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

Abstract

Cumulative and independent post-neutron product yields were measured for the photofission on 235U with 6.5, 7.0, and 8.4 MeV bremsstrahlung, applying γ-spectrometric methods on catcherfoils and pneumatically transported 235U-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 δ 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.