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Arsenyev N, Severyukhin A, Voronov V, Giai N. Microscopic description of the pygmy dipole resonance in neutron-rich Ca isotopes. EPJ WEB OF CONFERENCES 2018. [DOI: 10.1051/epjconf/201819404002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We study the effects of the phonon-phonon coupling on the low-energy electric dipole response within a microscopic model based on an effective Skyrme interaction. The finite rank separable approach for the quasiparticle random phase approximation is used. Choosing as an example the isotopic chain of Calcium, we show the ability of the method to describe the low-energy E1 strength distribution. With one and the same set of parameters we describe available experimental data for 48Ca and predict the electric dipole strength function for 50Ca.
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Tsoneva N, Lenske H. Impact of low-energy multipole excitations and pygmy resonances on radiative nucleon captures. EPJ WEB OF CONFERENCES 2016. [DOI: 10.1051/epjconf/201610705001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Lo Iudice N, Knapp F, Vesely P, Andreozzi F, De Gregorio G, Porrino A. Dipole response in neutron-rich nuclei within self-consistent approaches using realistic potentials. EPJ WEB OF CONFERENCES 2015. [DOI: 10.1051/epjconf/20159301018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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4
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Bracco A, Crespi F. Study of the γ decay of high-lying states in208Pb via inelastic scattering of17O ions. EPJ WEB OF CONFERENCES 2012. [DOI: 10.1051/epjconf/20123803001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Endres J, Litvinova E, Savran D, Butler PA, Harakeh MN, Harissopulos S, Herzberg RD, Krücken R, Lagoyannis A, Pietralla N, Ponomarev VY, Popescu L, Ring P, Scheck M, Sonnabend K, Stoica VI, Wörtche HJ, Zilges A. Isospin character of the pygmy dipole resonance in 124Sn. PHYSICAL REVIEW LETTERS 2010; 105:212503. [PMID: 21231295 DOI: 10.1103/physrevlett.105.212503] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Indexed: 05/30/2023]
Abstract
The pygmy dipole resonance has been studied in the proton-magic nucleus 124Sn with the (α, α'γ) coincidence method at Eα=136 MeV. The comparison with results of photon-scattering experiments reveals a splitting into two components with different structure: one group of states which is excited in (α, α'γ) as well as in (γ, γ') reactions and a group of states at higher energies which is only excited in (γ, γ') reactions. Calculations with the self-consistent relativistic quasiparticle time-blocking approximation and the quasiparticle phonon model are in qualitative agreement with the experimental results and predict a low-lying isoscalar component dominated by neutron-skin oscillations and a higher-lying more isovector component on the tail of the giant dipole resonance.
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Affiliation(s)
- J Endres
- Institut für Kernphysik, Universität zu Köln, Zülpicher Straße 77, D-50937 Köln, Germany.
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Wieland O, Bracco A, Camera F, Benzoni G, Blasi N, Brambilla S, Crespi FCL, Leoni S, Million B, Nicolini R, Maj A, Bednarczyk P, Grebosz J, Kmiecik M, Meczynski W, Styczen J, Aumann T, Banu A, Beck T, Becker F, Caceres L, Doornenbal P, Emling H, Gerl J, Geissel H, Gorska M, Kavatsyuk O, Kavatsyuk M, Kojouharov I, Kurz N, Lozeva R, Saito N, Saito T, Schaffner H, Wollersheim HJ, Jolie J, Reiter P, Warr N, deAngelis G, Gadea A, Napoli D, Lenzi S, Lunardi S, Balabanski D, LoBianco G, Petrache C, Saltarelli A, Castoldi M, Zucchiatti A, Walker J, Bürger A. Search for the pygmy dipole resonance in 68Ni at 600 MeV/nucleon. PHYSICAL REVIEW LETTERS 2009; 102:092502. [PMID: 19392515 DOI: 10.1103/physrevlett.102.092502] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2008] [Indexed: 05/27/2023]
Abstract
The gamma decay from Coulomb excitation of 68Ni at 600 MeV/nucleon on a Au target was measured using the RISING setup at the fragment separator of GSI. The 68Ni beam was produced by a fragmentation reaction of 86Kr at 900 MeV/nucleon on a 9Be target and selected by the fragment separator. The gamma rays produced at the Au target were measured with HPGe detectors at forward angles and with BaF2 scintillators at backward angles. The measured spectra show a peak centered at approximately 11 MeV, whose intensity can be explained in terms of an enhanced strength of the dipole response function (pygmy resonance). Such pygmy structure has been predicted in this unstable neutron-rich nucleus by theory.
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Affiliation(s)
- O Wieland
- INFN Sezione di Milano, I-20133 Milano, Italy
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Savran D, Fritzsche M, Hasper J, Lindenberg K, Müller S, Ponomarev VY, Sonnabend K, Zilges A. Fine structure of the pygmy dipole resonance in (136)Xe. PHYSICAL REVIEW LETTERS 2008; 100:232501. [PMID: 18643490 DOI: 10.1103/physrevlett.100.232501] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2008] [Indexed: 05/26/2023]
Abstract
The photoresponse of the semimagic N=82 nucleus (136)Xe was measured up to the neutron separation energy S(n) using the (gamma, gamma') reaction. A concentration of strong dipole excitations is observed well below S(n) showing a fragmented resonancelike structure. Microscopic calculations in the quasiparticle phonon model including complex configurations of up to three phonons agree well with the experimental data in the total integrated strength, in the shape and the fragmentation of the resonance, which allows us to draw conclusions on the damping mechanism of the pygmy dipole resonance.
