Theory 12/Nuclear Structure
Shells Close at an Asymmetry
The claim
Nuclear shell closures shift with neutron-proton asymmetry rather than being fixed by magic numbers, so a number that is magic in one isotope is not in another.
01The mechanism
The spin-orbit and tensor terms depend on the neutron excess, which moves the level spacing; closures are therefore contours in the nuclear chart rather than constants.
02Predictions
- P1Magic numbers should shift with asymmetry.
- P2Shell gaps should track the tensor term.
03Refutation
Magic numbers invariant across the chart would remove the asymmetry dependence.