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

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

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 (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.

Keywords: Nuclear Structure, Ring plus Extra Nucleon Model, Nuclear Symmetricity

Cite this paper: Li, X. , Liu, Q. , Li, G. , Li, Y. and Chu, Z. (2014) How Do the Nucleons Pack in an Atomic Nucleus?. World Journal of Nuclear Science and Technology, 4, 237-248. doi: 10.4236/wjnst.2014.44030.

References

[1]   Rowe, D.J. and Wood, J.L. (2010) Fundamentals of Nuclear Models, Foundational Models. World Scientific, Hackensack.
http://dx.doi.org/10.1142/6209

[2]   Martin, B.R. (2009) Nuclear and Particle Physics, an Introduction. 2nd Edition, Wiley, Hoboken.

[3]   Audi, G., Wapstra, A.H. and Thibault, C. (2003) The AME2003 Atomic Mass Evaluation (II). Tables, Graphs and References. Nuclear Physics A, 729, 337-676.
http://dx.doi.org/10.1016/j.nuclphysa.2003.11.003

[4]   Audi, G., Bersillon, O., Blachot, J. and Wapstra, A.H. (2003) The NUBASE Evaluation of Nuclear and Decay Properties. Nuclear Physics A, 729, 3-128.
http://dx.doi.org/10.1016/j.nuclphysa.2003.11.001

[5]   Holden, N.E. (2004) Table of the Isotopes. In: Lide, D.R., Ed., CRC Handbook of Chemistry and Physics, 85th Edition, CRC Press, Boca Raton.

[6]   Hansen, P.G. and Jonson, B. (1987) The Neutron Halo of Extremely Neutron-Rich Nuclei. Europhysics Letters, 4, 409414.
http://dx.doi.org/10.1209/0295-5075/4/4/005

[7]   Wilson R.R. (1952) Radii of Mirror Nuclei. Physical Review, 88, 350-351.
http://dx.doi.org/10.1103/PhysRev.88.350

[8]   Ivanter I.G. and Troitski M.A. (1964) Mass Difference of Mirror Nuclei. Journal of Experimental and Theoretical Physics, 47, 1773-1776.

[9]   Ajzenberg-Selove, F. (1996) Energy Levels of Light Nuclei A=13-15. Nuclear Physics A, 523, 1-196.
http://dx.doi.org/10.1016/0375-9474(91)90446-D

[10]   Bentley, M.A., et al. (2006) High-Spin Spectroscopy of Natural and Unnatural Parity States in the Mirror-Pair 45V/45Ti. Physical Review C, 73, 1-10.

[11]   Usoskin, L.G. and Kovalsov, G.A. (2008) Production of cosmogenic7Be isotope in the atmosphere: Full 3-D modeling. Journal of Geophysical Research, 113, 1-12.