Remote Raman Efficiencies and Cross-Sections of Organic and Inorganic Chemicals

• Published in: Applied spectroscopy Vol. 71; no. 5; pp. 1025 - 1038
• Main Authors: Acosta-Maeda, Tayro E., Misra, Anupam K., Porter, John N., Bates, David E., Sharma, Shiv K.
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01-05-2017
• Subjects: remote Raman; remote sensing; Raman spectroscopy; standoff Raman; planetary science instruments; Raman cross-section
• ISSN: 0003-7028; 1943-3530
• DOI: 10.1177/0003702816668531

We determined Raman cross-sections of various organic liquids and inorganic polyatomic ions in aqueous solutions with a 532 nm pulsed laser using remote Raman systems developed at the University of Hawaii. Using a calibrated integrating sphere as a light source, we converted the intensity counts in the spectrum of the light from the integrating sphere measured with UH remote Raman instrument to spectral radiance. From these data, a response function of the remote Raman instrument was obtained. With the intensity-calibrated instrument, we collected remote Raman data from a standard 1 mm path length fused silica spectrophotometer cell filled with cyclohexane. The measured value of the differential Raman cross-section for the 801 cm−1 vibrational mode of cyclohexane is 4.55 × 10−30 cm2 sr−1 molecule−1 when excited by a 532 nm laser, in good agreement with the values reported in the literature. Using the measured cyclohexane Raman cross-section as a reference and relative Raman mode intensities of the various ions and organic liquids, we calculated the Raman cross-sections of the strongest Raman lines of nitrate, sulfate, carbonate, phosphate ions, and organic liquids by maintaining same experimental conditions for remote Raman detection. These relative Raman cross-section values will be useful for estimating detection capabilities of remote Raman systems for planetary exploration.