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Description
Laser spectroscopy of neutron-deficient lutetium isotopes (Z=71) can provide insights into the evolution of nuclear structure towards the proton drip line, independent of any nuclear models. Probing the hyperfine structure with laser spectroscopy allows the measurement of nuclear spins, magnetic moments, quadrupole moments and isotope shifts of these exotic nuclei. The isotope shift can then be used to determine the charge radii across the isotopic chain, which in turn reveals how the nucleus deforms with varying neutron number [1].
This work investigated a more efficient ionization scheme compared to previous work done on lutetium in 1998 [2]. Additionally, this experiment was an opportunity to test the Laser Ion Source and Trap (LIST) and its newly-developed variant, the Perpendicularly Illuminated Laser Ion Source and Trap (PI-LIST). These are both useful methods for achieving high selectivity in resonance ionization spectroscopy. In LIST, resonance ionization occurs within a radiofrequency (RF) quadrupole, allowing only laser-ionized species to pass through while suppressing background ions. PI-LIST extends the capability of the LIST configuration by reducing doppler broadening effects, resulting in a higher resolution with spectral linewidths in the range of 200-300 MHz [3].
In September 2023 tests (LOI278) on lutetium isotopes conducted at ISOLDE utilised these techniques to investigate the sensitivity of a new resonance ionization scheme to the isotope shift, in preparation for future in-source laser spectroscopy of neutron-deficient lutetium with the PI-LIST setup.
Additionally, this project involves the commissioning of an RF transducer device to enhance the efficiency of the LIST setup. This device will incorporate phase-locking within a resonant LCL circuit to optimise signal stability and RFQ efficiency for improved performance. It has been demonstrated to achieve symmetric AC signals in the range of 2 MHz at 150 Vpp, which will optimise the transmission of ions through LIST and PI-LIST, particularly when dealing with low-yield isotopes. Upcoming plans will enable remote control of this device as well as modifications to improve thermal stability in operation.
This contribution presents an overview of the motivation for investigating neutron-deficient lutetium isotopes, a summary of the PI-LIST technique, results from Lu LOI278 and upgrades to the RF transducer box that planned for installation during LS3.
[1] Yang,X. et al. PPNP 129 (2020): 104005.
[2] Georg, U. et al. EPJ A 3 (1998): 225–235.
[3] Heinke, R. et al. Nucl. Instrum. Methods Phys. Res. B 541 (2023): 8-12.
