Neutrons from Radiative Pion Absorption on O16 and Si28 Nuclei

Abstract

Recently, much interest has centered on demonstrating that the excitation of giant resonances plays a dominant role in radiative pion absorption on complex nuclei.* After stopping in the target material, the pion is generally captured into highly excited, circular atomic orbits from which it cascades to lower orbits via Auger and radiative dipole transitions. For the light nuclei of interest, absorption occurs predominantly from the 2p atomic orbit accompanied by the emission of a high energy photon. One would expect the residual nucleus to be excited to the isobaric analogs of the giant resonance states of the capturing nucleus, which subsequently decay via neutron emission[1]. Observation of the energy spectra of the emitted particles would provide a means of studying these particular states. In addition, by exploiting the similarities and differences between this process, muon capture, and the electromagnetic excitation (both γ and (e,e’))of giant resonances in complex nuclei, one can hope to learn much about the structure of the giant resonance region.