Investigation of particle-core coupling in 69Ge

Abstract

The nucleus 69Ge has been studied in the reactions 66Zn(α,n) 69Ge and 60Ni( 12C,2pn) 69Ge. Using γ-spectroscopic methods energies, intensities, excitation functions, γγ-coincidences, angular distributions, and the linear polarization of γ-rays as well as lifetimes were measured. From the α-induced reaction, states up to spin J = 21 2 and E x = 4267 keV have been established in 69Ge including 178 new transitions and 62 new levels. Spin and parity were determined for 79 levels. High-spin states populated via the reaction 12C + 60Ni show 61 new transitions and 27 new levels up to spin J = 37 2 and E x = 9182 keV. For 19 levels ps-lifetimes were determined. Eight complete multiplets originating from the coupling of the odd neutron to the core 68Ge have been identified and candidates for further multiplets are proposed. Significant deviations from the simple De-Shalit core-coupling model were found. Shell-model calculations, which were performed for 68Ge and 69Ge with the code RITSSCHIL on a parallel computer in a large configuration space, show that proton excitations from the 2 p 3 2 to higher shells play an important role for the detailed structure of the particle-core multiplets.