How Do the Nucleons Pack in an Atomic Nucleus?
How Do the Nucleons Pack in an Atomic Nucleus?作者机构：Department of Chemistry and Biology College of Science National University of Defense Technology Changsha China
出 版 物：《World Journal of Nuclear Science and Technology》 (核科学与技术国际期刊（英文）)
年 卷 期：2014年第4卷第4期
页 面：237-248页
学科分类：1002[医学-临床医学] 100214[医学-肿瘤学] 10[医学]
主 题：Nuclear Structure Ring plus Extra Nucleon Model Nuclear Symmetricity
摘 要：A nuclear structure model of “ring plus extra nucleon is proposed. For nuclei larger than 4He, protons (P) and neutrons (N) are basically bound alternatively to form a ZP + ZN ring. The ring folds with a “bond angle of 90° for every 3 continuous nucleons to make the nucleons packed densely. Extra N(‘s) can bind to ring-P with the same “bond angle and “bond distance. When 2 or more P’s are geometrically available, the extra N tends to be stable. Extra P can bind with ring N in a similar way when the ratio of N/P 1 although the binding is weaker than that of extra N. Even-Z rings, as well as normal even-even nuclei, always have superimposed gravity centers of P and N;while for odd-Z rings, as well as all odd-A (A: number of nucleon) nuclei, the centers of P and N must be eccentric. The eccentricity results in a depression of binding energy (EB) and therefore odd and even Z dependent zigzag features of EB/A. This can be well explained by the shift of eccentricity by extra nucleons. Symmetrical center may present in even-Z rings and normal even-even nuclei. While for odd-Z ring, only antisymmetric center (every P can find an N through the center and vice versa) is possible. Based on this model, a pair of mirror nuclei, PX+nNX and PXNX+n, should be equivalent in packing structure just like black-white photo and the negative film. Therefore, an identical spin and parity was confirmed for any pair. In addition, the EB/A difference of mirror nuclei pair is nearly a constant of 0.184n MeV. Many other facts can also be easily understood from this model, such as the neutron halo, the unusual stability sequence of 9Be, 7Be and 8Be and so on.
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