ESR study of atomic hydrogen and tritium in solid T2 and T2:H2 matrices below 1 K. Issue 4 (9th January 2017)

• Record Type: Journal Article
• Authors: Sheludiakov, S.; Ahokas, J.; Järvinen, J.; Lehtonen, L.; Vainio, O.; Vasiliev, S.; Lee, D. M.; Khmelenko, V. V.
• Is Part Of: Physical chemistry chemical physics. Volume 19:Issue 4(2017)
• Page Start: 2834
• Page End: 2842
• Publication Date: 2017-01-09
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c6cp06933a
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : We studied record-high concentrations of H and T atoms (0.33% and 0.6%) in molecular hydrogen matrices at temperature 150 mK. Abstract : We report on the first ESR study of atomic hydrogen and tritium stabilized in solid T2 and T2 :H2 matrices down to 70 mK. The concentrations of T atoms in pure T2 approached 2 × 10 20 cm −3 (0.60%) and record-high concentrations of H atoms ∼1 × 10 20 cm −3 (0.33%) were reached in T2 :H2 solid mixtures where a fraction of T atoms became converted into H due to the isotopic exchange reaction T + H2 → 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 H2 and D2 matrices by other methods.