Some substances glow when irradiated with light. If the glow stops immediately when the light source goes out, this is known as fluorescence.
HOW DOES THIS WORK?
Electrons absorb the energy of the irradiated light. In a fraction of a second, they emit a large part of it again – also in the form of light, only with less energy.
WHERE DO WE ENCOUNTER FLUORESCENCE?
Fish and jellyfish can fluoresce. The chlorophyll in plants glows in the nonvisible infrared range. Body fluids, such as blood, fluoresce when exposed to UV radiation.
IN EVERYDAY LIFE
Fluorescent dyes in toothpaste and detergents brighten teeth and laundry. Highlighters also appear to glow thanks to such dyes.
Fluorescent molecules make individual cells and proteins in living organisms visible. In 2008, the Nobel Prize was awarded for what is referred to as the green fluorescent protein (GFP).
Some fabrics can glow for minutes or hours after the light source has gone out. This is called phosphorescence.
WHAT IS JÜLICH DOING?
Jülich researchers are using and developing measuring instruments based on fluorescence, studying, for example, plant photosynthesis, trace gases in the atmosphere and bacteria for biotechnology.
Illustrationen: Diane Köhne