arXiv subjects

J. Dobaczewski

Publications and source records attributed to J. Dobaczewski.

At least 19 recordsLinked to original sources

arXiv2026

Multipole tomography of atomic nuclei with symmetry-conserved theories

To define the intrinsic reference frame and multipole moments of angular-momentum-$J$-conserving many-body wave functions, we introduce two-body conditional probabilities of finding two nucleons at different positions in space. In this way, quadrupole deformations of states with $J\leq1/2$, which are not accessible via spectroscopic one-body quadrupole moments, can be characterized. We illustrate the method with nuclear density functional theory calculations for $J=0$ states of $^{16}$O and $^{20}$Ne, the latter obtained by restoring rotational symmetry of prolate or oblate intrinsic configurations. We show that the two-body quadrupole shape characterizations differ from one-body moments obtained from broken-symmetry states.

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arXiv2026

Interrogating the composition and distribution of nuclear magnetization via the hyperfine anomaly: experiment meets nuclear and atomic theory for short-lived $^{47}$K

To date, the magnetic structure of nuclei has been poorly constrained, with limited information on its spatial distribution. In this work, we address the composition and distribution of nuclear magnetization in a precision study of short-lived $^{47}$K. We measure the Larmor frequency with part-per-million precision using liquid-state $\beta$-detected nuclear magnetic resonance at CERN-ISOLDE, improving determination of the experimental differential hyperfine anomaly relative to $^{39}$K by more than an order of magnitude. By combining these experimental results with relativistic all-orders atomic calculations and nuclear density functional theory, we obtain the relative spin and orbital contributions to the nuclear magnetic moments. Our analysis reveals an overestimation of the spin contribution predicted by nuclear theory, that persists even after considering two-body currents. Conversely, we show that the measured hyperfine anomaly is reproduced when adopting the spatial distribution of nuclear magnetization provided by density functional theory. The methodology introduced in this work establishes a means to probe the detailed magnetic structure of the nucleus. This is critical for benchmarking nuclear structure theory and calculations of symmetry-violating nuclear moments relevant to searches for physics beyond the Standard Model in atoms and molecules.

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arXiv2026

Radiative decay and electromagnetic moments in $^{229}$Th determined within nuclear DFT

Using the nuclear DFT approach with symmetry breaking and restoration, we investigate the electromagnetic properties of the ground and isomeric states in $^{229}$Th. We determine the magnetic dipole transition strength B(M1; $3/2^+_1\rightarrow 5/2^+_1)$ between these two states and discuss the effects of parity breaking, configuration mixing, and time-odd core polarization. We also determine the corresponding spectroscopic magnetic dipole and octupole, and electric quadrupole moments. Because the octupole deformability of the Skyrme functionals used here is not described in sufficient detail, we analyze the results using a set of Skyrme functionals and perform a regression aligned with the measured electric octupole moments of neighboring even-even nuclei. Without parameter adjustment, the results compare favorably with the experimental data but also indicate the need to systematically adjust the octupole degrees of freedom in future functional parametrizations.

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arXiv2025

Electromagnetic and Exotic Moments in Nuclear DFT

Electromagnetic interactions serve as essential probes for studying and testing our understanding of the atomic nucleus, as they reveal emergent properties across the nuclear chart. We analyse their corresponding observables, which relate to charge and current distributions in nuclei expressed through their multipole components. We focus on theoretical results obtained within nuclear density functional theory (DFT) to derive self-consistent, symmetry-restored nuclear wave functions along with their spectroscopic multipole moments. We demonstrate how these compare with experimental data. We also discuss potential improvements in the formulation of magnetic dipole operators by including two-body meson-exchange contributions. Discussions of exotic symmetry-breaking moments emphasise their importance for understanding fine details of fundamental nuclear interactions. Detailed derivations are provided in the accompanying Supplemental Material.

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arXiv2025

Electromagnetic moments of ground and excited states calculated in heavy odd-N open-shell nuclei

Within nuclear DFT, we calculated spectroscopic magnetic dipole and electric quadrupole moments for various quasiparticle configurations of odd-$N$, even-$Z$, $83\leq{}N\leq125$ nuclei ranging from gadolinium to osmium. By tagging the blocked quasiparticles with single-particle states of the semi-magic dysprosium isotope, we efficiently computed 22 prolate and 22 oblate states for each of the 154 nuclei and tracked them across the entire major neutron shell. We compared this extensive set of theoretical results with experimental data for 82 states in the region. Breaking rotational, time-reversal, and signature symmetries, we aligned the intrinsic angular momenta along the axis of axial symmetry, thereby enabling full shape- and spin-self-consistent polarizations. The spectroscopic moments were then obtained by restoring rotational symmetry. We conducted a detailed analysis of the pattern of agreement and disagreement between theory and experiment in individual nuclei. For the magnetic dipole moments, agreement with the data varies and is characterized by an overall average and RMS deviation of 0.11 $\mu_N$ and 0.35 $\mu_N$, respectively. For the electric quadrupole moments, a good corresponding agreement of 0.16 b and 0.29 b was observed.

