Effects of impurity atoms and molecules on the lifetime of antiprotonic helium atoms

E. Widmann, I. Sugai, T. Yamazaki, R. S. Hayano, M. Iwasaki, S. N. Nakamura, H. Tamura, T. M. Ito, A. Kawachi, N. Nishida, W. Higemoto, Y. Ito, N. Morita, F. J. Hartmann, H. Daniel, T. von Egidy, W. Schmid, J. Hoffmann, J. Eades

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Delayed annihilation time spectra (DATS) of antiprotons in room-temperature helium gas have been studied as a function of the concentration of admixed noble gases (Ne, Ar, Kr, Xe) as well as molecular gases ([Formula Presented],[Formula Presented],[Formula Presented]) at the low-energy antiproton ring at CERN. The DATS were a superposition of two exponential components, one with a lifetime of several 100 ns and the other with a lifetime 1–3 μs. They showed a shorter average lifetime ([Formula Presented]) than DATS of pure helium. Ne, Ar, and Kr were found to affect [Formula Presented] only slightly even in concentrations up to 20%, while Xe showed a much stronger influence. In the case of molecular gases, the presence of [Formula Presented] influenced the DATS much less than [Formula Presented] and [Formula Presented], which destroyed the metastability almost completely in concentrations of 100 ppm and less. The decay rate of the slow component of DATS was found to exhibit a linear relation to the number density of the admixture. From this a collisional destruction (“quenching”) cross section [Formula Presented] was extracted. No evidence for a delayed annihilation of antiprotons in pure Ne, Kr, and Xe was observed.

Original languageEnglish
Pages (from-to)3129-3139
Number of pages11
JournalPhysical Review A - Atomic, Molecular, and Optical Physics
Issue number5
Publication statusPublished - 1996
Externally publishedYes

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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