Study of fragment angular excitation mechanism in low energy fission

A four-parameter correlation measurement, including two semiconductors and a liquid scintillator as well as a 60% HPGe detector, was employed to measure the correlations of neutron multiplicity and γ yield with the fission parameters, such as fragment mass number A* and total kinetic energy TKE of fragments. Because it is the first time that the absolute γ yield for the selected fragment is determined, so the angular momentum excitation of fragments can be investigated using the correlations of γ multiplicity with the neutron yield as well as with A* and TKE. The results show that there is the complex correlation between the angular momentum excitation and the fragment deformation. The measured data can not be explained on the basis of the bending and wriggling excitation modes, but it could be understood partly by the assumption that there exists the positive correlation between the angular momentum excitation of fragments and the excitation energy of fission nuclei at the scission.