Advances in laser spectroscopy of superheavy elements: Resonance ionization spectroscopy on 253,254,255Es and a new gas-jet based high-resolution spectroscopy setup
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Abstract
The first part aims towards the construction and development of a new gas-jet apparatus for high-resolution laser spectroscopy of heavy and superheavy elements. Here, laser spectroscopy is performed in a well-collimated, supersonic gas-jet created by a nozzle emerging from a high-pressure buffer gas stopping cell. From design and simulation studies, a first layout was assembled and off-line and on-line studies performed on natYb and 154-156Yb, leading to major design changes. After the implementation of these changes further measurements on natYb and 174Yb were performed, resulting in a spectral resolution of ≤ 400 MHz. The second part is dedicated to laser spectroscopy performed on the rare isotopes 253,254,255Es. With sample sizes ranging down to femtograms, ten ground-state transitions were investigated in 254Es with the hyperfine structure being resolved in five. The ground-state transition at 351.5 nm was measured additionally in 253,255Es, giving access to the isotope shifts for 253-255Es. Out of the hyperfine-structure analysis the hyperfine structure constants A and B were deduced for all three isotopes. From these constants the magnetic dipole moments and the spectroscopic electric quadrupole moments were derived. Additionally, the so far tentatively assigned nuclear spins were experimentally determined to I(254Es) = 7 and I(255Es) = 7/2.