Equilibria in Hydrogen—Tritium Mixtures. Steady States and Initial Reaction Rates at 76.7°K

H2, T2, and HT are brought to thermodynamic equilibrium by the tritium β particles at 299° and 192°K if precautions are taken to minimize impurities; otherwise the steady-state quotient, Q=(HT)2/(H2)(T2), tends to be higher than the equilibrium constant K. At 192°K the initial reaction rates in H2—T2 mixtures correspond to about 3000 molecules reacting per ion pair. The results can be understood in terms of the thermal ion—molecule chain reactions of Thompson and Schaeffer. If the chains are shortened by impurities, the importance of hot processes tending to make Q>K is emphasized. The hot processes may be hot atom—molecule reactions caused by hot atoms formed by the recombination of H3+ ions (chain-breaking step). At 76.7°K the behavior is quite different. Initial reaction rates correspond to only about 20 molecules reacting per ion pair. Q is in general significantly higher than K (76.7°K)=0.63 and approaches K only in the limits of zero pressure or zero tritium content. This behavior is discussed in terms of short thermal ion—molecule chains and of hot processes resulting from the products of recombination of H3+ ions. The importance of the hot processes seems to be determined by a competition between wall and volume recombination.