quadrupole deformation parameter a

quadrupole deformation parameter a₂₀

Last modification: 1996/3/21

A figure ( GIF file of 11KB or PS file of 183KB ). shows the quadrupole deformation parameter a₂₀ of the ground state solutions of the HF+BCS with SIII for even-even nuclei. Prolate (oblate) nuclei are designated with open (solid) circles whose diameter is proportional to |a₂₀|. The staircase-like lines represent two-nucleon drip lines from our calculations.

One can see that nuclei at major-shell closures are spherical except for some N=28 isotones, while the deformation develops between the major-shell closures. Such pattern of the development of a₂₀ looks regular for A > 100, while it is not so regular for A < 100, i.e., the change of deformation along isotope or isotone chains is not always smooth. In addition, oblate ground states are embedded here and there in light-mass region while for heavier-mass nuclei they are found only exceptionally in regions near major-shell closures.

A similar plot for the results of the FRDM [MNM94] has bee made in a figure ( GIF file of 14KB or PS file of 338KB ), which indicates systematic differences in

Z ~ N ~ 40 region, where our solutions tend to predict smaller deformations than those of the FRDM. We discuss on this difference in a different page.
a long and narrow region close to the proton drip line with 94 < = Z < = 102, where the FRDM predicts oblate shapes while our calculations give small prolate shapes, on which we do not discuss in this paper.

The largest deviation from the experimental a₂₀ is found in ¹²C, on which we discuss in a different page.

quadrupole deformation parameter a20

quadrupole deformation parameter a₂₀