The first direct mass measurement of Pd-93, the one-proton-decay daughter of the (21+) isomer in Ag-94, has been performed, resulting in a mass excess value of -59 127(35) keV and reducing the mass uncertainty by an order of magnitude. As a consequence, the excitation energies of the presumed parent states of the one-proton This shows that there is an incompatibility in the previously reported decay scheme of the 1p and 2p branches. Three scenarios are discussed, which could resolve this apparent contradiction, and elucidated by performing state-of-the-art shell-model and mean-field calculations. The latter confirm that, based on the reported decay information, the 2p emission cannot be fed from the same (21(+)) isomer as the 1p emission, but indicate that it could originate from a second, structurally different, high-spin state.

Shape competition and coexistence between the pear- and the tetrahedral-shape octupole deformations in actinide nuclei is investigated by employing the realistic nuclear mean-field theory with the phenomenological, so-called 'universal' Woods-Saxon Hamiltonian with newly adjusted parameters containing no parametric correlations. Both types of octupole deformations exhibit significant effects in , , and isotones. Nuclear potential energy calculations within the multi-dimensional deformation spaces reveal that the tetrahedral deformation effects generally lead to deeper energy minima in most nuclei with and . Interestingly, in the nuclei , , and , selected for the illustration of the studied effects, the influence of pear-shape octupole deformation is comparable to that of tetrahedral octupole deformation. Consequently, the coexistence of both kinds of octupole shapes is predicted by the potential energy calculations. In particular, we have reproduced the experimental results known for pear-shape rotational bands obtaining in this way an estimate of the quality of the modelling parametrisation. With the same Hamiltonian, we have predicted the properties of the tetrahedral symmetry rotational bands. To facilitate the possible experiment-theory cooperation we have derived the exact spin-parity tetrahedral-band structures by applying the standard methods of the group representation theory for the T d point-group.

In this article, we address the occurrence and properties of exotic point-group symmetries in nuclei. We focus on the relations between the specific gap openings in the single-nucleon spectra, which represent a measure of nuclear stability studied with the help of the nuclear mean-field theory and accompanying octupole shape properties manifesting the link between the particular stability configurations (magic octupole gaps) and resulting exotic geometrical forms. We employ a realistic phenomenological realisation of the nuclear mean-field theory with the so-called universal Woods–Saxon Hamiltonian and the group representation theory to formulate the experimental identification criteria of the addressed symmetries. We use the newest parameterisations of the Hamiltonian obtained employing the inverse problem theory. To stabilise the modelling predictions, we detect and eliminate parametric correlations. Following earlier articles introducing the octupole “fourfold magic numbers” and “universal magic numbers”, N=136 and 198 , examined in the heavy and super-heavy nuclei, we generalise these concepts for the whole mass table for the octupole magic chain N=32, 40, 56, 64, 70, 90, 112, 136, 198 . They bring in the so-called high-rank tetrahedral and octahedral point groups strengthening the specific shell effects and gap openings and implying the unique hindrance factors: at the exact tetrahedral symmetry limit, the collective electric quadrupole and dipole reduced transition probabilities vanish provoking new isomerism. Under these circumstances, many rotational states which in other nuclei manifest strong decay probabilities, in the high-rank symmetry case become isomeric—forming a new class of nuclear high-rank symmetry isomers. The consequences for the future experimental studies of those isomers are discussed especially in the domain of exotic nuclei.

