Transient Pairs in Gases: Quantum Effects on the Equilibrium Constant for O+H⇆OH* (X 2Πi)

The statistical mechanical theory of transient pairs in gases, formulated by Smith in 1963, is applied to O+H elastic scattering using the $X^2{\Pi }_i$ potential curve. The equilibrium constant and internal partition function are calculated by averaging the energy derivatives of the scattering phase shifts over the Boltzmann distribution. The equilibrium constant is partitioned into three components: (1) the resonant contribution produced by quantum mechanical tunneling through the outer maximum in the effective radial potential, (2) the orbit contribution, and (3) the nonresonant component. In the temperature range studied (10° to 2800°K), the resonant component dominates pair formation. This result lends support to recent theories of radical recombination.