Darmstadt 2016 – scientific programme
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HK: Fachverband Physik der Hadronen und Kerne
HK 28: Structure and Dynamics of Nuclei VII
HK 28.2: Talk
Tuesday, March 15, 2016, 17:00–17:15, S1/01 A04
Pygmy quadrupole resonance as a manifestation of the nuclear skin — •Nadia Tsoneva1,2 and Horst Lenske2 — 1Frankfurt Institute for Advanced Studies (FIAS), 60438 Frankfurt am Main, Germany — 2Institut fur Theoretische Physik, Universität Gießen, Heinrich-Buff-Ring 16, D-35392 Gieβen, Germany
Recently, a new mode of nuclear excitation called pygmy quadrupole resonance (PQR) was theoretically predicted in the framework of energy-density functional (EDF) theory plus three-phonon quasiparticle-phonon model (QPM) in Sn isotopic chain. It is closely connected with higher order multipole vibrations of nuclear skin induced by the action of the electromagnetic and hadronic external fields. The predictions initiated new experiments using (17O,17O′γ), (α,α′γ) and (γ,γ′) reactions which were carried out in 124Sn nucleus. The aim was to probe for the first time experimentally, the possibility of existence of PQR. The detailed analysis of the obtained experimental results in comparison with the EDF+QPM theory indicates clearly the presence of a multitude of discrete low-energy 2+ excitations of neutron type which can be addressed to PQR mode. The independent measurements of B(E2) values with different probes and the theory allow to identify the dominant isoscalar character of these states. Furthermore, newly determined γ-decay branching ratios exclude a statistical origin of the PQR strength. The latter are important to discriminate between PQR and multiphonon excitations.
The work is supported by the HIC for FAIR within the framework of the LOEWE program.