The radioactive decay properties of 242Es were studied at the gas -filled recoil separator TASCA. This isotope was produced in the 3n evaporation channel of the fusion reaction of 48Ca + 197Au. A half-life of 16.9(8) s was deduced from 662 alpha decays of 242Es, resulting in an alpha-decay branching of 41(3)%. Twenty-six fission events with a half-life of 18.2+4.5 -3.0 s were assigned to originate from the electron -capture delayed fission of 242Es. The probability for the electron -capture delayed fission was measured to be 0.015(4), which improves and resolves ambiguities in available experimental data. We discuss all known cases for electron -capture delayed fission in Es, Bk, and Am isotopes and compare experimental data with predictions from a recent semiempirical model. A cross section of 27(3) nb was measured for the production of 242Es.

Chemical reactivity of the superheavy elements nihonium (Nh, element 113) and moscovium (Mc, element 115) has been studied by the gas-solid chromatography method using a new combined chromatography and detection setup. The Mc isotope, 288Mc, was produced in the nuclear fusion reaction of 48Ca ions with 243Am targets at the GSI Helmholtzzentrum Darmstadt, Germany. After isolating 288Mc ions in the gas-filled separator TASCA, adsorption of 288Mc and its decay product 284Nh on silicon oxide and gold surfaces was investigated. As a result of this work, the values of the adsorption enthalpy of Nh and Mc on the silicon oxide surface were determined for the first time, −∆HadsSiO2Mc=54−5+11 kJ/mol and −∆HadsSiO2Nh=58−3+8 kJ/mol (68% c.i.). The obtained −ΔHads values are in good agreement with results of advanced relativistic calculations. Both elements, Nh and Mc, were shown to interact more weakly with the silicon oxide surface than their lighter homologues Tl and Bi, respectively. However, Nh and Mc turned out to be more reactive than the neighbouring closed-shell and quasi-closed-shell elements copernicium (Cn, element 112) and flerovium (Fl, element 114), respectively. The established trend is explained by the influence of strong relativistic effects on the valence atomic orbitals of these elements.

Sympathetic cooling of Th$^{3+}$ ions is demonstrated in an experiment where $^{229}$Th and $^{230}$Th are extracted from uranium recoil ion sources and are confined in a linear Paul trap together with laser-cooled $^{88}$Sr$^+$ ions. Because of their similar charge-to-mass ratios the ions are closely coupled and arrange themselves in two-species Coulomb crystals, containing up to a few tens of Th$^{3+}$ ions. To show the suitability of the sympathetically cooled Th$^{3+}$ ions for high-resolution laser spectroscopy, the absolute frequencies and isotope shifts of 5F$_{5/2}$\,$\rightarrow$\,6D$_{5/2}$ and 5F$_{7/2}$\,$\rightarrow$\,6D$_{5/2}$ transitions of $^{230}$Th$^{3+}$ have been measured. The system is developed for hyperfine spectroscopy of electronic transitions of nuclear ground and isomeric states in $^{229}$Th$^{3+}$.

ISOLDE's Offline 2 laboratory has been upgraded to facilitate development for the production and study of molecular ion beams. New gas injection systems have been implemented for both molecular formation in the ion source and in the radio-frequency quadrupole ion trap used for beam preparation. MagneToF detectors and time-resolved single ion counting data acquisition have been implemented for low intensity beams and studies of laser-atom or laser-molecule interactions. We present a study of the formation and ionization of BaF+ using the upgraded facility.

Accelerator-based techniques are one of the leading ways to produce radioactive nuclei. In this work, the isotope separation on-line method was employed at the CERN-ISOLDE facility to produce neptunium and plutonium from a uranium carbide target material using 1.4-GeV protons. Neptunium and plutonium were laser-ionized and extracted as 30-keV ion beams. A multireflection time-of-flight mass spectrometer was used for ion identification by means of time-of-flight measurements as well as for isobaric separation. Isotope shifts were investigated for the 395.6-nm ground state transition in 236,237,239Np and the 413.4-nm ground state transition in 236,239,240Pu.Rates of 235-241Np and 234-241Pu ions were measured and compared with predictions of in-target production mechanisms simulated with GEANT4 and FLUKA to elucidate the processes by which these nuclei, which contain more protons than the target nucleus, are formed. 241Pu is the heaviest nuclide produced and identified at a proton-accelerator-driven facility to date. We report the availability of neptunium and plutonium as two additional elements at CERN-ISOLDE and discuss the limit of accelerator-based isotope production at high-energy proton accelerator facilities for nuclides in the actinide region.

