Collision dynamics of three interacting atoms: Model calculations of H+H2 resonances

Collisions of H and H2 at thermal energies are studied within a three-body theory of atom--diatom rearrangement collisions. A previously developed general formalism based on a diabatic electronic representation is shown to be equivalent, for this system, to a treatment in terms of atomic spins. It further provides a novel approach to nuclear exchange symmetry. The interaction potential is parametrized by introducing a minimal valence-bond basis, and the collision dynamics is described with the Faddeev equations. These equations are reduced to two-body form, and are analyzed in terms of angular momentum components. A detailed description is given of the numerical procedure applied to the coupled integral equations that result from expanding in diatomic square integrable basis functions. Those equations are solved in momentum variables using quadrature techniques, and provide K-matrix elements. Converged calculations have been done for an s-wave model and for energies up to around the v = 3 threshold of H2. Resonances have been located from the singularities of the K-matrix elements and are found at 0.203 eV above the v = 1 threshold of H2, with a width of 0.167 eV, and at 0.202 eV above the v = 2 threshold with a width of 0.274 eV. The position of the first resonance is in very good agreement with previous results of three-dimensional calculations. The second resonance is above the energy range of previously published work