Vibrational State-Resolved Study of the O- + D2 Reaction: Direct Dynamics from 0.47 to 1.20 eV†

We present a crossed beam study of the title reaction over the collision energy range from 0.47 to 1.20 eV, over which the dynamics of particle transfer are direct. The data include vibrational state populations and vibrational-state dependent angular distributions. Over the entire collision energy range, the product vibrational state distributions are inverted, and the extent of that inversion as measured by the vibrational surprisal increases with increasing collision energy. The energy dependence of the product vibrational state distributions is partially consistent with mixed energy release in the Heavy + Light-Light mass combination, but it more closely resembles the behavior of proton transfer in the O+ HF system at low energies, where the attractive well induces corner cutting trajectories, leading to partitioning of increased reagent translation into product vibration. The most probable rotational energy is approximately constant as a function of vibrational quantum number and is effectively independent of collision energy. This saturation effect is consistent with the softening of the low energy repulsive wall as the collision geometry changes from collinear to bent. Several features of the data can be rationalized with extant ab initio calculations, but other features, especially the vibrational state populations, require additional theoretical insight for complete understanding.