Absorption of stopped π− in 59Co, 75As, 197Au and 209Bi investigated by in-beam and activation γ-ray spectroscopy

In-beam pionic X-ray and γ-ray spectra and activation γ-ray spectra following π^? absorption at rest in ⁵⁹Co, ⁷⁵As, ¹⁹⁷Au and ²⁰⁹Bi have been measured. The isotopic yield distributions and thus the (π^?, xnγp) reaction yields were determined. The mean numbers of emitted neutrons and protons are, respectively, 4.5 ± 0.2 and 1.48 ± 0.16 for ⁵⁹Co, 5.1 ± 0.3 and 1.02 ± 0.14 for ⁷⁵As, 6.6 ± 0.4 and 0.32 ± 0.14 for ¹⁹⁷Au, and 6.8 ± 0.4 and 0.37 ± 0.16 for ²⁰⁹Bi. The experimental results are compared with a pre-equilibrium exciton model calculation and proton-induced spallation reactions. High spin states in the residual nuclei were observed. For pionic X-rays absolute intensities of various transitions are given.