Inelastic H + H$^+_3$ Collision rates and their impact in the determination of the excitation temperature of H$^+_3$
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arXiv
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2024
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| author | Felix-Gonzalez, Daniel del Mazo-Sevillano, Pablo Aguado, Alfredo Roncero, Octavio Bourlot, Jacques Le Roueff, Evelyne Petit, Franck Le Bron, Emeric |
| author_facet | Felix-Gonzalez, Daniel del Mazo-Sevillano, Pablo Aguado, Alfredo Roncero, Octavio Bourlot, Jacques Le Roueff, Evelyne Petit, Franck Le Bron, Emeric |
| contents | Context. In dffuse interstellar clouds the excitation temperature derived from the lowest levels of H$^+_3$ is systematically lower than that derived from H2. The differences may be attributed to the lack of state-specific formation and destruction rates of H$^+_3$ needed to thermalize the two species. Aims. In this work, we want to check the role of rotational excitation collisions of H$^+_3$ with atomic hydrogen on its excitation temperature. Methods. A time independent close-coupling method is used to calculate the state-to-state rate coefficients, using a very accurate and full dimensional potential energy surface recently developed for H$^+_4$. A symmetric top approach is used to describe a frozen H$^+_3$ as equilateral triangle. Results. Rotational excitation collision rate coefficients of H$^+_3$ with atomic Hydrogen have been derived in a temperature range appropriate to diffuse interstellar conditions up to $(J; K; \pm) = (7; 6; +)$ and $(J; K; \pm) = (6; 4; +)$ for its ortho and para forms. This allows to have a consistent set of collisional excitation rate coefficients and to improve the previous study where these contributions were speculated. Conclusions. The new state-specific inelastic H$^+_3$ + H rate coeffcients yield differences up to 20% in the excitation temperature, and their impact increases with decreasing molecular fraction. We also confirm the impact of chemical state-to-state destruction reactions in the excitation balance of H$^+_3$ , and that reactive H + H$^+_3$ collisions are also needed to account for possible further ortho to para transitions |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2412_06697 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Inelastic H + H$^+_3$ Collision rates and their impact in the determination of the excitation temperature of H$^+_3$ Felix-Gonzalez, Daniel del Mazo-Sevillano, Pablo Aguado, Alfredo Roncero, Octavio Bourlot, Jacques Le Roueff, Evelyne Petit, Franck Le Bron, Emeric Astrophysics of Galaxies Solar and Stellar Astrophysics Chemical Physics Context. In dffuse interstellar clouds the excitation temperature derived from the lowest levels of H$^+_3$ is systematically lower than that derived from H2. The differences may be attributed to the lack of state-specific formation and destruction rates of H$^+_3$ needed to thermalize the two species. Aims. In this work, we want to check the role of rotational excitation collisions of H$^+_3$ with atomic hydrogen on its excitation temperature. Methods. A time independent close-coupling method is used to calculate the state-to-state rate coefficients, using a very accurate and full dimensional potential energy surface recently developed for H$^+_4$. A symmetric top approach is used to describe a frozen H$^+_3$ as equilateral triangle. Results. Rotational excitation collision rate coefficients of H$^+_3$ with atomic Hydrogen have been derived in a temperature range appropriate to diffuse interstellar conditions up to $(J; K; \pm) = (7; 6; +)$ and $(J; K; \pm) = (6; 4; +)$ for its ortho and para forms. This allows to have a consistent set of collisional excitation rate coefficients and to improve the previous study where these contributions were speculated. Conclusions. The new state-specific inelastic H$^+_3$ + H rate coeffcients yield differences up to 20% in the excitation temperature, and their impact increases with decreasing molecular fraction. We also confirm the impact of chemical state-to-state destruction reactions in the excitation balance of H$^+_3$ , and that reactive H + H$^+_3$ collisions are also needed to account for possible further ortho to para transitions |
| title | Inelastic H + H$^+_3$ Collision rates and their impact in the determination of the excitation temperature of H$^+_3$ |
| topic | Astrophysics of Galaxies Solar and Stellar Astrophysics Chemical Physics |
| url | https://arxiv.org/abs/2412.06697 |