Cold, two-body antiprotonic helium ions
p 4He2+ and
p 3He2+ with 100-ns-scale lifetimes, occupying circular states with the quantum numbers
ni=28−−32 and ${\ensuremath{\ell}}_{i}={n}_{i}\ensuremath{-}1$ have been observed. They were produced by cooling three-body antiprotonic helium atoms in an ultra-low-density helium target at temperature $T\ensuremath{\sim}10\text{ }\text{ }\mathrm{K}$ by atomic collisions, and then removing their electrons by inducing a laser transition to an autoionizing state. The lifetimes of
p 3He2+ against annihilation induced by collisions were shorter than those of
p 4He2+, and decreased for larger-
ni states.