First evidence of γ collectivity close to the doubly magic core Sn 132

Abstract

The Te138 and Xe140 nuclei have been reinvestigated using prompt γ-ray data from spontaneous fission of Cm248, collected with the EUROGAM2 Ge array. γ bands have been identified in both nuclei. The γ band observed in Te138, a nucleus with only six valence nucleons, indicates the presence of collectivity very close to the doubly magic Sn132 core. Such band is even more pronounced in Xe140, the N = 86 isotone of Te138. The newly observed bands are interpreted within the shell model, which reproduce well the γ collectivity at N = 86.