Volume 638, June 2020
|Number of page(s)||5|
|Section||Atomic, molecular, and nuclear data|
|Published online||12 June 2020|
Hyperfine excitation of SH+ by H
LOMC – UMR 6294, CNRS-Université du Havre, 25 rue Philippe Lebon, BP 1123, 76 063 Le Havre cedex, France
2 Instituto de Física Fundamental, CSIC, C/Serrano, 123, 28006 Madrid, Spain
3 Departamento de Quimica Fisica, Facultad de Ciencias Quimicas, Universidad de Salamanca, 37008 Salamanca, Spain
4 Firat University, Department of Physics, 23169 Elazi, Turkey
Accepted: 24 April 2020
Context. SH+ is a surprisingly widespread molecular ion in diffuse interstellar clouds. There, it plays an important role by triggering the sulfur chemistry. In addition, SH+ emission lines have been detected at the UV-illuminated edges of dense molecular clouds, so-called photo-dissociation regions (PDRs), and toward high-mass protostars. An accurate determination of the SH+ abundance and of the physical conditions prevailing in these energetic environments relies on knowing the rate coefficients of inelastic collisions between SH+ molecules and hydrogen atoms, hydrogen molecules, and electrons.
Aims. We derive SH+–H fine and hyperfine-resolved rate coefficients from recent quantum calculations for the SH+–H collisions, including inelastic, exchange, and reactive processes.
Methods. The method we used is based on the infinite-order sudden approach.
Results. State-to-state rate coefficients between the first 31 fine levels and 61 hyperfine levels of SH+ were obtained for temperatures ranging from 10 to 1000 K. Fine-structure resolved rate coefficients present a strong propensity rule in favor of Δj = ΔN transitions. The Δj = ΔF propensity rule is observed for the hyperfine transitions.
Conclusions. The new rate coefficients will help significantly in the interpretation of SH+ spectra from PDRs and UV-irradiated shocks where the abundance of hydrogen atoms with respect to hydrogen molecules can be significant.
Key words: molecular data / molecular processes / radiative transfer / methods: laboratory: molecular
© F. Lique et al. 2020
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