High-precision mass spectrometry of nobelium, lawrencium and rutherfordium isotopes and studies of long-lived isomers with SHIPTRAP

In this work, the first successful application of the recently developed Phase-Imaging Ion-Cyclotron Resonance (PI-ICR) technique in the region of the heaviest elements is presented. For the first time, the atomic masses of several nobelium (No, Z=102), lawrencium (Lr, Z=103) and rutherfordium (Rf, Z=104) isotopes and isomers have been measured directly, reaching uncertainties on the order of few keV/c2 using the Penning-trap mass spectrometer SHIPTRAP. These heavy radionuclides were produced in fusion-evaporation reactions and separated from the primary beam by the velocity filter SHIP located at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. The mass measurements were carried out at production rates of few ions per second down to few ions per minute. To improve the overall efficiency on stopped and thermalized ions, the recently developed cryogenic gas-stopping cell was implemented into the existing beam line. Its performance with respect to purity and efficiency has been characterized and improved. The overall efficiency of SHIPTRAP is increased by about one order of magnitude with respect to previous measurements on heavy ions

Direct high-precision mass spectrometry of superheavy elements with SHIPTRAP

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 δm/m ≈ 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.Federal Ministry of Education & Research (BMBF) 05P15HGFNA 05P19HGFNA 05P21HGFN1 05P15UMFNA 05P21UMFN1Max Planck SocietyFoundation CELLEXNetherlands Organization for Scientific Research (NWO) 680-91-103European Commission under Marie Sklodowska-Curie Action FP7 MSC COFUND scheme European Research Council (ERC) 819957Ministry of Science and Innovation, Spain (MICINN) Spanish Government FPA2015-67694-P PID2019-104093GB-I00/AE

Research of the NUSTAR departments : SHE departments and HIM SHE section

The SHE departments devoted to the research of superheavy elements, operate the recoil separators SHIP and TASCA and their ancillary installations including SHIPTRAP and a laser spectroscopy setup at SHIP as well as chemistry and nuclear spectroscopy setups at TASCA. In 2019, the activities at GSI focused on the UNILAC beamtime within the FAIR Phase-0 program and on the analysis of data obtained in prior beamtimes. At HIM, the advancement of actinide sample preparation, manipulation, and characterization for various applications was most central. In addition, technical developments, for example for single-ion mass measurements, have been performed

Precision Measurement of the First Ionization Potential of Nobelium

One of the most important atomic properties governing an element’s chemical behavior is the energy required to remove its least-bound electron, referred to as the first ionization potential. For the heaviest elements, this fundamental quantity is strongly influenced by relativistic effects which lead to unique chemical properties. Laser spectroscopy on an atom-at-a-time scale was developed and applied to probe the optical spectrum of neutral nobelium near the ionization threshold. The first ionization potential of nobelium is determined here with a very high precision from the convergence of measured Rydberg series to be 6.626   21 ± 0.000   05     eV . This work provides a stringent benchmark for state-of-the-art many-body atomic modeling that considers relativistic and quantum electrodynamic effects and paves the way for high-precision measurements of atomic properties of elements only available from heavy-ion accelerator facilities

Low-lying octupole isovector excitation in Nd-144

International audienceThe nature of low-lying 3− levels in Nd144 was investigated in the Nd143(n,γγ) cold neutron-capture reaction. The combination of the high neutron flux from the research reactor at the Institut Laue-Langevin and the high γ-ray detection efficiency of the EXILL setup allowed the recording of γγ coincidences. From the coincidence data precise branching ratios were extracted. Furthermore, the octagonal symmetry of the setup allowed angular-distribution measurements to determine multipole-mixing ratios. Additionally, in a second measurement the ultra-high resolution spectrometer GAMS6 was employed to conduct lifetime measurements using the gamma-ray induced Doppler-shift technique (GRID). The confirmed strong M1 component in the 33−→31− decay strongly supports the assignment of the 33− level at 2779keV as low-lying isovector octupole excitation. Microscopic calculations within the quasiparticle phonon model confirm an isovector component in the wave function of the 33− level, firmly establishing this fundamental mode of nuclear excitation in near-spherical nuclei

Probing Sizes and Shapes of Nobelium Isotopes by Laser Spectroscopy

Until recently, ground-state nuclear moments of the heaviest nuclei could only be inferred from nuclear spectroscopy, where model assumptions are required. Laser spectroscopy in combination with modern atomic structure calculations is now able to probe these moments directly, in a comprehensive and nuclear-model-independent way. Here we report on unique access to the differential mean-square charge radii of 252, 253, 254No, and therefore to changes in nuclear size and shape. State-of-the-art nuclear density functional calculations describe well the changes in nuclear charge radii in the region of the heavy actinides, indicating an appreciable central depression in the deformed proton density distribution in 252, 254No isotopes. Finally, the hyperfine splitting of 253No was evaluated, enabling a complementary measure of its (quadrupole) deformation, as well as an insight into the neutron single-particle wave function via the nuclear spin and magnetic moment

Impact of forwarding conditions on productivity of forwarder Kranman Bison 10000

The aim of this study is to investigate potential uses of Kranman Bison 10000 6WD forwarder in thinning under normal and difficult forwarding conditions, to determine productivity, average load size and forwarding costs. In normal forwarding conditions productivity of forwarding increase by 11%. The average forwarded load is 2.0 m³ and the average load capacity is 80%, accordingly. Prime cost of chainsaw-prepared roundwood is 8.7 € mᐨ ³,but, when using harvester for preparing roundwood, itis possible to reduce the prime cost by about 2.9 € mᐨ ³

A setup to develop novel Chemical Isobaric SEparation (CISE)

Gas catchers are widely used to thermalize nuclear reaction products and subsequently extract them for precision measurements. However, impurities in the inert stopping gas can chemically react with the ions and thus influence the extraction efficiency. So far, chemical reactions in the gas-catcher have not been investigated in detail. Therefore, we are currently building a new setup to develop Chemical Isobaric SEparation (CISE) with the aim to understand the chemistry inside the gas-catcher and to explore its potential as a new technique for separation of isobars. In this paper, we give a short description of the setup together with the ion transportation studies performed via ion-optics simulations