fluorescencemedical dictionary

<chemistry, physics> The emission of one or more photons by a molecule or atom activated by the absorption of a quantum of electro magnetic radiation.

Typically the emission, that is of longer wavelength than the excitatory radiation, occurs within 10exp 8 seconds: phosphorescence is a phenomenon with a longer or much longer delay in re radiation. Note that rays, X-rays, UV, visible light and IR radiations may all stimulate fluorescence.

(25 Jun 1999)