Absorption Spectral Analysis at Gemstones

TOKL author is Uwe G. B.Hollenbach, Germany

Purposes of the experiment

This measurement report presents results of absorption spectral analysis at colored gemstones according to the classification of hardness. Characteristic absorptions versus wavelength are measured within the visible spectral range of about 400 nm to 750 nm using an SMA Spectrometer from Thunder Optics. The measured spectral data are presented in spectral absorption diagrams and furthermore in spectral color bars. Both of them are computed with the software Spectragryph. In the following sections the motivation of the work, the measurement set up, the illumination, and light lunching in gemstones are described. At the end of the explanatory sections, a conclusion and an outlook for further work are given. The experimentally achieved results are grouped according to the type of gemstone and tabular placed in the appendix. They will be supplemented and edited over time.

Description of experimental setups

The measurement setup used for this work contains a wideband white light source, a spectrometer, an object holder and a netbook with analysis software to compute and illustrate the measured spectral data.

Main results of the experiment

In Tables of the appendix grouped according to the type of gemstone series of different colored gemstones are spectral analyzed. The spectral white lamp light is random polarized and not specific coupled into a defined crystal axis of the gemstones. Therefore the resulted spectral absorption curves in the appendix can’t discuss for axis orientated polarization states. All plots are contrast optimized by offset subtraction and normalization of the highest absorption peak within the VIS range. Therefor the visibility a) for small absorption lines and b) for low absorption in nearly colorless or high transparent gemstones can be improved. Also the spectral color bars which are additionally placed below the spectral absorption curves become better visibility about absorption lines and weakly wide absorption bands. The spectral diagrams and color bars vs. wavelength are generated by the software Spectragryph.

Materials

Absorption Spectral Analysis at Gemstones.pdf

*TOKL text and pictures are original and the Intellectual property of the author.