Formation of H$_3^-$ by radiative association of H$_2$ and H$^-$ in the interstellar medium

M. Ayouz (1) , Raphael Lopes (1) , Maurice Raoult (1) , Olivier Dulieu (1) , V. Kokoouline (1, 2)

1 LAC - Laboratoire Aimé Cotton
2 UCF | Physics - Department of Physics [Orlando]

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 would be a probe for the presence of H$^-$ in the interstellar medium.

Mots clés: H3-; radiative association; interstellar medium

Domaines: Physique Quantique [quant-ph]

M. Ayouz, Raphael Lopes, Maurice Raoult, Olivier Dulieu, V. Kokoouline. Formation of H$_3^-$ by radiative association of H$_2$ and H$^-$ in the interstellar medium. 2011. ⟨hal-00569370⟩