Quantum interference in H + HD → H2 + D between direct abstraction and roaming insertion pathways

Understanding quantum interferences is essential to the study of chemical reaction dynamics. Here, we provide an interesting case of quantum interference between two topologically distinct pathways in the H + HD → H2 + D reaction in the collision energy range between 1.94 and 2.21 eV, manifested as oscillations in the energy dependence of the differential cross section for the H2 (v′ = 2, j′ = 3) product (where v′ is the vibrational quantum number and j′ is the rotational quantum number) in the backward scattering direction. The notable oscillation patterns observed are attributed to the strong quantum interference between the direct abstraction pathway and an unusual roaming insertion pathway. More interestingly, the observed interference pattern also provides a sensitive probe of the geometric phase effect at an energy far below the conical intersection in this reaction, which resembles the Aharonov–Bohm effect in physics, clearly demonstrating the quantum nature of chemical reactivity.

Cold and controlled chemical reaction dynamics

State-to-state chemical reaction dynamics, with complete control over the reaction parameters, offers unparalleled insight into fundamental reactivity.

Crossed-beam chemical reaction dynamics probed with universal and state resolved ion imaging

The main goal of chemical reaction dynamics is to unravel the intimate motions of individual atoms during a chemical transformation. This information must generally be inferred from indirect macroscopic measurement. Very important information such as translational energy dependence of the reaction cross-section, vibrational mode-specific promotion of reactivity, product angular and velocity distributions are normally extracted. Understanding how these chemical reactions occur at the microscopic level gives us a better insight in understanding reactive intermediates and products of reaction. For a better understanding of the elementary chemical reactions, it is imperative that the studies are performed under well-defined laboratory conditions. Over the last few decades, the field has witnessed unprecedented advances in both experiment and theory. Advancements in generating reactants, state selection, improvement of crossed-molecular beam machines and products detection have gone a long way to improve our ability in studying chemical reactions in the gas phase. In 1986, Hershbach,[1] Lee[2] , and Polayni[3] together shared the Nobel Prize in Chemistry for their work on the dynamics of gas phase reactions.