In two recent articles we have formulated nuclear mean-field theory predictions of existence of a new form of magic numbers, referred to as fourfold magic numbers. These predictions stipulate the presence of strong shell closures at the neutron numbers $N=136$ (actinide region) and $N=196$ (superheavy region) simultaneously at nonvanishing all four octupole deformations ${\ensuremath{\alpha}}_{3\ensuremath{\mu}=0,1,2,3}\ensuremath{\ne}0$. In contrast to the traditional notion of magic numbers, the new notion refers to simultaneous nonspherical configurations (${\ensuremath{\alpha}}_{3\ensuremath{\mu}}\ensuremath{\ne}0, {\ensuremath{\alpha}}_{2\ensuremath{\mu}}=0$). In this article we study the nuclear equilibrium deformations with ${\ensuremath{\alpha}}_{33}\ensuremath{\ne}0$ combined with nonvanishing quadrupole deformation, ${\ensuremath{\alpha}}_{20}\ensuremath{\ne}0$. One easily shows that such geometrical shapes have a threefold symmetry axis and are invariant under the symmetry operations of the ${\mathrm{D}}_{3h}$ point group. We employ a realistic phenomenological mean-field approach with the so-called universal deformed Woods-Saxon potential and its recently optimized parametrization based on actualized experimental data with the help of the inverse problem theory methods. The presence of parametric correlations among 4 of 12 parameters in total was detected and removed employing Monte Carlo approach leading to stabilization of the modeling predictions. Our calculations predict the presence of three nonoverlapping groups of nuclei with ${\mathrm{D}}_{3h}$ symmetry, referred to as islands on the nuclear ($Z,N$) plane (mass table). These islands lie in the rectangle $110\ensuremath{\le}Z\ensuremath{\le}138$ and $166\ensuremath{\le}N\ensuremath{\le}206$. The ``repetitive'' structures with the ${\mathrm{D}}_{3h}$ symmetry minima are grouped in three zones of oblate quadrupole deformation, approximately, at ${\ensuremath{\alpha}}_{20}\ensuremath{\in}[\ensuremath{-}0.10,\ensuremath{-}0.20]$ (oblate normal deformed), around ${\ensuremath{\alpha}}_{20}\ensuremath{\approx}\ensuremath{-}0.5$ (oblate superdeformed) and ${\ensuremath{\alpha}}_{20}\ensuremath{\approx}\ensuremath{-}0.85$ (oblate hyperdeformed). Importantly, the energies of those latter exotic deformation minima are predicted to be very close to the ground-state energies. We illustrate, compare, and discuss the evolution of the underlying shell structures. Nuclear surfaces parametrized as usual with the help of real deformation parameters, ${{\ensuremath{\alpha}}_{\ensuremath{\lambda}\ensuremath{\mu}}^{}={\ensuremath{\alpha}}_{\ensuremath{\lambda}\ensuremath{\mu}}^{*}}$, are invariant under ${\mathcal{O}}_{xz}$-plane reflection, the symmetry also referred to as $y$ simplex (${\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{S}}_{y}$). For the shapes with odd-multipolarity ($\ensuremath{\lambda}\ensuremath{\rightarrow}{\ensuremath{\lambda}}_{\mathrm{odd}}=3,5,7,...$) it follows that $E(\ensuremath{-}{\ensuremath{\alpha}}_{{\ensuremath{\lambda}}_{\mathrm{odd}},\ensuremath{\mu}})=E(+{\ensuremath{\alpha}}_{{\ensuremath{\lambda}}_{\mathrm{odd}},\ensuremath{\mu}})$. It turns out that the predicted equilibrium deformations generate symmetric double (or ``twin'') minima separated by potential barriers, whose heights vary with the nucleon numbers, possibly inducing the presence of parity-doublets in the spectra. To facilitate possible experimental identification of such structures, we examine the appearance of such doublets solving the collective Schr\"odinger equation. Implied suggestions are illustrated and discussed.

In the paper, experimental results of high-energy gamma GDR (Giant Dipole Resonance) decay from the Pt-192 compound nucleus associated with the 4n decay channel leading to the Pt-188 evaporation residue are presented. The measurement, which was performed with the use of coupled nuBall and PARIS arrays, aimed to investigate the link between deformation of a hot nucleus and different deformations of the residual states. The high-energy gamma rays from the GDR decay measured using the PARIS phoswiches provided information on compound nucleus properties, particularly on its effective shape. Discrete transitions in evaporation residues, measured by the nuBall array, were used to select the final products of specific deforma-tions. As a result, the GDR strength functions measured for the particular decay paths were obtained.

