Coupled-channel picture of the core nucleus for the expansion of the nuclear size in the drip-line region

Abstract

We study the energy and radius of neutron rich nuclei toward to the drip-line region. We employ the cluster-orbital shell model approach to calculate the radius of the oxygen isotopes. The result shows that the calculated radius underestimates the observed one at 23O, though the binding energy and the drip-line of the oxygen isotopes are reproduced. Therefore, we propose a coupled-channel approach to explain the sudden increase of the radius of the oxygen isotopes at 23O. As a result, the sudden change of the radius can be descried in terms of the competition between the available valence neutron orbits and occupied orbits in the core nucleus. For the 23O case, we show that the excitation to the 1s1/2-orbit in the core nucleus is a key configuration to reproduce the radius.