Special Issue "Atomic Structure of the Heaviest Elements"

A special issue of Atoms (ISSN 2218-2004).

Deadline for manuscript submissions: closed (30 April 2022) | Viewed by 5888

Special Issue Editors

Dr. Mustapha Laatiaoui
E-Mail Website
Guest Editor
Department Chemie, Johannes Gutenberg University, 55128 Mainz, Germany
Interests: superheavy elements; laser spectroscopy; ion mobility spectrometry
Dr. Sebastian Raeder
E-Mail Website
Guest Editor
GSI Helmholtz Center for Heavy Ion Research, 64291 Darmstadt, Germany
Interests: superheavy elements; laser spectroscopy; trace analysis

Special Issue Information

Dear Colleagues,

Actinides exhibit a remarkable transition in terms of applied and fundamental research as they comprise the heaviest naturally occurring as well as fully manmade chemical elements. They have attracted the attention of atomic spectroscopists since their discovery as it was believed that many of their elemental properties could be deduced from knowledge of the electron configuration. The tiny quantity production of these elements did not prevent scientists from performing elaborate and extensive spectroscopy, such as with huge spectrographs. Thus, essential data about the atomic structure up to element 99 – einsteinium – were obtained even if some spectral lines could not be (or not correctly) assigned back then.

Today, we are much further along in atomic spectroscopy, although the actinides are far from being fully explored. In addition to better model descriptions of the atom, recent developments and advances in the field of optical spectroscopy have not only led to a better understanding of the atomic structure of the already measured elements but also to tackling the superheavy elements previously considered experimentally inaccessible.

This Special Issue of Atoms covers recent theoretical and experimental work about the atomic structure of actinides as well as related topics, such as transport properties in gases, nuclear properties, and medical applications. With the advancing technology for production and handling of actinides and transactinides, we hope that this issue will serve as a useful resource for future work in the field of optical spectroscopy and accelerator-based laser ion sources. We welcome original research articles as well as review articles on specific topics.

Dr. Mustapha Laatiaoui
Dr. Sebastian Raeder
Guest Editors

Manuscript Submission Information

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Keywords

  • optical spectroscopy
  • actinides
  • transactinides
  • superheavy elements
  • transport properties
  • atomic structure
  • electronic configuration
  • ion–atom interaction
  • relativistic effects
  • electron correlations

Published Papers (8 papers)

