  Single particle spin-orbit interaction energy problem in nuclear shell
structure is solved through negative harmonic oscillator in the
self-similar-structure shell model (SSM) [4] and considering quarks'
contributions on single particle spin and orbit momentum. The paper
demonstrates that single particle motion in normal nuclei is described better
by SSM negative harmonic oscillator than conventional shell model positive
harmonic oscillator[1][2][3]. The proposed theoretical formula for spin orbit
interaction energy agrees well to experiment measurements.
