Radiative Electron Attachment and Photodetachment Rate Constants for Linear Carbon Chains

Miguel Lara-Moreno (1) , Thierry Stoecklin (1) , Philippe Halvick (1)

1 ISM - Institut des Sciences Moléculaires

Since their recent detection in interstellar clouds and circumstellar envelopes, polyyne and cyanopolyyne anions have raised the question of their possible mechanisms of formation, destruction, and excitation. These anions are observed in the same regions as the corresponding neutral species, with anion-to-neutral abundance ratios of a few percent. It is believed that the abundance ratios are controlled mainly by the radiative attachment processes. We present a quantum study of the radiative electron attachment and photodetachment rate constants for selected linear carbonchain anions, namely the already detected interstellar anions as well as other potential candidates. The rate constants are calculated within the rigid molecule approximation, with the attached or ejected electron described by a plane wave. A qualitative agreement is obtained with the previous accurate quantum results. For the radiative electron attachment process, the discrepancies between the quantum rate constants calculated here and the statistical rate constants currently used in astronomical models are relatively small for the shortest carbon chains but increase strongly with the number of atoms in the chain.

Mots clés: Interstellar anions; Radiative electron attachment; Photodetachment; Polyynes; Cyanopolyynes Complex Organic Molecules (COMs) in Star-Forming Regions; Interstellar anions; radiative electron attachment; photodetachment; polyynes; cyanopolyynes

Domaines: Chimie théorique et/ou physique; Instrumentation et méthodes pour l'astrophysique [astro-ph.IM]

Miguel Lara-Moreno, Thierry Stoecklin, Philippe Halvick. Radiative Electron Attachment and Photodetachment Rate Constants for Linear Carbon Chains. ACS Earth and Space Chemistry, 2019, 3, pp.1556 - 1563. ⟨10.1021/acsearthspacechem.9b00098⟩. ⟨hal-03044624⟩