Is the nuclear spin-orbit interaction changing with neutron excess?
The energy difference of lowest states outside Z = 50 closed proton shell which increased with neutron excess was analyzed. The Sn(α,t) reaction for stable even Sn isotopes was measured and spectroscopic factors were constant for the lowest states. The energy difference was found in consistence with decrease in nuclear spin-orbit interaction. The spin-orbit interaction was sensitive to changes in region of radial distribution of core nucleons.