Title: atomic spectral lines
Long Title: IUPAC Gold Book - atomic spectral lines
DOI: 10.1351/goldbook.A00502
Status: current

Definition
Atomic and ionic spectral lines originate from specified electronic transitions between energy levels of atoms and ions, respectively. In the past it has been common usage to denote atomic lines as arc lines and ionic lines as spark lines. This usage is now considered to be incorrect. The correct way to indicate that lines are due to atomic or ionic transitions is: Element symbol I wavelength, e.g., Cu I \(324.7\ \rm{nm}\); and Element symbol II wavelength, e.g., Cu II \(213.6\ \rm{nm}\). Similarly for higher states of ionization, the type of line is represented by III, IV, etc.

Related Terms
- ionization: https://goldbook.iupac.org//terms/view/I03183
- wavelength: https://goldbook.iupac.org//terms/view/W06659

Source
- Orange Book, 2nd ed., p. 118 (https://media.iupac.org/publications/analytical_compendium/)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/A00502/html
- json: https://goldbook.iupac.org/terms/view/A00502/json
- xml: https://goldbook.iupac.org/terms/view/A00502/xml

Citation: Citation: 'atomic spectral lines' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.A00502
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Accessed: 2026-05-01T11:58:29+00:00