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The spontaneous fission of 252Cf was investigated experimentally in the cold fission region. The fission fragment mass and nuclear charge distributions were determined in total kinetic energy bins of 2MeV width parallel to the average Q(max) value as a function of mass from 1 to 15 MeV. In evaluation bin 6[ Q(max)-TKE = 11 MeV] 220 nuclides are identified, 59 of which lie outside the Karlsruhe Chart of Nuclides. Proton, neutron and mass odd-even effects are evaluated. There is no odd-even effect in the mass yield, whereas proton and neutron odd-even effects show linear dependence as function of (Q(max)-TKE), however with different slopes. The local proton odd-even effect at constant (Q(max)-TKE) shows an undulatory behaviour with a period of about five mass units. This structure persists even at (Q(max)-TKE) = 15 MeV, where the average is largely reduced. The neutron odd-even effect shows large changes with fragment mass from positive to negative values and from small to large amplitudes. The conclusion from the present results is that these odd-even effects cannot be interpreted as indicators of the intrinsic excitation energy at scission, and that the structure of five to six mass units observed in many fission parameters finds its explanation in the shape of the fission energy surface for the Q-value as a function of mass and nuclear charge.

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Bibliographic Reference: Paper presented: VI International School on Neutron Physics, Alustha, the Crimea (SU), Oct. 8-18, 1990 and Consultants' Meeting on Nuclear Data for Neutron Emission in the Fission Process, Wien (AT), Oct. 22-24, 1990
Availability: Available from (1) as Paper EN 35777 ORA
Record Number: 199011606 / Last updated on: 1994-12-02
Original language: en
Available languages: en