The physical meaning of nucleus spin
The spin of the nucleus is one of the most important characteristics of the nucleus. According to the rules of quantum mechanics, the nuclear spin takes half integer and multiple of h / 2π (h is Planck's constant). Where both the number of protons and the number of neutrons are even cores (even and even cores), their spins are zero; both are odd cores (odd and odd cores), and their spins are integer multiples of h / 2π. Kernels with odd mass numbers (odd A kernels) whose spin is a half-integer multiple of h / 2π follow the Fermi-Dirac statistical law. Kernels with even masses (even A kernels) follow the Bose-Einstein statistical law. More than half of the stable nuclides in nature are even-even nuclei, while odd-odd nuclei are only a few. The quantity characterizing the size of the atomic nucleus, also known as the nuclear radius, usually has several meanings: ① characterizing the radius of the nuclear charge distribution; ② characterizing the radius of the nuclear inner particle distribution; ③ characterizing the range of action of the nuclear force. They can be approximately expressed as R = r0A. In the formula, A is the mass number, and the value of r0 is in the range of (1.1 to 1.5) × 10-m.