Recoil studies of photonuclear reactions at intermediate energies

A review is given on the recoil studies of photonuclear reactions on complex nuclei at intermediate energies. Recoils of 167 radionuclides formed in the photonuclear reactions of 27Al, natV, natCu, 93Nb, natAg, natTa, and 197Au, induced by bremsstrahlung of end-point energies (E0) from 600 to 1100 MeV, have been investigated by the thick-target thick-catcher method. The recoil velocity from the first step and the mean kinetic energy of the residual nuclei in the second step were deduced based on the two-step vector velocity model and discussed by comparing with the reported results on proton-induced reactions. Recoils of 24Na produced from 27Al, natV, natCu, natAg, and 197Au are of special interest from a viewpoint of a change in the production mechanism with respect to target mass. Reaction yields of 58 and 63 radionuclides produced in the photofission of 197Au and 209Bi, respectively, were also measured at E0=300-1100 MeV by a catcher foil technique with the aid of intensive chemical separation. The fission characteristics such as the charge and mass distributions and the numbers of pre- and post-fission neutrons were determined. These results were compared with the calculations using the Photon-induced Intranuclear Cascade Analysis 3 code combined with the Generalized Evaporation Model code. (author)