Dissociative recombination and excitation of ${\mathrm{H}}_3^{+}$

Using the ASTRID heavy-ion storage ring, absolute cross sections for dissociative recombination and dissociative excitation of vibrationally cold ${\mathrm{H}}_3^{+}$ have been measured as a function of energy in the region $E=0\mathrm{}-34\hspace{0.5em}\mathrm{eV}.$ A thermal rate coefficient for dissociative recombination of $(1.0\mathrm{}\pm 0.2)\times {10}^{-7}\hspace{0.5em}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ at 300 K was obtained from cross sections at low energy. At high energy, capture into a group of doubly excited states of ${\mathrm{H}}_3$ gives rise to resonances in the dissociative recombination as well as in the dissociative excitation cross sections.