Two-Nucleon Interaction from Doublet Splittings

The splitting of closely spaced doublet levels, of spin $J+\frac{1}{2}$ and $J-\frac{1}{2}$, is investigated in cases which can be approximated by a core of spin $J$ and an $s$ nucleon. Allowance is made for the Thomas shifts of the levels. Using $j-j$ coupling wave functions, the exchange parameters and strength of the effective interaction between nucleons in the nucleus are determined by a least-squares fit to the doublet splittings and give some improvement over results obtained with previously accepted parameters. It is suggested that measurement of the sign of some doublet splittings would clarify the interaction further.