This instrument is important since it measures the absorption features due to electron defects or chromophore trace elements (colour causing elements). The energies of the bonding electrons are responsible for the absorption features.
- The UV-VIS-NIR (ultra violet – visible – near infrared) spectrum is expressed in nanometers and covers the region from 200 to 2500nm.
- Absorption features are due to electron defects.
- While taking a spectrum, defined orientation directions should be maintained for better results. In isotropic gemstones, any direction is considered. In anisotropic gemstones, the samples should be oriented using specific crystallographic orientations.
- This is important in the identification of the transitions responsible for colour and pleochroism.
These spectra help in detecting:
- Gem Identification – unknown gem material; Natural / synthetic identification.
- Identification of geological environment and origin of gemstone.
- Identification of the treatment i.e. heat, irradiation etc.
- Type classification of diamonds.