In two recent articles we have formulated nuclear mean-field theory predictions of existence of a new form of magic numbers, referred to as fourfold magic numbers. These predictions stipulate the presence of strong shell closures at the neutron numbers N = 136 (actinide region) and N = 196 (superheavy region) simultaneously at nonvanishing all four octupole deformations alpha 3 mu=0,1,2,3 not equal 0. In contrast to the traditional notion of magic numbers, the new notion refers to simultaneous nonspherical configurations (alpha 3 mu not equal 0, alpha 2 mu = 0). In this article we study the nuclear equilibrium deformations with alpha 33 not equal 0 combined with nonvanishing quadrupole deformation, alpha 20 not equal 0. One easily shows that such geometrical shapes have a threefold symmetry axis and are invariant under the symmetry operations of the D3h point group. We employ a realistic phenomenological mean-field approach with the so-called universal deformed Woods-Saxon potential and its recently optimized parametrization based on actualized experimental data with the help of the inverse problem theory methods. The presence of parametric correlations among 4 of 12 parameters in total was detected and removed employing Monte Carlo approach leading to stabilization of the modeling predictions. Our calculations predict the presence of three nonoverlapping groups of nuclei with D3h symmetry, referred to as islands on the nuclear (Z, N) plane (mass table). These islands lie in the rectangle 110 << Z << 138 and 166 << N << 206. The "repetitive" structures with the D3h symmetry minima are grouped in three zones of oblate quadrupole deformation, approximately, at alpha 20 e [-0.10, -0.20] (oblate normal deformed), around alpha 20 similar to -0.5 (oblate superdeformed) and alpha 20 similar to -0.85 (oblate hyperdeformed). Importantly, the energies of those latter exotic deformation minima are predicted to be very close to the ground-state energies. We illustrate, compare, and discuss the evolution of the underlying shell structures. Nuclear surfaces parametrized as usual with the help of real deformation parameters, {alpha lambda mu = alpha*lambda mu], are invariant under Oxz-plane reflection, the symmetry also referred to as y simplex (Sy). For the shapes with odd-multipolarity (lambda -> lambda odd = 3, 5, 7, ...) it follows that E(-alpha lambda odd,mu) = E(+alpha lambda odd,mu). It turns out that the predicted equilibrium deformations generate symmetric double (or "twin") minima separated by potential barriers, whose heights vary with the nucleon numbers, possibly inducing the presence of parity-doublets in the spectra. To facilitate possible experimental identification of such structures, we examine the appearance of such doublets solving the collective Schrodinger equation. Implied suggestions are illustrated and discussed.

"Shapes and Symmetries in Nuclei: From Experiment to Theory: SSNET'22." Nuclear Physics News, 32(3), pp. 34–35

We employ a realistic nuclear mean-field theory using the phenomenological, Woods-Saxon Hamiltonian with newly adjusted parameters containing no parametric correlations; originally present correlations are removed employing the Monte Carlo approach. We find very large neutron shell gaps at N = 136 for all the four octupole deformations alpha(3 mu)=0,1,2,3. These shell gaps generate well-pronounced double potential-energy minima in the standard multipole (alpha(20), alpha(22), alpha(3 mu), alpha(40)) representation, often at alpha(20) = 0, which in turn generate exotic symmetries C-2v, D-2d, T-d, and D-3h, discussed in detail. The main goal of the article is to formulate spectroscopic criteria for experimental identification. Calculations employing macroscopic-microscopic method are performed for nuclei with Z >= 82 and N >= 126 in multidimensional deformation spaces to analyze the expected exotic symmetries and octupole shape instabilities in the mass table "northeast" of the doubly magic Pb-208 nucleus. Whereas the proton-unperturbed properties of neutron-generated octupole shell effects are illustrated in detail for exotic Z=Pb-82(N>126) nuclei, our discussion is extended into even-even Z > 82 nuclei approaching the less exotic Z/N ratios, to encourage experiments which could identify the predicted exotic symmetries. In addition to the tetrahedral point group symmetry, T-d, of which experimental evidence has recently been published, we present D-2d symmetry resulting from a superposition of axially symmetric quadrupole and tetrahedral symmetries and two new point group symmetries, D-3h and C-2v, associated with the octupole alpha(33) and alpha(31) energy minima, respectively. The multidimensional n > 2 deformation spaces are treated as usual by projecting the total potential energies onto the n = 2 subspace. Using the representation theory of point groups we formulate quantum mechanical criteria for experimental identification of exotic symmetries through analysis of the specific properties of the collective rotational bands generated by the symmetries. The resulting band structures happen to be markedly distinct from the structure of the bands generated by ellipsoidal symmetry quantum rotors; those various rotational properties are discussed in detail.

