Darmstadt 2008 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 8: Kernphysik / Spektroskopie
HK 8.2: Talk
Monday, March 10, 2008, 14:15–14:30, 2G
Pygmy Dipole Strength in Exotic Nuclei. — •Nadia Tsoneva und Horst Lenske — Institut für Theoretische Physik, Universität Gießen
By incorporating HFB calculations for the nuclear ground states and
describing excited states by QPM theory we investigate low-energy
dipole excitations in spherical N=50, N=82 isotones and the Z=50
isotopes, known as Pygmy Dipole Resonances (PDR). The approach relies
on density functional theory providing us with the proper link between
a phenomenological description of nuclear ground state properties and
nuclear many-body theory. The properties of PDR excitations are
studied in detail by analyzing the corresponding neutron and proton
dipole transition densities from which we derive criteria for these
dipole excitations as generic modes in charge-asymmetric exotic
nuclei. From one-phonon QRPA calculations in N=50, N=82 and
110−132Sn nuclei (N>Z) a close connection between the total
neutron PDR strengths and the neutron skin thickness defined by the
relative difference of neutron and proton rms radii was found. An
interesting observation is the most exotic 100Sn nucleus (N=Z),
where at E*=8.3 MeV a state dominated by proton skin excitations was
found, hence indicating a proton PDR. The fragmentation pattern of the
low-energy dipole excitations is studied by multi-phonon QPM
theory. For that purpose we have performed calculations in large model
spaces including up to three-phonon components. The results are
compared to a variety of experimental data which are described rather
satisfactorily.
Supported by DFG, contract Le439/5 and GSI.