The Effects of Molecular Anions on the Chemistry of Dark Clouds

TL;DR

This study explores how molecular anions influence dark cloud chemistry, showing they slightly improve model-observation agreement with oxygen-rich abundances and enhance production of certain carbon-chain molecules.

Contribution

It demonstrates the impact of including anions in chemical models of dark clouds, particularly on the formation of unsaturated carbon-chain molecules.

Findings

Anions slightly improve model-observation agreement with oxygen-rich abundances.

Anions enhance production of long carbon-chain molecules like CnH, CnH2, and HCnN.

Using carbon-rich abundances with anions worsens model accuracy.

Abstract

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 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 CnH, CnH2, and HCnN. The use of carbon-rich elemental abundances in models of TMC-1 (CP) with anion chemistry worsens the agreement with observations obtained in the absence of anions.