X-ray decay of multiple-vacancy states produced in various oxygen compounds by energetic, heavy-ion collisions /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1988.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | Rapid electron transfer processes in multiply-ionized oxygen atoms were studied by measuring the Kα x-ray satellite and hypersatellite spectra of various solid oxides and oxygen-bearing molecular gases excited by 4.5 keV electrons and 1.0-2.0 MeV/amu beams of protons, He, C, Mg, and Ar ions extracted from the Texas A&M Variable Energy Cyclotron. High-resolution spectra were obtained using a 12.7 cm Johansson type curved-crystal spectrometer employing a TAP crystal for wavelength dispersion. The Kα satellite structure of the gases showed strong chemical sensitivity only with proton and He ion excitation, in which oxygen is predominantly singly- and doubly-ionized and x-rays arise mainly from molecular orbital (MO) transitions. With multiple ionization, the x-ray emission spectra become identical since x-rays originate from essentially free-atom oxygen. The KL^1 satellite line showed variation with the crystal structure of oxides in spectra excited with electrons. Significant chemical effects, which correlate well with the ionicity or covalency of the oxide, were observed for the Kα hypersatellite spectra. This is the first observation of extensive chemical effects on hypersatellite states. Systematically lower peak energies for the solids compared to those of the gases and the presence of Kβ hypersatellites indicate that electron transfer to n [greater than or equal to] 3 levels of oxygen from energy-matched outer levels of neighboring atoms occurs in solids prior to K x-ray emission. Resonant electron transfer (RET) from the metal outer np level to the oxygen 2p shell was also observed for the first time in states with double K-vacancies. Moreover the hypersatellite spectra provided evidence for correlated multiple RET, which can be supported by calculations employing a point-charge model with the inclusion of corrections for extra-atomic relaxation. A detailed analysis of the multiplet line structure of one-, two-, and three-electron states for oxygen recoil ions excited by 0.68 MeV/amu Ar^11+ was carried out. The O K x-ray spectra are dominated by H-, He-, and Li-like transitions of the series np - 1s, 1snp - 1s^2, and 1s^[2]2l - 1s2lnp. Measurements of the intensity ratio (1P/3P) for transitions from the 1s2p He-like oxygen states revealed a highly nonlinear dependence on pressure. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Chemistry." |
| Physical Description: | xix, 317 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references (leaves 243-256). |