Authors:	Naubereit, Pascal
Title:	Resonance Ionization Spectroscopy of Protactinium : Studies on Intrinsic Quantum Chaos and the Ionization Potential
Online publication date:	14-Oct-2020
Year of first publication:	2020
Language:	english
Abstract:	The rare and all-radioactive actinide element protactinium (Pa) is one of the very few examples where even the most powerful experimental technique of resonance ionization spectroscopy (RIS) ultimately reaches its limits. On the one hand, the chemical properties of this element hinders the efficient production of a stable ion beam using RIS in a hot cavity ion source. Additionally, only small sample sizes of Pa can be used for the measurements due to its radioactivity and due its availability at all. On the other hand, even in the case one does really succeed to record atomic spectra, the analysis is strongly hampered due to the extraordinary complexity of the observed level structure. The present thesis is addressing exactly these challenges. This is why the spectroscopy and espe- cially the subsequent analysis of the spectra make up the main part of this work. Beforehand, the method RIS as well as the apparatus used need to be introduced. Following a generalized introduc- tion, an explanation of RIS, the laser system and the spectrometer setup used, a first featured article, Resonance ionization spectroscopy of sodium Rydberg levels using difference frequency generation of high- repetition-rate pulsed Ti:sapphire lasers, validates RIS in combination with Rydberg analysis as method of choice for extraction of the ionization potential (IP) of almost any element. Additionally, the tool of difference frequency generation was applied to the Mainz Ti:sapphire lasers in order to significantly enlarge their available wavelength range. Most often, highly elaborate experiments are only possible if a functional and diversified research network of expert groups is working together. Luckily, the LARISSA working group has built up a set of several valuable collaborations. Exemplarily, the outcome of one of those collaborations is presented in the second featured article, Developments towards in-gas-jet laser spectroscopy studies of ac- tinium isotopes at LISOL, describing preparatory activities, which will give rise to many upcoming collaborative publications. Here, the novel technique of RIS in a supersonic gas jet was tested and ap- proved to be highly efficient as well as to offer extremely high spectral resolution in the obtained data, which both is necessary for on-line production and investigations of rare isotopes far-off stability. The main part of the present thesis comprises different studies on the actinide element protac- tinium. At first, a sketch of the history of its discovery and the challenges one has to face for its study are presented. In the following third publication, Excited atomic energy levels in protactinium by resonance ionization spectroscopy, the RIS measurements on protactinium are presented. A rather large contribution to this article is also the level analysis which was necessary to arrange the vast collec- tion of energy levels in proper order. More than 1500 energy levels with excitation energies of up to 50000 cm−1 were extracted from the extremely dense spectra. After spectroscopy, the subsequent chapter addresses the search for the IP of Pa. Since all conven- tional methods could not be successfully applied to the withstanding element, a procedure implying a combination of two different methods of analysis has been developed and is presented in detail. With this procedure the extraction of the IP from the complex level structure of the RIS spectra was achieved and led to an IP of E_Pa_IP = 49034(10) cm−1. Due to the extraordinary complexity of the Pa spectra, the presence of intrinsic quantum chaos (IQC) was speculated. Despite the fact, that this introduces a completely new research area to the LARISSA group, the last chapter of the thesis’ main part covers this assumption including a quali- tative introduction to quantum chaos and a complete analysis of the spectra regarding IQC aspects. The results of this analysis are comprised in a forth featured publication, Intrinsic quantum chaos and spectral fluctuations within the protactinium atom. Herein, the spectral statistics were investigated thoroughly and the influence of missing levels or mixed level sets was analyzed in detail.
DDC:	000 Allgemeines 000 Generalities 530 Physik 530 Physics
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 08 Physik, Mathematik u. Informatik
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-5183
URN:	urn:nbn:de:hebis:77-openscience-9ee9c553-27d4-40a5-93cc-1822afd011f52
Version:	Original work
Publication type:	Dissertation
License:	In Copyright
Information on rights of use:	https://rightsstatements.org/vocab/InC/1.0/
Extent:	xiii, 89 Seiten
Appears in collections:	JGU-Publikationen