UV and VUV photoionization of some metal atoms and ions
Lu, HuORCID: 0000-0001-5481-5078
(2021)
UV and VUV photoionization of some metal atoms and ions.
PhD thesis, Dublin City University and University of Padua.
The first part of the thesis concerns a study of vacuum ultraviolet (VUV) photoabsorption spectroscopy of metal atoms and ions using laser plasma generated continuum radiation at DCU. Photoabsorption spectra have been measured using the Dual Laser Plasma (DLP) photoaborption technique. Using this technique, the absorption spectra of lowly charged ions of lead and bismuth have been obtained. Then calculations with a relativistic time dependent local density approximation (RTDLDA) code are used to reproduce the overall spectral shapes of the spectra. Also, the calculations with the Cowan suite of atomic structure codes are used to identify unknown lines in the spectra. The simulated spectra broadened with our instrumental function are used to compared with experimental spectra and new features which are due to photoabsorption from both ground state and excited states of the Pb+, Bi+ and Bi2+ ions are identified.
The second part of the project was focused on optogalvanic spectroscopy (OGS) of molybdenum atoms. Three-step, two colour ionization of Mo was performed using a molybdenum hollow cathode lamp as the atomic Mo sample. Both the slow and fast optogalvanic signals were measured. There are few OGS studies of Mo in the literature the current study represents, to the best of the author’s knowledge, the first multicolour OGS study on Mo. The experiments were carried out at the Legnaro National Laboratories (LNL-INFN), Padova, Italy in the SPES (Selective Production of Exotic Species) laboratory. The focus is on isotope selection using tuned (resonant) laser ionization techniques of atomic vapours or the so-called AVLIS (atomic vapour laser ionization separation) technique. The experiments were designed to prove OGS as a simple and economic sensor for laser tuning. Specifically, the wavelength dependence of both ‘fast’ and ‘slow’ optogalvanic signals was studied, where the former comes from photo-generated electrons emitted during the laser pulse(s) and the latter originates from ion population redistribution following the laser pulse(s). Both the slow and fast optogalvanic signals are suitable for instantaneous laser tuning (and both are selective), however the former yields higher signal to noise ratios (SNRs).
Metadata
Item Type:
Thesis (PhD)
Date of Award:
March 2021
Refereed:
No
Supervisor(s):
Costello, John T., Nicolosi, Piergiorgio and Hayden, Patrick