Multitude of 2+ discrete states in Sn 124 observed via the (O 17, O ′ 17 γ) reaction: Evidence for pygmy quadrupole states

A multitude of discrete 2+ states in Sn124 with energy up to 5 MeV were populated and identified with the (O17, O′17γ) 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. © 2015 American Physical Society.