091 泡利不相容原理
Pauli Exclusion Principle
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泡利不相容原理
Pauli Exclusion Principle and Nuclear Stability
泡利不相容原理与核稳定性
Atomic nuclei consist of protons and neutrons, which attract each other through the nuclear force, while protons repel each other via the electromagnetic force due to their positive charge. These two forces compete, leading to various stability of nuclei. There are only certain combinations of neutrons and protons, which forms stable nuclei. Neutrons stabilize the nucleus, because they attract each other and protons , which helps offset the electrical repulsion between protons. As a result, as the number of protons increases, an increasing ratio of neutrons to protons is needed to form a stable nucleus. If there are too many (neutrons also obey the Pauli exclusion principle) or too few neutrons for a given number of protons, the resulting nucleus is not stable and it undergoes radioactive decay. Unstable isotopes decay through various radioactive decay pathways, most commonly alpha decay, beta decay, or electron capture. Many other rare types of decay, such as spontaneous fission or neutron emission are known.
原子核由质子和中子组成，它们通过核力相互吸引，而质子由于带正电荷而通过电磁力相互排斥。这两种力相互竞争，导致原子核具有不同的稳定性。只有中子和质子的某些组合才能形成稳定的原子核。中子能稳定原子核，因为它们相互吸引并吸引质子，这有助于抵消质子之间电的斥力。因此，随着质子数量的增加，中子与质子的比例就需要增加，才能形成稳定的原子核。对于给定数量的质子，如果有太多的中子（中子也遵循泡利不相容原理）或太少的中子，产生的原子核是不稳定的，并经历放射性衰变。不稳定同位素通过各种放射性衰变途径衰变，最常见的是α衰变、β衰变或电子俘获。许多其他稀有类型的衰变，如自发裂变或中子发射，已为人所知。
The Pauli exclusion principle also influences the critical energy of fissile and fissionable nuclei. For example, actinides with odd neutron number are usually fissile (fissionable with slow neutrons) while actinides with even neutron number are usually not fissile (but are fissionable with fast neutrons). Heavy nuclei with an even number of protons and an even number of neutrons are (due to Pauli exclusion principle) very stable thanks to the occurrence of ‘paired spin’. On the other hand, nuclei with an odd number of protons and neutrons are mostly unstable.
泡利不相容原理也影响易裂变和可裂变核的临界能量。例如，具有奇数中子数的锕系元素通常是易裂变的（对慢中子可裂变），而具有偶数中子数的锕系元素通常是不可裂变的（但对快中子可裂变）。由于“配对自旋”的出现，具有偶数个质子和偶数个中子的重原子核（由于泡利不相容原理）非常稳定。另一方面，质子和中子数量为奇数的原子核大多是不稳定的。
童年的泡利
（待续）