The ultraviolet-visible absorption spectrum is a molecular absorption spectrum produced by the transitions between electron levels of atoms, ions, and molecules in gemstones, as well as electrons on molecular orbitals, under the action of ultraviolet-visible electromagnetic radiation. 

This spectrum results from transitions between electron levels, accompanied by changes in vibrational and rotational energy levels, forming a band-like absorption spectrum composed of many line spectra. 

The UV-VIS ultraviolet-visible spectrophotometer can detect the types and components of gemstones, distinguish natural gemstones from synthetic gemstones, identify optimized treatment methods for gemstones, and study the coloring mechanism of gemstones.