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- Eklund, Gustav, 1990-
(author)
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Experiments on mutual neutralization using storage rings with merged ion beams
- 2020
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Doctoral thesis (other academic/artistic)abstract
- This thesis presents work on merged-beams experiments using the DESIREE facility, which consists of two electrostatic ion-storage rings operated at cryogenic temperatures of about 13 K. The two storage rings have a common straight section, where oppositely charged ions can interact at sub-eV collision energies. The work consists of development of the experimental method, tools for data analysis, and simulations for interpretation of the experimental results. This development has led to the first results from merged-beams experiments at DESIREE. The experiments are performed on mutual neutralization, a collision process where an electron is transferred from a negatively charged ion to a positively charged ion, resulting in two neutral products. This reaction is investigated for three systems: Li+ with D−, Na+ with D−, and Mg+ with D−. The reactions studied are of astrophysical interest, in particular for modeling of stellar atmospheres. The detection of the reaction products is done by using a position- and time-sensitive detector, and from this information it is possible to determine the quantum states involved in the reaction. The branching fractions of the reaction channels are measured and compared to theoretical modeling.
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| 2. |
- Fogle, Jr., Michael, 1974-
(author)
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Recombination and ionization of astrophysically abundant ions
- 2004
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Doctoral thesis (other academic/artistic)abstract
- The electron-ion recombination and electron-impact ionization of several astrophysically abundant C, N, O, and Ni ions have been investigated using the synchrotron storage ring CRYRING. The recombination rate coefficients predominanty used in the analyses of emission line spectra and for ionization balance calculations are determined from isoelectronic fits and extrapolations of theoretical and limited experimental results available from the literature. The rate coefficients reported by various authors differ by an order of magnitude for various ion species. For low temperature plasmas(<104 K), the available information on resonant recombination rate coefficients is even more limitied and, unfortunately, most available data has been determined from LS coupling calculations, which can have adverse effects on recombination rates due to the mistreatment of autoionizing states. For ions of C, N, and O, the production of metastable states complicates the experimental rate coefficient determinations. Some attempts have been made in this work to utilize both recombination and electron-impact ionization in estimating the metastable ion beam fractions present. Other metastable fractions have been determined by comparing the experimental recombination spectra to intermediate coupling calculations. Some of the absolute recombination rate coefficients reported in this work are given for the first time while many others vastly improve the spectral resolution of previous experiments, allowing for a more detailed study of the low energy resonances which contribute to the resonant recombination rate coefficient at low plasma electron temperatures. This increased resolution has also lead to the observation of trielectronic recombination resonances which greatly influence low temperature recombinaion rates in some ions.
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