Dynamical resonances in chemical reactions

Abstract

Gas-phase chemical reactions occur when one reactant collides with another followed by rearrangements of the atoms in the activated complex. This process is typically described by the reaction coordinate leading from the reactants to products via a transition state. In general, the transition state is only a whistle-stop for the reactive flux. However, an activated complex can sometimes be transiently trapped in the transition-state region as metastable quantum states. Such dynamical resonances can profoundly influence the dynamics of a chemical reaction. As a result, it has attracted much attention in the field of chemical dynamics over the past 30 years. Although signatures of dynamical resonances have been detected in several reactions [1–4], only the F + H2(HD) resonances have been elucidated [1–3]. It is thus exciting when a research team led by Profs Xueming Yang and Dong Hui Zhang in State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, unequivocally proved the existence of dynamical resonances in the Cl + HD (v = 1) → DCl + H reaction and elucidate them clearly through the state-of-the-art crossed molecular beams experiment and quantum dynamics calculations [5]. Experimentally, the first application of stimulated Raman pumping of HD molecules to the vibrationally excited v= 1 state in a crossed molecular beams study, in combination with the so-called differential cross-sections backward scattering spectroscopy method developed in their own laboratory, is Reaction coordinate Feshbach resonance pathway Shape resonance pathway