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intensity of a sample. A variety of molecular association can result in quenching. These include excited-state reactions, molecular rearrangements, energy transfer, ground-state complex formation, and collisional quenching.
Fluorescence is the property of atoms and molecules, so called fluorophores, to absorb light at a particular wavelength and to subsequently emit light of longer wavelength. Fluorescence microscopy can be based on autofluorescence or the addition of fluorescent dyes.
Fluorescence is used by scientists to detect different molecules that they are interested in studying further. For example, DNA can be detected by its binding to compounds that are brightly fluorescent under UV light.
Fluorescence occurs when a molecule absorbs light photons from the u.v.-visible light spectrum, known as excitation, and then rapidly emits light photons as it returns to it’s ground state. Fluorimetry characterizes the relationship between absorbed and emitted photons at specified wavelengths.
Fluorescence is a member of the ubiquitous luminescence family of processes in which susceptible molecules emit light from electronically excited states created by either a physical (for example, absorption of light), mechanical (friction), or chemical mechanism.
For example, organic compounds (i.e., hydrocarbons and derivatives) without double or triple bonds absorb light at wavelengths below 160nm, corre- sponding to a photon energy of >180kcalmol 1 (1cal¼4.184J), or >7.8eV
Fluorescence is also influenced by the structure of the molecule. For example the rigid molecules that present systems of conjugated double bonds, are well suited to the fluorescence : in particular molecules where there are aromatic structures, in which the resonance phenomenon of the double bonds are
