Dissociative recombination and excitation of H2O+ and HDO+

Dissociative recombination and excitation of H2O+ and HDO+ in the vibration al ground state have been studied at the heavy-ion storage ring ASTRID. Abs olute cross sections have been measured in the energy range from similar to 0.1 meV to similar to 50 eV. The total cross sections for dissociative rec ombination are essentially the same for the two molecular ions. Complete br anching ratios for all possible product channels in dissociative recombinat ion at E = 0 have been determined. Three-particle breakup accounts for simi lar to 60% of the recombination events. With 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 HDO+, where H + production is more likely than D+ production. [S1050-2947(99)01910-1].