Terbium and thulium thin films were produced by Molecular Plating under controlled conditions to elucidate a possible influence of water and carbon dioxide present in the plating solution. Platings were made in a glovebox with variable concentration of residual water and CO 2 in a controlled inert atmosphere to study the impact on the quality of the produced thin films and on deposition yields. The morphology of the thin films was analyzed by scanning electron microscopy. The deposition yield was determined by neutron activation analysis at the research reactor TRIGA Mainz. Chemical analysis of the deposited layers was conducted using a combination of infrared, Raman and X-ray photoelectron spectroscopy. The Raman and IR spectra reveal the formation of hydroxides, oxides and carbonates. Water in the plating solution affects the quality of the thin films when its concentration exceeds 1 vol%. The presence of CO 2 leads to an increased carbonate content, which negatively influences the film quality.

In preparation of gas-phase chemical experiments with moscovium (Mc, element 115), we studied the chemical behavior of the short-lived bismuth radioisotope 211Bi in helium, argon, and oxygen atmosphere. For that purpose, we performed off-line isothermal gas chromatography experiments at room temperature. Using different carrier gases, the short-lived volatile 219Rn precursor, provided from an 227Ac-source, was transported through the Recoil Transfer Chamber (RTC) at the gas-filled separator TASCA and into the mini-Cryo-Online Multi detector for Physics and Chemistry of Transactinides (miniCOMPACT) chromatography and detection setup. Internal chromatograms were recorded as a function of various parameters including carrier gas type and flow rate, thus characterizing the novel miniCOMPACT detector array. This aids to optimize the conditions for experiments with superheavy elements. The bismuth progeny of 219Rn deposited on the SiO2 surface of the miniCOMPACT via diffusion-controlled deposition. Bismuth showed the expected high reactivity towards the SiO2 surface of the miniCOMPACT. Experiments in argon and oxygen atmosphere showed no measurable differences in the deposition distribution of the activity. The intermediate 36-min 211Pb, a member of the 227Ac decay chain feeding the studied bismuth isotope, was taken into account. To extract thermodynamical data from the results, namely the lower limit of the value of the adsorption enthalpy (-Delta Hads) of Bi on SiO2, we performed Monte Carlo simulations, adapted to account for the precursor effect, and compared the experimental results to their output. Simulations were also performed for bismuth's heavier homologue, moscovium, using a theoretically predicted value for -Delta Hads of this element on SiO2. These suggest moscovium to adsorb in the first part of the miniCOMPACT detector array, in line with recent observations.

Thorium ions and molecules, recognized for their distinctive nuclear and atomic attributes, are central to numerous trapped-ion experiments globally. Our study introduces an effective, compact source of thorium atomic and molecular ions produced via laser ablation of microgram-scale, salt-based samples. We thoroughly analyze the variety of ion species and charge states generated at varying laser fluences. Utilizing 10 µg of thorium fluoride crystals and laser fluences between 1.00(5) and 6.75(35) J/cm2, we produce thorium molecular ions ThFx232n+ (with x=0–3 and charge states up to n=3), including ThF2+ and ThF3+. These species are particularly relevant for spectroscopy; ThF3+ is valuable due to its stable closed-shell configuration, while ThF2+, which is isoelectronic to RaF, offers a unique probe for studying nuclear structure and fundamental symmetries due to its simple electronic structure with a single unpaired electron. Density-functional-theory-based calculations of the electric charge distribution aid in understanding the formation of the observed species. Positive charges are found to be mainly located on the thorium atom, which points to an inhibition of immediate Coulomb explosion, thus supporting the existence of the observed ion species. The simplicity of the method and similarities among the actinide elements suggest that our approach will also be applicable to other actinide species.

Precise measurements of fundamental decay data such as energies and transition probabilities of radioactive isotopes are important for the development of corresponding nuclear modelling, activity determination and various applications in science and technology. The EMPIR project PrimA-LTD -“Towards new Primary Activity standardisation methods based on Low-Temperature Detectors” - aims to measure the electron-capture decay of 55Fe very precisely using Metallic Microcalorimeters (MMCs) with outstandingly high energy resolution. Using a high-statistics measurement, electron-capture probabilities shall be precisely determined and higher-order effects such as electron shake-up and shake-off shall be examined with unprecedented precision. A key to success for this project is sample preparation. This work reports on the implantation of 55Fe into the 140 μm × 140 μm gold absorbers of the MMCs as a proof of principle for scalability. Building up on preparatory laser-spectroscopic studies on stable 56Fe, laser resonance ionization at the RISIKO mass separator was used to produce a monoisotopic 55Fe ion beam with the required specifications. Successful implantations of this isotope (i) into 32 test absorbers with about 0.7(2) Bq each and (ii) into various on-chip absorbers with an activity close to the requested 5 Bq per absorber are presented. The impact of the implantation on the quality of spectra is highlighted on the basis of first MMC test measurements.

