Decay dynamics of the unbound ${}^{25}$O and ${}^{26}$O nuclei

Abstract

We study the ground and excited resonance states of ${}^{26}$O with a three-body model of ${}^{24}$O+n+n taking into account the coupling to the continuum. To this end, we use the new experimental data for the invariant mass spectroscopy of the unbound ${}^{25}$O and ${}^{26}$O nuclei, and present an update of three-body model calculations for the two-neutron decay of the ${}^{26}$O nucleus. With the new model inputs determined with the ground state decay of ${}^{26}$O, we discuss the di-neurtron correlations and a halo nature of this nucleus, as well as the structure of the excited states. For the energy of the 2${}^{+}$ state, we achieve an excellent agreement with the experimental data with this calculation. We show that the 2${}^{+}$ state consists predominantly of the $(d_{3/2}{)}^2$ configuration, for which the pairing interaction between the valence neutrons slightly decreases its energy from the unperturbed one. We also discuss the structure of excited 0${}^{+}$ states of the ${}^{26}$O nucleus. In particular, we show the existence of an excited 0${}^{+}$ state at 3.38 MeV, which is mainly composed of the $(f_{7/2}{)}^2$ configuration.

Comments: 12 pages, 13 figures. To appear in Phys. Rev. C