Long lived (0.8 ms, 6 ms, and > 3.8 s) states in C0 2+ have been observed for the first time by monitoring beams of 75-300 keV ions in the ion storage ring ASTRID. It is the first experimental evidence that a doubly charged molecule can be stable on a time scale of seconds. The results are theoretically interpreted by means of a multichannel Schrodinger analysis based on ah initio computations of potential energy curves and off-diagonal spin-orbit couplings. This analysis indicates that 3 n(v=0) accounts for the long lived component. The two decay components in the ms range probably derive from higher excited states in C0 2+ .

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Dissociative recombination and excitation of H 2 O ϩ and HDO ϩ 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 ϳ0.1 meV to ϳ50 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 Eϭ0 have been determined. Three-particle breakup accounts for ϳ60% of the recombination events. With HDO ϩ , recombination into ODϩH is twice as probable as recombination into OHϩD. An isotope effect is also evident in the cross sections for dissociative excitation of HDO ϩ , where H ϩ production is more likely than D ϩ production.

Using the ASTRID heavy-ion storage ring, absolute cross sections for dissociative recombination and dissociative excitation of vibrationally cold H 3 ϩ have been measured as a function of energy in the region Eϭ0Ϫ34 eV. A thermal rate coefficient for dissociative recombination of (1.0Ϯ0.2)ϫ10 Ϫ7 cm 3 s Ϫ1 at 300 K was obtained from cross sections at low energy. At high energy, capture into a group of doubly excited states of H 3 gives rise to resonances in the dissociative recombination as well as in the dissociative excitation cross sections.

Electrons have been scattered on in the energy range from 0 - 35 eV. A resonance structure in the detachment channel was observed at an energy of about 10 eV. To explain the structure, a potential curve was constructed from the isoelectronic ground-state potential curve and the repulsive Coulomb potential, and it is argued that the structure may be related to the population of a state. The state is predicted to decay primarily by electron emission since a large potential barrier prevents dissociation into .

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A beam of antiprotons with energies between 50 keV and 2 MeV has been used for measurements of non-dissociative and dissociative ionisation cross sections of H2. The results are compared with cross sections for equivelocity protons and electrons, and the role of interference effects in two-electron processes is discussed.

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