Octupole Deformation Research Articles

Octupole correlations in stable nucleus 153Eu within reflection-asymmetric particle rotor model

Abstract The observed low-lying K=5/2± positive- and negative-parity bands in the stable nucleus 153Eu are investigated by the reflection-asymmetric triaxial particle rotor model. The experimental energy spectra, the energy staggering parameters, as well as the intraband E2 and M1 transition probabilities are well reproduced. It is found that the calculated interband B(E1) values depend sensitively on the octupole deformation parameter β30, although the energy spectra and intraband E2 and M1 transitions can be reproduced without the octupole degree of freedom. The observed enhanced E1 transition probabilities can be reproduced with β30=0.05. The detailed analysis of the intrinsic wave functions shows these nearly degenerate positive- and negative-parity bands are built on two individual proton configurations, i.e., dominated by πg9/2[Ω=5/2] and πh11/2[Ω=5/2], respectively, which differs from the parity doublet bands built on a single parity-mixed configuration.

Vibration-rotational alternating-parity spectra of even–even nuclei with effective triaxiality

In the present work, a model combining vibration-rotational motion and effective triaxiality is developed for even–even nuclei with quadrupole and octupole deformations. The Davidson potential is used to solve the radial part of the vibration-rotational Schrödinger equation in the axial quadrupole and octupole variables. In an adiabatic approximation the contribution of the angular variable in the components of the moments of inertia is taken as a constant after which the triaxial-rotor energy is obtained. As a result the alternating-parity spectrum and wave functions of the nucleus with quadrupole-octupole degrees of freedom are obtained. The proposed model is used to describe the yrast and first-non-yrast alternating-parity bands of the even–even nuclei 150Nd, 154Sm, 154,160Gd, 156Dy, 162,164Er, 172Yb, 230,232Th, 230,232,234,236,238U and 238,240Pu. The relevance of the model for taking into account the collective quadrupole-octupole modes in a rather complete form is pointed out.

Coexistence of pure octupole shapes in the superheavy nucleus 286No

The shape of 286No is investigated with the relativistic density functional theory on a three-dimensional lattice space without any symmetry restriction in a microscopic and self-consistent way. It is found that the ground state of 286No has a pure non-axial octupole shape and coexists with a tetrahedral isomeric state. The energy difference between the two states is only 0.12 MeV, and they are separated by a potential barrier of about 0.5 MeV. The occurrence of the octupole correlations is analyzed with the evolution of the single-particle levels near the Fermi surface driven by the octupole deformations.

Emergence of High-Order Deformation in Rotating Transfermium Nuclei: A Microscopic Understanding.

The rotational properties of the transfermium nuclei are investigated in the full deformation space by implementing a shell-model-like approach in the cranking covariant density functional theory on a three-dimensional lattice, where the pairing correlations, deformations, and moments of inertia are treated in a microscopic and self-consistent way. The kinematic and dynamic moments of inertia of the rotational bands observed in the transfermium nuclei ^{252}No, ^{254}No, ^{254}Rf, and ^{256}Rf are well reproduced without any adjustable parameters using a well-determined universal density functional. It is found for the first time that the emergence of the octupole deformation should be responsible for the significantly different rotational behavior observed in ^{252}No and ^{254}No. The present results provide a microscopic solution to the long-standing puzzle on the rotational behavior in No isotopes, and highlight the risk of investigating only the hexacontetrapole (β_{60}) deformation effects in rotating transfermium nuclei without considering the octupole deformation.

Вихрова октупольна мода у кінетичній моделі колективних збуджень в ядрах

The nature of a new isoscalar octupole resonance found within a kinetic model based on the Vlasov equation for finite Fermi systems with moving surfaces is studied. It is shown that this octupole resonance is due to dynamic effects of the nuclear surface, like the low-energy isoscalar dipole resonance (vortex dipole mode) observed in heavy nuclei. It is found that the velocity field associated with the new octupole resonance has a vortex character in the surface region of the nuclear liquid and, moreover, the vortex motion of nucleons is fragmented into three areas near the nuclear surface. At the same time, the velocity field associated with the high-energy octupole resonance found within our kinetic model displays an octupole deformation form and includes a compression within the nuclear fluid, which is consistent with the corresponding quantum calculations in the random phase approximation.

