Rotational relaxation of HCO+ and DCO+ by collision with H2

Denis-Alpizar, Otoniel; Stoecklin, Thierry; Dutrey, Anne; Guilloteau, S.

doi:10.1093/mnras/staa2308

Cited by 37 publications

(20 citation statements)

References 40 publications

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“…The agreement improves with increasing temperature, with differences of less than 10% being observed for temperatures above 50 K. It should also be noted that for the most dominant transitions (k > 2 × 10 10 cm 3 s −1 ), differences stay lower than 10% for all the temperatures explored. This global agreement between para-and ortho-H 2 rate coefficients confirms what has already been observed for a wide variety of ion-molecule collisions (Massó & Wiesenfeld 2014;Walker et al 2017;Denis-Alpizar et al 2020;Balança et al 2020;Kłos & Lique 2011).…”

Section: Scattering Calculationssupporting

confidence: 88%

CF⁺ excitation in the interstellar medium

Desrousseaux

Lique

Goicoechea

et al. 2020

A&A

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The detection of CF + in interstellar clouds potentially allows astronomers to infer the elemental fluorine abundance and the ionization fraction in ultraviolet-illuminated molecular gas. Because local thermodynamic equilibrium (LTE) conditions are hardly fulfilled in the interstellar medium (ISM), the accurate determination of the CF + abundance requires one to model its non-LTE excitation via both radiative and collisional processes. Here, we report quantum calculations of rate coefficients for the rotational excitation of CF + in collisions with para-and ortho-H 2 (for temperatures up to 150 K). As an application, we present non-LTE excitation models that reveal population inversion in physical conditions typical of ISM photodissociation regions (PDRs). We successfully applied these models to fit the CF + emission lines previously observed toward the Orion Bar and Horsehead PDRs. The radiative transfer models achieved with these new rate coefficients allow the use of CF + as a powerful probe to study molecular clouds exposed to strong stellar radiation fields.

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Section: Scattering Calculationssupporting

confidence: 88%

CF⁺ excitation in the interstellar medium

Desrousseaux

Lique

Goicoechea

et al. 2020

A&A

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“…The rotational excitation of para-H 2 (j = 0 → j = 2) at low temperature has a low probability; the energy spacing between these states is 510 K, 45 which is larger than the temperatures analyzed in this work. Furthermore, the cross sections and rate coefficients using the averaged PES have been in reasonable agreement with those obtained from the fourdimensional PES for several systems, e.g., SiS, 46 HNC, 47 HCO + , 48,49 and CF + . 50 This approximation reduces calculation times significantly, and it was adopted in this work.…”

Section: Methodssupporting

confidence: 74%

Rotational Relaxation of AlNC and AlCN by para-H₂ (j = 0) at Low Temperatures

Urzúa-Leiva

Denis-Alpizar

2020

ACS Earth Space Chem.

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An accurate determination of the abundances of metal-containing molecules in the interstellar medium or circumstellar gas requires knowledge of molecular data, including the collisional rate coefficients. This work is focused on the study of the collision of the aluminum isocyanide (AlNC) molecule, as well as its isomer AlCN, with para-H2 (j = 0). For the AlNC + H2 and AlCN + H2 complexes, averaged potential energy surfaces are developed from ab initio energies computed at the coupled cluster with the single, double, and perturbative triple excitation level of theory. Such surfaces are used in close-coupling calculations. The rate coefficients at low temperature are compared with those for the collisions with He. The use of the mass scaling procedure is a good approximation in the case of AlCN. However, for the collision with AlNC, a different propensity rule is found between the rates with He and para-H2 (j = 0). Finally, rotational rate coefficients for the lowest 26 rotational levels of both molecules, AlCN and AlNC, by collision with para-H2 (j = 0) are reported.

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“…The grid of ab initio energies was fit following the same procedure as was recently used to study the HCO + +H 2 complex (Denis-Alpizar et al 2020). The analytical function employed has the form…”

Section: Analytical Four-dimensional Surfacementioning

confidence: 99%

Deexcitation rate coefficients of C₃ by collision with H₂ at low temperatures

Santander

Denis-Alpizar

Cárdenas

2022

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Context. An accurate analysis of the physical-chemical conditions in the regions of the interstellar medium in which C 3 is observed requires knowing the collisional rate coefficients of this molecule with He, H 2 , electrons, and H. Aims. The main goals of this study are to present the first potential energy surface for the C 3 +H 2 complex, to study the dynamics of the system, and to report a set of rate coefficients at low temperature for the lower rotational states of C 3 with para-and ortho-H 2 . Methods. A large grid of ab initio energies was computed at the explicitly correlated coupled-cluster with single-, double-, and perturbative triple-excitation level of theory, together with the augmented correlation-consistent quadruple zeta basis set (CCSD(T)-F12a/aug-cc-pVQZ). This grid of energies was fit to an analytical function. The potential energy surface was employed in closecoupling calculations at low collisional energies. Results. We present a high-level four-dimensional potential energy surface (PES) for studying the collision of C 3 with H 2 . The global minimum of the surface is found in the linear HH-CCC configuration. Rotational deexcitation state-to-state cross sections of C 3 by collision with para-and ortho-H 2 are computed. Furthermore, a reduced two-dimensional surface is developed by averaging the surface over the orientation of H 2 . The cross sections for the collision with para-H 2 using this approximation and those from the four-dimensional PES agree excellently. Finally, a set of rotational rate coefficients for the collision of C 3 with para-and ortho-H 2 at low temperatures are reported.

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Rotational relaxation of HCO+ and DCO+ by collision with H2

Cited by 37 publications

References 40 publications

CF⁺ excitation in the interstellar medium

CF⁺ excitation in the interstellar medium

Rotational Relaxation of AlNC and AlCN by para-H₂ (j = 0) at Low Temperatures

Deexcitation rate coefficients of C₃ by collision with H₂ at low temperatures

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Rotational relaxation of HCO+ and DCO+ by collision with H2

Cited by 37 publications

References 40 publications

CF+ excitation in the interstellar medium

CF+ excitation in the interstellar medium

Rotational Relaxation of AlNC and AlCN by para-H2 (j = 0) at Low Temperatures

Deexcitation rate coefficients of C3 by collision with H2 at low temperatures

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Product

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About

CF⁺ excitation in the interstellar medium

CF⁺ excitation in the interstellar medium

Rotational Relaxation of AlNC and AlCN by para-H₂ (j = 0) at Low Temperatures

Deexcitation rate coefficients of C₃ by collision with H₂ at low temperatures