High spin states and neutron multiplicities after pion capture in181Ta and209Bi

The absorption of stoppedπ− in181Ta and209Bi has been investigated by studying prompt and delayedγ-ray spectra. Absolute cross-sections for the yield of isotopes per capturedπ− in (π−, xn) reactions, as well as the relative probability of populating nuclear states of different spins have been measured for the hafnium and lead isotopes, respectively. A spin as high as 20 has been observed in the production of204Pb. The ground-state rotational bands of the hafnium isotopes are excited to spin values up to 16. Neutron multiplicities as large as 15 have been observed for both targets. A neutron multiplicity of ≃8 is most probable for both tantalum and bismuth targets.