Variation of Tensor Force due to Nuclear Medium Effect

The enhancement of $J^{\pi }(T)$=3${}^{+}$(0) state with isospin $T=0$ excited by the tensor force in the free ${}^6$Li nucleus has been observed, for the first time, relative to a shrinkable excitation in the ${}^6$Li cluster component inside its host nucleus. Comparatively, the excitation of $J^{\pi }(T)$=0${}^{+}$(1) state with isospin $T=1$ for these two ${}^6$Li formations take on an approximately equal excitation strength. The mechanism of such tensor force effect was proposed due to the intensive nuclear medium role on isospin $T$=0 state.