Fluorescence
Fluorescence is the property of certain molecules (fluorophores) to absorb light at one wavelength and emit light at a longer wavelength. The incident light excites the molecule to a higher level of vibrational energy. As the molecule returns to the ground state, the excited fluorophore emits a photon. This photon is the fluorescence emission. If the molecule returns to the ground state through an intermediate excited triple state, there is a delay in the emission of the photon. This delayed photon is termed a phosphorescence emission.
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