Experimental Resonance-Like Features in the Barrierless Reaction of O(¹D) + D₂ at Collision Energies from 20 to 168...

Reaction resonances have been extensively studied in barrier reactions, whereas the observation of reaction resonances is rarely reported in barrierless reactions. In this work, a high-resolution crossed molecular beam experiment using the D atom Rydberg tagging technique was systematically carried out to investigate the barrierless reaction of O(¹D) + D₂ → OD + D over a collision energy range of 20-168 cm^-1. Four experimental observations were found, including the dramatic changes of OD product angular distributions, the peak structures of collision energy-dependent differential cross sections (DCSs) in the forward and backward scattering directions, the ridge features in the 3D-DCS plot of σ(θ, E_c), and the valley structure of the collision energy-dependent integral cross section. These resonance-like features may offer fresh insights into the intricate dynamics of this prototype barrierless reaction at low collision energies.