Influence of the odd neutron on the fragment characteristics in the photofission of U-235

Cumulative and independent post-neutron product yields were measured for the photofission on U-235 With 6.5, 7.0, and 8.4 MeV bremsstrahlung, applying gamma-spectrometric methods on catcherfoils and pneumatically transported U-235-samples. The independent yields for the heavy (A = 128-149) fragments were deduced, Post-neutron mass and isotonic yield distributions were studied together with the elemental yield distributions and the proton odd-even effect. The mass distribution shows about an equal yield for the mass regions around A = 134 (N = 82) and A = 142 (N = 86-88), The proton odd-even effect for the fission of this odd-A nucleus remains at a constant value delta(p) = 25% in the studied compound nucleus excitation energy region, indicating that the odd neutron does not influence the energy transfer between the different degrees of freedom during the descent from saddle to scission point in a substantial way. (C) 1997 Elsevier Science B.V.