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Science 13 February 1959:
Vol. 129. no. 3346, pp. 361 - 367
DOI: 10.1126/science.129.3346.361
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Articles

Shape of the Nucleus

It varies widely, from spherical for doubly magic nuclei to ellipsoidal and sometimes pear shapes

Lawrence Wilets 1

1 Staff of the physics department, University of Washington, Seattle.

The gross features of nuclear morphology can be summarized as follows. Nuclei have shapes similar to a diffusesurfaced, liquid drop. The interior density is rather uniform, and also constant from nucleus to nucleus. The constancy of nuclear density implies an Afrac13 law for the mean nuclear radius, the proportionality constant being 1.07 x 1O–13 centimeter. The surface region is diffuse, the nuclear density falling from 90 to 10 percent of the central value in a distance of about 2.4 x 10–13 centimeter, independently of nuclear mass number.

Nuclear shapes can vary rather widely, with doubly magic nuclei preferring spherical symmetry. Some nuclei execute volume-preserving oscillations about spherical shape, while others possess permanent spheroidal deformations. The values of the deformation parameter, egr, for such spheroids possibly attains 0.85 for some light nuclei and 0.4 for some intermediate weight nuclei.

There is some evidence, based on the occurrence of "inversion" spectra and asymmetrical fission, that pear-shaped nuclei may also exist.

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Science. ISSN 0036-8075 (print), 1095-9203 (online)