What is fluorescence?
For reasons not entirely understood, certain diamonds emit a subtle blue glow when exposed to ultraviolet rays. This interesting phenomenon is called fluorescence. Many light sources including the sun, fluorescent office lights, and “black” lights emit ultraviolet rays. In normal lighting conditions, fluorescence cannot be seen.
Fluorescence is the property of some atoms or molecules to absorb light of a particular wavelength and re-emit later at a longer wavelength. The interval between absorption and re-emission is termed the fluorescence lifetime. Wave length Spectra • Light can be described as either a particle or a wave. • Light normally consisits of a mixture of electromagnetic waves of many different lengths. • As a wave, the energy of light can be quantified by wavelength. • E(energy in ergs)=h(Planck’s constant)*v(frequency of light) • Shorter wavelengths have higher amounts of energy than longer wavelengths. • The absorption of light is an all or nothing phenomenom. • Fluorescent molecules can only absorb light of specific wavelengths, known as absorption bands. Excitation Spectra • Absorption of light occurs very quickly (10^-15sec). • Absorption excites fluorescent molecules from the ground state to an excited state. • Fluorescent molecules relax almost immediately (10^-11sec) to a position referre
Fluorescence is a property of certain chemical compounds which can become “excited” when light energy falls on them. They first absorb the light energy and very quickly release the energy back in the form of light of a different colour. What sort of substances are fluorescent ? There are many examples of fluorescent substances all around us. The electric-blue fluorescence of quinine in bottles of Indian Tonic Water can be seen easily when viewed under the “black light” ( ultraviolet light ) illumination often found in bars and night clubs. The same “black light” induces strong blue fluorescence from articles of clothing which have been washed with detergents containing optical brighteners. Red ink often contains eosin: if a drop is diluted into a glass of water the greenish fluorescence of the eosin can be seen in a darkened room by shining a beam of light from a torch through the bottom of the glass.
Fluorescence as a term means that a diamond will glow in blue under a RV lamp. It was used originally in diamond certifications as additional information for identification. The impact of blue fluorescence on price depends on its notice ability. For some higher color stones, fluorescence gives the stones a whiter, brighter appearance. Some buyers regularly pay better prices for highly fluorescent “I” color and lower stones. Yellow fluorescence may require an additional 5 to 10 percent discount. Generally, the higher the quality and price per carat the stronger fluorescence lowers value.
