Nobelium in the limelight – Atom-at-a-time laser spectroscopy at SHIP gives first insight in heavy element’s atomic structure

The analysis of atomic spectra is of fundamental importance for our understanding of atomic structures. Until now, researchers were unable to examine heavy elements with corresponding optical spectroscopy because these elements do not occur in nature and cannot be artificially created in weighable amounts. However, an international team of scientists and engineers led by Dr. Mustapha Laatiaoui (SHE physics department at GSI and HIM) and Prof. Michael Block (GSI, HIM and JGU Mainz) together with collaborators from our own department as well as several other research groups have now looked for the first time into the inner structure of heavy elements.

As reported in a paper in Nature, the ground state transition in nobelium (element 102) from the 1S0 ground state to the 1P1 excited state was characterized with high precision, as is typical for laser-based studies. Furthermore, from the observation of high-lying Rydberg states, information on the IP1 was obtained. Studies included the isotopes 252No and 254No, yielding information on the isotope shift, giving access to nuclear properties. The obtained data are in good agreement with current Relativistic Coupled Cluster and Multi Configuration Dirac Fock-based theoretical calculations. A schematic of the experimental setup is shown in the Figure below.

Schematic of the experimental setup for the laser spectroscopic studies of No. No ions (denoted by ) are separated from the primary 48Ca beam by the velocity filter SHIP, which they exit through a 3.5 μm Mylar foil acting as a vacuum window. They are stopped in a buffer gas cell filled with 95 mbar Ar, and collected on a Ta filament. Periodically, the filament is heated to 1350 K, which leads to evaporation of No in elemental form (). Two tunable laser beams shining into the volume provide for two-step resonance ionization. Formed No ions are guided by extraction electrodes onto a PIPS α detector, where the radioactive decay of the No isotope under study is registered.
Figure: Mustapha Laatiaoui / GSI/HIM


Mustapha Laatiaoui*, Werner Lauth, Hartmut Backe, Michael Block, Dieter Ackermann, Bradley Cheal, Premaditya Chhetri, Christoph Emanuel Düllmann, Piet van Duppen, Julia Even, Rafael Ferrer, Francesca Giacoppo, Stefan Götz, Fritz Peter Heßberger, Mark Huyse, Oliver Kaleja, Jadambaa Khuyagbaatar, Peter Kunz, Felix Lautenschläger, Andrew Kishor Mistry, Sebastian Raeder, Enrique Minaya Ramirez, Thomas Walther, Calvin Wraith & Alexander Yakushev
Atom-at-a-time laser resonance ionization spectroscopy of nobeliumTh
Nature 538, 495 – 498 (2016)
DOI: 10.1038/nature19345
*Corresponding author