Title: spectrum
Long Title: IUPAC Gold Book - spectrum
DOI: 10.1351/goldbook.08291
Status: current

Definition
Graph of a quantity derived from the radiant power at each wavelength (frequency or wavenumber) as ordinate plotted against the wavelength (frequency or wavenumber) of electromagnetic radiation as abscissa.

Notes
1) In mid-infrared and Raman spectroscopy, wavenumber is mostly used today, while it is more commonly replaced by wavelength in near infrared spectroscopy.
2) Quantities plotted include absorbance, absorption coefficient, transmittance, reflectance, luminescence.

Related Terms
- Raman spectroscopy: https://goldbook.iupac.org//terms/view/08669
- electromagnetic radiation: https://goldbook.iupac.org//terms/view/08242
- mid-infrared: https://goldbook.iupac.org//terms/view/08617
- near infrared spectroscopy: https://goldbook.iupac.org//terms/view/08642
- wavelength: https://goldbook.iupac.org//terms/view/08300
- wavenumber: https://goldbook.iupac.org//terms/view/08302

Source
- PAC, 2021, 93, 647. 'Glossary of methods and terms used in analytical spectroscopy (IUPAC Recommendations 2019)' on page 675 (https://doi.org/10.1515/pac-2019-0203)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/08291/html
- json: https://goldbook.iupac.org/terms/view/08291/json
- xml: https://goldbook.iupac.org/terms/view/08291/xml

Citation: Citation: 'spectrum' 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.08291
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Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.
Accessed: 2026-05-30T22:36:26+00:00