Spectroscopy

Spectroscopy studies and measures how matter interacts with electromagnetic radiation or other signals, often by analyzing their spectra.

Electromagnetic spectrum: The full range of electromagnetic radiation, ordered by frequency or wavelength. Different regions probe different energies and reveal different properties of matter.
Quantum mechanics: The physical theory describing matter and radiation at atomic and subatomic scales. Its quantized states account for many discrete spectral features.
Mass spectrometry: An analytical technique that separates ions by mass-to-charge ratio and measures their abundances. It analyzes mass spectra rather than spectra of radiation interacting with matter.
Emission spectroscopy: A method that analyzes radiation emitted by excited atoms, ions, or molecules. It detects light produced by a sample, unlike absorption methods that measure removed light.
Atomic spectral line: A discrete frequency or wavelength emitted or absorbed during a transition between atomic energy levels. Sharp atomic lines are direct signatures of quantized energy changes.
Photon: A quantum of electromagnetic radiation carrying energy and momentum. Photon energy determines which transitions radiation can induce or detect.
Raman spectroscopy: A technique that identifies molecular vibrations through inelastic scattering of light. It reveals vibrational information complementary to infrared absorption.
Infrared spectroscopy: A method that measures infrared absorption or emission associated mainly with molecular vibrations. It is a specific spectral region and method, not the whole field.
Molecular vibration: Periodic motion of atoms within a molecule around their equilibrium positions. Vibrational transitions produce characteristic infrared absorption bands.
Energy level: A permitted value of energy for a quantum system. Spectral frequencies commonly encode differences between energy levels.

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