Abstract
The nature of quadrupole and octupole collectivity in Rn222 was investigated by determining the electric-quadrupole (E2) and octupole (E3) matrix elements using subbarrier, multistep Coulomb excitation. The radioactive Rn222 beam, accelerated to 4.23 MeV/u, was provided by the HIE-ISOLDE facility at CERN. Data were collected in the Miniball γ-ray spectrometer following the bombardment of two targets, Sn120 and Ni60. Transition E2 matrix elements within the ground-state and octupole bands were measured up to 10ℏ and the results were consistent with a constant intrinsic electric-quadrupole moment, 518(11)efm2. The values of the intrinsic electric-octupole moment for the 0+→3− and 2+→5− transitions were found to be respectively 2360−210+300efm3 and 2300−500+300efm3 while a smaller value, 1200−900+500efm3, was found for the 2+→1− transition. In addition, four excited non-yrast states were identified in this work via γ−γ coincidences.6 MoreReceived 10 December 2021Accepted 8 February 2022DOI:https://doi.org/10.1103/PhysRevC.105.024323Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasElectromagnetic transitionsNuclear structure & decaysPropertiesA ≥ 220Nuclear Physics
Highlights
Transition E 2 matrix elements within the ground-state and octupole bands were measured up to 10hand the results were consistent with a constant intrinsic electric-quadrupole moment, 518(11) e fm2
The Q2 = 518(11) e fm2 obtained from the fit of all transition E 2 matrix elements within the ground-state and octupole bands is slightly larger than the value Q2(21+ → 01+) = 484(14) e fm2 calculated
The value of Q2 = 480−+126400 e fm2 corresponding to the 21+||E 2||21+ matrix element is consistent with the values of Q2 corresponding to the transition E 2 matrix elements the large uncertainty in this value cannot rule out deviations as observed in the heavier Ra isotopes [3,5], either arising from nonaxial symmetry or from the effect of couplings to higher-lying collective bands
Summary
It is well established that nuclei outside of closed shells exhibit collective properties that can be best described in terms of nuclear shapes. Correlations which distort the spherical shape, causing the nucleus to become deformed. The prevalent distortion observed across the nuclear chart is quadrupole deformation, which can be either prolate or oblate, where the nucleus retains both axial and reflection symmetry. The low-lying excitations of an even-even nucleus with a quadrupoledeformed ground state exhibit a characteristic rotational band of positive-parity states that are connected by collective E 2 transitions. There is evidence from theoretical and experimental studies that some nuclei undergo the breaking of reflection symmetry in the intrinsic frame [1].
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