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Karl-Heinz Schmidt
Signatures of pairing correlation in nuclear fission The fission process of even-even nuclei has been found to produce fragments with even numbers of protons and neutrons with higher yields. This effect is known for a long time. The even-odd structure is a proof that the superfluid phase survives up to the scission point. The quantitative enhancement of even-Z yields has been interpreted as the probability for the completely paired proton configuration to be preserved up to scission. Thus, it was considered as a direct measure of the mean excitation energy acquired in the fission process. In his PhD thesis, Steffen Steinhäuser deduced from the GSI experiments with secondary beams that also in the fission of odd-Z nuclei the element distribution of the fission fragments generally shows a clear even-odd structure, in spite of the presence of at least one unpaired proton. Due to this finding, the previous interpretation of the even-odd structure has to be revised. Fanny Farget et al. developed a new theoretical model, based on the superfluid nuclear model, for the interpretation of the signatures of pairing correlations in nuclear fission. This model is also able to explain the large difference between the observed even-odd structures in proton and neutron numbers found in previous experiments.
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