SULFUR CHEMISTRY IN THE INTERSTELLAR MEDIUM: THE EFFECT OF VIBRATIONAL EXCITATION OF H{sub 2} IN THE REACTION S{sup +}+H{sub 2} →SH{sup +}+H
- Instituto de Estructura de la Materia (IEM-CSIC), C.S.I.C. Serrano 123, E-28006 Madrid (Spain)
- University Bordeaux, LAB, UMR 5804, F-33270 Floirac (France)
- Unidad Asociada UAM-CSIC. Departamento de Química Física, Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain)
- Instituto de Física Fundamental (IFF-CSIC), C.S.I.C. Serrano 123, E-28006 Madrid (Spain)
Specific rate constants for the S{sup +}+H{sub 2} reaction are calculated using the ground quartet state potential energy surface and quasi-classical trajectories method. The calculations are performed for H{sub 2} in different vibrational states v = 0-4 and thermal conditions for rotational and translational energies. The calculations lead to slow rate constants for the H{sub 2} vibrational levels v = 0, 1, but a significant enhancement of reactivity is observed when v > 1. The inverse reaction is also studied and rate constants for v = 0 are presented. For comparison, we also recompile previous results of state-to-state rate constants of the C{sup +}+H{sub 2} for H{sub 2} in rovibrational state v, j = (0,0), (1,0), (1,1), and (2,0). The calculated rate coefficients are fitted using an improved form of the standard three-parameter Arrhenius-like equation, which is found to be very accurate in fitting rate constants over a wide range of temperatures (10-4000 K). We investigate the impact of the calculated rate coefficients on the formation of SH{sup +} in the photon-dominated region Orion Bar and find an abundance enhancement of nearly three orders of magnitude when the reaction of S{sup +} with vibrationally excited H{sub 2} is taken into account. The title reaction is thus one of the principal mechanisms in forming SH{sup +} in interstellar clouds.
- OSTI ID:
- 22273300
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 146, Issue 5; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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