Laser developments and study of Rydberg and autoionizing Rydberg states in Tm, La and At using resonant ionization laser spectroscopy

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Mostamand, Maryam
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The resonant ionization laser ion source is an element-selective, efficient and versatile ion source which generates radioactive ion beams at on-line mass separator facilities. Elements with complex atomic structures and incomplete spectroscopic data require ionization scheme development. A grating-tuned titanium:sapphire (Ti:Sa) laser was used in applications for spectroscopy studies. A regiment of automated and continuous frequency-doubled and frequency tripled scans was developed to investigate different energy regions and electronic configurations of the elements. An intra-cavity frequency doubled chromium:forsterite laserwas built, to cover the spectral gap between the orange and red wavelengths as these are not attainable using Ti:Sa lasers. Laser resonance ionization spectroscopy has been performed on lanthanum (La) and thulium (Tm) at TRIUMF’s off-line laser ion source test stand to identify the highest efficiency ionization scheme for delivery of radioactive ion beams. Upon identification of possible two-step Ti:Sa laser based ionization schemes, systematic laser resonance ionization spectroscopy was performed by conducting laser scans across Rydberg states, ionization potentials, and auto-ionizing states. The spectroscopy of high-lying Rydberg states and auto-ionizing Rydberg states allowed to confirm and remeasure the ionization potential of Tm and La atom with improved accuracy. In-source resonance ionization spectroscopy of the purely radioactive astatine (At) atom was performed at the ISAC/TRIUMF radioactive ion beam facility to search for an efficient ionization scheme throughout auto-ionizing states. Apart from developing and implementing resonance ionization spectroscopy (RIS) schemes for elements, the issue of isobaric contamination in radioactive ion beam (RIB) delivery was addressed. On the newly implemented ion guide laser ion source (IG-LIS) for isobarically pure i ii RIB, operating modes and parameters were being developed and optimized. Design improvements are being implemented into the prototype for more robust and efficient on-line operation, and based on simulation (SIMION 8.0.4) studies further refinements are being implemented on the quadrupole ion guide based IG-LIS and a higher efficiency octupole based IG-LIS is being proposed.
Laser developments, Laser ion source, Laser resonance ionization spectroscopy, Lanthanum (La), Thulium (Tm), Astatine (At), Ion guide laser ion source (IG-LIS), Ti:Sa lasers, Cr:forsterite laser, Grating tuned laser, Ionization potential (IP) measurement, Rydberg states, Autoionizing states, SIMION simulation