TITLE:
How Do the Nucleons Pack in an Atomic Nucleus?
AUTHORS:
Xiaodong Li, Qijun Liu, Gongyi Li, Yihe Li, Zengyong Chu
KEYWORDS:
Nuclear Structure, Ring plus Extra Nucleon Model, Nuclear Symmetricity
JOURNAL NAME:
World Journal of Nuclear Science and Technology,
Vol.4 No.4,
October
16,
2014
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 -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.