First spectroscopic information from even-even nuclei in the region "southeast" of Sn 132: Neutron-excitation dominance of the 21+ state in Cd 132

The neutron-rich nucleus Cd132 has been studied at the RIKEN Radioactive Isotope Beam Factory using in-beam γ-ray spectroscopy with two-proton removal reactions from Sn134. A γ-ray transition was observed at 618(8) keV and was assigned to the 21+→0g.s.+ decay. The 21+ state provides the first spectroscopic information from the even-even nuclei located in the region "southeast" of the doubly magic nucleus Sn132. By comparing with the 21+ excitation energies in the semimagic nuclei Sn134 and Cd130, it is found that neutron excitations dominate the 21+ state in Cd132, in a similar manner to Te136. The results are discussed in terms of proton-neutron configuration mixing. © 2016 American Physical Society.