ESR study of atomic hydrogen and tritium in solid T 2 and T 2 :H 2 matrices below 1 K

• Published in: Physical chemistry chemical physics : PCCP 2017-01, Vol.19 (4), p.2834-2842
• Main Authors: Sheludiakov, S, Ahokas, J, Järvinen, J, Lehtonen, L, Vainio, O, Vasiliev, S, Lee, D M, Khmelenko, V V
• Format: Article
• Language: English
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c6cp06933a

We report on the first ESR study of atomic hydrogen and tritium stabilized in solid T and T :H matrices down to 70 mK. The concentrations of T atoms in pure T approached 2 × 10 cm (0.60%) and record-high concentrations of H atoms ∼1 × 10 cm (0.33%) were reached in T :H solid mixtures where a fraction of T atoms became converted into H due to the isotopic exchange reaction T + H → TH + H. The maximum concentrations of unpaired T and H atoms were limited by their recombination which becomes enhanced by efficient atomic diffusion due to the presence of a large number of vacancies and phonons generated in the matrices by β-particles. Recombination also appeared in an explosive manner, both being stimulated and spontaneously in thick films where sample cooling was insufficient. We suggest that the main mechanism for H and T migration is physical diffusion related to tunneling or hopping to vacant sites in contrast to tunneling chemical exchange reactions which govern diffusion of H and D atoms created in H and D matrices by other methods.