Mass measurements with the ISOLTRAP mass spectrometer at CERN-ISOLDE improve mass uncertainties of neutron-deficient tin isotopes towards doubly magic Sn100. The mass uncertainty of Sn103 was reduced by a factor of 4, and the new value for the mass excess of −67104(18)keV is compared with nuclear and density functional theory calculations. Based on these results and local trends in the mass surface, the masses of Sn101,103, as determined through their QEC values, were found to be inconsistent with the new results. From our measurement for Sn103, we extrapolate the mass excess of Sn101 to −60005(300)keV, which is significantly more bound than previously suggested. By correcting the mass values for Sn101,103, we also adjust the values of Sb104, Te105,107, I108, Xe109,111, and Cs112 near the proton drip line which are connected through their α and proton Q values. The results show an overall smoothening of the mass surface, suggesting the absence of deformation energy above the N=50 shell closure. Published by the American Physical Society 2025

Here we report online results with the in-gas-Jet Resonance Ionization Spectroscopy (JetRIS) apparatus. The S01↔P11 transition of No254 was successfully measured with sub-GHz resolution, marking a fivefold improvement over previous measurements. Recent developments in laser spectroscopy have allowed access to more exotic nuclei, but measurements of the heavy actinide region have been limited by line broadening mechanisms, limiting the precision with which nuclear properties can be deduced from the hyperfine spectrum. JetRIS provides a method to measure the heavy actinide region with a high level of sensitivity and higher resolution than previous experiments. The offline and online characterizations of the system are reported, and future perspectives are presented. Published by the American Physical Society 2024

The changes in mean-squared charge radii of neutron-deficient gold nuclei have been determined using the in-source, resonance-ionization laser spectroscopy technique, at the ISOLDE facility (CERN). From these new data, nuclear deformations are inferred, revealing a competition between deformed and spherical configurations. The isotopes ^{180,181,182}Au are observed to possess well-deformed ground states and, when moving to lighter masses, a sudden transition to near-spherical shapes is seen in the extremely neutron-deficient nuclides, ^{176,177,179}Au. A case of shape coexistence and shape staggering is identified in ^{178}Au which has a ground and isomeric state with different deformations. These new data reveal a pattern in ground-state deformation unique to the gold isotopes, whereby, when moving from the heavy to light masses, a plateau of well-deformed isotopes exists around the neutron midshell, flanked by near-spherical shapes in the heavier and lighter isotopes-a trend hitherto unseen elsewhere in the nuclear chart. The experimental charge radii are compared to those from Hartree-Fock-Bogoliubov calculations using the D1M Gogny interaction and configuration mixing between states of different deformation. The calculations are constrained by the known spins, parities, and magnetic moments of the ground states in gold nuclei and show a good agreement with the experimental results.

We present an updated view on the phenomenon of mutually enhanced magicity based on the current experimental knowledge of atomic masses, including some recent precision measurements performed with the ISOLTRAP mass spectrometer at ISOLDE/CERN. We discuss the trends of the proton and neutron empirical shell gaps computed either in the standard approach, along chains corresponding to magic numbers of protons and neutrons, respectively, or along the neighbouring isotonic chains differing by two nucleon numbers. We show that in the latter case the empirical shell-gap trend is anti-correlated to the one observed along the magic-number chains. We perform a theoretical investigation of the origin of this feature by an analysis of the contributions from the monopole, pairing and quadrupole interactions, focusing on the phenomenon of mutually enhanced magicity. We emphasize the role of quadrupole correlations for explaining the full range of experimental information.

In this paper we present the first high-resolution laser spectroscopy results obtained at the GISELE laser laboratory of the GANIL-SPIRAL2 facility, in preparation for the first experiments with the S$^3$-Low Energy Branch. Studies of neutron-deficient radioactive isotopes of erbium and tin represent the first physics cases to be studied at S$^3$. The measured isotope-shift and hyperfine structure data are presented for stable isotopes of these elements. The erbium isotopes were studied using the $4f^{12}6s^2$ $^3H_6 \rightarrow 4f^{12}(^3 H)6s6p$ $J = 5$ atomic transition (415 nm) and the tin isotopes were studied by the $5s^25p^2 (^3P_0) \rightarrow 5s^25p6s (^3P_1)$ atomic transition (286.4 nm), and are used as a benchmark of the laser setup. Additionally, the tin isotopes were studied by the $5s^25p6s (^3P_1) \rightarrow 5s^25p6p (^3P_2)$ atomic transition (811.6 nm), for which new isotope-shift data was obtained and the corresponding field-shift $F_{812}$ and mass-shift $M_{812}$ factors are presented.

