Experimental Study of the Two-Body Spin-Orbit Force in Nuclei

This is the authors' abstract. We don't add key points for this paper.

Energies and spectroscopic factors of the first 7/2^-, 3/2^-, 1/2^-, and 5/2^- states in the ³⁵Si₂₁ nucleus were determined by means of the (d, p) transfer reaction in inverse kinematics at GANIL using the MUST2 and EXOGAM detectors. By comparing the spectroscopic information on the ³⁵Si and ³⁷S isotones, a reduction of the p3/2-p1/2 spin-orbit splitting by about 25% is proposed, while the f7/2-f5/2 spin-orbit splitting seems to remain constant. These features, derived after having unfolded nuclear correlations using shell model calculations, have been attributed to the properties of the two-body spin-orbit interaction, the amplitude of which is derived for the first time in an atomic nucleus. The present results, remarkably well reproduced by using several realistic nucleon-nucleon forces, provide a unique touchstone for the modeling of the spin-orbit interaction in atomic nuclei.