0000000000313401
AUTHOR
P. Chhetri
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 ^{252,253,254}No, 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 densi…
A gas-jet apparatus for high-resolution laser spectroscopy on the heaviest elements at SHIP
© 2019 Elsevier B.V. Laser spectroscopy enables the determination of fundamental atomic and nuclear properties with high precision. In view of the low production rates of the heaviest elements, a high total efficiency is a crucial requirement for any experimental setup to be used in on-line experiments. The setup requires the use of gas stopping techniques to slow down the radionuclides of interest. In previous studies laser spectroscopy was performed inside a gas-filled stopping cell with a limited spectral resolution of a few GHz. Collisional broadening inside stopping cells ultimately limits the precision of laser spectroscopic studies and hampers in particular hyperfine spectroscopy. Th…
The 48Ca+181Ta reaction: Cross section studies and investigation of neutron-deficient 86 ≤ Z ≤ 93 isotopes
© 2019 Fusion-evaporation reactions with the doubly magic projectile 48 Ca were used to access neutron-deficient nuclei around neptunium at the velocity filter SHIP, and investigated using the COMPASS decay spectroscopy station. With the use of digital electronics, several isotopes produced via neutron, proton, and α evaporation channels were identified by establishing correlated α-decay chains with short-lived sub-μs members. Data are given on decay chains stemming from 225,226 Np, 225 U, and 222,223 Pa. New information on the isotopes 225,226 Np and 222 Pa was obtained. Production cross sections of nuclei in the region using a variety of projectiles are discussed. The measured production …
Developments for resonance ionization laser spectroscopy of the heaviest elements at SHIP
Abstract The experimental determination of atomic levels and the first ionization potential of the heaviest elements ( Z ⩾ 100 ) is key to challenge theoretical predictions and to reveal changes in the atomic shell structure. These elements are only artificially produced in complete-fusion evaporation reactions at on-line facilities such as the GSI in Darmstadt at a rate of, at most, a few atoms per second. Hence, highly sensitive spectroscopic methods are required. Laser spectroscopy is one of the most powerful and valuable tools to investigate atomic properties. In combination with a buffer-gas filled stopping cell, the Radiation Detected Resonance Ionization Spectroscopy (RADRIS) techniq…
COMPASS—A COMPAct decay spectroscopy set-up
Abstract A compact silicon detector array with high spatial granularity and fast, fully digital data recording has been developed and commissioned for the investigation of heavy and superheavy nuclear species. The detector array can be combined in close geometry with large volume germanium detectors. It offers comprehensive particle and photon coincidence and correlation spectroscopy by highly efficient evaporation residue, α , γ , conversion electron and X-ray detection supported by the high granularity of the implantation chip. Access to fast decay events in the sub-microsecond region is made possible by the fast timing properties of the digital signal processing. A novel Si-chip support …
Atom-at-a-time laser resonance ionization spectroscopy of nobelium
Resonance ionization spectroscopy of nobelium (atomic number 102) reveals its ground-state transition and an upper limit for its ionization potential, paving the way to characterizing even heavier elements via optical spectroscopy. Characterizing the heaviest elements in the periodic table is a gruelling task because they are radioactive, exist only for split seconds at a time and need to be artificially produced in sufficient quantities by complicated procedures. The heaviest element that has been characterized by optical spectroscopy is fermium, which has an atomic number of 100. Mustapha Laatiaoui et al. extend the methods used for fermium to perform optical spectroscopy on nobelium (ato…
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 st…
Recent Upgrades of the SHIPTRAP Setup: On the Finish Line Towards Direct Mass Spectroscopy of Superheavy Elements
With the Penning-trap mass spectrometer SHIPTRAP at GSI, Darmstadt, it is possible to investigate exotic nuclei in the region of the heaviest elements. Few years ago, challenging experiments led to the direct measurements of the masses of neutron-deficient isotopes with Z = 102,103 around N = 152. Thanks to recent advances in cooling and ion-manipulation techniques, a major technical upgrade of the setup has been recently accomplished to boost its efficiency. At present, the gap to reach more rare and shorter-lived species at the limits of the nuclear landscape has been narrowed. ispartof: pages:423-429 ispartof: Acta Physica Polonica B vol:48 issue:3 pages:423-429 ispartof: location:Zakopa…
The performance of the cryogenic buffer-gas stopping cell of SHIPTRAP
Direct high-precision mass spectrometry of the heaviest elements with SHIPTRAP, at GSI in Darmstadt, Germany, requires high efficiency to deal with the low production rates of such exotic nuclides. A second-generation gas stopping cell, operating at cryogenic temperatures, was developed and recently integrated into the relocated system to boost the overall efficiency. Offline measurements using 223Ra and 225Ac recoil-ion sources placed inside the gas volume were performed to characterize the gas stopping cell with respect to purity and extraction efficiency. In addition, a first online test using the fusion-evaporation residue 254No was performed, resulting in a combined stopping and extrac…
Impact of buffer gas quenching on the $^1S_0$ $\to$ $^1P_1$ ground-state atomic transition in nobelium
International audience; Using the sensitive Radiation Detected Resonance Ionization Spectroscopy (RADRIS) techniquean optical transition in neutral nobelium (No, Z = 102) was identified. A remnant signal when delaying the ionizing laser indicated the influence of a strong buffer gas induced de-excitation of the optically populated level. A subsequent investigation of the chemical homologue, ytterbium (Yb, Z = 70), enabled a detailed study of the atomic levels involved in this process, leading to the development of a rate equation model. This paves the way for characterizing resonance ionization spectroscopy (RIS) schemes used in the studyof nobelium and beyond, where atomic properties are c…
Simulation studies of the laser ablation ion source at the SHIPTRAP setup
Hyperfine interactions 241(1), 46 (2020). doi:10.1007/s10751-020-01708-0