DISSOCIATIVE RECOMBINATION OF D$_3$S$^+$: ABSOLUTE CROSS SECTION, BRANCHING FRACTIONS AND ASTROPHYSICAL APPLICATION
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Date
2008
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Publisher
Ohio State University
Abstract
The chemistry of sulfur bearing species in molecular clouds is a very important but still not fully explored field. One of the crucial processes occurring there is a dissociative recombination (DR) of H$_3$S$^+$, which is one of the suggested production pathways for H$_2$S. The DR of D$_3$S$^+$ has been studied at the heavy ion storage ring CRYRING in Stockholm, Sweden. It has been observed that the main production channel in this process leads to the formation of DS~+~2D, whereas D$_2$S~+~D is only a minor pathway. The obtained value for the reaction rate coefficient is 2.8$\times$10$^{-7}$ at 300\,K. We used the obtained data to investigate their effect on the predictions of the gas phase and gas-grain model calculations of the sulfur chemistry and deuterium fractionations in dark clouds employing the UMIST code. The results obtained agree well with observations for abundances and deuterium fractionations for several interstellar sulfur compounds. However, large discrepancies are found for H$_2$S and HCS$^+$, which are grossly underestimated in both models. We conclude that H$_2$S is formed mainly on grain surfaces and not through gas-phase reactions in dark clouds.
Description
Author Institution: Institute of Physics, Swietokrzyska Academy, Swietokrzyska 15, PL-25406, Kielce, Poland; Department of Physics, Albanova University Center, Stockholm University, SE-106 91, Stockholm, Sweden; Manne Siegbahn Laboratory, Freskativagen 24, SE-104 05, Stockholm, Sweden; Institute of Physics, Swietokrzyska Academy, Swietokrzyska 15, PL-25406, Kielce, Poland