Relativistic RPA plus phonon-coupling analysis of pygmy dipole resonances

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dc.creatorLitvinova, E.
dc.creatorRing, P.
dc.creatorVretenar, D.
dc.date2007-01-17
dc.date.accessioned2026-07-07T11:03:29Z
dc.date.available2026-07-07T11:03:29Z
dc.descriptionThe 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.
dc.description17 pages, 3 figures, 4 tables
dc.identifierhttps://arxiv.org/abs/nucl-th/0701046
dc.identifierhttp://arxiv.org/abs/nucl-th/0701046
dc.identifierPhys.Lett.B647:111-117,2007
dc.identifierdoi:10.1016/j.physletb.2007.01.056
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/188608
dc.subjectNuclear Theory
dc.titleRelativistic RPA plus phonon-coupling analysis of pygmy dipole resonances
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