The dissociative recombination of cold polyatomic molecular ions measured at a storage ring

Dissociative Recombination (DR) is a major process in planetary ionospheres and interstellar clouds. The branching ratio in the dissociative recombination of the astrophysically important species H3O+, H2O+ and CH3+ with low energy electrons is presented. The molecular ions were stored and vibrationally cooled in the ASTRID storage ring of Aarhus Denmark. The recombination was measured by merging the ions with the electron cooler. All the branching ratios were measured directly for the first time. The three body dissociation was found to be a major channel, a fact that was neglected previously in common interstellar chemical models.