Isotope effects on delayed annihilation time spectra of antiprotonic helium atoms in a low-temperature gas

B. Ketzer, F. J. Hartmann, H. Daniel, T. von Egidy, A. Niestroj, S. Schmid, W. Schmid, T. Yamazaki, I. Sugai, K. Nakayoshi, R. S. Hayano, F. E. Maas, H. A. Torii, T. Ishikawa, H. Tamura, N. Morita, D. Horváth, J. Eades, E. Widmann

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37 Citations (Scopus)

Abstract

The delayed annihilation time spectra (DATS) of antiprotonic helium atoms have been studied in isotopically pure low-temperature [Formula Presented] and [Formula Presented] gas at various densities. The DATS taken at 5.8 K and 400 mbar are very similar in shape except for (i) a small difference in the time scale and (ii) the presence of a distinct fast decay component in the case of [Formula Presented]. The ratio of overall trapping times (mean lifetimes against annihilation), R=[Formula Presented]He)/[Formula Presented]He), has been determined to be 1.144 ± 0.009, which is in good agreement with a theoretical estimate yielding R=[[Formula Presented](p¯[Formula Presented]He)/ [Formula Presented](p¯[Formula Presented]He)[Formula Presented]=1.14, where [Formula Presented] denotes the reduced mass of the p¯[Formula Presented]<enspace>system. The presence of a short-lived component with a lifetime of 0.154±0.007 μs in the case of [Formula Presented] suggests that the p¯[Formula Presented]atom has a state of intermediate lifetime on the border between a metastable zone and an Auger-dominated short-lived zone. The fraction of antiprotons trapped in metastable states at 5.8 K and 400 mbar is lower by 22.2(4)% for [Formula Presented] for [Formula Presented]. All the data can be fitted fairly well with simple three-level and four-level cascade models.

Original languageEnglish
Pages (from-to)2108-2117
Number of pages10
JournalPhysical Review A - Atomic, Molecular, and Optical Physics
Volume53
Issue number4
DOIs
Publication statusPublished - 1996
Externally publishedYes

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

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