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| Titel |
Stimulated infrared emission from rocks: assessing a stress indicator |
| VerfasserIn |
F. T. Freund, A. Takeuchi, B. W. S. Lau, A. Al-Manaseer, C. C. Fu, N. A. Bryant, D. Ouzounov |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1815-381X
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| Digitales Dokument |
URL |
| Erschienen |
In: eEarth ; 2, no. 1 ; Nr. 2, no. 1 (2007-01-10), S.7-16 |
| Datensatznummer |
250000409
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| Publikation (Nr.) |
 copernicus.org/ee-2-7-2007.pdf |
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| Zusammenfassung |
| To study the effect of stress-activated positive hole (p-hole) charge
carriers on the infrared (IR) emission from rocks, we subjected a portion
(~10 vol.%) of a large (30×60×7.5 cm3) block of
anorthosite, a nearly monomineralic (Ca-rich feldspar) igneous rock, to
uniaxial deviatory stress up to failure. We measured the IR emission from a
flat surface ≈40 cm from the stressed rock volume over the 800–1300 cm−1 (7.7–12.5 μm)
range. Instantly, upon loading, the emission
spectrum and intensity change. At first narrow bands appear at 930 cm−1
(10.75 μm), 880 cm−1 (11.36 μm), 820 cm−1 (12.4 μm)
plus additional narrow bands in the 1000–1300 cm−1 (7.7–10.0 μm)
range. The 10.75–12.4 μm bands are thought to arise from vibrationally
excited O-O stretching modes, which form when p-hole charge carriers, which
spread from the stressed rock volume into the unstressed rock, recombine at
the surface. They radiatively decay, giving rise to "hot" bands due to
transitions between excited states. Before failure the broad emission bands
at 1170 cm−1 and 1030 cm−1 (8.7 and 9.7 μm) also
increase slightly in intensity, suggesting a small increase in temperature
due to thermalization of the energy deposited into the surface through
p-hole recombination. Stimulated IR emission due to hole-hole recombination
and its follow-on effects may help understand the enhanced IR emission seen
in night-time satellite images of the land surface before major earthquakes
known as "thermal anomalies". |
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