| Summary: | We consider the formation of positive ions of antihydrogen H[over ¯]^{+} via radiative attachment of incident positrons e^{+} to antihydrogen atoms H[over ¯]. The formation mechanisms include (i) spontaneous radiative attachment in which the ion is formed due to spontaneous emission of a photon by a positron incident on H[over ¯]; (ii) induced radiative attachment where the formation proceeds in the presence of a laser field via induced photoemission; and (iii) two-center attachment which takes place in the presence of a neighboring atom B and in which an incident positron is attached to H[over ¯] via resonant transfer of energy to B with its subsequent relaxation through spontaneous radiative decay. We show that the mechanisms (ii) and (iii) can strongly dominate over the known mechanism (i). Besides, according to our estimates, in the range of positron energies (≃1eV) where the radiative channels are most efficient, the mechanism of (nonradiative) three-body attachment, in which one of two positrons incident on H[over ¯] forms the ion whereas the other one carries away the energy excess, is much weaker than the channel (i). We also briefly discuss three-body attachment where, instead of two positrons, a positron and an electron are incident on H[over ¯].
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