Raman Spectra of Carbonates

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Calcite

    Big calcite crystal on the left showing birefringence effect. The spectrum above has a low background. Calcite has a high intensity Raman scattering as can be seen by the very small intensity of the filtered laser line at 632.8 nm compared to Raman intensity. Calcite with its 3 peaks from around 200 cm-1 to above 1000 cm-1 could also be used to calibrate Raman spectra wavelengths.

 

Aragonite

     Spectrum of another Calcium carbonate crystal structure. The stretching carbonate ion vibration at 1080 cm-1 is common to both Calcite and Aragonite but the features around 200 cm-1 can be used to characterize both minerals. Raman spectroscopy can thus be used to identify such close chemical compositions.

 
 
 
 
 

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