Effect of γ-Ray Irradiation on the Recoil Tritium Reaction in Xenon–Hydrogen Mixtures at 77 and 4.2 K. Competition of the Tunneling Reaction with the Combination Reaction

Abstract

Recoil T-atom reactions have been studied in Xe–H2–D2 mixtures at 77 and 4.2 K. When T atom reactions were caused at 77 K by neutron irradiation at an extremely low dose rate of γ-rays, a large isotope effect (kHT/kDT≈7) on the formation of HT and DT was observed. When T-atom reactions were caused at 77 K by neutron irradiation at a high dose rate of γ-rays, there was no isotope effect (kHT/kDT≈1) on the formation of HT and DT. The production of H and D atoms by γ-irradiation of the Xe–H2–D2 mixtures was studied by ESR spectroscopy at 4.2 K. The significant effect of the dose rate of γ-rays on the HT and DT formation was interpreted in terms of competition between a tunneling reaction of thermal T atoms with H2(D2) and a combination reaction of thermal T atoms with H(D) atoms produced by γ-radiolysis.

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

“…Comparison of Isotope Effects of the Abstraction Reactions of T + H 2 → HT + H and T + D 2 → DT + H at Various Temperatures. The isotope effects for T + H 2 (D 2 ) → HT(DT) + H(D) at >77 K have been experimentally examined by some workers. − Table summarizes the results including the present results. Though the isotope effects in the gas phase somewhat depend on the experimental conditions, the values lie below 2.7.…”

“…The isotope effects for T + H 2 (D 2 ) f HT(DT) + H(D) at >77 K have been experimentally examined by some workers. [14][15][16] Table 2 summarizes the results including the present results. Though the isotope effects in the gas phase somewhat depend on the experimental conditions, the values lie below 2.7.…”

Large Isotope Effects in Tunneling Chemical Reactions

“…The isotope effect (k(T + H 2 )/k(T + D 2 )) in this case increases to 7, indicating a partial contribution of tunneling reaction of thermal T atoms. 12) Recently recoil T atoms are produced in the liquid helium at 1.3 K: 13) 3 He + n → T * + proton (12) T * + He → T + He * (13) T + D 2 → DT + D (14) T + H 2 → HT + H.…”