Coulomb Excitation of Neutron-Rich Zn Isotopes: First Observation of the21+State inZn80

Abstract

Neutron-rich, radioactive Zn isotopes were investigated at the Radioactive Ion Beam facility REX-ISOLDE (CERN) using low-energy Coulomb excitation. The energy of the 2(1)+ state in 78Zn could be firmly established and for the first time the 2+ --> 0(1)+ transition in 80Zn was observed at 1492(1) keV. B(E2,2(1)+ --> 0(1)+) values were extracted for (74,76,78,80)Zn and compared to large scale shell model calculations. With only two protons outside the Z=28 proton core, 80Zn is the lightest N=50 isotone for which spectroscopic information has been obtained to date. Two sets of advanced shell model calculations reproduce the observed B(E2) systematics. The results for N=50 isotones indicate a good N=50 shell closure and a strong Z=28 proton core polarization. The new results serve as benchmarks to establish theoretical models, predicting the nuclear properties of the doubly magic nucleus 78Ni.

Firstg(2+)measurement on neutron-rich72Zn, and the high-velocity transient field technique for radioactive heavy-ion beams

“…With respect to Ref. [9], a slight modification of the pairing (in particular on the f 5/2 diagonal matrix element) was made in light of the recent 2 + energy measurement in 80 Zn [49]. These modifications slightly improve the overall spectroscopy of all the nuclei studied around the island of inversion without any significant change in the wave functions.…”

Collectivity atN=50:Ge82andGade1, Baugher2, Bazin3 et al. 2010Phys. Rev. CSelf Cite619810View full textAdd to dashboardCite

“…The need for fairly high effective charges of e p ≈ 2 illustrates the importance of core excitations across the N = 50 shell gap which are outside of the employed model space. The experimental data stems from the present work and references [6,7,17,33,35,36]. …”

“…On the other side of the nuclear chart, the most neutron-rich selenium and germanium isotopes accessible for experiments are around the magic neutron number N = 50. Considerable experimental and theoretical efforts have recently been focused in this region on the investigation of the shell structure approaching the doubly magic nucleus 78 Ni (see, e.g., [14][15][16][17][18]). The description of nuclei in this region poses a challenge for shell-model calculations since the full pf shell and the neutron g 9/2 intruder orbital would be needed with the corresponding effective interaction.…”

Nuclear-structure studies of exotic nuclei with MINIBALL

“…No direct evidence was found for an enhanced Z=28 core polarization, but the larger proton effective charge needed in the SMI calculations to describe N=50 isotones with < Z 40 indicate a larger proton-core polarization for these isotopes. At this time no evidence appeared for breaking of the N=50 shell gap [16,21].…”

“…Simultaneously experiments along the chains of neutron-rich Ni, Cu and Zn isotopes were pursued in order to study collective and single particle properties in the vicinity of N=40 and the doubly-magic configuration at 78 Ni [16][17][18][19][20][21][22][23][24][25][26][27][28]. Moreover, the first g-factor measurement of excited states was successfully performed with a radioactive ion beam at ISOLDE in this region [24].…”