The Effects of Molecular Anions on the Chemistry of Dark Clouds

We have investigated the role of molecular anion chemistry in pseudo-time-dependent chemical models of dark clouds. With oxygen-rich elemental abundances, the addition of anions results in a slight improvement in the overall agreement between model results and observations of molecular abundances in Taurus molecular cloud 1 (TMC-1 (CP)). More importantly, with the inclusion of anions, we see an enhanced production efficiency of unsaturated carbon-chain neutral molecules, especially in the longer members of the families C _n H, C _n H₂, and HC _n N. The use of carbon-rich elemental abundances in models of TMC-1 (CP) with anion chemistry worsens the agreement with observations compared with model results obtained in the absence of anions.