Excitation functions for photonuclear reactions on complex nuclei in (3,3)-resonance region

This paper reports that photopion reactions has received interest and studied extensively in view of the Δ formation in electromagnetic nuclear interactions and the behavior of the excited nucleon (Δ) and its decay products (pion and nucleon) in the nucleus. However, the study has been rather restricted to yield measurements of the most simple type of (γ, π±) reactions or to inclusive measurements of emitted pions or nucleons (N) in (γ, πN) or (γ, N) reactions on light nuclei. The radiochemical method is suited to determine the individual product yields of (γ, π±) and (γ, π- xn) reactions of complex nuclei selectively from the dominated spallation and/or fission products, and vice versa. Due to the absence of high-energy monochromatic photon sources with sufficiently high intensity, a bremsstrahlung beam of continuous spectrum has been a unique tool in photonuclear studies, and an unfolding method should be used to extract the cross sections from the measured yields. Another problem that plagues radiochemical method is the presence of nonmesic interactions; secondary protons and neutrons lead to the same products of (γ, π±) and (γ, π-xn) reactions through (n,p) and (p, x'n) reactions, respectively. Despite these difficulties, the yield and/or cross section measurements of the photonuclear reactions deserve a detailed study, since they present a clean feature of photonuclear processes especially on complex nuclei. The authors have currently been performing radiochemical measurements of photonuclear reactions of more than 20 targets from 12C to 209Bi at bremsstrahlung end-point energies Eo = 30--1000 MeV in steps of 50 MeV or less