On the production of the positive antihydrogen ion H-bar + via radiative attachment

We provide an estimate of the cross section for the radiative attachment of a second positron into the (1S21Se) state of the H-bar + ion using Ohmura and Ohmura's (1960 Phys. Rev. 118 154) effective range theory and the principle of detailed balance. The H-bar + ion can potentially be created using interactions of positrons with trapped antihydrogen, and our analysis includes a discussion in which estimates of production rates are given. Motivations to produce H-bar + include its potential use as an intermediary to cool antihydrogen to ultra-cold (sub-mK) temperatures for a variety of studies, including spectroscopy and probing the gravitational interaction of the anti-atom. (paper)