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Research

Article
Electronic Structure of Lr+ (Z = 103) from Ab Initio Calculations
Atoms 2022, 10(2), 48; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10020048 - 09 May 2022
Viewed by 261
Abstract
The four-component relativistic Dirac–Coulomb Hamiltonian and the multireference configuration interaction (MRCI) model were used to provide the reliable energy levels and spectroscopic properties of the Lr+ ion and the Lu+ homolog. The energy spectrum of Lr+ is very similar to [...] Read more.
The four-component relativistic Dirac–Coulomb Hamiltonian and the multireference configuration interaction (MRCI) model were used to provide the reliable energy levels and spectroscopic properties of the Lr+ ion and the Lu+ homolog. The energy spectrum of Lr+ is very similar to that of the Lu+ homolog, with the multiplet manifold of the 7s2, 6d17s1 and 7s17p1 configurations as the ground and low-lying excited states. The results are discussed in light of earlier findings utilizing different theoretical models. Overall, the MRCI model can reliably predict the energy levels and properties and bring new insight into experiments with superheavy ions. Full article
(This article belongs to the Special Issue Atomic Structure of the Heaviest Elements)
Article
Update of Atomic Data for the First Three Spectra of Actinium
Atoms 2022, 10(2), 42; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10020042 - 22 Apr 2022
Viewed by 388
Abstract
The present article describes a complete reanalysis of all published data on observed spectral lines and energy levels of the first three spectra of actinium (Ac I–III). In Ac I, three previously determined energy levels have been rejected, 12 new energy levels have [...] Read more.
The present article describes a complete reanalysis of all published data on observed spectral lines and energy levels of the first three spectra of actinium (Ac I–III). In Ac I, three previously determined energy levels have been rejected, 12 new energy levels have been found; for six previously known levels, either the J values or the energies have been revised, and the ionization energy has been redetermined with an improved accuracy. In the line list of Ac I, three previous classifications have been discarded, 16 new ones have been found, and three have been revised. In Ac II, 16 new energy levels have been established, and 36 new identifications have been found for previously observed but unclassified lines. In both Ac I and Ac II, new sets of transition probabilities have been calculated. For all three spectra, complete datasets of critically evaluated energy levels, observed lines, and transition probabilities have been constructed to serve as recommended data on these spectra. Full article
(This article belongs to the Special Issue Atomic Structure of the Heaviest Elements)
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Article
Advancing Radiation-Detected Resonance Ionization towards Heavier Elements and More Exotic Nuclides
Atoms 2022, 10(2), 41; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10020041 - 21 Apr 2022
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Abstract
RAdiation-Detected Resonance Ionization Spectroscopy (RADRIS) is a versatile method for highly sensitive laser spectroscopy studies of the heaviest actinides. Most of these nuclides need to be produced at accelerator facilities in fusion-evaporation reactions and are studied immediately after their production and separation from [...] Read more.
RAdiation-Detected Resonance Ionization Spectroscopy (RADRIS) is a versatile method for highly sensitive laser spectroscopy studies of the heaviest actinides. Most of these nuclides need to be produced at accelerator facilities in fusion-evaporation reactions and are studied immediately after their production and separation from the primary beam due to their short half-lives and low production rates of only a few atoms per second or less. Only recently, the first laser spectroscopic investigation of nobelium (Z=102) was performed by applying the RADRIS technique in a buffer-gas-filled stopping cell at the GSI in Darmstadt, Germany. To expand this technique to other nobelium isotopes and for the search for atomic levels in the heaviest actinide element, lawrencium (Z=103), the sensitivity of the RADRIS setup needed to be further improved. Therefore, a new movable double-detector setup was developed, which enhances the overall efficiency by approximately 65% compared to the previously used single-detector setup. Further development work was performed to enable the study of longer-lived (t1/2>1 h) and shorter-lived nuclides (t1/2<1 s) with the RADRIS method. With a new rotatable multi-detector design, the long-lived isotope 254Fm (t1/2=3.2 h) becomes within reach for laser spectroscopy. Upcoming experiments will also tackle the short-lived isotope 251No (t1/2=0.8 s) by applying a newly implemented short RADRIS measurement cycle. Full article
(This article belongs to the Special Issue Atomic Structure of the Heaviest Elements)
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Article
Observation of Collisional De-Excitation Phenomena in Plutonium
Atoms 2022, 10(2), 40; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10020040 - 20 Apr 2022
Viewed by 408
Abstract
A program of research towards the high-resolution optical spectroscopy of actinide elements for the study of fundamental nuclear structure is currently ongoing at the IGISOL facility of the University of Jyväskylä. One aspect of this work is the development of a gas-cell-based actinide [...] Read more.
A program of research towards the high-resolution optical spectroscopy of actinide elements for the study of fundamental nuclear structure is currently ongoing at the IGISOL facility of the University of Jyväskylä. One aspect of this work is the development of a gas-cell-based actinide laser ion source using filament-based dispensers of long-lived actinide isotopes. We have observed prominent phenomena in the resonant laser ionization process specific to the gaseous environment of the gas cell. The development and investigation of a laser ionization scheme for plutonium atoms is reported, focusing on the effects arising from the collision-induced phenomena of plutonium atoms in helium gas. The gas-cell environment was observed to greatly reduce the sensitivity of an efficient plutonium ionization scheme developed in vacuum. This indicates competition between resonant laser excitation and collisional de-excitation by the gas atoms, which is likely being enhanced by the very high atomic level density within actinide elements. Full article
