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Title: State-to-state rate coefficients for HCS+ in rotationally inelastic collisions with H2 at low temperatures

Journal Article · · Monthly Notices of the Royal Astronomical Society
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HCS+ ions have been detected in several regions of the interstellar medium (ISM), but an accurate determination of the chemical-physical conditions in the molecular clouds where this molecule is observed requires detailed knowledge of the collisional rate coefficients with the most common colliders in those environments. In this work, we study the dynamics of rotationally inelastic collisions of HCS+ + H2 at low temperature, and report, for the first time, a set of rate coefficients for this system. We used a recently developed potential energy surface for the HCS+–H2 van der Waals complex and computed state-to-state rotational rate coefficients for the lower rotational states of HCS+ in collision with both para- and ortho-H2, analysing the influence of the computed rate coefficients on the determination of critical densities. Additionally, the computed rate coefficients are compared with those obtained by scaling the ones from HCS+ in collision with He (an approximation that is sometimes used when data is lacking), and large differences are found. Furthermore, the approximation of using the rates for the HCO+ + H2 collision as a rough approximation for those of the HCS+ + H2 system is also evaluated. Finally, the complete set of de-excitation rate coefficients for the lowest 30 rotational states of HCS+ by collision with H2 is reported from 5 to 100 K.

Research Organization:
Missouri Univ. of Science and Technology, Rolla, MO (United States)
Sponsoring Organization:
USDOE Office of Science (SC); Naional Science Foundation (NSF); CONICYT/FONDECYT/REGULAR
Grant/Contract Number:
SC0019740; OAC-1919789; 1200732
OSTI ID:
1863110
Alternate ID(s):
OSTI ID: 1864679
Journal Information:
Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Vol. 512 Journal Issue: 4; ISSN 0035-8711
Publisher:
Oxford University PressCopyright Statement
Country of Publication:
United Kingdom
Language:
English

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Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
astrochemistry
molecular data
molecular processes
scattering
ISM
molecules