Term: wavenumber, \(\sigma\), \(\tilde{\nu }\)
https://doi.org/10.1351/goldbook.W06664

Definition:
The reciprocal of the wavelength, λ, or the number of waves per unit length along the direction of propagation. The SI unit is m-1, but a commonly used unit is cm-1. Symbols ν ˜ in a vacuum, σ in a medium.

Related Terms:
1) wavelength (http://doi.org/10.1351/goldbook.W06659).
2) propagation (http://doi.org/10.1351/goldbook.P04881).

Source: Green Book, 2nd ed., p. 30 (https://goldbook.iupac.org/files/pdf/green_book_2ed.pdf)

Citation: 'wavenumber, \(\sigma\), \(\tilde{\nu }\)' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.W06664

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