Skyrme-QRPA calculations for low-lying excitation modes in deformed neutron-rich nuclei
Abstract
Low-frequency modes of excitation in deformed neutron-rich nuclei are studied by means of the quasiparticle random-phase approximation on the Skyrme-Hartree-Fock-Bogoliubov mean field. We investigate the microscopic structure of the soft Kπ=0+ modes systematically in neutron-rich Magnesium isotopes with N=22, 24, 26 and 28 close to the drip line, and it is found that the strong collectivity in 34Mg and 40Mg is acquired due to the coherent coupling between the β vibration and the pairing vibration of neutrons. Microscopic structure of the Kπ=2+ modes changes gradually associated with the location of the Fermi level of neutrons, and it is found that the proton particle-hole excitation generating the γ-vibrational mode in 24Mg continues to play a key role in the near-drip-line nucleus 40Mg. The low-frequency octupole excitations are also investigated and the microscopic mechanism for the enhancement of transition strengths is discussed.