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Erice, 16. - 24. September 2006 School on nuclear physics ‘`Radioactive Beams, Nuclear Dynamics and Nuclear Astro Physics‘. Theory of Pygmy Dipole Resonances in Exotic Nuclei. N. Tsoneva, H. Lenske. Institut für Theoretische Physik, Universität Giessen, Germany.
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Erice, 16. - 24. September 2006 School on nuclear physics ‘`Radioactive Beams, Nuclear Dynamics and Nuclear Astro Physics‘ Theory of Pygmy Dipole Resonances in Exotic Nuclei N. Tsoneva, H. Lenske Institut für Theoretische Physik, Universität Giessen, Germany
Electric Dipole Response of the Nucleus A. Zilges et al., ISNSP, Götingen, 2001
The Quasiparticle-Phonon Model V. G. Soloviev: Quasiparticles and Phonons, 1989
Ground state properties of Sn isotopes F. Hofmann and H. Lenske, Phys. Rev. C 57 (1998) 2281. N. Tsoneva, H. Lenske, Ch. Stoyanov, Phys. Lett. B 586 (2004) 213.
Calculation of ground state densities in Sn isotopes Radial distance (fm)
QMP calculations of dipole excitations below the particle threshold in comparison with experimental data / S. Volz et al., Nucl. Phys. Ain press /.
QRPA calculations of the total PDR strength (E*=0-8 MeV) in N=82 isotones A possible connection between the total PDR strength and the neutron skin thickness • Proton number increasing • Neutron skin decreasing S. Volz et al., Nucl. Phys. A, in press.
The Dipole Response in Sn Isotopes PDR PDR PDR
Calculations of one-phonon dipole transition densities in Sn isotopes
QRPA calculations of the total PDR strength in Z=50 Sn nuclei A possible connection between the total PDR strength and the neutron skin thickness Exp. in Sn-116 and Sn-124: K. Govaert et al, Phys. Rev. C 57 (1998) 2229. Exp. in Sn-112, B. Ozel et al, private communications.
Conclusions and outlook • The analysis of the corresponding neutron and proton transition densities in the mass region 110Sn-132Sn indicates almost pure neutron oscillations at the nuclear surface such that a PDR can be identified. • A close correlation between the total PDR strength and the size of the neutron skin is found. • The transition densities act as clear theoretical indicators characterizing the new quality of the PDR mode as a distinct and unique excitation, different from the well known GDR. • An interesting result is the observation that the neutron PDR strength in Z=50 nuclei changes gradually and smoothly with the neutron number and in 110Sn it completely vanishes. For the semimagic nuclei 100Sn,102Sn and 104Sn a proton PDR has been identified. • The calculations are compared to available data from photon scattering experiments for a number of Sn isotopes and members of the N=82 isotonic chain. A good agreement is obtained.
QRPA calculations of low-energy dipole states in N=82 nuclei S. Volz et al., Nucl. Phys. A, in press.
Structure and transitions probabilities of PDR states in Sn isotopes