The two-center convergent close-coupling method is used to calculate antihydrogen $\left(\overline{\mathrm{H}}\right)$ formation via positronium (Ps) scattering on antiprotons $\left(\overline{p}\right)$ at near threshold energies. For excited Ps of energy $\varepsilon$, the $1/\varepsilon$ behavior of the $\overline{\mathrm{H}}$ formation cross sections is valid strictly only at the respective threshold, as is the $1/\sqrt{\varepsilon }$ behavior for Ps in the ground state. Simple equations are given for the $\overline{\mathrm{H}}(n\le 4)$ formation cross sections from $\text{Ps}(n\le 3)$ from zero to around 0.1 eV above threshold. Some of the implications of using $\overline{p}$-Ps collisions to form antihydrogen in beams, and held in traps, are discussed.

• Received 18 November 2015

DOI:https://doi.org/10.1103/PhysRevA.93.012709