Effect of nuclear spin symmetry in cold and ultracold reactions: D + para/ortho-H₂

We report results for reaction and vibrational quenching of the collision D with para-H₂(v, j = 0) and ortho-H₂(v, j = 0) at cold and ultracold temperatures. We investigate the effect of nuclear spin symmetry for barrier dominated processes (0 ≤ V ≤ 4) and for one barrierless case (v = 5). We find resonant structures for energies in the range corresponding to 0.01-10 K, which depend on the nuclear spin of H₂, arising from contributions of specific partial waves. We discuss the implications on the results in this benchmark system for ultracold chemistry.