Observation of cold, long-lived antiprotonic helium ions |
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Authors: | Hori M Eades J Hayano R S Pirkl W Widmann E Yamaguchi H Torii H A Juhász B Horváth D Suzuki K Yamazaki T |
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Affiliation: | CERN, CH-1211 Geneva 23, Switzerland. |
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Abstract: | 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 li=ni-1 have been observed. They were produced by cooling three-body antiprotonic helium atoms in an ultra-low-density helium target at temperature T approximately 10 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. |
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