Alexandrite spectra.

 

Alexandrite section from Bahia, Brazil (~0.5mm thickness). This picture and the following illustrate the beautiful pleochroism from green to yellow to pink of the Alexandrite.

The spectra below were recorded on the green-pink and yellow-pink parts of the crystal changing the orientaion of the polarizer by 90. The presence of Cr3+ ions in the chrysoberyl structure gives the bimodal absorption feature responsible for the color and the pleochroism.

 

 

This enlargement of the region between 600 and 700 nm shows low intensities spin forbidden transition of the Cr3+ ion. The alexandrite spectrum is quite comparable to Ruby as presented previously.

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