Continuum Coupling and Pair Correlation in Weakly Bound Deformed Nuclei

The RI-beam facilities in the new generation will increase significantly the number of experimentally accessible nuclei, especially in medium and heavy mass regions. We may reach nuclei close to the neutron drip-line in the 10 ≤ Z ≤ 20 and N ≥ 20 region, where a bunch of deformed neutron-rich nuclei are expected1. This will provide us with a new opportunity to study interplay among the presence of weakly bound neutrons, the coupling to nuclear deformation effects, the pairing correlation, and the collective excitations. A promising theoretical framework to describe this situation may be the selfconsistent mean-field approaches.2 More specifically, we consider here the HartreeFock-Bogoliubov (HFB) method to construct the pair-correlated and deformed ground state, and the quasiparticle random phase approximation (QRPA) to describe the excitation modes built on the ground state. As commonly recognized, one has to describe precisely the nucleon wave function of weakly bound and unbound orbits, which should have proper asymptotic behaviours. There exist such formulations for spherical nuclei,3,4,5,6,7 but a new challenge here is that we have to do it for deformed nuclei. A method using the Pöschel-Teller-Ginocchio basis is proposed recently8. The quasiparticle motion in deformed Woods-Saxon potential is analyzed in detail in the coupled-channel formalism.9 We here take a slightly different approach based on the coordinate-space Green’s function technique since we plan to apply it also to the continuum QRPA6. In the present work, we shall