Coulomb excitation of 80Sr and the limits of the N ≈ Z ≈ 40 island of deformation

The region of N ≈ Z ≈ 40 has long been associated with strongly deformed nuclear configurations. The presence of this strong deformation was recently confirmed through lifetime measurements in N ≈ Z Sr and Zr nuclei. Theoretically, however, these nuclei present a challenge due to the vast valence space required to incorporate all necessary orbitals. Recent state-of-the-art predictions indicate a near axial prolate deformation for N = Z and N = Z + 2 nuclei between N = Z = 36 and N = Z = 40. In this work we investigate the shores of this island of deformation through a sub-barrier Coulomb excitation study of the N = Z + 4 nucleus, 80Sr. Extracting a spectroscopic quadrupole moment of Qs(21 +) = 0.5+ − 0 0 . . 8 9 eb, we find that 80Sr is inconsistent with significant axial prolate deformation with a significance of 1.5σ. This result, albeit with a large uncertainty, indicates that the predicted region of strong prolate deformation around N = Z = 40 is tightly constrained to the quartet of nuclei: 76,78Sr and 78,80Zr.