Fluorescent dyes emit light after absorbing light energy and transitioning to an excited state, subsequently releasing energy as light when returning to their ground state. This process is called fluorescence.
Here's a more detailed breakdown:
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Absorption: A fluorescent dye molecule (also called a fluorophore) absorbs light energy of a specific wavelength. This absorption causes an electron within the molecule to jump to a higher energy level, also known as an excited state. The wavelengths absorbed are typically shorter (e.g., ultraviolet or blue) than the wavelengths emitted.
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Excited State Lifetime: The fluorophore remains in the excited state for a brief period (typically nanoseconds). During this time, the molecule can undergo various interactions with its surrounding environment, losing some energy through vibrational relaxation or other non-radiative processes.
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Emission: The fluorophore then returns to its ground state, releasing the remaining energy as a photon of light. Because some energy was lost during the excited state lifetime, the emitted light has a longer wavelength (lower energy) than the absorbed light. This difference in wavelength is known as the Stokes shift.
In summary, the fluorescence process involves:
- Excitation: Absorption of light by the fluorophore.
- Excited State: A brief period where the molecule is in a higher energy state.
- Emission: Release of light (fluorescence) as the molecule returns to its ground state.
