The magnetic dipolar splitting of a $p$-wave Feshbach resonance is governed by the spin-orbital configuration of the valence electrons in the triplet molecular state. We perform high-resolution trap-loss spectroscopy on ultracold ${}^6\mathrm{Li}$ atoms to resolve this splitting with sub-milligauss precision. By comparing electron-spin-polarized ($|m_S|=1$) and electron-spin-mixture ($m_S=0$) configurations of the triplet state, we observe a clear spin-dependent reversal in the splitting structure, confirmed via momentum-resolved absorption imaging. This behavior directly reflects the interplay between electron spin projection $m_S$ and orbital angular momentum $m_{\ell }$ in the molecular states. Our results provide a stringent benchmark for dipole-dipole interaction models and lay the groundwork for controlling the pairing in $p$-wave superfluid systems.

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• Ultracold collisions
• Feshbach resonance