The study of nuclear structure of neutron-rich 81Ge and its contribution in the r-process via the neutron transfer reaction 80Ge(d,p)

The study of low-lying levels of nuclei near closed shells not only elucidates the evolution of nuclear shell structure far from stability, but also affects estimates of heavy element nucleosynthesis in supernova explosions. Especially, the properties of the low-lying levels in ⁸¹Ge[Germanium 81] are important because the sensitivity study of the r-process pointed out that the properties of the nucleus can affect the final bundance pattern. Also, the spins and parities measurements of the states are essential to understand the shape coexistence in odd-mass N = 49 isotones.

This work describes the study of the odd-mass N = 49 nucleus, ⁸¹Ge in the region of neutron magic number N = 50 using an inverse kinematics (d,p) transfer reaction. The d(⁸⁰Ge[Germanium 80],p)⁸¹Ge neutron transfer reaction was measured by bombarding a 174 µg[microgram]/cm2[centimetersquared] (CD₂)_n[deuterated polyethylene] target with a 310 MeV beam of radioactive ⁸⁰Ge at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL). The new ORNL DAQ ASICs system was commissioned for a first implementation of the development in the experiment.

The excitation energies of low-lying levels were measured. From analysis of the observed angular distributions, the spins and the parities were determined, and spectroscopic factors were extracted for the first time. Neutron capture cross sections on ⁸⁰Ge have been calculated in a direct-semidirect model using extracted spectroscopic factors. Furthermore, two intruder states were confirmed and their properties were compared with other odd-mass N = 49 isotones.