Analogous to ‘Young’s double slit’, microscopic particles occur matter-wave interference due to its wave-like behavior of quantum nature. When particles have multiple pathways leading to the same destination, the resultant phase difference of different pathways give rise to possible interference. However, such manifestations of matter-wave interference are rare in chemical reactions, which is difficult to observe attributed to the average effect of reactants with multiple quantum states. Recently, chemists have revealed a number of examples in which quantum interference are found in chemical reactions, thanks to developments in both experiment techniques and calculation methods. One such example is the work of Xueming Yang et al on photodissociation of H2O in B state. There are two distinct dissociating paths in the photodissociation of H2O in B state, one is via the conical intersection at HOH linear configuration and the other is at HHO linear configuration. The interference of two paths causes oscillations in rotational product distribution, which is a manifestation analogous to Young’s double slit experiment and is known as ‘Chemical Double Slit’.
Very recently, Prof. Daiqian Xie’s research group at School of Chemistry and Chemical Engineering, Nanjing University, and the collaborators have revealed the existence of quantum interference in the photodissociation of HCO in A state. From the high-resolution experiments, the oscillations in the rotational product distributions, which are not found in previous work, have been observed. Quantum dynamics calculation has reproduced the experimental result. Revealed by the quasi-classical trajectory calculation, the dissociative H atom is deflected by the barrier on potential energy surface of excited state in the dissociating path. In particular, the topology of a barrier can deflect different trajectories with the same angle, which is similar to ‘rainbow effect’ in inelastic collisions. Different phases associated to different paths leading to the same spatial destination or the same final product state give rise to the interference. Such interference results in alternations of even and odd states in the CO product distribution. Unlike the H2O case, the interference of different trajectories occurs on the same potential energy surface in the current HCO case, which is due to the unique topology of the potential energy surface.
This work has uncovered an example in which the wave-matter interference is caused by the unique topology of potential energy surface, broadening the horizon on this interference subject in chemical reactions. This research is collaborated with Prof. Hua Guo’s group at the University of New Mexico, Prof. Jinsong Zhang’s group at University of California Riverside, and Prof. Richard Dawes’ group at Missouri University of Science and Technology.
This work entitled by ‘Dynamical interference in the vibronic bond breaking reaction of HCO ’ was published on Science Advances, 2019, 5, eaau0582. This research has been supported by the National Key Research and Development Program of China and the National Natural Science Foundation of China.