Flerovium isotopes (element Z = 114) were produced in the fusion-evaporation reactions 48Ca + 242,244Pu and studied with an upgraded TASISpec decay station placed in the focal plane of the gas-filled separator TASCA at the GSI Helmholtzzentrum fur Schwerionenforschung in Darmstadt, Germany. Twenty-nine flerovium decay chains were identified by means of correlated implantation, alpha decay, and spontaneous fission events. Data analysis aspects and statistical assessments, primarily based on measured rates of various events, which laid the foundation for the comprehensive spectroscopic information on the flerovium decay chains, are presented in detail. Various decay scenarios of an excited state observed in 282Cn are examined in depth with the help of GEANT4 simulations and assessed by predictions of beyond mean-field calculations including triaxial shape degrees of freedom. Previous, revised, and newly derived fission probabilities of even-even superheavy nuclei are compared with various theoretical predictions.

The in-gas laser ionization and spectroscopy (IGLIS) technique has been a cornerstone in the study of heavy elements. The addition of a convergent–divergent (de Laval) nozzle to perform laser ionization in a cold hypersonic gas jet greatly improves the achievable resolution. Recent efforts have focused on preparing the in-gas-jet method for the study of the low-lying 229Th isomer. Tailor-made recoil sources of 233U are installed inside a fast extraction gas cell to provide the (isomeric) thorium ions. A level search above the second ionization potential (IP) uncovered several auto-ionizing states, greatly improving the laser ionization efficiency of singly charged thorium ions.

Fifteen correlated alpha-decay chains starting from the odd-A superheavy nucleus 289Fl were observed following the fusion-evaporation reaction Ca-48 + Pu-244. The results call for at least two parallel alpha-decay sequences starting from at least two different states of (289)Fl. This implies that close-lying levels in nuclei along these chains have quite different spin-parity assignments. Further, observed alpha-electron and alpha-photon coincidences, as well as the alpha decay fine structure along the decay chains, suggest a change in the ground-state spin assignment between (285)Cn and (281)Ds. Our experimental results, on the excited level structure of the heaviest odd-N nuclei to date, provide a direct testing ground for theory. This is illustrated by comparison with new nuclear structure calculations based on the symmetry-conserving configuration mixing theory.

The use of radioactive molecules for fundamental physics research is a developing interdisciplinary field limited dominantly by their scarce availability. In this work, radioactive molecular ion beams containing actinide nuclei extracted from uranium carbide targets are produced via the Isotope Separation On-Line technique at the CERN-ISOLDE facility. Two methods of molecular beam production are studied: extraction of molecular ion beams from the ion source, and formation of molecular ions from the mass-separated ion beam in a gas-filled radio-frequency quadrupole ion trap. Ion currents of U+, UO1-3+, UC1-3+, UF1-4+, UF1,2O1,2+ are reported. Metastable tantalum and uranium fluoride molecular ions are identified. Formation of UO1-3+, U(OH)1-3+, UC1-3+, UF1,2O1,2+ from mass-separated beams of U+, UF1,2+ with residual gas is observed in the ion trap. The effect of trapping time on molecular formation is presented.

The ECHo experiment has been designed for the determination of the effective electron neutrino mass by means of the analysis of the end-point region of the Ho-163 electron capture spectrum. Metallic magnetic calorimeters enclosing Ho-163 are used for the high energy resolution calorimetric measurement of the 163Ho spectrum. For the first phase of the experiment, ECHo-1k, a 72-pixel MMC array has been developed. The single-pixel design has been optimised to reach 100% stopping power for the radiation emitted in the 163Ho electron capture process (besides the electron neutrino) and an energy resolution delta-FWHM < 10 eV. We describe the design of the ECHo-1k detector chip, the fabrication steps and the characterisation at room temperature, at 4 K and at the final operation temperatures. In particular, a detailed analysis of the results from these tests allowed to define a quality check protocol based on parameters measurable at room temperature. We discuss the performance achieved with the two ECHo-1k detector chips - the first one with Ho-163 implanted in gold and the second one with Ho-163 implanted in silver - which have been used for the high statistics measurement of the ECHo-1k experiment. An average activity per pixel of 0.81 Bq and 0.71 Bq and an average energy resolution of 6.07 eV FWHM and 5.55 eV FWHM have been achieved with these two detectors, fulfilling the requirements for the first phase of the ECHo experiment.

Laser resonance ionization spectroscopy was performed on the rare einsteinium isotopes Es253-255 at the RISIKO mass separator in Mainz. With low sample sizes ranging down to femtograms, the prominent 352 nm-ground-state transition was measured in all three einsteinium isotopes, and four additional ground-state transitions were measured in Es-254. Hyperfine-structure analysis resulted in assigned spin values of I(Es-254) ) = 7 and I(Es-255) = 7/2. From the extracted coupling constants, nuclear magnetic dipole moments of mu(I)(Es-254 ) = 3.42(7) mu(N) and( )mu(I)(Es-255) = 4.14(10) mu(N) as well as spectroscopic electric quadrupole moments of Q(S)(Es-254) = 9.6(1.2) eb and Q(S) (Es-255) = 5.1(1.7) eb were derived. Our value for Es-254 deviates from the value of vertical bar mu(I)(Es-254)vertical bar = 4.35(41) mu(N) extracted from the angular anisotropy of alpha-radiation emitted by Es-254.

