Gamma-ray spectroscopy of neutron-rich Mo and Ge isotopes far from stability

Ozge Aktas (GANIL, France)

Excited states in the neutron-rich nuclei ¹⁰⁹Mo and ¹¹¹Mo were studied following nucleon knock-out reactions. Seven γ-ray transitions, some of them in prompt mutual coincidence, were identified for the first time in ¹¹¹Mo using the DALI2 and MINOS detector systems at the BigRIPS and ZeroDegree electromagnetic fragment separator at the RIBF, RIKEN, Japan. Total Routhian surface (TRS) and Particle-Plus-Rotor calculations have been performed to investigate the predicted shape coexistence and its effect on the structure of nuclei in this region of the nuclear chart. Following the results of the calculations, theoretical level schemes are proposed for positive and negative parity states and compared with the experimental findings. Gamma-ray transitions have been identified for the first time in the extremely neutron-rich (N = Z + 25) nucleus ⁸⁷Ge following nucleon knockout reactions studied at the RIBF, RIKEN, Japan. Previously unknown γ-ray transitions between excited states in ⁸⁵Ge were also observed and placed in a tentative level scheme. The results are compared with large-scale shell-model calculations and potential energy surface calculations based on the total Routhian surface formalism.