The excitation of CNCN in the interstellar medium: hyperfine resolved rate coefficients and non-LTE modelling

Ndaw, D; Bop, Cheikh T; Dieye, Gora; Faye, Ndeye Arame Boye; Lique, François

doi:10.1093/mnras/stab775

Cited by 9 publications

(3 citation statements)

References 36 publications

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“…The hyperfine structure due to the nuclear spin of nitrogen is not considered in this work but it can be derived from our data using the Infinite Order Sudden (IOS) approximation. 16,17 The cross sections (σ ) were calculated for the 15 low-lying rotational levels of NS + ( j 1 = 0 − 14) for total energies ranging up to at least 500 cm −1 . The energy range was spanned using a fine step size of 0.1 cm −1 to correctly describe the resonances.…”

Section: B Cross Sections and Rate Coefficientsmentioning

confidence: 99%

Rotational excitation of NS+ by H2 revisited: A new global potential energy surface and rate coefficients

Bop

Kalugina

Lique

2022

The Journal of Chemical Physics

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Due to the lack of specific collisional data, the abundance of NS+ in cold dense interstellar clouds was determinedusing collisional rate coefficients of CS as substitute. To better understand the chemistry of sulfur in the interstellarmedium, further abundance modeling using the actual NS+ collisional rate coefficients are needed. For this purpose,we have computed the first full 4D potential energy surface of the NS+−H2 van der Waals complex using the explicitly correlated coupled cluster approach with single, double, and non-iterative triple excitation in conjunction withthe augmented-correlation consistent-polarized valence triple zeta basis set. The potential energy surface exhibitsa global minimum of 848.24 cm−1 for a planar configuration of the complex. The long-range interaction energy, described using multipolar moments, is sensitive to the orientation of H2 up to radial distances of ∼ 50 a0. From thisnew interaction potential, we derived excitation cross sections, induced by collision with ortho- and para-H2, for the15 low-lying rotational levels of NS+ using the quantum mechanical close-coupling approach. By thermally averagingthese data, we determined downward rate coefficients for temperatures up to 50 K. By comparing them with the previous NS+−H2 data, we demonstrated that reduced dimensional approaches are not suited for this system. In addition,we found that the CS collisional data underestimate ours results by up to an order of magnitude. The differences clearlyindicate that the abundance of NS+, in cold dense clouds retrieved from observational spectra, must be reassessed usingthese new collisional rate coefficients.

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Section: B Cross Sections and Rate Coefficientsmentioning

confidence: 99%

Rotational excitation of NS+ by H2 revisited: A new global potential energy surface and rate coefficients

Bop

Kalugina

Lique

2022

The Journal of Chemical Physics

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“…One recommended dataset is available for CNCN. BASECOL2023 was updated with a dataset (Ndaw et al 2021) for the rotational de-excitation of CNCN by He (30 levels; T = 5-150 K); the authors calculated a new PES.…”

Section: Cncnmentioning

confidence: 99%

BASECOL2023 scientific content

Dubernet,

Boursier,

Denis-Alpizar

et al. 2024

A&A

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The global context of making numerous data produced by researchers available requires collecting and organising the data, assigning meaningful metadata, and presenting the data in a meaningful and homogeneous way. The BASECOL database, which collects inelastic rate coefficients for application to the interstellar medium and to circumstellar and cometary atmospheres, meets those requirements. We aim to present the scientific content of the BASECOL2023 edition. While the previous versions relied on finding rate coefficients in the literature, the current version is populated with published results sent by the producers of data. The paper presents the database, the type of data that can be found, the type of metadata that are used, and the Virtual Atomic and Molecular Data Centre (VAMDC) standards that are used for the metadata. Finally, we present the different datasets species by species. As the BASECOL database, interconnected with the VAMDC e-infrastructure, uses the VAMDC standards, the collisional data can be extracted with tools using VAMDC standards and can be associated with spectroscopic data extracted from other VAMDC connected databases such as the Cologne database for molecular spectroscopy (CDMS), the jet propulsion laboratory molecular spectroscopy database (JPL), and the high-resolution transmission molecular absorption database (HITRAN).

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“…Concerning physical conditions of the source of interest, i.e. TMC-1, the H 2 volume density (𝑛) is smoothly increased from 10 2 cm −3 to 10 8 cm −3 and the gas kinetic temperature (𝑇) is set to 10 ± 2 K as usually done in the literature (Ndaw et al 2021;Bop et al 2021). The column densities (𝑁) of C 3 O and C 5 O are smoothly increased from 10 10 cm −2 to 10 13 cm −2 and 10 9 cm −2 to 10 12 cm −2 , respectively.…”

Section: Radiative Transfer Studymentioning

confidence: 99%

The effect of scattering calculations on non-LTE modelling of the C3O and C5O abundances in TMC-1

Bop

Khadri

Hammami

2022

Monthly Notices of the Royal Astronomical Society

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Tricarbon and pentacarbon monoxides have been detected towards TMC-1 with relatively important abundances. Understanding their chemical formation of these molecules requires interpreting their observational spectra by mean of non-local thermodynamical equilibrium modelling. For this purpose, we report rate coefficients of C3O and C5O induced by collision with He for temperatures up to 100 K. These data are obtained by calculating inelastic cross sections for the 31 low-lying rotational levels of C3O and C5O using the close-coupling approach. The comparison of the new rate coefficients with those of HC3N and HC5N, previously used to interpret the observational spectra of C3O and C5O, reveals differences of up to an order of magnitude. The effect of the new collisional rate coefficients in radiative transfer calculations is checked by computing the excitation temperatures for some transitions and simulating the C3O and C5O column densities observed towards TMC-1. Our findings suggest that the use of HCnN as template for CnO may lead to local thermodynamic equilibrium conditions for gas densities as low as ∼103 cm−3. Regarding the interpretation of the observational spectra, using radiative transfer modelling based on the actual CnO collisional rate coefficients instead of rotational diagram analysis leads to underestimate the column densities reported in the literature by up to 25% and accordingly the C3O/ C5O abundance ratio by up to 50%. We expect that the new rate coefficients and the radiative transfer calculations presented in this work will encourage further modellings of the CnO abundance and accordingly constrain the chemistry.

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The excitation of CNCN in the interstellar medium: hyperfine resolved rate coefficients and non-LTE modelling

Cited by 9 publications

References 36 publications

Rotational excitation of NS+ by H2 revisited: A new global potential energy surface and rate coefficients

Rotational excitation of NS+ by H2 revisited: A new global potential energy surface and rate coefficients

BASECOL2023 scientific content

The effect of scattering calculations on non-LTE modelling of the C3O and C5O abundances in TMC-1

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