Deformations and magnetic rotations in theNi60nucleus

Abstract

Data from three experiments using the heavy-ion fusion evaporation-reaction 36 Ar+ 28 Si have been combined to study high-spin states in the residual nucleus 60 Ni, which is populated via the evaporation of four protons from the compound nucleus 64 Ge. The GAMMASPHERE array was used for all the experiments in conjunction with a 4π charged-particle detector arrays (MICROBALL, LUWUSIA) and neutron detectors (NEUTRON SHELL) to allow for the detection of γ rays in coincidence with the evaporated particles. An extended 60 Ni level scheme is presented, comprising more than 270γ-ray transitions and 110 excited states. Their spins and parities have been assigned via directional correlations of γ rays emitted from oriented states. Spherical shell-model calculations in the fp-shell characterize some of the low-spin states, while the experimental results of the rotational bands are analyzed with configuration-dependent cranked Nilsson-Strutinsky calculations.

Single-particle and collective excitations in63Ni

“…Figure 7(b) illustrates the angular momentum gain I x vs rotational frequency for selected bands in 56 Ni (SD2 in [32,33]), 57 Ni (SD1 in [34,35]), 58 Ni (B3 in [37]), 59 Ni (B2 in [39]), and 60 Ni (W D2 in [41]): all are close to the trajectory of the ν(g 9/2 ) 2 excitation in 60 Fe. In fact, configurations assigned to the respective bands in [57][58][59][60] Ni include at least two particles (protons and/or neutrons) in the g 9/2 orbitals while, for band SD2 in 56 Ni, the configuration involves a single g 9/2 proton.…”

“…From the discussion above, it is clear that an interpretation within the framework adopted for the description of most of the collective bands observed in the Ni [32,33,35,37,39,41] and Zn [52][53][54][55][56] isotopic chains is warranted. Hence, calculations were performed within the configuration-dependent cranked Nilsson-Strutinsky (CNS) model with the formalism described in Refs.…”

“…7. (Color online) Spin along the rotational axis I x vs rotational frequency ω for (a) bands D1, D2, and D3 in 63 Ni and the ground-state band in 60 Fe (GSB in [21]); (b) selected rotational bands in 56 Ni (SD2 in [32,33]), 57 Ni (SD1 in [34,35]), 58 Ni (B3 in [37]), 59 Ni (B2 in [39]), and 60 Ni (W D2 in [41]) together with the trajectory of the yrast band in 60 Fe in the I = 8-20 range, where this sequence is associated with a configuration with two aligned g 9/2 neutrons; (c) same as (b), but for selected bands in 60 Zn (SD in [53]), 61 Zn (SD in [54]), 62 Zn (SD in [55] and SD1 in [56]), and 65 Zn (SD1 in [52]). See text for details.…”

“…Rotational sequences have been reported at moderate and high spin in some of the lighter even-even Ni isotopes: highly deformed and even superdeformed bands, built upon lower-lying single-particle excitations, have been observed in doubly-magic 56 Ni [32,33], as well as in 57 Ni [34,35], 58 Ni [36][37][38], 59 Ni [39], and 60 Ni [40,41]. Remarkably, partial proton and alpha decays out of some of these bands have been reported in 56 Ni and 58 Ni.…”

Magnetic rotation and quasicollective structures in58Fe: Influence of theνg9/2orbital

“…The presence of magnetic rotational bands in the f p shell, however, is extremely scarce. To date, only one experimental case has been reported for 60 Ni [42], where four candidate bands were identified.…”