INFLUENCE OF THE ODD NEUTRON ON THE FRAGMENT CHARACTERISTICS IN THE PHOTOFISSION OF U-235

Cumulative and independent post-neutron product yields were measured f or the photofission on U-235 With 6.5, 7.0, and 8.4 MeV bremsstrahlung , applying gamma-spectrometric methods on catcherfoils and pneumatical ly transported U-235-samples. The independent yields for the heavy (A = 128-149) fragments were deduced, Post-neutron mass and isotonic yiel d distributions were studied together with the elemental yield distrib utions and the proton odd-even effect. The mass distribution shows abo ut 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 o dd-A nucleus remains at a constant value delta(p) = 25% in the studied compound nucleus excitation energy region, indicating that the odd ne utron does not influence the energy transfer between the different deg rees of freedom during the descent from saddle to scission point in a substantial way. (C) 1997 Elsevier Science B.V.