Even-odd effects in prompt emission of spontaneously fissioning even-even Pu isotopes

As in the previously studied cases (233,235U(nth,f), 239Pu(nth,f), 252Cf(SF)) the even-odd effects in the prompt emission of 236-244Pu(SF) are mainly due to the Z even-odd effects in fragment distributions and charge polarizations and the N even-odd effects in the average neutron separation energies from fragments 〈Sn〉. The size of the global N even-odd effect in 〈Sn〉 is decreasing with the fissility parameter, being higher for the Pu(SF) systems compared to the previously studied systems. The prompt neutron multiplicities as a function of Z, ν(Z), exhibit sawtooth shapes with a visible staggering for asymmetric fragmentations. The size of the global Z even-odd effect in ν(Z) exhibits a decreasing trend with increasing fissility. The average prompt neutron multiplicities as a function of TKE show an increase of the even-odd effect with increasing TKE, with global effect sizes close to each other (a decrease of the effect for heavier fissioning nuclei is not observed here). The amounts of the global even-odd effect in Y(Z) and of the N even-odd effect in 〈Sn〉 of 240Pu(SF) are larger compared to 239Pu(nth,f). This fact affects the prompt emission leading to a lower Z even-odd effect in the prompt neutron multiplicity of 240Pu(SF) compared to 239Pu(nth,f).