Microscopic derivation of the octupole magic numbers from symmetry considerations

The valence shells of medium mass and heavy nuclei consist of the normal and the intruder parity orbitals; therefore the Shell Model SU(3) symmetry of Elliott cannot have a straightforward application on them. The proxy-SU(3) can be applied instead, since it uses a unitary transformation, meant to act on the intruder orbitals to alter their parity and transform them to their proxy orbitals. The inverse unitary operator transforms the proxy orbitals back to the intruder ones. The highest weight proxy-SU(3) irreducible representations (irreps) allows one to determine the corresponding number of occupied intruder orbitals. In this way we obtain the so-called ‘octupole magic numbers’ 32, 56, 90, 134 and 194 without any parameter. Moreover, the proxy (unitary) mapping and its inverse transformation make the proxy space eligible for the calculation of observables associated with octupole deformation and the relevant treatment of mixed parity states. The implemented study validates the proxy-SU(3) approach with respect to the octupole deformation and suggests its full applicability in the corresponding mass regions.

Evolution of quadrupole-octupole collectivity in the even–even 54 ≤ Z ≤ 58 nuclei

We explore the quadrupole-octupole collectivity in the mass region of even–even 54 ≤ Z ≤ 58 (Xe, Ba and Ce) nuclei by analysing the fine structure of energy spectra. As a basic criterion for the presence of reflection-asymmetric degree of freedom we consider the formation of alternating-parity level-sequences. As a clear-cut criterion for the emergence of pronounced octupole deformation we consider the reduction of the parity-shift at certain angular momentum and the formation of a single energy sequence which can be interpreted as an octupole band. Applying these criteria we select out alternating-parity bands (APBs) in the region of Xe, Ba and Ce isotopes for which a manifestation of pronounced octupole collectivity can be considered. Their fine structure is probed in a collective quadrupole-octupole rotation model (QORM) providing a detailed analysis in terms of odd–even staggering diagrams. The obtained model descriptions of the energy levels and staggering patterns reveal the most characteristic features of the quadrupole-octupole deformations in this mass region and outline a clearly determined area of manifestation of nuclear reflection-asymmetric shapes.

Study of Octupole Transitions in Xe, Ba, Ce and Nd Nuclei within Interacting Boson Model

For nuclei with 54≤Z≤60 and 86≤N≤94, the results regarding the excitation spectra at low energies, both in positive and negative parity, as well as the transition probabilities for electric dipole (B(E1)), quadrupole (B(E2)), and octupole transitions (B(E(3)), indicate the emergence of significant octupole behavior. These observations have been made using the Interacting Boson Model-1 (IBM-1). The study examines the onset of octupole deformation and its impact on the spectroscopic characteristics in even-even neutron-rich lanthanide isotopes, specifically in the Ba and Nd nuclei. The investigation compares the results obtained from the Interacting Boson Model-1 (IBM-1) with the existing experimental data. The focus is on understanding how the addition of neutrons influences the development of octupole deformation and its manifestation in the observed spectroscopic features. The onset of strong octupolarity for Z≈ 56 and N ≈ 88 nuclei is indicated by the results obtained for the electric dipole, quadrupole, and octupole transition probabilities, as well as the low-energy positive and negative-parity excitation spectra. Conversely, discrepancies between the spectroscopic data and the IBM results suggest that the mapping quality needs to be evaluated in order to determine if the mapped boson Hamiltonian or the fermionic calculations are the source of the issues.

Octupole deformation in two-quasiparticle states of even–even deformed nuclei

Following the Skyrme-Hartree–Fock-BCS approach with blocking to two-quasiparticle states describing K-isomeric states of deformed even–even nuclei as presented in an earlier work of some of us Minkov N et al (2022 Phys. Rev. C 105 044 329), we study the emergence of axial-octupole deformation in excited states of this nature. We select two representative nuclei in the rare-earth and actinide mass regions, namely 148Ce (octupole-deformed in its ground state) and 234U (with a left-right symmetric ground-state shape), and several low-lying two-quasiparticle configurations illustrating cases where, in the same nucleus, some such excited states are calculated to be octupole deformed and some others are not. Then we investigate the mechanism favoring the appearance of left-right asymmetric shapes in the two-quasiparticle excited states of one-particle-one-hole type. We find in particular that strong octupole coupling between the blocked hole and particle states of a two-quasiparticle configuration does not favor pear-like shapes. In contrast, octupole coupling of the blocked particle (resp. hole) state with another particle (resp. hole) state located slightly above (resp. below) it in the single-particle spectrum favors pear-like shapes in the two-quasiparticle state.

