Unique and complementary information on shape coexistence in the neutron-deficient Pb region derived from Coulomb excitation

Abstract

Neutron-deficient isotopes of Pt-Hg-Pb-Po-Rn are the classic region in the investigation of shape coexistence in atomic nuclei. A large programme of Coulomb-excitation experiments has been undertaken at the REX-ISOLDE facility in CERN with a number of even-even isotopes in this region. These experiments have been used to probe the electromagnetic properties of yrast and non-yrast states of even-even exotic nuclei, above and below Z=82. Amongst a large amount of different complementary techniques used to study nuclear structure, Coulomb excitation brings substantial and unique information detailing shape coexistence. In this paper we review the Coulomb-excitation campaign at REX-ISOLDE in the light-lead region together with most recently obtained results. Furthermore, we present some new interpretations that arise from this data and show testing comparisons to state-of-the-art nuclear models.

Electromagnetic properties of low-lying states in neutron-deficient Hg isotopes: Coulomb excitation of 182Hg, 184Hg, 186Hg and 188Hg

“…In order to draw firm conclusions from Coulombexcitation experiments with exotic beams, complementary spectroscopic data are crucial [2]. Recently performed β/EC decay of neutron-deficient even-even Tl isotopes at HIE-ISOLDE intend to provide these data i.e., precisely measure γ-ray branching ratios, conversion coefficients and mixing ratios for the low-lying (yrast and non-yrast) states in Hg isotopes [66].…”

“…The neutron-deficient mercury isotopes (Z = 80) serve as an illustrative example of shape coexistence [1,2], whereby at low excitation energies near-degenerate nuclear states are characterized by different shapes. The first observation of a dramatic change in the ground-state mean-square charge radii was observed through isotope shift measurements in 183 Hg and 185 Hg, when comparing to heaviermass mercury isotopes [3].…”

“…The population of the 2 + 1 , 2 + 2 , 4 + 1 states in 184 Hg is clearly visible, as well as intense K Xray peaks. Additionally, in the experiment performed with the 120 Sn target, a weak 4 + 2 → 2 + 2 γ-ray transition (552 keV) and the 2 + 3 → 0 + 2 & 2 + 3 → 2 + 1 doublet (around 610 keV) in 184 Hg were observed.Figure 6(c) is adapted from ref [2]…”

Global analysis of quadrupole shape invariants based on covariant energy density functionals

“…Quadrupole shape invariants have been extensively used to investigate shape coexistence in many regions of the nuclear chart [1,[6][7][8][9][10][11][12].…”

Nuclear-structure studies of exotic nuclei with MINIBALL

“…Albers et al [38,39] measured the transition E2 matrix element between the ground and the first + 2 state, and the diagonal matrix element of the + 2 state, for 92,94,96 Kr, using CE. While the quadrupole moment increases significantly between N=56 and N=60, no sudden onset of deformation was observed.…”