Information content of the low-energy electric dipole strength: Correlation analysis

被引:81
作者
Reinhard, P. -G. [1 ]
Nazarewicz, W. [2 ,3 ,4 ]
机构
[1] Univ Erlangen Nurnberg, Inst Theoret Phys 2, D-91058 Erlangen, Germany
[2] Univ Tennessee, Dept Phys & Astron, Knoxville, TN 37996 USA
[3] Oak Ridge Natl Lab, Div Phys, Oak Ridge, TN 37831 USA
[4] Univ Warsaw, Inst Theoret Phys, PL-00681 Warsaw, Poland
来源
PHYSICAL REVIEW C | 2013年 / 87卷 / 01期
关键词
GIANT-RESONANCES; SUM-RULES; NUCLEI; ISOSCALAR; NEUTRON; MODES; RPA;
D O I
10.1103/PhysRevC.87.014324
中图分类号
O57 [原子核物理学、高能物理学];
学科分类号
070202 ;
摘要
Background: Recent experiments on the electric dipole (E1) polarizability in heavy nuclei have stimulated theoretical interest in the low-energy electric dipole strength, both isovector and isoscalar. Purpose: We study the information content carried by the electric dipole strength with respect to isovector and isoscalar indicators characterizing bulk nuclear matter and finite nuclei. To separate isoscalar and isovector modes, and low-energy strength and giant resonances, we analyze the E1 strength as a function of the excitation energy E and momentum transfer q. Methods: We use the self-consistent nuclear density functional theory with Skyrme energy density functionals, augmented by the random phase approximation, to compute the E1 strength and covariance analysis to assess correlations between observables. Calculations are performed for the spherical, doubly magic nuclei Pb-208 and Sn-132. Results: We demonstrate that E1 transition densities in the low-energy region below the giant dipole resonance exhibit appreciable state dependence and multinodal structures, which are fingerprints of weak collectivity. The correlation between the accumulated low-energy strength and the symmetry energy is weak, and dramatically depends on the energy cutoff assumed. On the other hand, a strong correlation is predicted between isovector indicators and the accumulated isovector strength at E around 20 MeV and momentum transfer q similar to 0.65 fm(-1). Conclusions: Momentum-and coordinate-space patterns of the low-energy dipole modes indicate a strong fragmentation into individual particle-hole excitations. The global measure of low-energy dipole strength correlates poorly with the nuclear symmetry energy and other isovector characteristics. Consequently, our results do not support the suggestion that there exists a collective "pygmy dipole resonance," which is a strong indicator of nuclear isovector properties. By considering nonzero values of momentum transfer, one can isolate individual excitations and nicely separate low-energy excitations from the T = 1 and T = 0 giant collective modes. That is, measurements at q > 0 may serve as a tool to correlate the E1 strength with certain bulk observables, such as incompressibility and symmetry energy. DOI: 10.1103/PhysRevC.87.014324
引用
收藏
页数:9
相关论文
共 59 条
[1]   Evidence for pygmy and giant dipole resonances in 130Sn and 132Sn -: art. no. 132501 [J].
Adrich, P ;
Klimkiewicz, A ;
Fallot, M ;
Boretzky, K ;
Aumann, T ;
Cortina-Gil, D ;
Pramanik, UD ;
Elze, TW ;
Emling, H ;
Geissel, H ;
Hellström, M ;
Jones, KL ;
Kratz, JV ;
Kulessa, R ;
Leifels, Y ;
Nociforo, C ;
Palit, R ;
Simon, H ;
Surówka, G ;
Sümmerer, K ;
Walus, W .
PHYSICAL REVIEW LETTERS, 2005, 95 (13)
[2]  
[Anonymous], 2000, NUCL MANY BODY PROBL
[3]   Pygmy dipole resonance: Collective features and symmetry energy effects [J].
Baran, V. ;
Frecus, B. ;
Colonna, M. ;
Di Toro, M. .
PHYSICAL REVIEW C, 2012, 85 (05)
[4]   Self-consistent mean-field models for nuclear structure [J].
Bender, M ;
Heenen, PH ;
Reinhard, PG .
REVIEWS OF MODERN PHYSICS, 2003, 75 (01) :121-180
[5]  
Bohr A., 1975, NUCL STRUCTURE, VII
[6]   EFFECT OF PIGMY RESONANCE ON CALCULATIONS OF NEUTRON CAPTURE CROSS SECTION [J].
BRZOSKO, JS ;
GIERLIK, E ;
SOLTAN, A ;
WILHELMI, Z .
CANADIAN JOURNAL OF PHYSICS, 1969, 47 (24) :2849-&
[7]   Constraints on the symmetry energy and neutron skins from pygmy resonances in 68Ni and 132Sn [J].
Carbone, Andrea ;
Colo, Gianluca ;
Bracco, Angela ;
Cao, Li-Gang ;
Bortignon, Pier Francesco ;
Camera, Franco ;
Wieland, Oliver .
PHYSICAL REVIEW C, 2010, 81 (04)
[8]   Convergence of Density-Matrix Expansions for Nuclear Interactions [J].
Carlsson, B. G. ;
Dobaczewski, J. .
PHYSICAL REVIEW LETTERS, 2010, 105 (12)
[9]   Impact of the nuclear symmetry energy on the pygmy dipole resonance [J].
Daoutidis, I. ;
Goriely, S. .
PHYSICAL REVIEW C, 2011, 84 (02)
[10]   Structure of the pygmy dipole resonance in 124Sn [J].
Endres, J. ;
Savran, D. ;
Butler, P. A. ;
Harakeh, M. N. ;
Harissopulos, S. ;
Herzberg, R. -D. ;
Kruecken, R. ;
Lagoyannis, A. ;
Litvinova, E. ;
Pietralla, N. ;
Ponomarev, V. Yu. ;
Popescu, L. ;
Ring, P. ;
Scheck, M. ;
Schlueter, F. ;
Sonnabend, K. ;
Stoica, V. I. ;
Woertche, H. J. ;
Zilges, A. .
PHYSICAL REVIEW C, 2012, 85 (06)