Observation of enhanced rate coefficients in the H+H→H+H reaction at low collision energies.

The energy dependence of the rate coefficient of the H+H→H+H reaction has been measured in the range of collision energies between k⋅10K and k⋅300mK. A clear deviation of the rate coefficient from the value expected on the basis of the classical Langevin-capture behavior has been observed at collision energies below k⋅1K, which is attributed to the joint effects of the ion-quadrupole and Coriolis interactions in collisions involving ortho-H molecules in the  j = 1 rotational level, which make up 75% of the population of the neutral H molecules in the experiments. The experimental results are compared to very recent predictions by Dashevskaya et al. [J. Chem. Phys. 145, 244315 (2016)], with which they are in agreement.