Dissociative recombination of coldHD+at the Test Storage Ring

The dissociative recombination cross section between ${\mathrm{HD}}^{+}$ molecules and electrons at energies between 0.3 and 40 eV has been measured for the first time in an ion storage ring. The ion beam, stored with a mean lifetime of ∼5 s, was observed to be vibrationally cold. In the measured cross section, theoretically predicted high-energy resonances appeared, which can be attributed to recombination via doubly excited Rydberg states of HD.