A survey of nuclear quadrupole deformation in order to estimate the nuclear MQM and its relative contribution to the atomic EDM

Measurement of a non-zero permanent electric dipole moment (EDM) in fundamental particles, such as in an electron or a neutron, or in nuclei or atoms, can help us gain a handle on the sources of Charge-Parity (CP) violation, both in the Standard Model (SM) and beyond. The nuclear magnetic quadrupole moment (MQM), the central topic of this work, is also CP, P, and T violating. Nucleons and nuclei have a non-zero MQM from sources within the SM, but the nuclear MQM is dramatically enhanced if the nuclei are structurally quadrupole deformed. Multiple sources contribute to an atomic EDM namely: (i) nuclear EDM through its Schiff moment, which is enhanced by nuclear octupole deformation, (ii) CP violating interactions between the electrons and the nuclei, and (iii) the nuclear MQM that contributes to the atomic EDM in atoms with an unpaired valence electron. Our survey of nuclear quadrupole deformation identified 48 isotopes as ideal systems in which to search for a CP violating EDM via their enhanced nuclear MQM. Of these candidates, 223,225\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{223,225}$$\\end{document}Fr, 223\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{223}$$\\end{document}Ra, 223,225,227\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{223,225,227}$$\\end{document}Ac, 229\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{229}$$\\end{document}Th, and 229\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{229}$$\\end{document}Pa also have maximally enhanced nuclear Schiff moment contribution due to their octupole deformation. Laser cooling of the isotopes of Fr and Ra, among a few others, has already been demonstrated, making 223,225\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{223,225}$$\\end{document}Fr and 223\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{223}$$\\end{document}Ra some of the best systems in which to measure an EDM.

A study of U-isotope ground state properties with Covariant Energy Density Functional

Abstract In this paper we have systematically analyzed the ground state of uranium isotopes from 225 to 240. In our calculations, we used the covariant energy density functional of density dependent meson exchange interaction (DD-ME2) with separable pairing interaction (TMR). Using the multiple deformation constraint, we calculate the potential energy surface (PES) of the uranium isotopes for
both even-even and even-odd nuclei with quadrupole and octupole deformation. By comparison with experimental data and Hartree-Fock-Bogoliubov calculations with Gogny D1S, the ground state of the uranium isotopes is always preferred to reflection-asymmetric deformation with our calculation.

Quadrupole-octupole collective excitations in medium mass nuclei

A quadrupole-octupole axially symmetric collective model is used to describe the alternate parity bands observed in even–even medium mass nuclei. The nature of the octupole correlations in considered nuclei is ascertained from the phenomenology of the adopted model and the obtained parameters. It is found that the model parameters have a regular evolution as a function of neutron number, suggesting that the shape phase transition around N = 90 from low to well deformed shapes is also accompanied by the increase of the vibrational character for the octupole deformation. Model extrapolations are performed for various types of excited states and electromagnetic properties of measured energy levels.

Studies of reflection asymmetry in heavy nuclei

For certain combinations of protons and neutrons it is expected that the shape of atomic nuclei can undergo octupole deformation, which would give rise to reflection asymmetry or a ‘pear shape’. Here it is described how recent experiments carried out at CERN using the HIE-ISOLDE facility to accelerate radioactive beams and detect the subsequent γ-emission using the Miniball spectrometer have provided evidence that several radium and radon isotopes have either stable pear shapes or are octupole vibrational in nature. Their behaviour is compared with that of nuclei with A ≈ 150 exhibiting strong octupole correlations. It will be shown that the data on transition moments present some challenges for theory. The relevance of these measurements for atomic EDM searches will also be discussed.

Axially symmetric quadrupole-octupole incorporating sextic potential

We present an extended application of the analytic quadrupole octupole axially symmetric model, originally employed to study the octupole deformation and vibrations in light actinides using an infinite well potential (IW). In this work, we extend the model's applicability to a broader range of nuclei exhibiting octupole deformation by incorporating a sextic potential instead of the Davidson potential. Similarly to conventional models, such as AQOA-IW (for infinite square potential) and AQOA-D (for the Davidson potential), our proposed model is referred to as AQOA-S. By employing the sextic potential, phenomenologically represented as v(β˜)=a1β˜2+a2β˜4+a3β˜6, we can derive analytical expressions for the energy spectra and transition rates (B(E1), B(E2), B(E3)). The energy spectra of the model are essentially governed by two critical parameters: ϕ0, indicating the balance between octupole and quadrupole strain, and α, a key factor in adjusting the shape and behavior of the spectra through the sextic potential. In terms of applications, the study encompasses five isotopes, namely 222−226Ra and 224,226Th. Significantly, our model demonstrates remarkable agreement with the corresponding experimental data, particularly for the recently determined B(EL) transition rates of 224Ra, surpassing the performance of the model that employs the Davidson potential. The stability of the octupole deformation in 224Ra adds particular significance to these findings.

