Rotational excitation of OCS by Ar: new potential energy surface, collisional cross sections and rate coefficients

ABSTRACT Molecular ions play an important role in the astrochemistry of interstellar and circumstellar media. C3H+ has been identified in the interstellar medium recently. A new potential energy surface of the C3H+–He van der Waals complex is computed using the ab initio explicitly correlated coupled cluster with the single, double and perturbative triple excitation [CCSD(T)-F12] method and the augmented correlation consistent polarized valence triple zeta (aug-cc-pVTZ) basis set. The potential presents a well of 174.6 cm−1 in linear geometry towards the H end. Calculations of pure rotational excitation cross-sections of C3H+ by He are carried out using the exact quantum mechanical close-coupling approach. Cross-sections for transitions among the rotational levels of C3H+ are computed for energies up to 600 cm−1. The cross-sections are used to obtain the collisional rate coefficients for temperatures T ≤ 100 K. Along with laboratory experiments, the results obtained in this work may be very useful for astrophysical applications to understand hydrocarbon chemistry.

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First quantum study of the rotational excitation of HCN by para-H2O: Convergence of quantum results, influence of the potential energy surface, and approximate rate coefficients of interest for cometary atmospheres.

Molecular Astrophysics ◽

10.1016/j.molap.2019.100046 ◽

2019 ◽

Vol 16 ◽

pp. 100046 ◽

Cited By ~ 4

Author(s):

M.L. Dubernet ◽

Ernesto Quintas-Sánchez

Keyword(s):

Potential Energy ◽

Potential Energy Surface ◽

Energy Surface ◽

Rate Coefficients ◽

Rotational Excitation ◽

Approximate Rate

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Rotational de-excitation of tricarbon monosulfide (C3S) in collision with (He): potential energy surface and rates

Astrophysics and Space Science ◽

10.1007/s10509-020-03892-5 ◽

2020 ◽

Vol 365 (12) ◽

Author(s):

E. Sahnoun ◽

M. Ben Khalifa ◽

F. Khadri ◽

K. Hammami

Keyword(s):

Potential Energy ◽

Interstellar Medium ◽

Potential Energy Surface ◽

Cross Sections ◽

Energy Surface ◽

Accurate Determination ◽

Carbon Chain ◽

Basis Sets ◽

Rate Coefficients

AbstractDespite that the tricarbon monosulfide (C3S) is among the first sulfur-containing carbon-chain molecules to be detected in the interstellar medium, no studies focused on the determination of its collisional rates. These rate coefficients are essential to estimate the abundance of C3S in the interstellar medium. Computations of the C3S($^{1}\Sigma^{+}$ Σ + 1 ) downward rate coefficients, induced by collision with He, are performed by averaging the integral cross sections at low temperature (below $25~\text{K}$ 25 K ). Calculations of the cross sections in the close-coupling quantum time independent formalism for $E_{c}\leq110~\text{cm}^{-1}$ E c ≤ 110 cm − 1 and $J\leq10$ J ≤ 10 are based on a new 2-D potential energy surface. This PES is obtained from the explicit correlated coupled cluster with a single, double and perturbative triple excitation [ccsd(t)-f12] ab initio approach and the aug-cc-pVTZ basis sets. The PES have a global minimum of $-55.69~\text{cm}^{-1}$ − 55.69 cm − 1 located at $R=6.25$ R = 6.25 bohr and $\theta=94^{\circ}$ θ = 94 ∘ , and a second minimum of $-36.95~\text{cm}^{-1}$ − 36.95 cm − 1 at $R=9.35$ R = 9.35 bohr and $\theta=0^{\circ}$ θ = 0 ∘ . A comparison of C3S rates with those of the isoelectronic molecule C3O was made. The results indicate a great temperature dependence of the rates for transitions of $\Delta J>2$ Δ J > 2 . We expect that the new collisional data will allow for accurate determination of the C3S abundance in several interstellar regions.

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Rotational quenching of HD induced by collisions with H2 molecules

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1735 ◽

2019 ◽

Vol 488 (1) ◽

pp. 381-386

Author(s):

Yier Wan ◽

N Balakrishnan ◽

B H Yang ◽

R C Forrey ◽

P C Stancil

Keyword(s):

Potential Energy ◽

Potential Energy Surface ◽

Cross Sections ◽

Energy Surface ◽

Rate Coefficients ◽

Quantum Mechanical ◽

Cooling Efficiency ◽

Close Coupling ◽

Rotational Transitions ◽

Good Agreement

ABSTRACT Rate coefficients for rotational transitions in HD induced by H2 impact for rotational levels of HD j ≤ 8 and temperatures 10 K ≤ T ≤ 5000 K are reported. The quantum mechanical close-coupling (CC) method and the coupled-states (CS) decoupling approximation are used to obtain the cross-sections employing the most recent highly accurate H2–H2 potential energy surface (PES). Our results are in good agreement with previous calculations for low-lying rotational transitions The cooling efficiency of HD compared with H2 and astrophysical applications are briefly discussed.

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Modelling the emission of HNCO towards IRAS16293-2422 using a new set of collisional coefficients

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317006809 ◽

2017 ◽

Vol 13 (S332) ◽

pp. 435-439

Author(s):

A. Hernández-Gómez ◽

E. Sahnoun ◽

E. Caux ◽

L. Wiesenfeld ◽

L. Loinard ◽

...

Keyword(s):

Potential Energy ◽

Potential Energy Surface ◽

Energy Surface ◽

Isocyanic Acid ◽

Rotational Excitation ◽

Simple Molecule ◽

Prebiotic Molecule ◽

Low Mass

AbstractIsocyanic acid (HNCO) is a simple molecule containing the four main atoms essential for life and can be considered as a prebiotic molecule. To model the HNCO emission in the IRAS16293-2422 class 0 low-mass protostar, we used a new set of HNCO collisional coefficients with ortho-H2and para-H2, computed from a set of rotational excitation quenching rates between HNCO and H2based on a novel potential energy surface for the rigid molecules interactions. We present here the HNCO Potential Energy Surface used to compute this new set of collisional coefficients and the result of the IRAS16293-2422 HNCO spectrum modelling using them.

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