报告题目：Remarks on fission dynamics in medium and heavy nuclei

报 告 人：Artur Dobrowolski，波兰玛丽居里大学理论物理研究所

报告时间：2020-01-15 14:00

报告地点：物理系理科楼B315

报告摘要：The first part of the talk will pertain to the time-dependent generator coordinate method with the Gaussian overlap approximation (TDGCM+GOA) formalism applied to describe the fission of 252Cf nucleus. An analysis of fission from the initial states laying in the energetic range from the ground state to the state located 4 MeV above the fission barrier is performed. The fission fragment mass distributions obtained for different parity, energy of levels, and types of mixed states are calculated and compared with experimental data. The impact of the total time of wave packet propagation on the final results is studied as well. The weak dependence of obtained mass yields on the initial conditions is shown.

Another part of the talk is devoted to the kinetic properties of the fissioning system. In particular, the fission fragment mass yields are obtained by using an approximate solution of the collective Hamiltonian defined on the space of the most relevant degrees of freedom on the way to fission, as nuclear elongation, mass asymmetry of left and right fragments and shape of the neck. The latter is given within the effective Fourier shape parametrization which describes well nuclear shapes in the 3D collective model. The predicted mass fragmentations for isotopic chains of Pt to Rn even-even nuclei are compared with available experimental data. Their main characteristics are well reproduced when the neck rapture probability depends on the neck shape. The potential energy surface entering the Hamiltonian is evaluated in the macroscopic-microscopic approach based on the LSD macroscopic energy and Yukawa-folded mean-field potential. A phenomenological inertia parameters are used to simulate the dynamics of the fission process in a simplistic way.

Finally, one will propose an approximate analytical expression allowing for a fast and quite accurate evaluation of transmission coefficients (TC) for emission of neutrons, protons and alpha particles from deformed nuclei that carry both a thermal and rotational excitation. This expression is based on the famous Weisskopf formula. For a proton or alpha particle the TC is given within the Hill-Wheeler WKB approach.