(This article belongs to the Special Issue Atomic Structure of the Heaviest Elements)
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Article
Extending Our Knowledge about the 229Th Nuclear Isomer
Atoms 2022, 10(1), 24; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10010024 - 14 Feb 2022
Viewed by 946
Abstract
The first nuclear excited state in 229Th possesses the lowest excitation energy of all currently known nuclear levels. The energy difference between the ground- and first-excited (isomeric) state (denoted with 229mTh) amounts only to ≈8.2 eV (≈151.2 nm), which results [...] Read more.
The first nuclear excited state in 229Th possesses the lowest excitation energy of all currently known nuclear levels. The energy difference between the ground- and first-excited (isomeric) state (denoted with 229mTh) amounts only to ≈8.2 eV (≈151.2 nm), which results in several interesting consequences: Since the excitation energy is in the same energy range as the binding energy of valence electrons, the lifetime of 229mTh is strongly influenced by the electronic structure of the Th atom or ion. Furthermore, it is possible to potentially excite the isomeric state in 229Th with laser radiation, which led to the proposal of a nuclear clock that could be used to search for new physics beyond the standard model. In this article, we will focus on recent technical developments in our group that will help to better understand the decay mechanisms of 229mTh, focusing primarily on measuring the radiative lifetime of the isomeric state. Full article
(This article belongs to the Special Issue Atomic Structure of the Heaviest Elements)
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Article
First Offline Results from the S3 Low-Energy Branch
Atoms 2022, 10(1), 21; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10010021 - 09 Feb 2022
Viewed by 1043
Abstract
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, [...] Read more.
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 4f126s23H64f12(3H)6s6p optical transition. Full article
(This article belongs to the Special Issue Atomic Structure of the Heaviest Elements)
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Article
Structure Calculations in Nd III and U III Relevant for Kilonovae Modelling
Atoms 2022, 10(1), 18; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10010018 - 07 Feb 2022
Cited by 1 | Viewed by 754
Abstract
The detection of gravitational waves and electromagnetic signals from the neutron star merger GW170817 has provided evidence that these astrophysical events are sites where the r-process nucleosynthesis operates. The electromagnetic signal, commonly known as kilonova, is powered by the radioactive decay of [...] Read more.
The detection of gravitational waves and electromagnetic signals from the neutron star merger GW170817 has provided evidence that these astrophysical events are sites where the r-process nucleosynthesis operates. The electromagnetic signal, commonly known as kilonova, is powered by the radioactive decay of freshly synthesized nuclei. However, its luminosity, colour and spectra depend on the atomic opacities of the produced elements. In particular, opacities of lanthanides and actinides elements, due to their large density of bound–bound transitions, are fundamental. The current work focuses on atomic structure calculations for lanthanide and actinide ions, which are important in kilonovae modelling of ejecta spectra. Calculations for Nd III and U III, two representative rare-earth ions, were achieved. Our aim is to provide valuable insights for future opacity calculations for all heavy elements. We noticed that the opacity of U III is about an order of magnitude greater than the opacity of Nd III due to a higher density of levels in the case of the actinide. Full article
(This article belongs to the Special Issue Atomic Structure of the Heaviest Elements)
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Article
Level Structure and Properties of Open f-Shell Elements
Atoms 2022, 10(1), 7; https://0-doi-org.brum.beds.ac.uk/10.3390/atoms10010007 - 12 Jan 2022
Cited by 2 | Viewed by 762
Abstract
Open f-shell elements still constitute a great challenge for atomic theory owing to their (very) rich fine-structure and strong correlations among the valence-shell electrons. For these medium and heavy elements, many atomic properties are sensitive to the correlated motion of electrons and, [...] Read more.
Open f-shell elements still constitute a great challenge for atomic theory owing to their (very) rich fine-structure and strong correlations among the valence-shell electrons. For these medium and heavy elements, many atomic properties are sensitive to the correlated motion of electrons and, hence, require large-scale computations in order to deal consistently with all relativistic, correlation and rearrangement contributions to the electron density. Often, different concepts and notations need to be combined for just classifying the low-lying level structure of these elements. With Jac, the Jena Atomic Calculator, we here provide a toolbox that helps to explore and deal with such elements with open d- and f-shell structures. Based on Dirac’s equation, Jac is suitable for almost all atoms and ions across the periodic table. As an example, we demonstrate how reasonably accurate computations can be performed for the low-lying level structure, transition probabilities and lifetimes for Th2+ ions with a 5f6d ground configuration. Other, and more complex, shell structures are supported as well, though often for a trade-off between the size and accuracy of the computations. Owing to its simple use, however, Jac supports both quick estimates and detailed case studies on open d- or f-shell elements. Full article
(This article belongs to the Special Issue Atomic Structure of the Heaviest Elements)
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