Optical spectroscopy

Optical spectroscopy studies how matter absorbs, emits, or scatters ultraviolet, visible, and infrared radiation, using those interactions to characterize physical and chemical properties.

Absorption spectroscopy: A spectroscopic method that measures how much radiation a sample absorbs at different wavelengths. Absorption bands identify electronic, vibrational, and rotational transitions in the sample.
Electromagnetic spectrum: The full range of electromagnetic radiation, ordered by frequency or wavelength. Optical spectroscopy uses its ultraviolet, visible, and infrared regions.
UV–visible spectroscopy: A technique that measures ultraviolet and visible absorption or transmission by a sample. It probes electronic transitions and often quantifies dissolved compounds.
Mass spectrometry: An analytical technique that separates ions by mass-to-charge ratio and measures their abundance. It identifies and quantifies molecules through ions rather than optical transitions.
Emission spectroscopy: A method that analyzes radiation emitted by excited atoms, molecules, or materials. Its emitted wavelengths reveal transitions as excited states lose energy.
Photon: A quantum of electromagnetic radiation carrying energy and momentum. Photon energy determines which transitions a wavelength can excite or probe.
Infrared spectroscopy: A technique that measures infrared absorption associated chiefly with molecular vibrations. Its absorption bands help identify chemical bonds and functional groups.
Nuclear magnetic resonance spectroscopy: A method that probes atomic nuclei in a magnetic field using radiofrequency radiation. It reveals molecular structure through nuclear spin behavior, outside the optical range.
Scattering spectroscopy: Spectroscopy that analyzes radiation redirected or frequency-shifted by interactions with matter. Scattered light carries structural and vibrational information without requiring direct absorption measurements.
Energy level: A discrete allowed energy value for a quantum system. Spectral features arise when matter changes between energy levels.

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