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

• Published in: Astrophysics and space science 2020-12, Vol.365 (12), Article 183
• Main Authors: Sahnoun, E., Ben Khalifa, M., Khadri, F., Hammami, K.
• Format: Article
• Language: English
• Subjects: Astrobiology; Astronomy; Astrophysics; Astrophysics and Astroparticles; Cosmology; Coupling (molecular); Cross-sections; Excitation; Interstellar chemistry; Interstellar matter; Interstellar medium; Low temperature; Observations and Techniques; Original Article; Physics; Physics and Astronomy; Potential energy; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Sulfur; Temperature dependence; Tricalcium silicate
• ISSN: 0004-640X; 1572-946X
• DOI: 10.1007/s10509-020-03892-5

Despite that the tricarbon monosulfide (C 3 S) 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 C 3 S in the interstellar medium. Computations of the C 3 S( Σ + 1 ) downward rate coefficients, induced by collision with He, are performed by averaging the integral cross sections at low temperature (below 25 K ). Calculations of the cross sections in the close-coupling quantum time independent formalism for E c ≤ 110 cm − 1 and 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 cm − 1 located at R = 6.25 bohr and θ = 94 ∘ , and a second minimum of − 36.95 cm − 1 at R = 9.35 bohr and θ = 0 ∘ . A comparison of C 3 S rates with those of the isoelectronic molecule C 3 O was made. The results indicate a great temperature dependence of the rates for transitions of Δ J > 2 . We expect that the new collisional data will allow for accurate determination of the C 3 S abundance in several interstellar regions.