Atomic spectroscopy

Atomic spectroscopy studies how free atoms absorb, emit, or scatter electromagnetic radiation. These interactions reveal atomic energy levels and identify or quantify elements.

Atomic energy level: A discrete allowed energy state of an atom, specified by its electronic configuration and quantum numbers. Radiation changes an atom’s energy by moving it between these discrete states.
Atomic absorption spectroscopy: An analytical technique that measures light absorbed by free ground-state atoms to determine elemental concentrations. It applies atomic absorption to quantitative analysis of prepared samples.
Quantum mechanics: The physical theory describing matter and radiation at atomic and subatomic scales. Its rules determine the discrete states and radiation transitions measured in atomic spectra.
Molecular spectroscopy: The study of how molecules interact with electromagnetic radiation through electronic, vibrational, and rotational transitions. Molecules add vibrational and rotational structure absent from spectra of isolated free atoms.
Fraunhofer lines: Dark absorption lines in the solar spectrum, systematically catalogued by Joseph von Fraunhofer in the nineteenth century. Their patterns helped connect atomic absorption to the spectrum of sunlight.
Absorption spectroscopy: A spectroscopic method that measures radiation absorbed by matter as a function of wavelength or frequency. Atoms absorb selected wavelengths when incident photons match energy gaps.
Inductively coupled plasma atomic emission spectroscopy: An elemental analysis technique that measures light emitted by atoms and ions in an inductively coupled plasma. A hot plasma excites many elements for simultaneous emission-based measurement.
Atomic orbital: A quantum state describing the spatial distribution and properties of an electron in an atom. Electron orbitals help determine atomic energy levels and spectral transitions.
Optical spectroscopy: The study of matter through its interaction with ultraviolet, visible, and infrared radiation. Atomic spectroscopy is one domain within the broader study of optical interactions.
Kirchhoff's laws of spectroscopy: Rules relating emission and absorption spectra to the conditions and composition of luminous bodies. They established how spectral lines can identify elements in hot sources and cooler intervening gas.

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