Discharge

Fluorescence is a luminescence that is mostly found as an optical phenomenon. The term fluorescence was coined by George Gabriel Stokes in a 1852 paper. The name was given as a description of the essence of the mineral fluorite, composed of calcium fluoride, which gave a visible emission when illuminated with UV radiation.

The common fluorescent tube relies on fluorescence. Inside the glass tube is a partial vacuum and a small amount of mercury. An electric discharge in the tube causes the mercury atoms to emit light. The emitted light is in the ultraviolet range, is invisible, and is harmful to most living organisms. The tube is lined with a coating of a fluorescent material, called the phosphor, which absorbs the ultraviolet and re-emits visible light.

All plants, algae, and cyanobacteria are naturally fluorescent, since chlorophyll a is fluorescent. Some flowers also contain other more visibly fluorescent pigments like betaxanthins, increasing visibility to pollinators.

Plants have also been genetically modified to fluoresce. There are many types of green fluorescent proteins that absorb and emit at different wavelengths. This enables the production of many differently labeled fluorescent molecules in a single plant.

Plant fluorescence is being found to be highly useful for the University of Florida and the NASA staff. These individuals are working together to learn more about the planet Mars. These scientists and engineers have chosen the Arabidopsis mustard plant to go to Mars, for many reasons.

Reporter genes have been added to this plant to glow for different environmental stressors. These stressors include temperature, drought, disease, metal content in the soil and peroxides. Each stressor will glow at a different wavelength that will be monitored. By doing such an experiment more will be learned about the environment on Mars in order to modify plant life to be able to survive there.

Crude oil (petroleum) fluoresces in a range of colors, from dull brown for heavy oils and tars through to bright yellowish and bluish white for very light oils and condensates. This phenomenon is used in oil exploration drilling to identify very small amounts of oil in drill cuttings and core samples.

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