Isotopic distributions of thermal-neutron-induced fission fragments of near-symmetric fission of $^{239,241}\mathrm{Pu}$ determined using calorimetric low-temperature detectors
Résumé
Isotopic distributions were measured for the light fragment group in the transition region from asymmetric to symmetric fission for thermal neutron induced fission of and using the novel technology of calorimetric low temperature detectors in combination with the passive absorber method. Nuclear charge distributions were determined for 24 masses in the range to for for the first time with the LOHENGRIN mass spectrometer. Moving from asymmetric to symmetric fission, known data were supplemented for masses from to for and from to for . The isotopic yields were used to evaluate the charge polarization and the proton odd-even effect with emphasis on the borderline between asymmetric and symmetric fission. This highlighted a virtual shell effect near which mirrors the effect of the shell in the complementary heavy fragment group of the two Pu isotopes studied.