Exotic collective excitation patterns in triaxially deformed <sup>131</sup>Ba

<sec>In the last two decades, several unique phenomena in triaxially deformed nuclei, such as chiral doublet bands and wobbling motion have been revealed. Up to now, there are still many open questions which require further experimental and theoretical studies. To explore the collective motion in <sup>131</sup>Ba, an experiment was performed using the XTU Tandem accelerator in the Legnaro laboratory, Italy. High-spin states of <sup>131</sup>Ba have been populated via the heavy-ion fusion-evaporation <sup>122</sup>Sn(<sup>13</sup>C, 4n) reaction. <i>γ</i>-rays, charged particles and neutrons emitted from the residues were detected by the GALILEO array, EUCLIDES silicon ball, and the Neutron Wall, respectively. A total of 1.2<inline-formula><tex-math id="M12">\begin{document}$ \times $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240212_M12.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240212_M12.png"/></alternatives></inline-formula>10<sup>9</sup> triple- or higher-fold events were collected by the GALILEO data acquisition system. The <i>γ</i>-<i>γ</i>-<i>γ</i> coincidence events were sorted into a three-dimensional histogram (cube) and the analysis was carried out with the RADWARE and GASPWARE software packages.</sec><sec>Through analysis of the coincidences between <i>γ</i>-rays, the most comprehensive level schemes of <sup>131</sup>Ba to date was deduced from the present work. The extended level-scheme consists of 15 rotational bands, and newly observed transitions are marked in red. Three nearly degenerate pairs of doublet bands (Band 3–8) are identified in <sup>131</sup>Ba. Two pairs of chiral doublets (Band 3–6) with configuration <inline-formula><tex-math id="M20">\begin{document}$ {\textit{\pi}}h_{11/2}(g_{7/2},d_{5/2}){\otimes}{\nu}h_{11/2} $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240212_M20.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240212_M20.png"/></alternatives></inline-formula> are interpreted as a set of pseudospin-chiral quartet bands. The quartet bands are fed by another pair of chiral doublet bands (Band 7–8) built on a <inline-formula><tex-math id="M21">\begin{document}$ {\textit{\pi}}h^2_{11/2}{\otimes}{\nu}h_{11/2} $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240212_M21.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="11-20240212_M21.png"/></alternatives></inline-formula> configuration via a series of enhanced E1 transitions. We extracted the energy displacement <i>δ</i>E and the B(E1)/B(E2) branching ratios between the positive-parity band 3 and the negative-parity band 7 in <sup>131</sup>Ba and in comparison with those in <sup>124</sup>Ba, <sup>224</sup>Th, <sup>133</sup>Ce and <sup>135</sup>Nd. The energy displacement <i>δ</i>E and the B(E1)/B(E2) branching ratios in <sup>131</sup>Ba are comparable with those in <sup>124</sup>Ba but deviate appreciably from those in <sup>224</sup>Th which has been reported to have stable octupole deformation. The results indicate the existence of octupole correlations in <sup>131</sup>Ba without stable octupole deformation. A new rotational band (Band 10) discovered in the low-spin region exhibits a level structure similar to a wobbling band. Assuming it as a wobbling band, the wobbling frequency was extracted and compared with other reported wobbling bands in the neighboring nuclei. The wobbling frequency of this band decreases with increasing angular momentum, and even exhibits negative value at the highest spin. Considering that the wobbling phonon should contribute a positive amount to the excitation energy, this band is unlikely to be explained by this mechanism. The band may originate from other collective excitation mechanisms such as <i>γ</i> vibration. The newly identified rotational band (Band 9) composed of M1 transitions is tentatively assigned as a magnetic rotational band through a systematic analysis of the level structure. Finally, the configurations of other 4 bands, Band 12-15, are also suggested based on previous researches and the extracted quasiparticle alignments.</sec>

Cluster properties of heavy nuclei predicted with the Barcelona-Catania-Paris-Madrid energy density functional

We study the cluster emission properties of 224\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{224}$$\\end{document}Ra and 238\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{238}$$\\end{document}Pu employing the Barcelona-Catania-Paris-Madrid (BCPM) energy density functional (EDF). Starting from two-dimensional potential energy surfaces, coexisting fission paths are identified. A fission valley located at large octupole deformations, corresponding to a highly-asymmetric mass distribution, is found in both nuclei. As the corresponding fragments are dominated by the presence of 208\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{208}$$\\end{document}Pb, we can relate this fission path to the emergence of cluster emission. Using the octupole moment as collective degree of freedom, we compute the cluster decay half-lives and study the impact of collective inertias, pairing strength and collective zero-point energy. The agreement with experimental data resembles the results obtained for spontaneous fission half-lives, indicating the capability of BCPM to consistently describe a large variety of fission phenomena, including cluster emission.