We introduce the concept of the nuclear octupole fourfold (i.e., applying simultaneously to all the four octupole deformations alpha 30, alpha 31, alpha 32, and alpha 33) neutron "magic number" N = 196 and discuss the physical consequences of its presence. Our theoretical predictions are obtained using the realistic phenomenological mean-field approach with the deformed Woods-Saxon potential, the latter employing the new parametrization optimized in our preceding articles. Correlations among 4 parameters in the set of 12 parameters of the Woods-Saxon potential are detected and removed employing Monte Carlo approach leading to stabilization of the predictive power of the modeling. Our main focus is examining the impact of the four-fold octupole magic number N = 196 on the stability properties of superheavy nuclei with 114 Z 130 and 166 N 206. Calculations suggest that majority of the examined nuclei are either spherical or octupole deformed, octupole-tetrahedral geometry playing the dominating role lowering the ground-state energy by up to 8 MeV. The origin and manifestations of this domination are illustrated and discussed. It turns out that, in several cases, alternative point-group symmetries may lead to noticeable lowering of the nuclear energy; this concerns the C2v geometry associated with alpha 31, the D3h geometry related to alpha 33, and D2d corresponding to the combination of alpha 32 and alpha 20 quadrupole component.

Nuclear properties across the chart of nuclides are key to improving and validating our understanding of the strong interaction in nuclear physics. We present high-precision mass measurements of neutron-rich Fe isotopes performed at the TITAN facility. The multiple-reflection time-of-flight mass spectrometer (MR-ToFMS), achieving a resolving power greater than 600 000 for the first time, enabled the measurement of Fe63-70, including first-time high-precision direct measurements (delta m/m approximate to 10(-7)) of Fe68-70, as well as the discovery of a long-lived isomeric state in Fe-69. These measurements are accompanied by both mean-field and ab initio calculations using the most recent realizations which enable theoretical assignment of the spin-parities of the Fe-69 ground and isomeric states. Together with mean-field calculations of quadrupole deformation parameters for the Fe isotope chain, these results benchmark a maximum of deformation in the N = 40 island of inversion in Fe and shed light on trends in level densities indicated in the newly refined mass surface.

High-accuracy mass measurements of neutron-deficient Yb isotopes have been performed at TRIUMF using TITAN's multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). For the first time, an MR-TOF-MS was used on line simultaneously as an isobar separator and as a mass spectrometer, extending the measurements to two isotopes further away from stability than otherwise possible. The ground state masses of ^{150,153}Yb and the excitation energy of ^{151}Yb^{m} were measured for the first time. As a result, the persistence of the N=82 shell with almost unmodified shell gap energies is established up to the proton drip line. Furthermore, the puzzling systematics of the h_{11/2}-excited isomeric states of the N=81 isotones are unraveled using state-of-the-art mean field calculations.