In the present work, a K isomeric state in No-250, which is more stable against fission than the ground state, was experimentally studied. The aim was to measure the fission branch of this isomeric state. In total, 780 fission events attributed to the decay of No-250 were detected. Among them 133 cases were attributed to the ground-state decay with a half-life of 4.0(4) mu s, which was populated by the deexcitation of the isomeric state via electromagnetic transitions with a half-life of 23(4) mu s. In addition, in two more cases, this long-lived isomeric state was populated in the deexcitation of a hitherto unknown, yet higher-lying and short-lived isomeric state with a half-life of 0.7(-0.3)(+1.4) mu s. No direct fission from the long-lived isomeric state, i.e., with a lifetime of longer than 40 mu s, was identified. This results in an upper limit of 0.035 for the branching ratio for fission. This is a significantly more strict limit than the previously known value of 0.5. Nonobservation of fission branching of the long-lived isomer is discussed relative to theoretical predictions and within various semiempirical ways, which resulted in an attribution of a lower limit of 10(4) for the fission-hindrance factor, caused by the K quantum number. The presences of multiple high-K isomeric states seemingly is a widespread phenomenon in deformed heavy nuclei.

Superheavy elements are produced via fusion reactions, by bombarding thin target foils with intense beams of energetic ions with energies around the Coulomb barrier. Currently, production of targets of rare isotopes relies mainly on the molecular plating (MP) method, which yields thin films of the desired target material on a backing foil. Intense heavy-ion beams are known to modify the film structure, which leads to deterioration of the targets over irradiation time. To gain a better understanding of the processes at a microscopic scale, comparative tests were carried out using Coulomb barrier heavy-ion beams provided from the UNILAC accelerator at GSI Darmstadt, Germany. For this purpose, targets of lead were prepared using MP and Drop-on-Demand inkjet-printing. Lead targets were baked-in and analysed by digital optical microscopy, scanning electron microscopy and confocal Raman spectroscopy.

Flerovium (Fl, element 114) is the heaviest element chemically studied so far. To date, its interaction with gold was investigated in two gas-solid chromatography experiments, which reported two different types of interaction, however, each based on the level of a few registered atoms only. Whereas noble-gas-like properties were suggested from the first experiment, the second one pointed at a volatile-metal-like character. Here, we present further experimental data on adsorption studies of Fl on silicon oxide and gold surfaces, accounting for the inhomogeneous nature of the surface, as it was used in the experiment and analyzed as part of the reported studies. We confirm that Fl is highly volatile and the least reactive member of group 14. Our experimental observations suggest that Fl exhibits lower reactivity towards Au than the volatile metal Hg, but higher reactivity than the noble gas Rn.

Direct mass measurements in the region of the heaviest elements were performed with the Penning-trap mass spectrometer SHIPTRAP at GSI Darmstadt. Utilizing the phase-imaging ion-cyclotron-resonance massspectrometry technique, the atomic masses of 251No (Z = 102), 254Lr (Z = 103), and 257Rf (Z = 104) available at rates down to one detected ion per day were determined directly for the first time. The ground-state masses of 254No and 255,256Lr were improved by more than one order of magnitude. Relative statistical uncertainties as low as delta m/m approximate to 10-9 were achieved. Mass resolving powers of 11 000 000 allowed resolving long-lived low-lying isomeric states from their respective ground states in 251,254No and 254,255Lr. This provided an unambiguous determination of the binding energies for odd-A and odd-odd nuclides previously determined only indirectly from decay spectroscopy.

In the heaviest elements, the instability of atomic nuclei against spontaneous fission leads to ever shorter nuclear half-lives. Upon falling below a timescale of 10(-14) s, the border of existence of isotopes is crossed because this is the timescale on which the formation of atomic shells occurs. Analysis of the experimental data on the spontaneous fission half-lives of Rf isotopes in relation with their expected single-particle orbitals hint at a potentially abrupt decrease in half-lives of unknown neutron-deficient Rf isotopes with neutron numbers <149, which suggests that the isotopic border is already almost reached. However, this conjecture, which cannot be explained within the current knowledge, was directly related to uncertainty in the experimental data on (253)Rf. We revisited the decay of (253)Rf and identified two fission activities, which are attributed to decays of the two different states with half-lives of 12.8(-3.4)(+7.0) ms and 44(-10)(+17) mu s. In addition, hitherto unknown alpha decay in (253)Rf, which is followed by alpha decay of the new isotope No-249 with a half-life of 15(7)(+74) ms, was observed. Based on our new data, no abrupt decreases in half-lives of the neutron-deficient No and Rf isotopes are expected, which is in line with theoretical predictions. Fission half-lives of the two different states in (253)Rf are benchmark cases for the theoretical description of the single-particle orbital influence on the fission process.