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Affiliation(s)
- D Savran
- Institut für Kernphysik, TU Darmstadt, Darmstadt, Germany.
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Paar N, Vretenar D, Khan E, Colò G. Exotic modes of excitation in atomic nuclei far from stability. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2007; 70:R02. [PMID: 34996293 DOI: 10.1088/0034-4885/70/5/r02] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2006] [Indexed: 06/14/2023]
Abstract
We review recent studies of the evolution of collective excitations in atomic nuclei far from the valley of β-stability. Collective degrees of freedom govern essential aspects of nuclear structure, and for several decades the study of collective modes such as rotations and vibrations has played a vital role in our understanding of complex properties of nuclei. The multipole response of unstable nuclei and the possible occurrence of new exotic modes of excitation in weakly bound nuclear systems, present a rapidly growing field of research, but only few experimental studies of these phenomena have been reported so far. Valuable data on the evolution of the low-energy dipole response in unstable neutron-rich nuclei have been gathered in recent experiments, but the available information is not sufficient to determine the nature of observed excitations. Even in stable nuclei various modes of giant collective oscillations had been predicted by theory years before they were observed, and for that reason it is very important to perform detailed theoretical studies of the evolution of collective modes of excitation in nuclei far from stability. We therefore discuss the modern theoretical tools that have been developed in recent years for the description of collective excitations in weakly bound nuclei. The review focuses on the applications of these models to studies of the evolution of low-energy dipole modes from stable nuclei to systems near the particle emission threshold, to analyses of various isoscalar modes, those for which data are already available, as well as those that could be observed in future experiments, to a description of charge-exchange modes and their evolution in neutron-rich nuclei, and to studies of the role of exotic low-energy modes in astrophysical processes.
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Affiliation(s)
- Nils Paar
- Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstrasse 9, Darmstadt D-64289, Germany
- Physics Department, Faculty of Science, University of Zagreb, Bijenička 32, Zagreb 10000, Croatia
| | - Dario Vretenar
- Physics Department, Faculty of Science, University of Zagreb, Bijenička 32, Zagreb 10000, Croatia
| | - Elias Khan
- Institut de Physique Nucléaire, IN2P3-CNRS/Université Paris-Sud, Orsay 91406, France
| | - Gianluca Colò
- Dipartimento di Fisica dell'Università degli Studi and INFN, Sezione di Milano, via Celoria 16, Milano 20133, Italy
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Savran D, Babilon M, van den Berg AM, Harakeh MN, Hasper J, Matic A, Wörtche HJ, Zilges A. Nature of the pygmy dipole resonance in 140Ce studied in (alpha, alpha' gamma) experiments. PHYSICAL REVIEW LETTERS 2006; 97:172502. [PMID: 17155468 DOI: 10.1103/physrevlett.97.172502] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2006] [Indexed: 05/12/2023]
Abstract
A concentration of electric-dipole excitations below the particle threshold, which is frequently denoted as the pygmy dipole resonance, has been studied in the semimagic nucleus 140Ce in (alpha, alpha' gamma) experiments at E alpha = 136 MeV. The technique of alpha-gamma coincidence experiments allows the separation of E1 excitations from states of other multipolarities in the same energy region and provides an excellent energy resolution to allow a detailed analysis for each state. The experimental results show that the PDR splits into two parts with different nuclear structure: one part which is excited in (alpha, alpha' gamma) as well as (gamma, gamma') experiments and one part which is excited only in (gamma, gamma').
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Affiliation(s)
- D Savran
- Institut für Kernphysik, TU Darmstadt, Schlossgartenstrasse 9, D-64289 Darmstadt, Germany.
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Paar N, Vretenar D, Ring P. Proton electric pygmy dipole resonance. PHYSICAL REVIEW LETTERS 2005; 94:182501. [PMID: 15904364 DOI: 10.1103/physrevlett.94.182501] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2005] [Indexed: 05/02/2023]
Abstract
The evolution of the low-lying E1 strength in proton-rich nuclei is analyzed in the framework of the self-consistent relativistic Hartree-Bogoliubov model and the relativistic quasiparticle random-phase approximation (RQRPA). Model calculations are performed for a series of N=20 isotones and Z=18 isotopes. For nuclei close to the proton drip line, the occurrence of pronounced dipole peaks is predicted in the low-energy region below 10 MeV excitation energy. From the analysis of the proton and neutron transition densities and the structure of the RQRPA amplitudes, it is shown that these states correspond to the proton pygmy dipole resonance.
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Affiliation(s)
- N Paar
- Institut für Kernphysik, Technische Universität Darmstadt, Schlossgartenstrasse 9, D-64289 Darmstadt, Germany
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