Shape Coexistence in $^{72}$Se

One of the original candidates for shape co-existence in nuclei was $^{72}$Se [1,2]. We have collected extensive new data, both ``in-beam'' following the $^{40}$Ca($^{36}$Ar,4p)$^{72}$Se reaction using Gammasphere at Argonne's ATLAS accelerator, and from the decay of $^{72}$Br populated in the $^{58}$Ni($^{16}$O,pn) reaction studied at WNSL Yale. A new J$^{\pi }$=0$^{+}$ state was found at 1876 keV, the published [2] decay scheme was corrected, and twenty-six new levels were established. This detailed spectroscopy of low-lying states helps to delineate the two shape minima. The mixing of prolate-deformed and near-spherical states can be now quantified, and the gamma decay path from high-spin can be followed. The inferred groundstate shape is consistent with trends in experiment and calculation of the selenium isotopes [3,4]. \\[4pt] [1] J.H. Hamilton, \textit{et al.,} Phys. Rev. Letts. 32 239 (1974)\\[0pt] [2] W.E. Collins, \textit{et al., }Phys.Rev. C9, 1457 (1974)\\[0pt] [3] S.M. Fischer, \textit{et al.,} Phys.Rev.Lett. 84, 4064 (2000)\\[0pt] [4] J. Ljungvall, \textit{et al., }Phys.Rev.Lett. 100, 102502 (2008)