The Super Separator Spectrometer-Low Energy Branch (S3-LEB) is a low-energy radioactive ion beam experiment under commissioning as part of the GANIL-SPIRAL2 facility. It will be used for the production and study of exotic nuclei by in-gas laser ionization and spectroscopy (IGLIS), decay spectroscopy, and mass spectrometry. We report recent results from the off-line commissioning of S3-LEB, including first laser spectroscopy measurements in both the gas cell and the supersonic gas jet, the determination of the transport efficiency of laser ions from the gas cell through the RFQ chain, and time-of-flight measurements with the multi-reflection time-of-flight mass spectrometer PILGRIM. The measurements were performed using erbium, introduced by evaporation from a heated filament in the gas environment. The reported laser spectroscopy results include a characterization of the pressure broadening in the gas cell, proof-of-principle isotope shift measurements, and hyperfine-structure measurements.

The nucleus of the radioisotope thorium-229 (${}^{229}$Th) features an isomer with an exceptionally low excitation energy that enables direct laser manipulation of nuclear states. For this reason, it is a leading candidate for use in next-generation optical clocks. This nuclear clock will be a unique tool, amongst others, for tests of fundamental physics. While first indirect experimental evidence for the existence of such an extraordinary nuclear state is significantly older, the proof of existence has been delivered only recently by observing the isomer's electron conversion decay and its hyperfine structure in a laser spectroscopy study, revealing information on the isomer's excitation energy, nuclear spin and electromagnetic moments. Further studies reported the electron conversion lifetime and refined the isomer's energy. In spite of recent progress, the isomer's radiative decay, a key ingredient for the development of a nuclear clock, remained unobserved. In this Letter, we report the detection of the radiative decay of this low-energy isomer in thorium-229 (${}^{229\mathrm{m}}$Th). By performing vacuum-ultraviolet spectroscopy of ${}^{229\mathrm{m}}$Th incorporated into large-bandgap CaF${}_2$ and MgF${}_2$ crystals at the ISOLDE facility at CERN, the photon vacuum wavelength of the isomer's decay is measured as 148.71(42) nm, corresponding to an excitation energy of 8.338(24) eV. This value is in agreement with recent measurements, and decreases the uncertainty by a factor of seven. The half-life of ${}^{229\mathrm{m}}$Th embedded in MgF${}_2$ is determined to be 670(102) s. The observation of the radiative decay in a large-bandgap crystal has important consequences for the design of a future nuclear clock and the improved uncertainty of the energy eases the search for direct laser excitation of the atomic nucleus.

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 multireflection 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, 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.

We present the first results obtained from the S3 Low-Energy Branch, the gas cell setup at SPIRAL2-GANIL, which will be installed behind the S3 spectrometer for atomic and nuclear spectroscopy studies of exotic nuclei. The installation is currently being commissioned offline, with the aim to establish optimum conditions for the operation of the radio frequency quadrupole ion guides, mass separation and ion bunching, providing high-efficiency and low-energy spatial spread for the isotopes of interest. Transmission and mass-resolving power measurements are presented for the different components of the S3-LEB setup. In addition, a single-longitudinal-mode, injection-locked, pumped pulsed-titanium–sapphire laser system has been recently implemented and is used for the first proof-of-principle measurements in an offline laser laboratory. Laser spectroscopy measurements of erbium, which is the commissioning case of the S3 spectrometer, are presented using the 4f126s23H6→4f12(3H)6s6p optical transition.

The yield of 18 ion beams of radioactive gold nuclei produced in the thick uranium target at ISOLDE (CERN) by 1.4-GeV protons was measured. The production-efficiency dependence on the half-life (efficiency curve) was derived using the in-target production calculations by the FLUKA-CERN code. The irregularities in the efficiency curve for long-lived high-spin gold isomers (187,191,193Aum) were found. Three release models were tested for the efficiency-curve description.

