Abstract
We present an extensive experimental study of the recently predicted pygmy quadrupole resonance (PQR) in Sn isotopes, where complementary probes were used. In this study, (α, α'γ ) and (γ , γ') experiments were performed on 124Sn. In both reactions, Jπ = 2+ states below an excitation energy of 5MeV were populated. The E2 strength integrated over the full transition densities could be extracted from the (γ , γ') experiment, while the (α, α'γ ) experiment at the chosen kinematics strongly favors the excitation of surface modes because of the strong α-particle absorption in the nuclear interior. The excitation of such modes is in accordance with the quadrupole-type oscillation of the neutron skin predicted by a microscopic approach based on self-consistent density functional theory and the quasiparticle-phonon model (QPM). The newly determined γ -decay branching ratios hint at a non-statistical character of the E2 strength, as it has also been recently pointed out for the case of the pygmy dipole resonance (PDR). This allows us to distinguish between PQR-type and multiphonon excitations and, consequently, supports the recent first experimental indications of a PQR in 124Sn.
Original language | English |
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Pages (from-to) | 102-107 |
Number of pages | 6 |
Journal | Physics Letters B |
Volume | 752 |
DOIs | |
State | Published - 10 Jan 2016 |