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Proceedings Paper

Study of minerals, organic, and biogenic materials through time-resolved Raman spectroscopy
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Paper Abstract

A compact remote Raman spectroscopy system was developed at NASA Langley Research center and was previously demonstrated for its ability to identify chemical composition of various rocks and minerals. In this study, the Raman sensor was utilized to perform time-resolved Raman studies of various samples such as minerals and rocks, Azalea leaves, and a few fossil samples. The Raman sensor utilizes a pulsed 532 nm Nd:YAG laser as excitation source, a 4-inch telescope to collect the Raman-scattered signal from a sample several meters away, a spectrograph equipped with a holographic grating, and a gated intensified CCD (ICCD) camera system. Time resolved Raman measurements were carried out by varying the gate delay with fixed short gate width of the ICCD camera, allowing measurement of both Raman signals and fluorescence signals. Rocks and mineral samples were characterized, including marble, which contains CaCO3. Analysis of the results reveals the short (~10-13 s) lifetime of the Raman process and shows that the Raman spectra of some mineral samples contain fluorescence emission due to organic impurities. Also analyzed were a green (pristine) and a yellow (decayed) sample of Gardenia leaves. It was observed that the fluorescence signals from the green and yellow leaf samples showed stronger signals compared to the Raman lines. It was also observed that the fluorescence of the green leaf was more intense and had a shorter lifetime than that of the yellow leaf. For the fossil samples, Raman shifted lines could not be observed due to the presence of very strong short-lived fluorescence.

Paper Details

Date Published: 1 May 2009
PDF: 9 pages
Proc. SPIE 7312, Advanced Environmental, Chemical, and Biological Sensing Technologies VI, 731210 (1 May 2009); doi: 10.1117/12.818169
Show Author Affiliations
Christopher S. Garcia, Old Dominion Univ. (United States)
M. Nurul Abedin, NASA Langley Research Ctr. (United States)
Syed Ismail, NASA Langley Research Ctr. (United States)
Shiv K. Sharma, Univ. of Hawaii (United States)
Anupam K. Misra, Univ. of Hawaii (United States)
Trac Nguyen, Old Dominion Univ. (United States)
Hani Elsayed-Ali, Old Dominion Univ. (United States)


Published in SPIE Proceedings Vol. 7312:
Advanced Environmental, Chemical, and Biological Sensing Technologies VI
Tuan Vo-Dinh; Robert A. Lieberman; Günter Gauglitz, Editor(s)

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