Dissociative recombination of the thioformyl (HCS+) and carbonyl sulfide (OCS+) cations

• Branching ratios and absolute cross sections have been measured for the dissociative recombination of HCS+ and OCS+ at the CRYRING ion storage ring. In the case of OCS+, the channel leading to CO + S ( 83%) dominates, whereas the other exoergic pathways leading to CS + O (14%) and C + SO (3%) are of lesser importance. In the case of HCS+, fracture of the C - S bond is predominant (81%), with the production of H + CS accounting for the remainder (19%). The cross section of the reaction could be fitted by the expressions sigma = 1.41 x 10(-15)E(eV)(-1.11) and 4.47 x 10(-16)E(eV) (-1.14) cm(2) for HCS+ and OCS+, respectively. The derived energy dependences of the thermal reaction rate coefficients can be fitted by k(T) 9.7 x 10(-7)(T/300)(-0.57) and 3.5 x 10(-7)(T/300)(-0.62) cm(3) s(-1) for HCS+ and OCS+, respectively. We use these data to perform model calculations on the HCS+/CS abundance ratio in dark clouds and find that the models using the UMIST and Ohio State University databases have even more difficulty in accounting for the large observed ratio.

Ämnesord

NATURVETENSKAP  -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)

Nyckelord

astrochemistry

ISM : clouds

ISM : molecules

Astronomy and astrophysics

Astronomi och astrofysik

Publikations- och innehållstyp

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