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

Publikation: Beitrag in FachzeitschriftArtikelBegutachtung

38 Zitate (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.

OriginalspracheEnglisch
Seiten (von - bis)2108-2117
Seitenumfang10
FachzeitschriftPhysical Review A
Jahrgang53
Ausgabenummer4
DOIs
PublikationsstatusVeröffentlicht - 1996

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