Mean-field calculations in multidimensional deformation spaces are performed and the shape coexistence and isomers generated by exotic nuclear configurations and toroidal and superdeformed ones are addressed. We use a phenomenological mean-field Hamiltonian of Woods-Saxon type with its universal parametrization involving eight parameters fixed once for all for the full periodic table. Original parametric correlations existing in this type of Hamiltonians are removed using methods of inverse problem theory of applied mathematics. Stochastic analysis of uncertainties of the final nuclear energy predictions with the obtained correlation-free parametrization is performed and the viability tests are illustrated and discussed. Prediction capacities of resulting model related to the description of the nuclear shape properties are cross-checked using the experimental information available, revealing full coherence. Presented results encourage experimental verification of predicted exotic structures; suggestions related to identification possibilities are formulated and discussed.

In this article, we discuss the effects of the shape instability against the first order tetrahedral-symmetry nuclear shape deformation t(1) equivalent to alpha(32) for the Z = N nuclei in the vicinity of Z = 40 using a deformed Woods-Saxon realistic mean-field Hamiltonian. We specifically focus on the effects of the tetrahedral deformation in its formally leading order, t(1), since the recent discovery of the experimental evidence of the corresponding symmetry in the Sm-152 nucleus opens the new perspectives in experimental identification of the corresponding exotic nuclear configurations by proposing explicit unprecedented techniques for such applications.

Long-lived isomeric states in 97Ag and 101−109In were investigated with the FRS Ion Catcher at GSI. In the isotope 97Ag, a long-lived (1/2−) isomeric state was discovered, and its excitation energy was determined to be 618(38) keV. This is simultaneously the first discovery of a nuclear isomeric state by multiple-reflection time-of-flight mass spectrometry. The measured excitation energies were compared to large-scale shell-model calculations, which indicated the importance of core excitation around 100Sn. Furthermore, advanced mean-field calculations for the 97Ag nucleus and relevant neighboring nuclei were performed, which have contributed to a better understanding of the repetitive appearance of certain isomeric structures in neighboring nuclei, and which have supported the discovery of the isomeric state in 97Ag in a global shell-evolution scheme.

A recent publication announcing the first identification of the tetrahedral and octahedral symmetries in subatomic physics the symmetries often referred to as "high-rank" is taken as an opportunity for a presentation of the series of turning points, which have lead to this discovery. It is known that the nuclear collective E2 (and E1) transitions vanish at the exact high-rank symmetry limit. Consequently, the first experimental tests aimed at studying the collective tetrahedral rotational bands with the deexciting transitions assumed very weak. At the same time, it has been assumed that the two symmetries will be broken, at least to an extent, and at least via the Coriolis angular momentum alignment and via the zero-point quadrupole motion around high-rank symmetric minima. Accordingly, the spin-parity sequences of the tetrahedral rotational bands were sought under the supposition that they resemble well-known octupole band properties. This strategy led to a few encouraging results but turned out to be inexact; the new strategy, based on the group and group-representation theories led finally to the evidence of signals from both tetrahedral and octahedral symmetries in one single nucleus: Sm-152. Evolution covering nearly 25 years of this research is presented and the perspectives are discussed.

New physics opportunities are opening up by the Advanced Gamma Tracking Array, AGATA, as it evolves to the full 4 $$\pi $$ instrument. AGATA is a high-resolution $$\gamma $$ -ray spectrometer, solely built from highly segmented high-purity Ge detectors, capable of measuring $$\gamma $$ rays from a few tens of keV to beyond 10 MeV, with unprecedented efficiency, excellent position resolution for individual $$\gamma $$ -ray interactions, and very high count-rate capability. As a travelling detector AGATA will be employed at all major current and near-future European research facilities delivering stable and radioactive ion beams.

We discuss and illustrate a computer-designed algorithm allowing to construct the nuclear potential energy surfaces generated by a mean field Hamiltonian H(α) as functions of the ensemble of nuclear deformation variables α for multi-particle multi-hole excited configurations. The algorithm in question serves to eliminating the undesired effect of the so-called avoided crossing mechanism, a consequence of the well-known property referred to as Landau–Zener non-crossing rule.