In rare cases, the removal of a single proton (Z) or neutron (N) from an atomic nucleus leads to a dramatic shape change. These instances are crucial for understanding the components of the nuclear interactions that drive deformation. The mercury isotopes (Z = 80) are a striking example1,2: their close neighbours, the lead isotopes (Z = 82), are spherical and steadily shrink with decreasing N. The even-mass (A = N + Z) mercury isotopes follow this trend. The odd-mass mercury isotopes 181,183,185Hg, however, exhibit noticeably larger charge radii. Due to the experimental difficulties of probing extremely neutron-deficient systems, and the computational complexity of modelling such heavy nuclides, the microscopic origin of this unique shape staggering has remained unclear. Here, by applying resonance ionization spectroscopy, mass spectrometry and nuclear spectroscopy as far as 177Hg, we determine 181Hg as the shape-staggering endpoint. By combining our experimental measurements with Monte Carlo shell model calculations, we conclude that this phenomenon results from the interplay between monopole and quadrupole interactions driving a quantum phase transition, for which we identify the participating orbitals. Although shape staggering in the mercury isotopes is a unique and localized feature in the nuclear chart, it nicely illustrates the concurrence of single-particle and collective degrees of freedom at play in atomic nuclei. Spectroscopy and shell model calculations reveal the 181Hg isotope as the endpoint of the shape-staggering of Hg nuclei, a consequence of neutron removal which arises from the interplay of single-particle and collective degrees of freedom.

We present a robust analysis code developed in the Python language and incorporating libraries of the ROOT data analysis framework for the state-of-the-art mass spectrometry method called phase-imaging ion-cyclotron-resonance (PI-ICR). A step-by-step description of the dataset construction and analysis algo-rithm is given. The code features a new phase-determination approach that offers up to 10 times smaller statistical uncertainties. This improvement in statistical uncertainty is confirmed using extensive Monte-Carlo simulations and allows for very high-precision studies of exotic nuclear masses to test, among others, the standard model of particle physics. Program summary Program Title: PI-ICR analysis software CPC Library link to program files: https://doi.org/10.17632/5jxkxbkkkr.1 Developer's repository link: https://doi.org/10.5281/zenodo.4553515 Licensing provisions: MIT Programming language: Python Nature of problem: Analysis software for the next-generation mass spectrometry technique PI-ICR for radioactive isotopes and isomers. Solution method: Using Jupyter notebooks in the Python programming language and libraries of the ROOT analysis framework, the full PI-ICR analysis from the raw data to the final mass value is presented. Fur-thermore, a new phase-determination approach is introduced offering up to ten times smaller statistical uncertainties on the same dataset compared to the state-of-the-art approaches that are based on X/Y projection fits [14]. This improvement was confirmed by extensive Monte-Carlo simulations. Additional comments including restrictions and unusual features: 1. A new phase-determination approach is presented offering up to ten times smaller statistical uncer-tainties on the same dataset compared to state-of-the-art approaches. 2. The code features a robust and precise cyclotron-frequency ratio determination based on simultane-ous polynomial fitting with several advantages over the commonly used linear extrapolation. 3. The use of Jupyter notebooks and Python allows for a cloud-based analysis on any device or op-erating system offering a web browser through services such as CERN's SWAN platform or Google Colab. 4. The entire frequency determination is based on Bayesian analysis using unbinned maximum likeli-hood estimation. (C) 2021 Elsevier B.V. All rights reserved.

The tin isotope 100Sn is of singular interest for nuclear structure due to its closed-shell proton and neutron configurations. It is also the heaviest nucleus comprising protons and neutrons in equal numbers—a feature that enhances the contribution of the short-range proton–neutron pairing interaction and strongly influences its decay via the weak interaction. Decay studies in the region of 100Sn have attempted to prove its doubly magic character1 but few have studied it from an ab initio theoretical perspective2,3, and none of these has addressed the odd-proton neighbours, which are inherently more difficult to describe but crucial for a complete test of nuclear forces. Here we present direct mass measurements of the exotic odd-proton nuclide 100In, the beta-decay daughter of 100Sn, and of 99In, with one proton less than 100Sn. We use advanced mass spectrometry techniques to measure 99In, which is produced at a rate of only a few ions per second, and to resolve the ground and isomeric states in 101In. The experimental results are compared with ab initio many-body calculations. The 100-fold improvement in precision of the 100In mass value highlights a discrepancy in the atomic-mass values of 100Sn deduced from recent beta-decay results4,5.

