Structure of 61Cu via 58Ni( 4He, pγ) high-resolution prompt p-γ coincidence spectrometry

Abstract

The level structure and the detailed decay properties of the levels in 61Cu have been studied via prompt γ-ray energy and intensity measurements utilizing a NaI(T1)-Ge(Li) anti-Compton spectrometer and pγ prompt coincidence techniques via the 58Ni( 4He, pγ) 61Cu reaction with 4He ++ energies in the range 4.6–12.5 MeV. Many of the γ-rays associated with levels in 61Cu were identified with the ( 4He, pγ) reaction by means of extensive on-beam pγ coincidence measurements employing a 41 cm 3 Ge(Li) γ-ray detector and several annular Si(Li) or surface-barrier charged-particle detectors. Characterization of many levels in 61Cu was aided considerably by a high-resolution study of the proton spectrum from the 58Ni( 4He, p) reaction employing a tandem Van de Graaf accelerator and a split-pole Enge magnetic spectrograph. It was thus established that 50 levels up to 4.0 MeV in excitation are populated by this reaction in 61Cu and that these accommodate 98γ-rays. Branching ratios for the γ-de-excitation of 48 levels in 61Cu were obtained by averaging the measured angular correlation of each γ-ray about the beam direction. The directional correlation of 18 primary γ-rays in coincidence with protons detected at approximately 180° with respect to the beam direction were measured and the results were used to assign definite J-values for many levels in 61Cu. A detailed level scheme for the de-excitation of levels in 61Cu is offered.