Dissociative recombination and excitation ofH2O+andHDO+

Abstract

Dissociative recombination and excitation of ${\mathrm{H}}_{2}{\mathrm{O}}^{+}$ and ${\mathrm{HDO}}^{+}$ in the vibrational ground state have been studied at the heavy-ion storage ring ASTRID. Absolute cross sections have been measured in the energy range from $\ensuremath{\sim}0.1$ meV to $\ensuremath{\sim}50$ eV. The total cross sections for dissociative recombination are essentially the same for the two molecular ions. Complete branching ratios for all possible product channels in dissociative recombination at $E=0$ have been determined. Three-particle breakup accounts for $\ensuremath{\sim}60%$ of the recombination events. With ${\mathrm{HDO}}^{+},$ recombination into OD+H is twice as probable as recombination into OH+D. An isotope effect is also evident in the cross sections for dissociative excitation of ${\mathrm{HDO}}^{+},$ where ${\mathrm{H}}^{+}$ production is more likely than ${\mathrm{D}}^{+}$ production.