Identification of significant E0 strength in the 22+→21+ transitions of 58,60,62Ni

Abstract

The E0 transition strength in the 2 + 2 → 2 + 1 transitions of 58,60,62 Ni have been determined for the first time following a series of measurements at the Australian National University (ANU) and the University of Kentucky (UK). The CAESAR Compton-suppressed HPGe array and the Super-e solenoid at ANU were used to measure the δ(E2/M 1) mixing ratio and internal conversion coefficient of each transition following inelastic proton scattering. Level half-lives, δ(E2/M 1) mixing ratios and γ-ray branching ratios were measured at UK following inelastic neutron scattering. The new spectroscopic information was used to determine the E0 strengths. These are the first 2 + → 2 + E0 transition strengths measured in nuclei with spherical ground states and the E0 component is found to be unexpectedly large; in fact, these are amongst the largest E0 transition strengths in medium and heavy nuclei reported to date.

Detailed spectroscopy of Ca46 : A study of the β− decay of KPore1, Andreoiu2, Smith3 et al. 2019Phys. Rev. CSelf Cite60131View full textAdd to dashboardCite

“…Similar pictures have been drawn when analyzing electromagnetic moments and transitions in other systems with valence particles of only neutrons, such as the light calcium [41] and nickel isotopes [42,43]. While this has been well studied with phenomenological shell-model calculations, it is still a challenge for ab initio methods using the valence-space paradigm.…”

Evidence for shape coexistence in 52Cr through conversion-electron and pair-conversion spectroscopy

“…Unfortunately, there is a large uncertainty on the reported E0 strengths in this work due to the uncertainty in the state lifetimes, and the transition branching and mixing ratios. The unprecedented strength in this region (Ca -Ni) [7,8,14,15] is still not understood, and further measurements of both the E0 transition strengths, along with other spectroscopic quantities like mixing ratios, are needed to reduce the uncertainty on the E0 transition strengths and to understand the structure of these nuclei.…”

“…Large E0 strengths have been recently observed in the Ni isotopes (Z = 28) [7,8], but it is unknown if shape coexistence is present in the N = 28 isotones between doubly magic 48 Ca and 56 Ni. Theoretically, shape coexistence has been predicted in the N = 28 isotones [9], resulting from the excitation of a neutron pair across the N = 28 closed neutron shell from the f 7/2 shell into the f p shell.…”

“…In order to resolve these limitations, an experimental campaign investigating these properties of 52 Cr is planned to take place at the University of Kentucky Accelerator Laboratory (UKAL). The inelastic neutron scattering reaction, (n, n ), has been successfully used to measure nuclear lifetimes via the Doppler-shift attenuation method (DSAM) and mixing ratios via angular distributions in the Ni isotopes, which were needed for accurate E0 strength determination [7,8,28].…”

The Heavy Ion Accelerator Facility: Research Achievements and Aspirations

“…More recently, pair spectroscopy has been used to study E0 transitions in relatively low-Z nuclei. Examples are 0 + → 0 + transitions in the N = Z nuclei 24 Mg and 40 Ca, and a systematic study of E0 transition strengths near N = 28 and Z = 28 that is finding that strong E0 transitions occur only in the semimagic isotopes [39][40][41].…”