Resonance Laser Ionisation of Lanthanides: A case study of Praseodymium and Europium at CERN

Nuclear physics is the field that studies the nuclear force, nuclear structure, and nuclear reactions. Moreover, it describes the nucleus using a nuclear model, which depends on the type of nucleus. Lanthanides form a challenge to explain with a nuclear model due to their strong deformation and complex electronic shell structure. To be able to describe them with a good model, more information on their nuclear structure is required. A facility where such experiments on the nuclear structure take place is ISOLDE at CERN. This thesis focuses on the investigation of two lanthanides, praseodymium and europium. For this investigation, Resonance Ionisation Laser Ion Source, or RILIS at CERN is used. For praseodymium, the laser technique is applied with a focus on spectroscopy applications. For europium, the laser ionisation prioritises production applications. Many experiments take place at ISOLDE, often quickly one after another. Moreover, different elements require different laser setups. To be able to quickly change gear between experiments with different elements, a versatility in the laser setup is necessary. Titanium-doped sapphire lasers, also Ti:Sa lasers, are preferred in the RILIS laser setup because of their easier setup and reduced maintenance compared to the dye lasers. After a literature study, two laser schemes were developed for both praseodymium and europium, exclusively using titanium-doped sapphire lasers. Following this, the schemes were evaluated for their practical utility. An atomic sample was implemented in the Photo-Ionization Spectroscopy Apparatus, the so-called PISA. The atomic vapour that came out of the PISA's oven, was irradiated by lasers with the frequencies of the theoretical laser scheme. The laser setup used a Z-fold Ti:Sa in resonance with the first step of the laser scheme. A grating Ti:Sa was used to scan across the ionisation potential. Each time the grating Ti:Sa is in resonance with a Rydberg state, an increased ion signal is observed. The Rydberg states converge to the ionisation potential, hence the peaks converge until they can no longer be resolved. For praseodymium, no signal was found for either laser scheme. For europium, both laser schemes yielded a signal. Subsequently, they were used to investigate the current literature value of the ionisation potential. After an analysis, the resulting Rydberg scans generated values for the ionisation potential for europium per scan and per wave. The weighted average provided one value for the ionisation value at 5.670242±0.000003 eV. However, due to observed systematic fluctuations and taking into account the limitations of the experimental setup, it is more instructive to present an ionisation region.