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Phys. Rev. Lett. 94, 063401 (2005) [4 pages]

Observation of Cold, Long-Lived Antiprotonic Helium Ions

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M. Hori1, J. Eades2, R. S. Hayano2, W. Pirkl2, E. Widmann2, H. Yamaguchi2, H. A. Torii3, B. Juhász4, D. Horváth5, K. Suzuki6, and T. Yamazaki7
1CERN, CH-1211 Geneva 23, Switzerland
2Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
3Institute of Physics, University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan
4Institute of Nuclear Research of the Hungarian Academy of Sciences, H-4001 Debrecen, Hungary
5KFKI Research Institute for Particle and Nuclear Physics, H-1525 Budapest, Hungary
6Physik-Department, Technische Universität München, D-85747 Garching, Germany
7Heavy Ion Nuclear Physics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan

Received 31 July 2004; published 14 February 2005

Cold, two-body antiprotonic helium ions p̅  4He2+ and p̅  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∼10  K by atomic collisions, and then removing their electrons by inducing a laser transition to an autoionizing state. The lifetimes of p̅  3He2+ against annihilation induced by collisions were shorter than those of p̅  4He2+, and decreased for larger-ni states.

© 2005 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.94.063401
DOI:
10.1103/PhysRevLett.94.063401
PACS:
36.10.–k, 25.43.+t, 34.90.+q
 
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