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We review the gas-phase chemistry in extraterrestrial space that is driven by reactions with atomic and molecular ions. Ions are ubiquitous in space and are potentially responsible for the formation of increasingly complex interstellar molecules. Until recently, positively charged atoms and molecules were the only ions known in space; however, this situation has changed with the discovery of various molecular anions. This review covers not only the observation, distribution and reactions of ions in space, but also laboratory-based experimental and theoretical methods for studying these ions. Recent results from space-based instruments, such as those on the Cassini-Huygens space mission and the Herschel Space Observatory, are highlighted.

The dissociative recombination of OPCl+ and OPCl2+ has been studied at the storage ring CRYRING. The rate constants as a function of electron temperature have been derived to be 7.63×10-7(Te/300)-0.89 and >1.2×10-6(Te/300)-1.22 cm3 s-1, respectively. The lower limit quoted for the latter rate constant reflects the experimental inability to detect all of the reaction products. The branching fractions from the reaction have been measured for OPCl+ at ≈0 eV interaction energy and are determined to be N(O+P+Cl)=(16±7)%, N(O+PCl)=(16±3)% and N(OP+Cl)=(68±5)%. These values have been obtained assuming that the rearrangement channel forming P+ClO is negligible, and ab initio calculations using GAUSSIAN03 are presented for the ion structures and energetics to support such an assumption. Finally, the limitations to using heavy ion storage rings such as CRYRING for studies into the dissociative recombination of large singly charged molecular ions are discussed. [ABSTRACT FROM AUTHOR]

Product branching ratios and thermal rate coefficients for the dissociative recombination of C3D7+ and C4D9+ have been measured in the ion storage ring CRYRING. The results for C3D7+ are believed to be slightly more accurate than those obtained earlier for C3H7+. Only the C–C bond breaking channels could be measured for C4D9+ and were found to be in excellent agreement with earlier data. [ABSTRACT FROM AUTHOR]

Dissociative recombination is a corner-stone reaction in the synthesis of interstellar molecules and plays an important role in the ionised layers of the atmospheres of the Earth, other planets, and their satellites. The studies of dissociative recombination reactions was for a long time dominated by afterglow techniques, and these techniques are used in improved versions also today, but the bulk of the relevant data have in recent years been produced at ion storage rings. We review briefly these different experimental techniques. As examples of recent developments in the field, we discuss in particular the dissociative recombination of [image omitted], the role of dissociative recombination in the chemistry of hydrocarbons and sulphur compounds in the interstellar medium and planetary ionospheres, and the synthesis of interstellar methanol. [ABSTRACT FROM AUTHOR]

Product branching ratios and thermal rate coefficients for the dissociative recombination of C3D7+ and C4D9+ have been measured in the ion storage ring CRYRING. The results for C3D7+ are believed to be slightly more accurate than those obtained earlier for C3H7+. Only the C–C bond breaking channels could be measured for C4D9+ and were found to be in excellent agreement with earlier data. [ABSTRACT FROM AUTHOR]