivity of the spin-orbital excited states of the chlorine atom became smaller and smaller as compared to that of the ground state, implying that the Born-Oppenheimer approximation was effective under high collision energies.

Meanwhile, detailed theoretical results obtained via complete quantum scattering kinetic calculations for this reaction system by Prof. ZHANG Donghui of DICP, in collaboration with Prof. XIE Daiqian of the Nanjing University and Prof. Millard H. Alexander of the Maryland University, USA, were in good consistency with the experimental results mentioned above. This also implies that theoretical studies in three-atom non-adiabatic kinetics have attained a very high precision.