Possible scenarios for SiS formation in the interstellar medium: Electronic structure calculations of the potential energy surfaces for the reactions of the SiH radical with atomic sulphur and S2

Rosi, Marzio; Mancini, Luca; Skouteris, Dimitrios; Ceccarelli, C.; Faginas-Lago, Noelia; Podio, L.; Codella, C.; Leflóch, B.; Balucani, Nadia

doi:10.1016/j.cplett.2018.01.053

Cited by 39 publications

(25 citation statements)

References 44 publications

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“…In the case of the reaction between Si and SO 2 , we assume that the channels leading to SiO and SiS are equally rapid, with a rate coefficient of 10 −10 cm 3 s −1 . This same value is adopted for the SiS-forming reactions SiH + S and SiH + S 2 , which have been calculated to be barrierless by Rosi et al (2018), although in our calculations these reactions are not important routes to SiS. The reason is that SiH is not efficiently formed in gas phase from Si because the reaction between Si and H 2 to yield SiH is endothermic by about 35 kJ/mol, and thus too low even at 500K The reaction of SiS with atomic oxygen, which is calculated to be rapid, is also included.…”

Section: Astrochemical Impactmentioning

confidence: 99%

“…(2) Assumed value for exothermic and spin-allowed reaction. (3) Assumed value for barrierless reaction studied by Rosi et al (2018).…”

Section: Figmentioning

confidence: 99%

“…In this article we study various potentially important processes that can drive the formation and destruction of SiS in interstellar and circumstellar media. In a recent work, Rosi et al (2018) proposed the formation of this molecule through the reactions SiH + S and SiH + S 2 and carried out electronic structure calculations of the stationary points along the reactive potential energy surfaces. In this work we study a different chemical route, the formation of SiS via the reaction Si + SO and its destruction through the SiS + O reaction.…”

Section: Introductionmentioning

confidence: 99%

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Formation and Destruction of SiS in Space

Zanchet

Roncero

Agúndez

et al. 2018

ApJ

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The presence of SiS in space seems to be restricted to a few selected types of astronomical environments. It is long known to be present in circumstellar envelopes around evolved stars and it has also been detected in a handful of star-forming regions with evidence of outflows, like Sgr B2, Orion KL and more recently L1157-B1. The kinetics of reactions involving SiS is very poorly known and here we revisit the chemistry of SiS in space by studying some potentially important reactions of formation and destruction of this molecule. We calculated potential energy surfaces of the SiOS system and computed rate coefficients in the temperature range 50-2500 K for the reaction of destruction of SiS, in collisions with atomic O, and of its formation, through the reaction between Si and SO. We find that both reactions are rapid, with rate coefficients of a few times 10 cm s, almost independent of temperature. In the reaction between Si and SO, SiO production is 5-7 times more efficient than SiS formation. The reaction of SiS with O atoms can play an important role in destroying SiS in envelopes around evolved stars. We built a simple chemical model of a postshock gas to study the chemistry of SiS in protostellar outflows and we found that SiS forms with a lower abundance and later than SiO, that SiS is efficiently destroyed through reaction with O, and that the main SiS-forming reactions are Si + SO and Si + SO.

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Section: Astrochemical Impactmentioning

confidence: 99%

“…(2) Assumed value for exothermic and spin-allowed reaction. (3) Assumed value for barrierless reaction studied by Rosi et al (2018).…”

Section: Figmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Formation and Destruction of SiS in Space

Zanchet

Roncero

Agúndez

et al. 2018

ApJ

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“…Properties from reactive molecular collisions in the gas phase are usually predicted in terms of MEP profiles [2,3,4]. The absence of a saddle point in the MEP for the approximation of the colliding partners is commonly identified with a barrier-less process [5,6,7]. The absence of a saddle point in the MEP for the approximation of the colliding partners is commonly identified with a barrier-less process [5,6,7].…”

Section: Introductionmentioning

confidence: 99%

“…The absence of a saddle point in the MEP for the approximation of the colliding partners is commonly identified with a barrier-less process [5,6,7]. The absence of a saddle point in the MEP for the approximation of the colliding partners is commonly identified with a barrier-less process [5,6,7]. In the classical trajectories view, the MEP is mistakenly confused with the more-likely pathway for reactive or complex-forming trajectories.…”

Section: Introductionmentioning

confidence: 99%