Periodic Reporting for period 4 - LRC (Laser Resonance Chromatography of Superheavy Metals)
Reporting period: 2023-12-01 to 2024-12-31
Currently, optical spectroscopy ends at element 102, nobelium. Beyond that, the atomic structure is experimentally unknown, and experiments become extremely challenging. Contemporary methods based on the detection of fluorescent atoms are not sensitive enough and are therefore not suitable for such studies. Our novel way of spectroscopy is called laser resonance chromatography and combines the advantages of high sensitivity - as in resonance ionization-based techniques - with the "simplicity" of optical probing as in fluorescence spectroscopy. The technique is fast and efficient and thus best suited for laser probing of fusion product ions as emitted by gas traps behind in-flight separators. Until the end of the project no optical spectroscopy of Lr+ ions could be performed, but now that we know the spectral regions in which to search for these lines, and with our meanwhile established spectroscopy method, the time is ripe to catch up and tackle optical spectroscopy of this elusive element behind the S3 separator of the GANIL/SPIRAL2 facility.
Experimentally, the Laser Resonance Chromatography setup is operational, see attached image (LRC_apparatus.jpg). The chromatographic performance of the apparatus was evaluated by analyzing the arrival time distributions (ATDs) of laser ablated Hf+ ions and the ATD peak separations when comparing Lu+ with Yb+ ions in their ground states. For the first time, a metastable ATD peak was observed in the Lu+ arrival time distributions. Also for the first time, laser resonance chromatography was successfully demonstrated by initiating the resonant 1S0-3P1 optical transition in this ion, allowing optical pumping to the 3D1 metastable state, see attached image (LRC_signal.png). Systematic studies were then performed to elucidate the effect of drift pressure on collision-induced quenching and the effect of sideband cooling on the broadening of the arrival time distributions. For the first time, we measured the hyperfine parameters of the 3P1 state in 176Lu+ and determined the isotope shift of the spectral line relative to the line of 175Lu+. To measure the extraction and transmission efficiencies, we used a 223Ra source, which provides 219Rn+ recoil ions. In a typical bunching mode operation, the overall efficiency of the apparatus is found to be 0.6 %, similar to efficiencies reported for laser resonance ionization-based techniques. The results of the inaugural experiments, including the efficiency measurements, have recently been reported in [NIMB 555 (2024) 165461]. Another manuscript is in preparation in which we report laser resonance chromatography on the two stable Lu+ isotopes. We expect these experimental results to be published by the end of this year.