dorsal/arxiv
View SchemaRelativistic RPA plus phonon-coupling analysis of pygmy dipole resonances
| Authors | E. Litvinova, P. Ring, D. Vretenar |
|---|---|
| Categories | |
| ArXiv ID | nucl-th/0701046 |
| URL | https://arxiv.org/abs/nucl-th/0701046 |
| DOI | 10.1016/j.physletb.2007.01.056 |
| Journal | Phys.Lett.B647:111-117,2007 |
Abstract
The relativistic random-phase approximation (RRPA) plus phonon-coupling (PC) model is applied in the analysis of E1 strength distributions in $^{208}$Pb and $^{132}$Sn, for which data on pygmy dipole resonances (PDR) have recently been reported. The covariant response theory is fully consistent: the effective nuclear interaction NL3 is used both to determine the spectrum of single-nucleon Dirac states, and as the residual interaction which determines the collective phonon states in the relativistic RPA. It is shown that the picture of the PDR as a resonant oscillation of the neutron skin against the isospin saturated proton-neutron core, and with the corresponding RRPA state characterized by a coherent superposition of many neutron particle-hole configurations, remains essentially unchanged when particle-vibration coupling is included. The effect of two-phonon admixtures is a weak fragmentation and a small shift of PDR states to lower excitation energy. Even though the PDR calculated in the extended model space of $ph \otimes$phonon configurations contains sizeable two-phonon admixtures, it basically retains a one-phonon character and its dynamics is not modified by the coupling to low-lying surface vibrations.
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"abstract": "The relativistic random-phase approximation (RRPA) plus phonon-coupling (PC)\nmodel is applied in the analysis of E1 strength distributions in $^{208}$Pb and\n$^{132}$Sn, for which data on pygmy dipole resonances (PDR) have recently been\nreported. The covariant response theory is fully consistent: the effective\nnuclear interaction NL3 is used both to determine the spectrum of\nsingle-nucleon Dirac states, and as the residual interaction which determines\nthe collective phonon states in the relativistic RPA. It is shown that the\npicture of the PDR as a resonant oscillation of the neutron skin against the\nisospin saturated proton-neutron core, and with the corresponding RRPA state\ncharacterized by a coherent superposition of many neutron particle-hole\nconfigurations, remains essentially unchanged when particle-vibration coupling\nis included. The effect of two-phonon admixtures is a weak fragmentation and a\nsmall shift of PDR states to lower excitation energy. Even though the PDR\ncalculated in the extended model space of $ph \\otimes$phonon configurations\ncontains sizeable two-phonon admixtures, it basically retains a one-phonon\ncharacter and its dynamics is not modified by the coupling to low-lying surface\nvibrations.",
"arxiv_id": "nucl-th/0701046",
"authors": [
"E. Litvinova",
"P. Ring",
"D. Vretenar"
],
"categories": [
"nucl-th"
],
"doi": "10.1016/j.physletb.2007.01.056",
"journal_ref": "Phys.Lett.B647:111-117,2007",
"title": "Relativistic RPA plus phonon-coupling analysis of pygmy dipole resonances",
"url": "https://arxiv.org/abs/nucl-th/0701046"
},
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