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Dinucleon correlation of $^9$Li, $^{10}$Be, and $^{9,10}$C

We study the dinucleon (dineutron and diproton) correlation of the ground states of $^9$Li, $^{10}$Be, and $^{9,10}$C. We assume an $α+t$ core for $^9$Li, an $α+α$ core for $^{10}$Be and $^{10}$C, and an $α+^3$He core for $^9$C, and investigate the effect of core structure changes on the degree of dineutron formation and spatial expansion from the core. For $^9$Li, $t$ cluster breaking in the core significantly enhances the dineutron component inside the nuclei. Moreover, its component markedly depends on the strength of the spin-orbit interaction since a dineutron is fragile and dissociates readily due to the spin-orbit interaction. Compared with $^9$Li, the dineutron of $^{10}$Be dissociates largely due to the stronger spin-orbit attraction from the $α+α$ core than the $α+t$ core. We also investigate diproton features in $^{9,10}$C, the mirror nuclei of $^9$Li and $^{10}$Be, respectively, and compare them with the dineutron features of $^9$Li and $^{10}$Be. No qualitative difference is observed between diprotons and dineutrons in the degree of formation at the surface, but a quantitative difference may exist in the degree of dinucleon-size change far from the core.