Nuclear Moments of Germanium Isotopes around $N$ = 40

Collinear laser spectroscopy measurements were performed on Ge69,71,73 isotopes (Z=32) at ISOLDE-CERN. The hyperfine structure of the 4s24p2P13→4s24p5sP1o3 transition of the germanium atom was probed with laser light of 269 nm, produced by combining the frequency-mixing and frequency-doubling techniques. The hyperfine fields for both atomic levels were calculated by using state-of-the-art atomic relativistic Fock-space coupled-cluster method. A new Ge73 quadrupole moment was determined from these calculations and previously measured precision hyperfine parameters, yielding Qs=−0.198(4) b, in excellent agreement with the literature value from molecular calculations. The moments of Ge69 have been revised: μ=+0.920(5)μN and Qs=+0.114(8)b, and those of Ge71 have been confirmed. The experimental moments around N=40 are interpreted with large-scale shell-model calculations using the JUN45 interaction, revealing rather mixed wave-function configurations, although their g factors are lying close to the effective single-particle values. Through a comparison with neighboring isotones, the structural change from the single-particle nature of nickel to deformation in germanium is further investigated around N=40.