T. Day Goodacre,1, 2, 3, ∗ A.V. Afanasjev,4 A.E. Barzakh,5 L. Nies,2, 6 B.A. Marsh,2 S. Sels,2, 7 U.C. Perera,4 P. Ring,8 F. Wienholtz,2, 6, † A.N. Andreyev,9, 10 P. Van Duppen,7 N.A. Althubiti,1, 11 B. Andel,7, 12 D. Atanasov,13, ‡ R.S. Augusto,3 J. Billowes,1 K. Blaum,13 T.E. Cocolios,1, 7 J.G. Cubiss,9 G.J. Farooq-Smith,1, 7, § D.V. Fedorov,5 V.N. Fedosseev,2 K.T. Flanagan,1, 14 L.P. Gaffney,7, 15, L. Ghys,7, 16 A. Gottberg,3, 17 M. Huyse,7 S. Kreim,13, 2 P. Kunz,3, 18 D. Lunney,19, ∗∗ K.M. Lynch,1, 2 V. Manea,13, ∗∗ Y. Martinez Palenzuela,7, 2 T.M. Medonca,2 P.L. Molkanov,5 M. Mougeot,2 J.P. Ramos,2 M. Rosenbusch,6, †† R.E. Rossel,2, 20 S. Rothe,2 L. Schweikhard,6 M.D. Seliverstov,5 P. Spagnoletti,15 C. Van Beveren,7 M. Veinhard,2 E. Verstraelen,7 A. Welker,2, 21 K. Wendt,20 R.N. Wolf,13, 6, ‡‡ A. Zadvornaya,7 and K. Zuber21 1Department of Physics and Astronomy, School of Natural Science, The University of Manchester, Manchester, M13 9PL, United Kingdom 2CERN, CH-1211 Geneva 23, Switzerland 3TRIUMF, Vancouver V6T 2A3, Canada 4Department of Physics and Astronomy, Mississippi State University, MS 39762, USA 5Petersburg Nuclear Physics Institute, NRC Kurchatov Institute, Gatchina 188300, Russia 6Universität Greifswald, Institut für Physik, 17487 Greifswald, Germany 7KU Leuven, Instituut voor Kernen Stralingsfysica, B-3001 Leuven, Belgium 8Fakultät für Physik, Technische Universität München, D-85748 Garching, Germany 9Department of Physics, University of York, York, YO10 5DD, United Kingdom 10Advanced Science Research Center (ASRC), Japan Atomic Energy Agency (JAEA), Tokai-mura, Japan 11Physics Department, Faculty of Science, Jouf University, Aljouf, Saudi Arabia 12Department of Nuclear Physics and Biophysics, Comenius University in Bratislava, 84248 Bratislava, Slovakia 13Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany 14The Photon Science Institute, The University of Manchester, Manchester, M13 9PL, United Kingdom 15School of Computing, Engineering, and Physical Sciences, University of the West of Scotland, Paisley PA1 2BE, United Kingdom 16Belgian Nuclear Research Center SCK•CEN, Boeretang 200, B-2400 Mol, Belgium 17University of Victoria, Department of Physics and Astronomy, Victoria, BC V8W 2Y2, Canada 18Department of Physics, Simon Fraser University, Burnaby, BC, V5A 1S6, Canada 19CSNSM-IN2P3, Université de Paris Sud, Orsay, France 20Institut für Physik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany 21Institut für Kernund Teilchenphysik, Technische Universität Dresden, Dresden 01069, Germany (Dated: November 23, 2021)

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The mean-square charge radii of ^{207,208}Hg (Z=80, N=127, 128) have been studied for the first time and those of ^{202,203,206}Hg (N=122, 123, 126) remeasured by the application of in-source resonance-ionization laser spectroscopy at ISOLDE (CERN). The characteristic kink in the charge radii at the N=126 neutron shell closure has been revealed, providing the first information on its behavior below the Z=82 proton shell closure. A theoretical analysis has been performed within relativistic Hartree-Bogoliubov and nonrelativistic Hartree-Fock-Bogoliubov approaches, considering both the new mercury results and existing lead data. Contrary to previous interpretations, it is demonstrated that both the kink at N=126 and the odd-even staggering (OES) in its vicinity can be described predominately at the mean-field level and that pairing does not need to play a crucial role in their origin. A new OES mechanism is suggested, related to the staggering in the occupation of the different neutron orbitals in odd- and even-A nuclei, facilitated by particle-vibration coupling for odd-A nuclei.

