Collective structures in 62Cu

Abstract

A common feature for the nuclei in the mass A ≈ 60 region is that moderately deformed or single-particle structures dominate at low spins. They involve the negative-parity f7/2, p3/2, f5/2, and p1/2 orbitals. Well-deformed or superdeformed rotational structures occur at relatively high spins where the positive-parity deformation-driving 1g9/2 orbital plays a crucial role. With particles and holes in high-j shells, such as a neutron in the νg9/2 shell and a proton hole in the π f7/2 shell, magnetic rotational structures have also been reported in this region, such as in 58Fe [1] and 60Ni [2], etc. Due to the competition and interplay between the collective and the single-particle degrees of freedom, the level schemes in these nuclei are very complex but provide a good opportunity to test the predictions of different theoretical models.For the Cu isotopes lying above the doubly magic nucleus 56Ni, well-deformed and superdeformed structures have been observed in 58Cu [3],59Cu [4], and 61Cu [5] isotopes. So far,although the structure of the heavier 62Cu nucleus has been studied in a variety of experiments [6], including heavy-ion fusion-evaporation studies [7,8], no obvious collective struc tures have been reported. The observed energy spectra were interpreted in terms of the interacting boson-fermion-fermion model [7] and the shell model [8]. Here, we report an experimental investigation of the level structures in 62Cu via the 54Cr(12C, 1p3n) 62Cu fusion-evaporation reaction. Three negative-parity and three positive-parity level sequences in 62Cu are observed, including two new γ -ray transitions and one new level. The collective structures of these sequences are discussed in terms of systematic comparison and the tilted axis cranking covariant density functional theory(TAC-CDFT) [9].