Shell structure of the neutron-rich isotopes Co69,71,73

Abstract

The structures of the neutron-rich 69,71,73 Co isotopes were investigated via (p, 2p) knockout reactions at the Radioactive Isotope Beam Factory, RIKEN. Isotopes of interest were studied using the DALI2 γ-ray detector array combined with the MINOS target and tracker system. Level schemes were reconstructed using the γ-γ coincidence technique, with tentative spin-parity assignments based on the measured inclusive and exclusive cross sections. Comparison with shell-model calculations using the Lenzi-Nowacki-Poves-Sieja LNPS and PFSDG-U interactions suggests coexistence of spherical and deformed shapes at low excitation energies in the 69,71,73 Co isotopes. The distorted-wave impulse approximation (DWIA) framework was used to calculate the single-particle cross sections. These values were compared with the experimental findings.

An experimental view on shape coexistence in nuclei

“…3 agree within uncertainties with the values for the Ni cores. The systematics of (9/2 − ) states was extended beyond N = 40 in 69,71,73 Co, and the energies of the tentative (9/2 − ) → (7/2 − ) transitions are similar to those of the 2 + 1 → 0 + 1 transitions in the corresponding 70,72,74 Ni cores [180]. It should be emphasized that the uncertainties of the B(E2) values are large and the δ(E2/M1) mixing ratios are, mostly, not measured.…”

“…The measured hindrance factors for the Hg → Pt α decay, combined with the information on mixing in the Pt daughter nuclei obtained from the perturbation of energies in the rotational bands [479], were used to estimate the mixing of normal-order and intruder 0 + states in 180,182,184 Hg. This analysis yielded a 3% admixture of the deformed configuration in the ground state of 180 Hg, while mixing of 16% and 18% was obtained for 182 Hg and 184 Hg, respectively [478].…”

First spectroscopic study of V63 at the N=40 island of inversion

“…The spectrum contains a two-component background: a low-energy part (<500 keV) originating from atomic processes and a high-energy part coming from other sources mainly the reactions of the scattered particles on the materials surrounding the target [36,37]. This background was modeled by a double-exponential function with four free parameters which proved to be successful for other reactions of this experiment [21,[38][39][40][41] as well as for our earlier similar experiments [19,37,[42][43][44][45][46][47]. The spectrum clearly shows two peaks at around 700 keV and 900 keV and some other candidates at higher energies.…”

Quasifree Neutron Knockout Reaction Reveals a Small s -Orbital Component in the Borromean Nucleus B17

“…In order to analyze the momentum distribution of the knocked-out neutron and extract the 0d 5/2 and 1s 1/2 spectroscopic factors in 17 B, we carried out the distortedwave impulse approximation (DWIA) calculation [79]. This model has recently been applied in several (p, pn) and (p, 2p) experiments [32,33,[80][81][82][83][84][85][86]. The singleparticle wave function and the nuclear density were obtained using the Bohr-Mottelson potential [87].…”