Proportional counter measurements of ?-mesonic X-Rays

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Abstract
A xenon filled proportional counter has proved to be a very useful instrument for the study of π-mesonic x-rays from light elements. Measurements of the Kα energies from 6Li, 7Li, 9Be, 10B and 11B are described. Energy shifts due to the short range pion-nucleon forces are observed, confirming the scintillation counter measurements. The experimental values of the energy shift are fitted equally well by the theories of Deser et al. (1954) or Karplus (1956). Measurements of Lα energies are used to deduce a value for the π-meson mass equal to 272.5±0.8 me. The natural broadening of the beryllium Kα line due to the short lifetime for capture of the π-meson from the Is state has been measured. A width T=l.2±0.2 kev was observed. Intensity ratios of Kα and Kβ and Lα, Lβ and Lγ lines are also reported.