A case study in ultracold reactive scattering: D+H-2

We report theoretical results for reaction and vibrational quenching of the ultracold collision D + H-2 (nu, j = 0) for a wide range of initial vibrationally excited states nu. The nu-dependence of the zero-temperature limit of the reaction rate coefficient shows two distinct regimes: a barrier dominated regime for 0 <= nu <= 4, and a barrierless regime for nu >= 5. We also present detailed distributions over the rovibrational states of the products. We find an approximate conservation of the internal vibrational energy; namely, the branching ratios always favor the highly excited final states, which have vibrational energies similar to that of the entrance channel.