The quantum-mechanical nuclear-shell structure determines the stability and limits of the existence of the heaviest nuclides with large proton numbers Z ≳ 100 (refs. 1-3). Shell effects also affect the sizes and shapes of atomic nuclei, as shown by laser spectroscopy studies in lighter nuclides4. However, experimental information on the charge radii and the nuclear moments of the heavy actinide elements, which link the heaviest naturally abundant nuclides with artificially produced superheavy elements, is sparse5. Here we present laser spectroscopy measurements along the fermium (Z = 100) isotopic chain and an extension of data in the nobelium isotopic chain (Z = 102) across a key region. Multiple production schemes and different advanced techniques were applied to determine the isotope shifts in atomic transitions, from which changes in the nuclear mean-square charge radii were extracted. A range of nuclear models based on energy density functionals reproduce well the observed smooth evolution of the nuclear size. Both the remarkable consistency of model prediction and the similarity of predictions for different isotopes suggest a transition to a regime in which shell effects have a diminished effect on the size compared with lighter nuclei.

Molecules containing short-lived, radioactive nuclei are uniquely positioned to enable a wide range of scientific discoveries in the areas of fundamental symmetries, astrophysics, nuclear structure, and chemistry. Recent advances in the ability to create, cool, and control complex molecules down to the quantum level, along with recent and upcoming advances in radioactive species production at several facilities around the world, create a compelling opportunity to coordinate and combine these efforts to bring precision measurement and control to molecules containing extreme nuclei. In this manuscript, we review the scientific case for studying radioactive molecules, discuss recent atomic, molecular, nuclear, astrophysical, and chemical advances which provide the foundation for their study, describe the facilities where these species are and will be produced, and provide an outlook for the future of this nascent field.

Laser ablation is performed on an oxidized, roughly 35-year-old 232Th foil. The produced anionic and cationic molecules are investigated utilizing precision mass measurements by a multireflection time-of-flight mass spectrometer. Molecules with up to three thorium atoms are identified. This includes oxides ThnO+x containing up to 2n - 1 oxygen atoms and further species incorporating carbon or nitrogen. In addition, signals of U+, UO+, and the compound species ThUO+2 are found. Photoexcitation reveals selected molecules' dissociation patterns. The experimental findings are compared to density functional theory calculations.

The borders of the periodic table of the elements and of the chart of nuclides are not set in stone. The desire to explore the properties of atoms and their nuclei in a regime of very large numbers of electrons, protons and neutrons has motivated new experimental facilities to create new elements and nuclides at the limits of atomic number and mass. But the small production rates and short lifetimes of superheavy nuclei and their atoms mean that ‘atom-at-a-time’ studies are the only experimental way to probe them. The physical and chemical data obtained so far, augmented by theoretical calculations, indicate significant deviations from extrapolations from lighter elements and isotopes. This situation raises the following question: how much further can one push the limits of the periodic table? In this Review, we describe the major challenges in the field of the superheavy elements and speculate about future directions.

Monte Carlo simulations are commonly used to model the behavior of chemical species of the heaviest elements and their homologs in gas chromatography experiments. In this paper, we present an extension of the fundamental Monte Carlo simulation proposed by Zvara in 1985. While preserving the core functionality, our code features two enhancements: first, it allows simulating experiments in which a primary radioisotope decays into a daughter isotope belonging to a different element, hence exhibiting different chemical properties. Second, it allows modeling scenarios where conversion of an initial chemical species to a different one can occur at temperatures high enough to overcome an activation barrier, facilitating simulations of related physisorption and chemisorption processes. This Monte Carlo code is applicable to open tubular and rectangular chromatography columns.

The atomic structure of neptunium (Np) was investigated by two-step resonance ionization spectroscopy. The study involved exploring ground-state transitions as well as following transitions to high-lying states just below the ionization potential (IP) or auto-ionizing states above the IP. That resulted in the identification of two-step ionization schemes, suitable for trace analysis and nuclear structure investigations. The lifetimes of two excited states located at 25,342.48 cm^-1 and 25,277.64 cm^-1 were determined as 230(12) ns and 173(9) ns, respectively. Because of the absence of Rydberg series in wide-ranging spectra recorded, the first IP was determined through the field ionization of high-lying, weakly-bound states using a well-controlled static electric field. By applying the saddle-point model, an IP value of 50,535.54(15) cm ^-1 [6.265608(19) eV] was derived. This value agrees with the current literature value of 50,535(2) cm ^-1 , while providing a more than ten times higher precision.

