Evidence for very large deformation in neutron deficient nuclei withZ≃40

A detailed study of very neutron deficient nuclei with $Z\simeq 40$ (Sr,Zr) and $N\simeq 40$ has been carried out. Total potential energy surfaces taking into account both quadrupole and hexadecapole deformation have been calculated for the Zr ($Z=40\mathrm{}$) nuclei, starting from the Nilsson model. Also oddmass nuclei have subsequently been studied when coupling the odd particle to the deformed even-even core. After extensive band mixing calculations for the ${}_{38}{}^{79}{}_{}{}^{}\mathrm{Sr}_{41}^{}{}_{}{}^{}$ nucleus, comparison to the existing experimental data [energy spectra for positive and negative parity ${\frac{5}{2}}^{+}$ [422] and ${\frac{3}{2}}^{-}$ [301] bands; static moments $\mu$, $Q$; mixing ratios $\delta \left(\frac{E2\mathrm{}}{M1\mathrm{}}\right)$ and branching ratios] has been carried out. We have also concentrated on the excited state properties of even-even Sr nuclei within the framework of the interacting boson model. A critical analysis of the interacting boson model parameters, as obtained from calculations in nearby nuclei, i.e., ${}_{34}{}^{}{}_{}{}^{}\mathrm{Se}$, ${}_{36}{}^{}{}_{}{}^{}\mathrm{Kr}$ is carried out, especially for the behavior of $\kappa$, ${\chi }_{\pi }$ and ${\chi }_v$.