Combining laser spectroscopy in a Versatile Arc Discharge and Laser Ion Source, with Penning-trap mass spectrometry at the CERN-ISOLDE facility, this work reports on mean-square charge radii of neutron-rich mercury isotopes across the $N = 126$ shell closure, the electromagnetic moments of $^{207}$Hg and more precise mass values of $^{206-208}$Hg. The odd-even staggering (OES) of the mean square charge radii and the kink at $N = 126$ are analyzed within the framework of covariant density functional theory (CDFT), with comparisons between different functionals to investigate the dependence of the results on the underlying single-particle structure. The observed features are defined predominantly in the particle-hole channel in CDFT, since both are present in the calculations without pairing. However, the magnitude of the kink is still affected by the occupation of the $1i_{11/2}$ and $2g_{9/2}$ orbitals with a dependence on the relative energies as well as pairing.

The strength of the N = 28 magic number in neutron-rich argon isotopes is examined through high-precision mass measurements of Ar46-48, performed with the ISOLTRAP mass spectrometer at ISOLDE/CERN. The new mass values are up to 90 times more precise than previous measurements. While they suggest the persistence of the N = 28 shell closure for argon, we show that this conclusion has to be nuanced in light of the wealth of spectroscopic data and theoretical investigations performed with the SDPF-U phenomenological shell model interaction. Our results are also compared with ab initio calculations using the valence space in-medium similarity renormalization group and the self-consistent Green's function approaches. Both calculations provide a very good account of mass systematics at and around Z = 18 and, generally, a consistent description of the physics in this region. This combined analysis indicates that Ar-46 is the transition between the closed-shell Ca-48 and collective S-44.

M. Mougeot ,1,* D. Atanasov ,2,3,† C. Barbieri ,4,5,6 K. Blaum ,2 M. Breitenfeld,7 A. de Roubin,2,‡ T. Duguet,8,9 S. George,2 F. Herfurth,10 A. Herlert ,11 J. D. Holt,12 J. Karthein ,2,7 D. Lunney ,1 V. Manea ,2,7 P. Navrátil ,12 D. Neidherr,10 M. Rosenbusch,13,§ L. Schweikhard,13 A. Schwenk,14,15,2 V. Somà,8 A. Welker ,3,7 F. Wienholtz ,13,7,‖ R. N. Wolf,2,16 and K. Zuber 3 1CSNSM-IN2P3-CNRS, Université Paris-Sud, 91405 Orsay, France 2Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany 3Technische Universität Dresden, 01069 Dresden, Germany 4Department of Physics, University of Surrey, Guildford GU2 7XH, United Kingdom 5Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria 16, I-20133 Milano, Italy 6INFN, Sezione di Milano, Via Celoria 16, I-20133 Milano, Italy 7CERN, 1211 Geneva, Switzerland 8IRFU, CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette, France 9KU Leuven, Instituut voor Kernen Stralingsfysica, 3001 Leuven, Belgium 10GSI Helmholtzzentrum für Schwerionenforschung GmbH, Planckstraße 1, 64291 Darmstadt, Germany 11FAIR GmbH, Planckstraße 1, 64291 Darmstadt, Germany 12TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 2A3 13Universität Greifswald, Institut für Physik, 17487 Greifswald, Germany 14Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt, Germany 15ExtreMe Matter Institute EMMI, GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany 16ARC Centre of Excellence for Engineered Quantum Systems, The University of Sydney, NSW 2006, Australia

We probe the N=82 nuclear shell closure by mass measurements of neutron-rich cadmium isotopes with the ISOLTRAP spectrometer at ISOLDE-CERN. The new mass of ^132Cd offers the first value of the N=82, two-neutron shell gap below Z=50 and confirms the phenomenon of mutually enhanced magicity at ^132Sn. Using the recently implemented phase-imaging ion-cyclotron-resonance method, the ordering of the low-lying isomers in ^129Cd and their energies are determined. The new experimental findings are used to test large-scale shell-model, mean-field and beyond-mean-field calculations, as well as the ab initio valence-space in-medium similarity renormalization group.