Fluorescence spectroscopy

Fluorescence spectroscopy measures light emitted by a substance after it absorbs radiation. Its emission wavelengths and intensities reveal molecular identity, environment, and concentration.

Jablonski diagram: An energy-level diagram showing electronic states and transitions involved in molecular absorption, emission, and relaxation. It maps the excited-state pathways that produce the measured emission.
Fluorescence microscopy: Microscopy that uses fluorescent emission to form images of labeled structures or molecules. It applies fluorescence detection to spatially resolved samples.
Fluorescence: The emission of light by a substance following absorption of radiation, typically ending soon after excitation stops. Spectroscopy measures this emission as a function of wavelength or time.
Phosphorescence spectroscopy: A technique that measures delayed light emission from long-lived excited states after a substance absorbs radiation. Its delayed emission contrasts with fluorescence’s typically rapid emission.
Stokes shift: The difference between a substance’s absorption and fluorescence emission wavelengths, usually with emission at the longer wavelength. It separates emitted fluorescence from the excitation light.
Fluorescence assay: An analytical test that uses changes in fluorescence to detect or quantify a target substance. Assays turn emission signals into measurements of specific analytes.
Electronic spectroscopy: Spectroscopic methods that probe transitions between electronic energy states using light. Fluorescence is one kind of electronic spectroscopic signal.
Raman spectroscopy: A technique that identifies molecular vibrations through inelastic scattering of monochromatic light. It detects scattered excitation light rather than fluorescence emission.
Fluorescence lifetime: The average time a molecule remains in an excited fluorescent state before emitting a photon or losing energy otherwise. Time-resolved measurements distinguish signals that steady-state intensity cannot.
Fluorescence correlation spectroscopy: A method that analyzes fluorescence fluctuations to estimate molecular concentrations, diffusion, and interactions. It extracts molecular dynamics from fluctuations in fluorescence intensity.

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