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Study of possible mechanisms of formation and destruction for anions in the interstellar medium.

Abstract : The mechanisms of formation and destruction of molecular anions have become a field of special interest after the recent detection of six molecular anions (C4H-,C6H-, C8H-, CN-, C3N-, C5N-) in the interstellar medium. The main channel of formation of these anions is expected to be radiative electron attachment in environments where the density of electron is relatively important. There is however at themoment a lack of experimental and theoretical data allowing to assess this hypothesis. Photodetachment, on the other hand, is the main source of destruction of the anions in diffuse clouds and photodissociation regions. A single center expansion approach is applied to the study of both processes: photodetachment and radiative electron attachment. The results obtained with the present method are compared to previously reported experimental and theoretical data and show a good agreement.This method is then employed to determine the rate constants which are needed to confirm whether or not these mechanisms are crucial for the chemistry of the interstellar anions. Along with the formation and destruction rates, rotational excitation rate coefficients are needed to accurately model the observed anions abundances.We focus on the calculation of state-to-state rotational transitions rate coefficients of the C3N- molecule in its ground vibrational state in collisions with H2 and He using new potential energy surfaces
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Miguel Lara Moreno. Study of possible mechanisms of formation and destruction for anions in the interstellar medium.. Theoretical and/or physical chemistry. Université de Bordeaux, 2018. English. ⟨NNT : 2018BORD0220⟩. ⟨tel-02003699⟩

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