Spin, moments, and mean square nuclear charge radius ofSr77

The neutron deficient ${}_{}{}^{77}{}_{}{}^{}\mathrm{Sr}$ nucleus was studied by fast ion beam collinear laser spectroscopy with a detection scheme based on optical pumping, state selective neutralization, and atom counting. From the measured hyperfine splitting and isotope shift of the Sr II transition 5s ${}_{}{}^2{}_{}{}^{}$ ${\mathit{S}}_{1/2}$→5p ${}_{}{}^2{}_{}{}^{}$ ${\mathit{P}}_{3/2}$ the nuclear spin I=5/2, the nuclear moments μ=-0.348(4)${\mathrm{\mu }}_{\mathit{N}}$, ${\mathit{Q}}_{\mathit{s}}$=1.40(11) b, and the change in mean square charge radius δ〈${\mathit{r}}^2$ ${\mathrm{〉}}^{88,77}$=0.248(12) ${\mathrm{fm}}^2$ were deduced. These ground-state properties indicate a large prolate deformation of ${\mathrm{\epsilon }}_2$≃0.4 and allow a comparison with calculations performed in the particle-plus-deformed-core model, assigning a [422]5/2 Nilsson configuration to the ground state of ${}_{}{}^{77}{}_{}{}^{}\mathrm{Sr}$.