Nihonium (Nh, element 113) and flerovium (Fl, element 114) are the first superheavy elements in which the 7p shell is occupied. High volatility and inertness were predicted for Fl due to the strong relativistic stabilization of the closed 7p 1/2 sub-shell, which originates from a large spin-orbit splitting between the 7p 1/2 and 7p 3/2 orbitals. One unpaired electron in the outermost 7p 1/2 sub-shell in Nh is expected to give rise to a higher chemical reactivity. Theoretical predictions of Nh reactivity are discussed, along with results of the first experimental attempts to study Nh chemistry in the gas phase. The experimental observations verify a higher chemical reactivity of Nh atoms compared to its neighbor Fl and call for the development of advanced setups. First tests of a newly developed detection device miniCOMPACT with highly reactive Fr isotopes assure that effective chemical studies of Nh are within reach.

A nuclear spectroscopy experiment was conducted to study α-decay chains stemming from isotopes of flerovium (element Z=114). An upgraded TASISpec decay station was placed behind the gas-filled separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. The fusion-evaporation reactions ^{48}Ca+^{242}Pu and ^{48}Ca+^{244}Pu provided a total of 32 flerovium-candidate decay chains, of which two and eleven were firmly assigned to ^{286}Fl and ^{288}Fl, respectively. A prompt coincidence between a 9.60(1)-MeV α particle event and a 0.36(1)-MeV conversion electron marked the first observation of an excited state in an even-even isotope of the heaviest man-made elements, namely ^{282}Cn. Spectroscopy of ^{288}Fl decay chains fixed Q_{α}=10.06(1)  MeV. In one case, a Q_{α}=9.46(1)-MeV decay from ^{284}Cn into ^{280}Ds was observed, with ^{280}Ds fissioning after only 518  μs. The impact of these findings, aggregated with existing data on decay chains of ^{286,288}Fl, on the size of an anticipated shell gap at proton number Z=114 is discussed in light of predictions from two beyond-mean-field calculations, which take into account triaxial deformation.

To study the chemical properties of the heaviest elements, a fast and efficient stopping and extraction of the highly energetic residues from heavy ion fusion reactions into the chemistry setup is essential. Currently used techniques like Recoil Transfer Chambers (RTC) relying on gas flow extraction provide high efficiencies for chemically non-reactive volatile species, but operate at extraction times t(extr) of about 0.5 s or more. Buffer Gas Cells (BGC) with electric and Radio-Frequency (RF) fields offer much faster extraction times. Here, we demonstrate the successful coupling of a BGC to a gas chromatography setup as is used for studies of chemical properties of superheavy elements. Using Ra-223 and Ac-225 recoil ion sources providing Rn-219 and Fr-221 ions for off-line tests, an extraction time t(extr) = 55(4) ms and an extraction efficiency of 35(3)% were achieved for the non-reactive Rn-219, while Fr-221 was retained. The results show a BGC-based setup to be suitable for gas-phase experiments with short-lived volatile transactinide elements like Cn and Fl with half-lives substantially below 1 s.

In two recent papers by Pore et al. and Khuyagbaatar et al., discovery of the new isotope ^{244}Md was reported. The decay data, however, are conflicting. While Pore et al. report two isomeric states decaying by α emission with E_{α}(1)=8.66(2)  MeV, T_{1/2}(1)=0.4_{-0.1}^{+0.4}  s and E_{α}(2)=8.31(2)  MeV, T_{1/2}(2)≈6   s, Khuyagbaatar et al. [Phys. Rev. Lett. 125, 142504 (2020).PRLTAO0031-900710.1103/PhysRevLett.125.142504] report only a single transition with a broad energy distribution of E_{α}=(8.73-8.86)  MeV and T_{1/2}=0.30_{-0.09}^{+0.19}  s. The data published in Pore et al. are very similar to those published for ^{245m}Md [E_{α}=8.64(2), 8.68(2) MeV, T_{1/2}=0.35_{-0.16}^{+0.23}  s [V. Ninov, F. P. Heßberger, S. Hofmann, H. Folger, G. Münzenberg, P. Armbruster, A. V. Yeremin, A. G. Popeko, M. Leino, and S. Saro, Z. Phys. A 356, 11 (1996).ZPAHEX0939-792210.1007/s002180050141] ]. Therefore, we compare the data presented for ^{244}Md in Pore et al. with those reported for ^{245}Md in Ninov et al. and also in Khuyagbaatar et al. We conclude that the data presented in Pore et al. shall be attributed to ^{245}Md with small contributions (one event each) from ^{245}Fm and probably ^{246}Md.