Theoretical Studies of Dissociative Recombination

We are currently investigating the dissociative recombination (DR) of electrons with molecular ions such as $\mathrm{N}_2\mathrm{H}^+$ and $\mathrm{C}_3\mathrm{H}_3^+$. Both these ions exist in the interstellar medium, and accurate DR rate constants are needed for astrophysical models. Elaborate electronic structure calculations of potential surfaces for $e^- + \mathrm{N}_2\mathrm{H}^+ \rightarrow \mathrm{N}_2 + \mathrm{H}$ have been carried out in the linear geometry [D. Talbi, Chem.~Phys. {\bfseries 332} 289--303 (2007)]. Additional work is necessary to determine the autoionization width $\Gamma$, which is essential for a dynamics calculation. We are using the block diagonalization method to determine both diabatic potential curves and $\Gamma$; the status of the calculations will be presented at the conference. In addition, preliminary work on the $\mathrm{C_3H_3^+}$ molecular ion has investigated the normal modes of the motion. We expect that energy flow into and out of the vibration of a single CH bond may influence the overall DR dynamics, and we account for this effect using an appropriate quantum mechanical wave function for the initial state.