Isoscalar and Isovector Splitting of Pygmy Dipole Structures

Journal Article · Fri Jul 17 04:00:00 EDT 2009 · Physical Review Letters

DOI:https://doi.org/10.1103/PHYSREVLETT.103.032502· OSTI ID:21347058

Paar, N; Vretenar, D ^[1]; Niu, Y F ^[1]; Meng, J ^[2]

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1. Physics Department, Faculty of Science, University of Zagreb (Croatia)
2. State Key Laboratory for Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China)

The electric-dipole response of {sup 140}Ce is investigated using the fully consistent relativistic quasiparticle random phase approximation. By analyzing the isospin structure of the E1 response, it is shown that the low-energy (pygmy) strength separates into two segments with different isospin character. The more pronounced pygmy structure at lower energy is composed of predominantly isoscalar states with surface-peaked transition densities. At somewhat higher energy the calculated E1 strength is primarily of isovector character, as expected for the low-energy tail of the giant dipole resonance. The results are in qualitative agreement with those obtained in recent (gamma, gamma{sup '}) and (alpha, alpha{sup '}gamma) experiments, and provide a simple explanation for the splitting of low-energy E1 strength into two groups of states with different isospin structure and radial dependence of the corresponding transition densities.

• OSTI ID: 21347058
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 3 Vol. 103; ISSN 0031-9007; ISSN PRLTAO
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
APPROXIMATIONS
CALCULATION METHODS
CERIUM 140
CERIUM ISOTOPES
DIPOLES
ELECTRIC DIPOLES
ENERGY RANGE
EVEN-EVEN NUCLEI
INTERMEDIATE MASS NUCLEI
ISOSPIN
ISOTOPES
ISOVECTORS
MULTIPOLES
NUCLEI
PARTICLE PROPERTIES
RANDOM PHASE APPROXIMATION
RARE EARTH NUCLEI
RELATIVISTIC RANGE
RESONANCE
STABLE ISOTOPES
TENSORS
VECTORS