The Nuclear Structure of Exotic Fission Fragments

原子的核心是原子核，它是一个非常微小的物体，需要数百亿个端对端放置才能构成一根头发的宽度。原子核本身是由更小的粒子——中子和质子组成的。中子，顾名思义，不带电荷，而质子带正电荷。因此，原子核中的质子总数决定了原子核的电荷，并用原子序数Z表示。正是这种净正电荷使带负电荷的电子能够“粘”在原子核上，形成中性原子。原子核内的电作用力试图将质子推开，只有中子和质子之间存在强的、短程的吸引核力，才能使原子核处于稳定状态。中子和质子的总数称为质量数，a。原子核只有在Z和a的特定组合下才稳定。如果我们试图用给定数量的质子制造一个中子太多的原子核，它就会变得不稳定，并试图通过一个被称为衰变的过程衰变成总质量更低的产物。对于非常高的原子序数，质子之间的远距离电斥力与原子核的吸引力竞争。为了保持稳定，这些高z原子核比低z原子核需要更多的中子和质子。一些高Z的原子核可以裂变成两个较轻的原子核，释放出大量的能量。裂变过程产生的产物与母核的Z/A比值大致相同。由于母体含有丰富的中子，产物也。因此，裂变是产生不稳定的富含中子的原子核的自然方式。这些原子核非常重要，因为它们被用作天体物理快速中子捕获过程的垫脚石，而快速中子捕获过程是制造比铁重的元素的机制。裂变也很重要，因为它是目前w

At the heart of the atom lies the atomic nucleus, an object so minute that it would take tens of billions laid end-to-end to make up the width of a human hair. The nucleus is itself composed of even smaller particles called neutrons and protons. The neutrons, as the name suggests, carry no electrical charge while the protons have a positive charge. Thus, the total number of protons in a nucleus determines the nuclear charge and is denoted by Z, the atomic number. It is this net positive charge that enables negatively-charged electrons to 'stick' to the nucleus to make neutral atoms. The electric forces within the nucleus try to push the protons apart and it is only the presence of the the strong, short-range attractive nuclear force between neutrons and protons that enables nuclei to exist in a stable state. The total number of neutrons and protons is called the mass number, A. Atomic nuclei are stable only for particular combinations of Z and A. If we try to make a nucleus with too many neutrons for a given number of protons it becomes unstable and tries to decay to products with lower total mass by a process known as beta decay. For very high atomic numbers the long-range electric repulsion between the protons becomes competitive to the nuclear attraction. These high-Z nuclei need proportionately more neutrons to protons than low-Z nuclei in order to be stable. Some high Z nuclei can be made to fission into two lighter nuclei with a large release of energy. The fission process results in products with roughly the same Z/A ratio as the parent nucleus. Since the parent is rich in neutrons, the products are also. Fission is therefore a natural way in which to produce unstable neutron-rich nuclei. Such nuclei are of great importance since they are used as stepping stones in the astrophysical rapid neutron-capture process that is the mechanism by which elements heavier than iron are made. Fission is also important in that it is currently the only way in which w