Tunneling Abstraction Reactions of Tritium Atoms with HD and with Mixtures of H₂ and D₂ in Superfluid and Normal-Fluid ³He−⁴He Media at 1.3 K

Abstract

The abstraction reactions, T + HD(DH) f HT(DT) + D(H) and T + H 2 (D 2 ) f HT(DT) + H(D) were studied experimentally in liquid 3 He-4 He media at 1.3 K and theoretically using the gas-phase reaction model. The experimental reaction system has two characteristics; one is that the tritium atom (T) is produced from one of the constituents, 3 He, through 3 He(n, p)T nuclear reaction, and the other is that superfluid or normalfluid reaction medium can be chosen arbitrarily by changing the composition and temperature of the sample. The experimental isotope effect defined by {[HT]/[H 2 ]}/{[DT]/[D 2 ]} for the reactions T + H 2 (D 2 ) f HT-(DT) + H(D) was found to be 158 in superfluid and 146 in normal-fluid solutions. The large isotope effects observed were qualitatively explained via quantum mechanical tunneling on the basis of the theoretical calculations of thermal rate constants for these reactions. In the T + HD(DH) f HT(DT) + D(H) reactions, the experimental isotope effect was <19.8. From the considerations on both the reaction processes based on the experimental results and the theoretical calculations, it has been suggested that the quantum mechanical tunneling abstraction through van der Waals complex plays a predominant role for both the reactions.

Chemistry on the border of two centuries — achievements and prospects

“…58 Synthesis of metallic hydrogen (which has been mentioned above) and the reaction of tritium with hydrogen and deuterium in normal liquid helium and in superfluid quantum helium should be noted as the latest achievements of the `extreme' chemistry. 59 It was found that the exceptionally large isotope effects observed in this reaction (this is predictable) are different for normal and quantum helium (this is unexpected). If this finding is confirmed, new and unusual evidence for chemical coherence will be thus obtained.…”

Theoretical Analysis of Phase-Transition Temperature of Hydrogen-Bonded Dielectric Materials Induced by H/D Isotope Effect

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Large Isotope Effects in Tunneling Chemical Reactions

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