Date of Award
Doctor of Philosophy (PhD)
Physics and Astronomy
Dr. Endre Takacs, Committee Chair
Dr. Chad Sosolik
Dr. Joan Marler
Dr. Mark Leising
Highly charged ions have enhanced relativistic eï¬€ects and compressed electronic wave functions, making their atomic transitions relevant in studies of fundamental atomic and nuclear properties. Accurate atomic data such as wavelengths, energy levels, and tran-sition probabilities are vital to the plasma communities. We report the extreme ultraviolet spectroscopy (EUV) of highly charged yttrium and xenon ions that were produced and conï¬ned with an electron beam ion trap (EBIT). The EUV spectra from these ions were recorded with a ï¬‚at-ï¬eld grazing incidence grating spectrometer. In the ﬁrst part of this work, new and previously observed EUV spectral lines were identiﬁed corresponding to the L-shell and a few M-shell yttrium ions (Y26+ – Y36+) in the wavelength range of 4 nm to 20 nm. The wavelength of the Li-like Y resonances, (2s - 2p1/2) and (2s - 2p3/2) and the Na-like D lines in Y, (3s - 3p1/2) and (3s - 3p3/2) were measured with an EBIT for the ﬁrst time. The wavelength uncertainties of the identiﬁed transitions ranged between 0.0004 nm and 0.002 nm. Fifty nine spectral lines corresponding to ∆ n = 0 transitions within the n = 2 and n = 3 shell were identiﬁed. Line identiﬁcation was assisted by the collisional-radiative non-Maxwellian code NOMAD. A few magnetic-dipole lines were measured, and the potential application of these transitions in electron density and temperature diagnostics was analyzed. In the second part of this work, we report a new method based on EUV spectroscopy of Na-like D transitions to measure the variation in mean square charge radii of Xe isotopes. The isotope shift of the Na-like D1 (3s - 3p1/2) transitions between 124Xe and 136Xe isotopes was measured and used to determine this variation by comparison with atomic structure calculations. The calculations were performed using the Relativistic Many-Body Perturba-tion (RMBPT) and Multi-Conï¬guration Dirac-Hartree-Fock (MCDHF) methods that were in excellent agreement with each other. The electron beam energy during the measurement was ï¬xed at 6 keV. The diï¬€erence in the mean-square charge radii, Î´ < r2 > was determined to be 0.269(0.042) fm2, which agrees well with previous measurements and a recommended value reported by [AM13]. The Mg-like (3s2 - 3s3p) transitions were also employed to de-termine the diï¬€erences in the mean square charge radii. Systematic studies of the measured shift were performed, providing conï¬dence in the obtained results.
Silwal, Roshani, "Extreme ultraviolet spectra of highly charged Y and Xe ions: line identification, diagnostic potential, and isotope shift" (2018). All Dissertations. 2107.