Leadership, Ethics of

Evolution of theN= 28 shell closure: a test bench for nuclear forces

“…The B(E2) values are small and remarkably similar for all N = 20 isotopes, except again for 32 20 Mg. This picture is consistent with a strong shell closure N = 20 which persists from Z = 20 to Z = 14, and disappears below Z = 14 (see [16] for further discussions). On the other hand, the behavior of the N = 28 isotones is different.…”

“…46 Ar [13,14], and 48 Ar [15]. Figure 3 shows the evolution of the 2 + 1 energies and of the reduced transition probabilities B(E2; 0 + 1 → 2 + 1 ) as a function of the neutron number in the 12 Mg, 14 Si, 16 S, 18 Ar and 20 Ca isotopes. At N = 20, the 2 + energies are high for all isotones, except for 32 20 Mg, in which a drop in energy is observed instead.…”

“…The result obtained when removing this tensor part is shown with a red line. The role of tensor forces is mainly seen at N = 28 seem to rise after N = 20, but not as much as in the 16 S one (see the right part of Figure 3). Whether the B(E2) values remain small, steadily increase up to N = 28, or follow a parabola cannot be judged at the present time as the quoted experimental error bars are too large.…”