Dissociative Recombination Measurements of Chloronium Ions (D2Cl+) using an Ion Storage Ring

Novotný, O.; Buhr, H.; Geppert, W.; Grieser, M.; Hamberg, M.; Krantz, C.; Mendes, M. B.; Petrignani, A.; Repnow, R.; Savin, Daniel Wolf; Schwalm, D.; Stützel, J.; Wolf, A.

We report our plasma rate coefficient and branching ratio measurements for dissociative recombination (DR) of ${{\rm{D}}}_{2}{\mathrm{Cl}}^{+}$ with electrons. The studies were performed in a merged-beams configuration using the TSR heavy-ion storage ring located at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. Starting with our absolute merged-beams recombination rate coefficient at a collision energy of ≈0 eV, we have extracted the cross section and produced a plasma rate coefficient for a translational temperature of ≈8 K. Furthermore, extrapolating our cross-section results using the typical low-energy DR behavior, we have generated a plasma rate coefficient for translational temperatures from 5 to 500 K. We find good agreement between our extrapolated results and previous experimental DR studies on ${{\rm{D}}}_{2}{\mathrm{Cl}}^{+}$. Additionally, we have investigated the three fragmentation channels for DR of ${{\rm{D}}}_{2}{\mathrm{Cl}}^{+}$. Here we report on the dissociation geometry of the three-body fragmentation channel, the kinetic energy released for each of the three outgoing channels, the molecular internal excitation for the two outgoing channels that produce molecular fragments, and the fragmentation branching ratios for all three channels. Our results, in combination with those of other groups, indicate that any remaining uncertainties in the DR rate coefficient for ${{\rm{H}}}_{2}{\mathrm{Cl}}^{+}$ appear unlikely to explain the observed discrepancies between the inferred abundances of HCl and ${{\rm{H}}}_{2}{\mathrm{Cl}}^{+}$ in molecular clouds and predictions from astrochemical models.


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The Astrophysical Journal

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Academic Units
Astronomy and Astrophysics
Published Here
March 15, 2023