Proportional counter measurements of π-mesonic X-Rays

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 K_α 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 L_α energies are used to deduce a value for the π-meson mass equal to 272.5±0.8 m_e.

The natural broadening of the beryllium K_α 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 K_α and K_β and L_α, L_β and L_γ lines are also reported.