Three-body model calculation of the 2^+ state in ²⁶O

We discuss the energy of the excited 2$^+$ state in the unbound nucleus $^{26}$O using the three-body model of $^{24}$O+$n$+$n$. This model fully takes into account the continuum effects as well as the dineutron correlation of the valence neutrons. The present calculation yields the energy of 1.354 MeV, which is slightly smaller than the unperturbed energy, 1.54 MeV. The energy shifts for the ground and the 2$^+$ states with respect to the unperturbed energy suggest that 0$^+$ and the 2$^+$ states in $^{26}$O show a typical spectrum well described by a short-range pairing interaction acting on two valence nucleons in the same orbit.