How Do the Nucleons Pack in an Atomic Nucleus?

Xiaodong Li^*, Qijun Liu, Gongyi Li, Yihe Li, Zengyong Chu

Department of Chemistry and Biology, College of Science, National University of Defense Technology, Changsha, China.

DOI: 10.4236/wjnst.2014.44030                

Abstract

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 (E_B) and therefore odd and even Z dependent zigzag features of E_B/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, P_X+nN_X and P_XN_X+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 E_B/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.

Keywords

Nuclear Structure, Ring plus Extra Nucleon Model, Nuclear Symmetricity

Conflicts of Interest

The authors declare no conflicts of interest.

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