| Autor: |
R.W. Vook, C.A. Colmenares, R.G. Gutmacher, R.L. Smith |
| Rok vydání: |
1982 |
| Předmět: |
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| Zdroj: |
Journal of Luminescence. 27:115-126 |
| ISSN: |
0022-2313 |
| DOI: |
10.1016/0022-2313(82)90013-8 |
| Popis: |
The cathodoluminescence (2–6 keV incident electrons) observed from thorium (111) and (533) crystal faces was recorded and analyzed for surfaces produced under various conditions. The blue luminescence observed in the presence of a partial oxygen pressure ∼ 133 μPa (∼10-6 Torr) was found to consist of a broad asymmetric major band that peaked around 468 nm on which weak bands or lines were superimposed at approximately 433, 489, 502, and 534 nm. The emission was almost totally extinguished in the presence of a partial CO pressure ∼ 133 μPa (∼10-6 Torr). The thorium-oxygen cathodoluminescence (CL) is interpreted as arising from the formation of ThO2 and the excitation of luminescence centers by the incident electron beam and their subsequent decay. The major luminescence at 468 nm arises from F centers in ThO2. The weak bands at 433 and 534 nm may arise from surface F+ and F centers designated as F+s and Fs. The former may also be due to an OH luminescence center. The two longer wavelength lines (489, 502 nm) superimposed on the broad major band at approximately 468 nm are interpreted as arising from Pr3+ impurities in the thorium lattice that gave rise to fluorescence emission. The line at 468 nm also may be due in part to the fluorescence of ThO. The cathodoluminescence spectra observed in the presence of CO, and (CO+O2) and (CO+H2) gas mixtures were consistent with an interpretation that O2 in the gas phase was required in order to obtain ThO2 on and below the surface to produce significant luminescence. Auger spectroscopy showed that exposure to CO left approximately as much oxygen on the surface as in the case of O2 but did not produce appreciable cathodoluminescence. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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