The investigation of the absolute scale of the effective neutrino mass remains challenging due to the exclusively weak interaction of neutrinos with all known particles in the standard model of particle physics. At present, the most precise and least-model-dependent upper limit on the electron antineutrino mass is set by the Karlsruhe Tritium Neutrino Experiment (KATRIN) from the analysis of the tritium beta-decay. Another promising approach is the electron capture in Ho-163, which is under investigation using microcalorimetry by the Electron Capture in Holmium (ECHo) and HOLMES collaborations. An independently measured Q value for this process is vital for the assessment of systematic uncertainties in the neutrino mass determination. Here we report a direct, independent determination of this Q value by measuring the free-space cyclotron frequency ratio of highly charged ions of Ho-163 and Dy-163 in the Penning-trap experiment PENTATRAP. Combining this ratio with atomic physics calculations of the electronic binding energies yields a Q value of 2,863.2 +/- 0.6 eV c(-2), which represents a more than 50-fold improvement over the state of the art. This will enable the determination of the electron neutrino mass on a sub-electronvolt level from the analysis of the electron capture in Ho-163.

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

Molecular plating is a well-established and widely used method for producing thin films of various elements, which are used in variety of nuclear physics applications. Sixty years have passed since the method was established, and some insights into the chemical process underlying the method and the composition of the thin films have been gained. A brief overview of what has been learned about molecular plating since its introduction and the methods applied in the characterization of molecular plated thin films is given here. Through various spectroscopic and microscopic methods, the process of molecular plating and the chemical composition are gradually being elucidated, albeit we still do not understand all aspects.

We report on high-resolution laser spectroscopy studies on 249-253Cf with spectral linewidths in the order of 100 MHz carried out at the RISIKO mass separator at Mainz University. In total three atomic ground-state transitions were investigated and the hyperfine parameters for the odd-A isotopes and isotope shift for all examined isotopes have been determined from the measured spectra. The isotope shift measurements allowed tracking of changes in mean-squared charge radii across the deformed nuclear shell closure at N = 152, whereby shape discontinuities were not observed. Experimental hyperfine coupling constants of the atomic ground state were combined with relativistic many-body atomic calculations to extract the nuclear magnetic-dipole moment of 249Cf with improved precision to mu I(249Cf) = -0.395(17 )mu N, whereas mu I(251Cf) = -0.571(24 )mu N and mu I(253Cf) = -0.731(35 )mu N were derived for the first time. Additionally, the spectroscopic quadrupole moments QS(249Cf) = 6.27(33) eb and QS(253Cf) = 5.53(51) eb were extracted.

The radiation detection resonance ionization spectroscopy (RADRIS) technique enables laser spectroscopic investigations of the heaviest elements which are produced in atom-at-a-time quantities from fusion-evaporation reactions. To achieve a high efficiency, laser spectroscopy is performed in a buffer-gas environment used to thermalize and stop the high-energy evaporation residues behind the velocity filter SHIP. The required cyclic measurement procedure in combination with the applied filament collection for neutralization as well as confinement of the stopped ions and subsequent pulse-heat desorption constrains the applicability of the technique. Here, some of these limitations and also opportunities that arise from this unique measurement setup will be evaluated.

Article Corrigendum to: Application of a novel gas phase synthesis approach to carbonyl complexes of accelerator-produced 5d transition metals (Radiochim. Acta 2022; 110 (2): 75–86) was published on January 30, 2023 in the journal Radiochimica Acta (volume 0, issue 0).

We give an overview of the special challenges regarding target development and production for accelerator-based heavy and superheavy-nuclei experiments in the past and perspectives for the future. Production of ever heavier elements, studies of heavy-element production in fusion or transfer reactions, spectroscopic investigations on their nuclear structure and decay and on the fission processes with fragment analyses, laser spectroscopic studies of their atomic structure, high-precision mass measurements as well as chemical studies are lively fields of current science. The ever-increasing beam intensities, feasible with new accelerator development, are crucial for the synthesis of superheavy elements because of the low cross sections for many of the reactions. Therefore, the development of target and backing materials with higher durability and experiment lifetime is increasingly important. Here we concentrate on the techniques necessary for the production of targets that are needed for experiments in this special field of interest. For the future, also development on target monitoring, target cooling, and beam intensity profile shaping techniques will play an important role, but are not in the focus of this article.