Spin-Orbit Interaction in Nuclei

The spin-orbit interaction in nuclei is derived in terms of the two-body interaction between nuclear particles. A second order Born approximation with the tensor force gives an interaction of the right order of magnitude, but apparently somewhat too small. A more general approach using the two-body reaction matrix seems to predict the ${\mathrm{Ca}}^{41}$ and ${\mathrm{O}}^{17}$ level splittings. The Thomas interaction is seen to be small. The mixed density function for the nucleus is computed to evaluate the matrix elements.