Tunnelling chemical reactions of hydrogen isotopes in quantum solids

The kinetics of tunnelling reactions of hydrogen isotopes in solid molecular nanoclusters immersed in superfluid helium and the changes in the environment of the atoms during the course of these reactions are reviewed. Results of pulsed electron spin resonance show that a very large fraction (50%–60%) of the stabilised atoms reside on the surfaces of the nanoclusters. The results of studies of the recombination and the exotic behaviour of hydrogen atoms in a solid molecular hydrogen matrix at ultralow temperatures (0.15–0.9 K) are also discussed.