Study of octupole deformations in Pb-Pb collisions at 5.02 TeV

In this letter, we present the study of the role of octupole deformation in non-spherical nuclei in most-central Pb-Pb collisions at LHC energy regime. The sensitivity of octupole deformation β3 to the QGP observables is presented by employing Monte-Carlo HYDJET++ model. Motivated by the discrepancies in the v2-to-v3 puzzle found in Pb-Pb collisions and the low-energy nuclear structure calculations of nuclear deformation, we studied the first basic observables necessary for any study in heavy-ion collisions. Using HYDJET++ framework, we calculate the pseudorapidity distribution, transverse momentum (pT) spectra and average anisotropic flow (v2 and v3) of primary charged hadrons with different parameters in two geometrical configurations: body-body and tip-tip type of Pb-Pb collisions. The kinematic ranges 0<pT<20 GeV/c and |η|<0.8 are considered. We observe that the charged hadron multiplicity and transverse momentum spectra are dependent on the strength of octupole deformation parameter. 〈v2〉 and 〈v3〉 in body-body collisions show weak positive correlation with β3 while average anisotropic flow in tip-tip collisions are weakly correlated to β3 in most-central collision region.

Rare isotope-containing diamond colour centres for fundamental symmetry tests.

Detecting a non-zero electric dipole moment in a particle would unambiguously signify physics beyond the Standard Model. A potential pathway towards this is the detection of a nuclear Schiff moment, the magnitude of which is enhanced by the presence of nuclear octupole deformation. However, due to the low production rate of isotopes featuring such 'pear-shaped' nuclei, capturing, detecting and manipulating them efficiently is a crucial prerequisite. Incorporating them into synthetic diamond optical crystals can produce defects with defined, molecule-like structures and isolated electronic states within the diamond band gap, increasing capture efficiency, enabling repeated probing of even a single atom and producing narrow optical linewidths. In this study, we used density functional theory to investigate the formation, structure and electronic properties of crystal defects in diamond containing [Formula: see text], a rare isotope that is predicted to have an exceptionally strong nuclear octupole deformation. In addition, we identified and studied stable lanthanide-containing defects with similar electronic structures as non-radioactive proxies to aid in experimental methods. Our findings hold promise for the existence of such defects and can contribute to the development of a quantum information processing-inspired toolbox of techniques for studying rare isotopes. This article is part of the Theo Murphy meeting issue 'Diamond for quantum applications'.

Nuclear Structure and Decay Data for A = 222 Isobars

Evaluated data are presented for 11 known A=222 nuclides (Bi, Po, At, Rn, Fr, Ra, Ac, Th, Pa, U, and Np), and relevant Jπ and T1/2 data for A=226 nuclei decaying by α-decay to A=222 nuclei. For 222Bi, only the isotopic identification is established with no measurement of its half-life. For 222Po, 222At, 222Fr, 222U, and 222Np, data are available only for the ground states, with static magnetic dipole and electric quadrupole moments, and charge radius measurements for the 222Fr ground state. For 222Ac and 222Pa, two low-lying levels are known from 226Pa α decay, and 226Np decay, respectively, but with no information about Jπ assignments and γ decays of these levels. For 222Pa, a long-lived isomeric state is known, decaying dominantly by α decay. 222Rn, 222Ra, and 222Th have been investigated in detail, the low-spin states by α decay and the high-spin studies of ground-state and octupole bands by in-beam γ-ray studies for all the three nuclei, as well as by Coulomb excitation for 222Rn and 222Ra. Low-spin levels in 222Ra have been investigated also through the β− decay of 222Fr. Half-lives of the excited states are known for 7 levels in 222Rn, 12 levels in 222Ra, and 3 levels in 222Th. Octupole deformations, with the presence of alternating-parity bands up to (16+) and (21−) in 222Rn, (20+) and (19−) in 222Ra, and (26+) and (25−) in 222Th, and with interband E1 transitions, have been established in these three nuclei. The present evaluation supersedes the previous A=222 ENSDF evaluations: (2011Si24), (1996El01), (1987El06) and (1977To14).

Semiclassical origin of nuclear ground-state octupole deformations

Semiclassical origin of nuclear ground-state octupole deformations