Nuclear-charge polarization at scission in proton-induced fission of light actinides

Nishinaka, Ichiro; Tanikawa, Masashi*; Nagame, Yuichiro ; Nakahara, Hiromichi*

In the 12 MeV proton-induced fission of Th and U, primary and secondary fragment mass yields as well as the average neutron multiplicity have been studied with a double time-of-flight technique. From these experimental data of fission fragments and the literature data of fission products, the nuclear-charge polarization at scission was derived. It was found that the nuclear charge polarization is characterized by the liquid-drop properties of nuclei and the proton shell effects = 50 of heavy fragments. The fragment mass dependence of the nuclear-charge polarization in the present systems agrees with that in the thermal-neutron-induced fission of U, indicating that the nuclear-charge polarization is practically insensitive to mass and excitation energy of the fissioning nucleus for the asymmetric fission in the region of light actinides.