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arXiv2025

Laser spectroscopy and CP-violation sensitivity of actinium monofluoride

The apparent invariance of the strong nuclear force under combined charge conjugation and parity (CP) remains an open question in modern physics. Precision experiments with heavy atoms and molecules can provide stringent constraints on CP violation via searches for effects due to permanent electric dipole moments and other CP-odd properties in leptons, hadrons, and nuclei. Radioactive molecules have been proposed as highly sensitive probes for such searches, but experiments with most such molecules have so far been beyond technical reach. Here we report the first production and spectroscopic study of a gas-phase actinium molecule, $^{227}$AcF. We observe the predicted strongest electronic transition from the ground state, which is necessary for efficient readout in searches of symmetry-violating interactions. Furthermore, we perform electronic- and nuclear-structure calculations for $^{227}$AcF to determine its sensitivity to various CP-violating parameters, and find that a realistic, near-term experiment with a precision of 1 mHz would improve current constraints on the CP-violating parameter hyperspace by three orders of magnitude. Our results thus highlight the potential of $^{227}$AcF for exceptionally sensitive searches of CP violation.

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arXiv2025

Extraction of ground-state nuclear deformations from ultra-relativistic heavy-ion collisions: Nuclear structure physics context

The collective-flow-assisted nuclear shape-imaging method in ultra-relativistic heavy-ion collisions has recently been used to characterize nuclear collective states. In this paper, we assess the foundations of the shape-imaging technique employed in these studies. We argue that some current UHIC nuclear imaging techniques neglect fundamental aspects of spontaneous symmetry-breaking and symmetry-restoration in colliding ions and incorrectly infer one-body multipole moments from studies of nucleonic correlations. Therefore, the impact of this approach on nuclear structure research has been overstated. Conversely, efforts to incorporate existing knowledge on nuclear shapes into analysis pipelines can be beneficial for benchmarking tools and calibrating models used to extract information from ultra-relativistic heavy-ion experiments.

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arXiv2025

Quadrupole Strength in Isobaric Triplets

The dependence of the $E2$ matrix elements on isospin projection $T_z$ is linked to the conservation of the isospin symmetry. To study this conjecture, we calculated the ${B(E2: 2^+ \rightarrow 0^+)}$ rates for the even-even $T=1$ mirror nuclei with $42$ $\leq$ $A$ $\leq$ $98$ within nuclear density functional theory, employing the generalized Bohr Hamiltonian, and carrying out angular momentum projection. We demonstrated that collective effects are crucial for describing experimental data near the $N=Z$ line without invoking explicit beyond-Coulomb isospin symmetry-breaking corrections. We also determined the $B(E2\downarrow)$ values for odd-odd $T_z=0$ nuclei $^{70}Br$ and $^{78}Y$ in doubly-blocked configurations. We discussed the requirements for accurately describing isobaric analog states and emphasized how current theoretical results should be interpreted within the study of isospin symmetry across isospin triplets.

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arXiv2025

Reduction in nuclear size and quadrupole deformation of high-spin isomers of 127,129In

We employed laser spectroscopy of atomic transitions to measure the nuclear charge radii and electromagnetic properties of the high-spin isomeric states in neutron-rich indium isotopes (Z = 49) near the closed proton and neutron shells at Z = 50 and N = 82. Our data reveal a reduction in the nuclear charge radius and intrinsic quadrupole moment when protons and neutrons are fully aligned in 129In(N = 80), to form the high spin isomer. Such a reduction is not observed in 127In(N = 78), where more complex configurations can be formed by the existence of four neutron-holes. These observations are not consistently described by nuclear theory.

