LEVELS IN ${}_{38}^{80}{\rm Sr}$, ${}_{39}^{83}{\rm Y}$ AND ${}_{40}^{83}{\rm Zr}$ AND THE NEW REGION OF STRONG DEFORMATION AROUND N=Z≈38

The energy levels in ${}_{39}^{83}{\rm Y}$ and ${}_{40}^{83}{\rm Zr}$ were identified and investigated along with 80Sr via in-beam γ-ray spectroscopy to explore the new region of strong deformation centered around N=Z=38. The reaction 51V(32S, p2n)80Sr was studied at the Holifield Heavy Ion Research Facility and reactions 54Fe(32S, α2p)80Sr; 54Fe(32S, 3p)83Y and 54Fe(32S, 2pn)83Zr at the Max Planck Tandem. The deformation in the ground state band in 80Sr observed to 12+ shows a significant increase as N decreases toward 38. A 9/2+ ground state band in ${}_{39}^{83}{\rm Y}$ observed to (29/2+) exhibits larger deformation than an excited (9/2+) band in ${}_{40}^{83}{\rm Zr}$ as expected as Z moves away from 38. These nuclei support the proposal that the large deformation observed in this region arises from the reinforcing of the proton and neutron shape driving force as both N and Z approach shell gaps at large deformation for N and Z of 38.