标题： 钙诱导反应形成钍同位素的准裂变中的壳效应 显示英文标题

标题： Shell effects in quasi-fission for calcium induced reactions forming thorium isotopes

摘要： 量子壳效应在锕系元素中诱导出一种不对称的裂变模式，这种模式在中子不足的同位素中消失。 准裂变在低能重离子碰撞中以显著的质量转移为特征，预计会受到类似的壳效应影响。 这是通过时依赖哈特里-福克方法在40-56Ca+176Yb反应中进行研究的。 所有反应都表现出一个质量平衡过程，当形成具有约54个质子的重碎片时停止。 与钍复合核的裂变不同，准裂变在中子不足体系中不表现出向对称模式的转变。 这一现象被解释为势能面的特性，显示出不对称谷的持续存在，随着屏障的增加，阻止了其在最中子不足的钍同位素裂变中的填充。 显示英文摘要

摘要： Quantum shell effects induce an asymmetric fission mode in actinides, which disappears in neutron deficient isotopes. Quasi-fission, characterized by a significant mass transfer in heavy ion collisions at low-energies, is expected to be affected by similar shell effects. This is studied in 40-56Ca+176Yb reactions with the time-dependent Hartree-Fock approach. All reactions exhibit a mass equilibration process that stops when a heavy fragment with Z~54 protons is formed. Unlike the fission of thorium compound nuclei, quasi-fission does not exhibit a transition to symmetric modes in neutron deficient systems. This observation is interpreted in terms of potential energy surfaces that show a persistence of an asymmetric valley with an increasing barrier preventing its population in fission of the most neutron deficient thorium isotopes.