1. Formation of interstellar SH+ from vibrationally excited H2: Quantum study of S+ + H2 ⇄ SH+ + H reaction and inelastic collision
- Author
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Octavio Roncero, Javier R. Goicoechea, François Lique, Alexandre Zanchet, Niyazi Bulut, Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), Institut Universitaire de France, Turkish Academy of Sciences, Zanchet, Alexandre [0000-0002-0471-5658], Lique, François [0000-0002-0664-2536], Roncero, Octavio [0000-0002-8871-4846], Goicoechea, Javier R. [0000-0001-7046-4319], Bulut, Niyazi [0000-0003-2863-7700], Instituto de Física Fundamental [Madrid] (IFF), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC), Laboratoire Ondes et Milieux Complexes (LOMC), Centre National de la Recherche Scientifique (CNRS)-Université Le Havre Normandie (ULH), Normandie Université (NU)-Normandie Université (NU), Firat University, Zanchet, Alexandre, Lique, François, Roncero, Octavio, Goicoechea, Javier R., and Bulut, Niyazi
- Subjects
Physics ,[PHYS]Physics [physics] ,Photodissociation ,Inelastic collision ,Astronomy and Astrophysics ,Astrophysics ,01 natural sciences ,Potential energy ,Molecular physics ,Molecular processes ,ISM: molecules ,3. Good health ,Photon-dominated region (PDR) ,Reaction rate constant ,Space and Planetary Science ,Yield (chemistry) ,Excited state ,0103 physical sciences ,010306 general physics ,010303 astronomy & astrophysics ,Collisional excitation ,ComputingMilieux_MISCELLANEOUS ,molecules [ISM] ,Bar (unit) - Abstract
8 pags., 7 figs., 4 tabs., The rate constants for the formation, destruction, and collisional excitation of SH are calculated from quantum mechanical approaches using two new SH potential energy surfaces (PESs) of A″ and A″ electronic symmetry. The PESs were developed to describe all adiabatic states correlating to the SH(ς) + H(S) channel. The formation of SH through the S + H reaction is endothermic by ≈9860 K, and requires at least two vibrational quanta on the H molecule to yield significant reactivity. Quasi-classical calculations of the total formation rate constant for H(v? =? 2) are in very good agreement with the quantum results above 100 K. Further quasi-classical calculations are then performed for v? =? 3, 4, and 5 to cover all vibrationally excited H levels significantly populated in dense photodissociation regions (PDR). The new calculated formation and destruction rate constants are two to six times larger than the previous ones and have been introduced in the Meudon PDR code to simulate the physical and illuminating conditions in the Orion bar prototypical PDR. New astrochemical models based on the new molecular data produce four times larger SH column densities, in agreement with those inferred from recent ALMA observations of the Orion bar., The research leading to these results has received funding from MICIU under grants No. FIS2017-83473-C2 and AYA2017- 85111-P. FL acknowledges financial support from the Institut Universitaire de France. NB acknowledges the computing facilities by TUBITAK-TRUBA.
- Published
- 2019