Deviation of the rate of the reaction from Langevin behaviour below 1 K, branching ratios for the and product channels, and product-kinetic-energy distributions

The reactions between ground-state H2+ (X 2Σg+(v=0,J=0)) and D2 forming HD2++H H2D++D were investigated in the range of collision energies Ecoll Ecoll/kB=0 10 K using a merged-beam approach. reaction rates measured experimentally are compared to those obtained for H2 H3++H under similar experimental conditions. Below 1 K, clear enhancement rate coefficient Langevin at higher was observed both systems. This is interpreted as originating from interaction charge quadrupole para ortho molecules J = rotational level. with found be significantly less than that H2, reflecting relative population level (75%) (33%) natural samples low temperatures. Simulations results based on theoretical predictions cross sections by Dashevskaya et al. [J. Chem. Phys. 145, 244315 (2016)] reveal agreement within uncertainties. branching ratio η involving H2D+ D (η=[H2D+][H2D+]+[HD2+]) near Ecoll=0 determined 0.341(15). Time-of-flight measurements velocity distributions products compatible an isotropic product emission average total kinetic energy 0.45(5) eV channels, representing about 30% released reaction.