Three-body, diatomic association in cold hydrogen plasmas

Because of its fundamental role in cold hydrogen plasmas such as those in certain astrophysical or fusion reactor environments, and as a prototype for the study of similar processes in other cold plasmas, three-body, diatomic association (often referred to by the general term three-body recombination) is considered. In three-body collisions involving two hydrogen atoms and a proton this process results in the formation of H 2 or H 2 + while the third, scattering particle carries away the excess energy. To reach an understanding of its dynamics and effectiveness, we present the first study of this process by using an extended coupled-channel formalism, treating the rotations of the associating particles through the sudden approximation. We describe the three-particle configuration space by a large set of relevant bound and continuum states, the latter being obtained by discretization of the vibrational continuum in a large quantization space. The association rate coefficients, resolved in final vibrational states, are calculated and show that the production of H 2 + is significantly faster than that of H 2 due to the strong charge transfer between the corresponding continua and a favourable distribution of highly excited vibrational states in the case of H 2 + .