FLUORESCENCE

Fluorescence is the phenomenon by which a substance absorbs radiation, often ultraviolet, then re-emits it almost instantaneously as visible light; the emission stops as soon as the excitation ceases, which distinguishes it from phosphorescence, which persists in darkness. In watchmaking, this principle is used for nighttime readability: the luminescent materials applied to the hands and Index (hour marker), such as Super-LumiNova, charge up with light and then release a glow, through a mechanism related to phosphorescence. Fluorescence itself is also used for Testing and authentication: under UV lamp, certain Materials, glues, oils or gems reveal a characteristic reaction allowing their nature to be verified. In gemology, the fluorescence of diamonds and precious stones constitutes an identification criterion. This optical behavior, at the boundary between physics and materials chemistry, thus finds applications both decorative and technical in the world of Time measurement.