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AGATA Collaboration(Pellegri, L. et al), & Gadea, A. (2014). Pygmy dipole resonance in Sn-124 populated by inelastic scattering of O-17. Phys. Lett. B, 738, 519–523.
Abstract: The gamma decay from the high-lying states of Sn-124 was measured using the inelastic scattering of O-17 at 340 MeV. The emitted gamma rays were detected with high resolution with the AGATA demonstrator array and the scattered ions were detected in two segmented Delta E-E silicon telescopes. The angular distribution was measured both for the gamma rays and the scattered O-17 ions. An accumulation of E1 strength below the particle threshold was found and compared with previous data obtained with (gamma,gamma') and (alpha,alpha'gamma) reactions. The present results of elastic scattering, and excitation of E2 and E1 states were analysed using the DWBA approach. From this comprehensive description the isoscalar component of the 1-excited states was extracted. The obtained values are based on the comparison of the data with DWBA calculations including a form factor deduced using a microscopic transition density.
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Pellegri, L. et al, & Gadea, A. (2015). Multitude of 2(+) discrete states in Sn-124 observed via the (O-17, O-17 'gamma) reaction: Evidence for pygmy quadrupole states. Phys. Rev. C, 92(1), 014330–7pp.
Abstract: A multitude of discrete 2(+) states in Sn-124 with energy up to 5 MeV were populated and identified with the (O-17, O-17'gamma) reaction at 340 MeV. Cross sections were compared with distorted wave Born approximation predictions and in general a good agreement was found. The measured energy and intensity distributions of the 2(+) states are very similar to the predictions based on self-consistent density functional theory and extended QRPA approach accounting for multiphonon degrees of freedom. This provides evidence of the excitation of the pygmy quadrupole resonance in skin nuclei.
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