Collisions of ultra-cold helium* atoms

Cold, two-body antiprotonic helium ions $\overline{p}\text{ }^{4}\mathrm{H}\mathrm{e}^{2+}$ and $\overline{p}\text{ }^{3}\mathrm{H}\mathrm{e}^{2+}$ with 100-ns-scale lifetimes, occupying circular states with the quantum numbers ${n}_{i}=28--32$ 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 $\overline{p}\text{ }^{3}\mathrm{H}\mathrm{e}^{2+}$ against annihilation induced by collisions were shorter than those of $\overline{p}\text{ }^{4}\mathrm{H}\mathrm{e}^{2+}$ , and decreased for larger- ${n}_{i}$ states.Cold, two-body antiprotonic helium ions $\overline{p}\text{ }^{4}\mathrm{H}\mathrm{e}^{2+}$ and $\overline{p}\text{ }^{3}\mathrm{H}\mathrm{e}^{2+}$ with 100-ns-scale lifetimes, occupying circular states with the quantum numbers ${n}_{i}=28--32$ 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 $\overline{p}\text{ }^{3}\mathrm{H}\mathrm{e}^{2+}$ against annihilation induced by collisions were shorter than those of $\overline{p}\text{ }^{4}\mathrm{H}\mathrm{e}^{2+}$, and decreased for larger-${n}_{i}$ states.

Physical Review LettersFeb 14, 200545 citations

Cold, two-body antiprotonic helium ions

\overline{p}\text{ }^{4}\mathrm{H}\mathrm{e}^{2+}

and

\overline{p}\text{ }^{3}\mathrm{H}\mathrm{e}^{2+}

with 100-ns-scale lifetimes, occupying circular states with the quantum numbers

{n}_{i}=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

\overline{p}\text{ }^{3}\mathrm{H}\mathrm{e}^{2+}

against annihilation induced by collisions were shorter than those of

\overline{p}\text{ }^{4}\mathrm{H}\mathrm{e}^{2+}

, and decreased for larger-

{n}_{i}

states.