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arXiv2025

Electromagnetic moments in the Sn-Gd region determined within nuclear DFT

Within the nuclear DFT framework, employing the Skyrme UNEDF1 functional and incorporating pairing correlations, we determined the spectroscopic electric quadrupole and magnetic dipole moments of the $\nu11/2^{-}$ and $\pi7/2^{+}$ configurations in heavy, deformed, open-shell odd nuclei with $50\leq Z \leq 64$. The notions of self-consistent shape and spin polarisations due to odd nucleons responsible for generating total electric quadrupole and magnetic dipole moments were transformed into detailed computational procedures. The alignment of intrinsic angular momentum along the axial symmetry axis, necessitating signature and time-reversal symmetry breaking, followed by the restoration of rotational symmetry, proved to be essential components of the method. In contrast, the restoration of particle number symmetry yields modifications of only about 1%. With the isovector spin-spin terms of the functional previously adjusted in near doubly magic nuclei across the mass chart, the calculations were parameter-free. Effective charges and $g$-factors were not employed. A reasonably good agreement was achieved between the calculated and measured electric quadrupole moments. A similarly fair description of the magnetic dipole moments was obtained for the intruder configurations $\nu11/2^{-}$ alongside a poor description of those for $\pi7/2^{+}$.

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arXiv2023

Electromagnetic Properties of Indium Isotopes Elucidate the Doubly Magic Character of $^{100}$Sn

Our understanding of nuclear properties in the vicinity of $^{100}$Sn, suggested to be the heaviest doubly magic nucleus with equal numbers of protons (Z=50) and neutrons (N=50), has been a long-standing challenge for experimental and theoretical nuclear physics. Contradictory experimental evidence exists on the role of nuclear collectivity in this region of the nuclear chart. Using precision laser spectroscopy, we measured the ground-state electromagnetic moments of indium (Z=49) isotopes approaching the N=50 neutron number down to 101In, and nuclear charge radii of 101-131In spanning almost the complete range between the two major neutron closed-shells at N=50 and N=82. Our results for both nuclear charge radii and quadrupole moments reveal striking parabolic trends as a function of the neutron number, with a clear reduction toward these two neutron closed-shells, thus supporting a doubly magic character of $^{100}$Sn. Two complementary nuclear many-body frameworks, density functional theory and ab initio methods, elucidate our findings. A detailed comparison with our experimental results exposes deficiencies of nuclear models, establishing a benchmark for future theoretical developments.

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arXiv2023

Shape polarization in the tin isotopes near $N=60$ from precision $g$-factor measurements on short-lived $11/2^-$ isomers

The $g$ factors of $11/2^-$ isomers in semimagic $^{109}$Sn and $^{111}$Sn (isomeric lifetimes $\tau = 2.9(3)$ ns and $\tau = 14.4(7)$ ns, respectively) were measured by an extension of the Time Differential Perturbed Angular Distribution technique, which uses \LaBr detectors and the hyperfine fields of a gadolinium host to achieve precise measurements in a new regime of short-lived isomers. The results, $g(11/2^-; {^{109}\textrm{Sn}}) = -0.186(8)$ and $g(11/2^-; {^{111}\textrm{Sn}}) = -0.214(4)$, are significantly lower in magnitude than those of the $11/2^-$ isomers in the heavier isotopes and depart from the value expected for a near pure neutron $h_{11/2}$ configuration. Broken-symmetry density functional theory calculations applied to the sequence of $11/2^-$ states reproduce the magnitude and location of this deviation. The $g(11/2^-)$ values are affected by shape core polarization; the odd $0h_{11/2}$ neutron couples to $J^{\pi}=2^+,4^+,6^+...$ configurations in the weakly-deformed effective core, causing a decrease in the $g$-factor magnitudes.

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arXiv2023

Isomeric excitation energy for $^{99}$In$^{m}$ from mass spectrometry reveals constant trend next to doubly magic $^{100}$Sn

The excitation energy of the 1/2$^-$ isomer in $^{99}$In at ${N=50}$ is measured to be 671(37) keV and the mass uncertainty of the 9/2$^+$ ground state is significantly reduced using the ISOLTRAP mass spectrometer at ISOLDE/CERN. The measurements exploit a major improvement in the resolution of the multi-reflection time-of-flight mass spectrometer. The results reveal an intriguing constancy of the $1/2^-$ isomer excitation energies in neutron-deficient indium that persists down to the $N = 50$ shell closure, even when all neutrons are removed from the valence shell. This trend is used to test large-scale shell model, \textit{ab initio}, and density functional theory calculations. The models have difficulties describing both the isomer excitation energies and ground-state electromagnetic moments along the indium chain.

