Formation of H3- by radiative association of H2 and H- in the interstellar medium

We develop the theory of radiative association of an atom and a diatomic molecule within a close-coupling framework. We apply it to the formation of H-3(-) after the low-energy collision (below 0.5 eV) of H-2 with H-. Using recently obtained potential energy and permanent dipole moment surfaces of H-3(-), we calculate the lowest rovibrational levels of the H-3(-) electronic ground state and the cross section for the formation of H-3(-) by radiative association between H- and ortho- and para-H-2. We discuss the possibility for the H-3(-) ion to be formed and observed in the cold and dense interstellar medium in an environment with a high ionization rate. Such an observation could be a probe for the presence of H- in the interstellar medium.