Theory 13/Atomic Physics
Isotope Shifts Bend
The claim
Isotope shifts in heavy atoms become nonlinear at a critical neutron number because the nuclear charge radius changes shape, not just size, so a linear extraction of radius misleads.
01The mechanism
The field shift is proportional to the change in mean square radius, but deformation adds a shape term that becomes significant as the neutron number passes a shell.
02Predictions
- P1Nonlinearity should appear at a shell crossing.
- P2Linear fits should fail for heavy isotopes.
03Refutation
Shifts remaining linear across the chart would remove the shape term.