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arXiv2022

A new avenue in the search for CP violation: Moessbauer spectroscopy of 227-Ac

This work proposes a new avenue in the search for CP-violating odd-electric and even-magnetic nuclear moments. A promising candidate to find such moments in the ground state is the quadrupole-deformed and octupole-correlated nucleus 227-actinium. In this nucleus, the 27.4-keV $E1$~transition that connects the $3/2^+$ parity-doublet partner and the $3/2^-$ ground state is perfectly suited to apply the sensitive technique of recoil-free selfabsorption, commonly known as M\"ossbauer spectroscopy. In this experimental approach, the lifetime of the $3/2^+$ upper parity-doublet partner allows an estimate of the lower limit of $\Delta E = 2\cdot \Gamma_{\gamma}$= $23.7(1) \times 10^{-9}$ eV for the achievable energy resolution to be made. This resolution must be exceeded by the interaction of a CP-violating moment and the corresponding multipole moment of the field distribution in the lattice. This work presents the first ideas for patterns caused by CP-violating moments on the expected quadrupole splitting and nuclear Zeeman effect.

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arXiv2022

Nuclear DFT electromagnetic moments in heavy deformed open-shell odd nuclei

Within the nuclear DFT approach, we determined the magnetic dipole and electric quadrupole moments for paired nuclear states corresponding to the proton (neutron) quasiparticles blocked in the p11/2- (n13/2+) intruder configurations. We performed calculations for all deformed open-shell odd nuclei with 63<=Z<=82 and 82<=N<=126. Time-reversal symmetry was broken in the intrinsic reference frame and self-consistent shape and spin core polarizations were established. We determined spectroscopic moments of angular-momentum-projected wave functions and compared them with available experimental data. We obtained good agreement with data without using effective g-factors or effective charges in the dipole or quadrupole operators, respectively. We also showed that the intrinsic magnetic dipole moments, or those obtained for conserved intrinsic time-reversal symmetry, do not represent viable approximations of the spectroscopic ones.

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arXiv2021

Nuclear DFT analysis of electromagnetic moments in odd near doubly magic nuclei

We use the nuclear density functional theory to determine nuclear electric quadrupole and magnetic dipole moments in all one-particle and one-hole neighbours of eight doubly magic nuclei. We align angular momenta along the intrinsic axial-symmetry axis with broken time-reversal symmetry, which allows us to explore fully the self-consistent charge, spin, and current polarisation. Spectroscopic moments are determined for symmetry-restored wave functions and compared with available experimental data. We find that the obtained polarisations do not call for using quadrupole- or dipole-moment operators with effective charges or effective g-factors.

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arXiv2021

Solution of universal nonrelativistic nuclear DFT equations in the Cartesian deformed harmonic-oscillator basis. (IX) HFODD (v3.06h): a new version of the program

We describe the new version (v3.06h) of the code HFODD that solves the universal nonrelativistic nuclear DFT Hartree-Fock or Hartree-Fock-Bogolyubov problem by using the Cartesian deformed harmonic-oscillator basis. In the new version, we implemented the following new features: (i) zero-range three- and four-body central terms, (ii) zero-range three-body gradient terms, (iii) zero-range tensor terms, (iv) zero-range isospin-breaking terms, (v) finite-range higher-order regularized terms, (vi) finite-range separable terms, (vii) zero-range two-body pairing terms, (viii) multi-quasiparticle blocking, (ix) Pfaffian overlaps, (x) particle-number and parity symmetry restoration, (xi) axialization, (xii) Wigner functions, (xiii) choice of the harmonic-oscillator basis, (xiv) fixed Omega partitions, (xv) consistency formula between energy and fields, and we corrected several errors of the previous versions.

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arXiv2020

Precision measurement of the magnetic octupole moment in $^{45}$Sc as a test for state-of-the-art atomic- and nuclear-structure theory

We report on measurements of the hyperfine $A, B$ and $C$-constants of the $3d4s^2 ~^2D_{5/2}$ and $3d4s^2 ~^2D_{3/2}$ atomic states in $^{45}$Sc. High-precision atomic calculations of the hyperfine fields of these states and second-order corrections are performed, and are used to extract $C_{5/2}=-0.06(6)$ kHz and $C_{3/2}=+0.04(3)$ kHz from the data. These results are one order of magnitude more precise than the available literature. From the combined analysis of both atomic states, we infer the nuclear magnetic octupole moment $\Omega = -0.07(53) \mu_N b$, including experimental and atomic structure-related uncertainties. With a single valence proton outside of a magic calcium core, scandium is ideally suited to test a variety of nuclear models, and to investigate in-depth the many intriguing nuclear structure phenomena observed within the neighboring isotopes of calcium. We perform nuclear shell-model calculations of $\Omega$, and furthermore explore the use of Density Functional Theory for evaluating $\Omega$. From this, mutually consistent theoretical values of $\Omega$ are obtained, which are in agreement with the experimental value. This confirms atomic structure calculations possess the accuracy and precision required for magnetic octupole moment measurements, and shows that modern nuclear theory is capable of providing meaningful insight into this largely unexplored observable.

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