Pygmy dipole mode in deformed neutron-rich Mg isotopes close to the drip line

Journal Article · Thu Oct 15 00:00:00 EDT 2009 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.80.044324· OSTI ID:21293937

Yoshida, Kenichi ^[1]

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1. RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama 351-0198 (Japan)

We investigate the microscopic structure of the low-lying isovector-dipole excitation mode in neutron-rich {sup 36,38,40}Mg close to the drip line by means of the deformed quasiparticle random-phase approximation employing the Skyrme and the local pairing energy-density functionals. It is found that the low-lying bump structure above the neutron emission-threshold energy develops when the drip line is approached, and that the isovector dipole strength at E{sub x}<10 MeV exhausts about 6.0% of the classical Thomas-Reiche-Kuhn dipole sum rule in {sup 40}Mg. We obtained the collective dipole modes at around 8-10 MeV in Mg isotopes, that consist of many two-quasiparticle excitations of the neutron. The transition density clearly shows an oscillation of the neutron skin against the isoscalar core. We found significant coupling effects between the dipole and octupole excitation modes due to the nuclear deformation. It is also found that the responses for the compressional dipole and isoscalar octupole excitations are much enhanced in the lower energy region.

• OSTI ID: 21293937
• Journal Information: Physical Review. C, Nuclear Physics, Vol. 80, Issue 4; Other Information: DOI: 10.1103/PhysRevC.80.044324; (c) 2009 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
COUPLING
DIPOLES
EXCITATION
FUNCTIONALS
ISOVECTORS
MAGNESIUM 36
MAGNESIUM 38
MAGNESIUM 40
MEV RANGE 01-10
NEUTRON EMISSION
NEUTRONS
NUCLEAR DEFORMATION
OCTUPOLES
OSCILLATIONS
PAIRING ENERGY
RANDOM PHASE APPROXIMATION
SKIN
SKYRME POTENTIAL
SUM RULES
THRESHOLD ENERGY