Date of Award
5-2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Physics and Astronomy
Committee Chair/Advisor
Joan Marler
Committee Member
Endre Takacs
Committee Member
Bradley Meyer
Committee Member
Jonathan Zrake
Abstract
Analysis of astrophysical phenomena requires an understanding of the electronic
structure and transition probabilities of the elements present in that environment,
yet there are still many charge states of heavy elements whose electronic
structures and spectroscopic properties are not yet well understood. To address this,
we investigated the spectroscopic properties of three different elements through an
analysis of spectra collected from three different experimental apparatuses.
In order to better understand the spectroscopic properties of Ni I and II, we
analyzed spectra collected from the Compact Toroidal Hybrid (CTH) apparatus at
Auburn University. In this experiment, a nickel sample was inserted into the CTH
plasma, where nickel atoms where ablated and then excited by a pulsed plasma.
Emitted photons are collected by a UV/VIS spectrometer for analysis. The wavelength
range studied in this experiment was 200nm to 800 nm. Nickel peaks in the
resulting spectra were identified by looking at the dependence of peak intensity upon
the depth of the sample into the plasma, as well as by comparing to spectra collected
using a gold sample in the CTH. In this experiment, 130 previously reported nickel
lines were observed as well as 18 lines that, to the best of our knowledge, have not
been previously observed. Additionally, 19 previously observed Ni II emission lines
were confirmed and one new emission line was identified which was not previously
observed. These previously unobserved lines were identified by using known energy levels from the National Institute of Technology (NIST) Atomic Spectral Database
(ASD) to calculate the Ritz wavelength of electric dipole-allowed transitions. We
also present preliminary benchmarks of recent Ni II R-matrix calculations using our
experimentally observed lines.
Using the results of the above, we then conducted the first analysis of nickel
and iron emission lines in comet Hyakutake. Our experimental spectra, along with
previously published emission lines of nickel and iron, and a fluorescence model that
calculates the predicted emission of nickel and iron in the comet coma, were used to
identify emission lines present in the comet and analyze the line intensities to estimate
abundances of nickel and iron. These abundances and their spatial distributions
within the comet’s coma were then used to analyze which parent molecules in the
comet could have led to gaseous nickel and iron in the coma.
Our spectral analyses were extended beyond nickel by analyzing the emission
between 200 and 1500nm of Ir I and II lines from a hollow cathode lamp (HCL). The
aim of this project was to identify previously unobserved emission lines of Ir as well
as to analyze how the observed lines change with electron temperature. These results
could also be used to inform future studies of Ir in the CTH. Because the HCL is
filled with a neon buffer gas, the collected spectra only contains significant emission
from Ir and Ne, making the spectra cleaner and easier to identify lines. Additionally,
the steady state nature of the HCL allowed us to use longer exposure times than
those used in the CTH, making it possible to observe weak emission lines. Although
this analysis is not yet complete, significant progress has been made to analyze the
spectra and identify observed Ir I and II lines.
A third apparatus, the electron beam ion trap (EBIT) facility at the National
Institute of Standards and Technology (NIST), was used study highly charged Pr.
An EBIT, which traps and ionizes atoms via electron impact ionization, allows one to observe different high charge states by varying the electron beam energy. For this
study, the NIST EBIT produced Pr25+ through Pr33+ and their emitted spectra was
observed. The EBIT was run with varying electron beam energies, and the light
emitted between 8nm and 25.5nm was collected by a spectrometer. These spectra
were then compared to theoretical spectra produced using the Flexible Atomic Code
(FAC) as well as the NOMAD collisional-radiative model, and the change in line
intensity with respect to electron beam energy was analyzed in order to identify Pr
emission lines.
Recommended Citation
Neff, Brynna, "Experimental Analyses of Emission Lines in the UV/VIS/NIR Range for Astrophysically-Important Elements: From the Iron Group to R-Process Elements" (2024). All Dissertations. 3642.
https://tigerprints.clemson.edu/all_dissertations/3642