Studying the structure of the heaviest actinide elements by laser spectroscopy

by Jessica Warbinek (GSI Darmstadt)

Tuesday 12 Mar 2024, 16:00 → 17:00 Europe/Zurich

26/1-022 (CERN)

Experimental studies tailored to unveil fundamental properties of the heaviest actinide elements have recently gained increasing interest and yet the available information remains sparse. Nuclides in this region of the nuclear chart are stabilized by shell effects that retard spontaneous fission and they feature properties distinctly different from those of lighter nuclides.
In addition, the atomic structure of these heavy elements features an enhanced impact of relativistic effects impacting their chemical properties compared to the lighter homologes [1]. Expeirmental investigations however are hampered by limited production capabilities and short half-lives of these nuclides. Laser spectroscopy is a powerful tool to investigate atomic and nuclear structures of these heavy, exotic elements [2]. First experimental observations of this kind were pioneered by the dedicated RAdiation Detected Resonance Ionization Spectroscopy (RADRIS) method in the heavy actinide element nobelium (Z = 102) produced in atom-at-a-time quantities at the SHIP separator at GSI [3,4]. Recent advancements of the setup and a novel indirect production scheme gave access to nuclides which were previously not in reach. This enabled first on-line laser spectroscopy studies of fermium (Z = 100) down to minute production rates. On-line and off-line laser spectroscopy techniques were combined and significantly advanced to study a chain of eight isotopes on both sides of the known deformed shell gap at N = 152. Tackling investigations in even heavier elements, such as the search for atomic levels in the heaviest actinide, lawrencium (Z = 103), with a tenfold lower production rate as in the nobelium isotone, the increased sensitivity of this technique [5] will give a decisive benefit.
Recent results and methodological advancements will be discussed in view of further perspectives for laser spectroscopy of the heaviest elements. The presented experimental observations give insight into the nuclear structure of the heavy actinides supporting new developments in theoretical models which will eventually improve their predictive power.

[1] M. Block et al., Prog Part Nucl Phys 116, 103834 (2021).
[2] X. Yang et al., Prog Part Nucl Phys 104005 (2023).
[3] M. Laatiaoui et al., Nature 538, 495–498 (2016).
[4] S. Raeder et al., Phys Rev Lett 120, 232503 (2018).
[5] J. Warbinek et al., Atoms 10, 41 (2022).