Phase‐space theory of atomic dissociation and recombination reactions: H + H + H ⇄ H₂ + H

The modified phase‐space theory of reaction rates was coupled with Monte Carlo trajectory calculations to yield rate constants and energy distributions of reactants and products for the three‐atom dissociation and recombination reactions of hydrogen at 4000°K. Sample trajectories selected from those crossing a surface in phase space were calculated in forward and reverse directions to determine the classical rates of formation of bound and quasibound molecules from atoms. The probability of stabilization of quasibound molecules in successive collisions with hydrogen atoms was determined from additional trajectory calculations. The steady state correction factor for recombination, which accounts for dissociation of newly formed bound H₂ molecules, was estimated from similar calculations. The computed rate constant for recombination is 3.1×10¹⁵ cm⁶ mole⁻² sec⁻¹. For equilibrium between free atoms and quasibound molecules established through tunneling, the over‐all rate constant is estimated to be 75% higher. In either case the process of termolecular recombination to produce bound molecules makes a substantial contribution to the over‐all rate.