The yields of various radioactive nuclides produced in 133Cs and 139La as a result of the (γ, xnyp) reactions with 250 MeV bremsstrahlung have been measured with the aid of radiochemical techniques in order to study the features of the photospallation reactions on nuclei in the heavy mass region. When yields were plotted against the difference in mass between target and product nuclei, it has been found that the curves thus obtained showed a similar Gaussian form for any separated element and that the peak yields occurred at about three mass units to the neutron-deficient side of the valley of the beta-stability. The general behavior observed in the yield distributions was quite similar to that associated with spallation reactions with high-energy particles in this mass region.
