Tunneling chemical exchange reaction D plus HD -> D-2 + H in solid HD and D-2 at temperatures below 1 K

: Sheludiakov S, Ahokas J, Jarvinen J, Zvezdov D, Lehtonen L, Vainio O, Vasiliev S, Lee DM, Khmelenko VV

Publisher: ROYAL SOC CHEMISTRY

: 2016

: Physical Chemistry Chemical Physics

: PHYSICAL CHEMISTRY CHEMICAL PHYSICS

: PHYS CHEM CHEM PHYS

: 18

: 42

: 29600

: 29606

: 7

: 1463-9076

DOI: https://doi.org/10.1039/c6cp05486b

We report on a study of the exchange tunneling reaction D + HD -> D-2 + H in a pure solid HD matrix and in a D-2 matrix with a 0.23% HD admixture at temperatures between 130 mK and 1.5 K. We found that the exchange reaction rates, k(exHD) similar to 3 x 10(-27) cm(3) s(-1) in the pure HD matrix, and k(exD2) = 9(4) x 10(-28) cm(3) s(-1) in the D-2 matrix, are nearly independent of temperature within this range. This confirms the quantum tunnelling nature of these reactions, and their ability to proceed at temperatures down to absolute zero. Based on these observations we concluded that exchange tunneling reaction H + H-2 -> H-2 + H should also proceed in a H-2 matrix at the lowest temperatures. On the other hand, the recombination of H atoms in solid H-2 and D atoms in solid D-2 is substantially suppressed at the lowest temperatures as a result of a decreased probability of resonant tunneling of atoms when they approach each other.